[DISCUSS] Java code style

[Fabian Hueske-2]

OK, I'll try to summarize the discussion so far (please correct me if I got
something wrong):

Everybody is in favor of adding a stricter code style based on the Google
Java code style.
Main points of discussion are:
1) Line length
2) JavaDocs
3) Tabs vs. Spaces

-- Line length
Issue:
Google code style demands 80 or 100 chars line length limit.
Some people find this too narrow.

Discussion so far:
Nobody objected against a limit of 120 chars, AFAIR.

-- JavaDocs
Issue:
Google code style says "At the *minimum*, Javadoc is present for every
public class, and every public or protected member of such a class, with a
few exceptions noted below." Exceptions are self-explanatory methods like
getters and setters and overwritten method.
Significant parts of the Flink code base do not comply with this
requirement. It would be a huge effort to add the corresponding code
documentation.

Discussion so far:
Disable JavaDoc checks when adding the code style and opening JIRAs for
adding JavaDocs on a per Maven module level (with potentially subissues)
with target dates. Once a module complies to the rule, the JavaDoc check is
enabled in the checkstyle.

-- Tabs vs. Spaces
Issue:
The Google code style requires two spaces for indention. The Java code base
of Flink uses tabs. Moving from tabs to spaces would touch every line of
Java code and therefore might make the tracking of changes in the past much
harder.
Max provided some numbers for applying the Google code style on the current
code base: The style checker found 28k violations (possibly multiple ones
per LOC) on 121k LOC of Java code in 1601 out of 3251 Java classes. So
Google code style without spaces would touch every second file and about
every 4th line of code. The question I have, would it be easier to track
history with a commit that touches 1/2 (or 1/4) of the code base compared
to one that touches everything.

Discussion so far:
AFAIR, nobody said to have a personal preferences of tabs over spaces.
However, some people raised concerns that the implied changes of moving the
code base from tabs to spaces would be too massive and the "benefits" would
not justify the "cost" of the change.
I think, this is the main point of discussion, right now.

If we want to come to a conclusion, we should not let this discussion fall
asleep (as happened a few times in the past).

Does anybody NOT agree with the "solutions" for line length and JavaDocs,
i.e., 120 chars and "lazy" adding of JavaDocs with JIRA tracking, or has
another proposal?
How can we resolve the Tabs vs. Spaces discussion?

Cheers, Fabian



2015-10-30 18:16 GMT+01:00 Maximilian Michels <[hidden email]>:

> I looked up if the Checkstyle plugin would also support tabs with a
> fixed line length. Indeed, this is possible because a tab can be
> mapped to a fixed number of spaces.
>
> I've modified the default Google Style Checkstyle file. I changed the
> indention to tabs (2 spaces) and increased the line length to 120:
> https://gist.github.com/mxm/2ca4ef7702667c167d10
>
> The scan of the entire Flink project resulted in 27,992 items in 1601
> files. This is roughly corresponds to the number of lines we would
> have to touch to comply with the style rules. Note that, one line may
> contain multiple items. A lot of the items are import statements.
>
> Next, I tried running the vanilla Google Style Checkstyle file over
> the entire code base but my IntelliJ crashed. Using Maven, I wasn't
> able to get a total result displayed but I'm assuming it would be
> almost all lines of Flink code that had a violation due to tabs.
>
> On Mon, Oct 26, 2015 at 6:56 PM, Suneel Marthi <[hidden email]>
> wrote:
> > 2 spaces is the convention that's followed on Mahout and Oryx.
> >
> > On Mon, Oct 26, 2015 at 1:42 PM, Till Rohrmann <[hidden email]>
> wrote:
> >
> >> Concerning question 2 Tabs vs. Spaces, in case of spaces we would have
> to
> >> decide on the number of spaces, too. The Google Java style says to use
> a 2
> >> space indentation, which is in my opinion sufficient to distinguish
> >> different indentations levels from each other. Furthermore, it would
> save
> >> some space.
> >>
> >> I would not vote -1 if we keep tabs.
> >>
> >>
> >>
> >> On Sat, Oct 24, 2015 at 8:33 PM, Henry Saputra <[hidden email]
> >
> >> wrote:
> >>
> >> > +1 for adding restriction for Javadoc at least at the header of public
> >> > classes and methods.
> >> >
> >> > We did the exercise in Twill and seemed to work pretty well.
> >> >
> >> > On Fri, Oct 23, 2015 at 1:34 AM, Maximilian Michels <[hidden email]>
> >> > wrote:
> >> > > I don't think lazily adding comments will work. However, I'm fine
> with
> >> > > adding all the checkstyle rules one module at a time (with a jira
> >> > > issue to keep track of the modules already converted). It's not
> going
> >> > > to happen that we lazily add comments because that's the reason why
> >> > > comments are missing in the first place...
> >> > >
> >> > > On Fri, Oct 23, 2015 at 12:05 AM, Henry Saputra <
> >> [hidden email]>
> >> > wrote:
> >> > >> Could we make certain rules to give warning instead of error?
> >> > >>
> >> > >> This would allow us to cherry-pick certain rules we would like
> people
> >> > >> to follow but not strictly enforced.
> >> > >>
> >> > >> - Henry
> >> > >>
> >> > >> On Thu, Oct 22, 2015 at 9:20 AM, Stephan Ewen <[hidden email]>
> >> wrote:
> >> > >>> I don't think a "let add comments to everything" effort gives us
> good
> >> > >>> comments, actually. It just gives us checkmark comments that make
> the
> >> > rules
> >> > >>> pass.
> >> > >>>
> >> > >>> On Thu, Oct 22, 2015 at 3:29 PM, Fabian Hueske <[hidden email]
> >
> >> > wrote:
> >> > >>>
> >> > >>>> Sure, I don't expect it to be free.
> >> > >>>> But everybody should be aware of the cost of adding this code
> style,
> >> > i.e.,
> >> > >>>> spending a huge amount of time on reformatting and documenting
> code.
> >> > >>>>
> >> > >>>> Alternatively, we could drop the JavaDocs rule and make the
> >> transition
> >> > >>>> significantly cheaper.
> >> > >>>>
> >> > >>>> 2015-10-22 15:24 GMT+02:00 Till Rohrmann <[hidden email]>:
> >> > >>>>
> >> > >>>> > There ain’t no such thing as a free lunch and code style.
> >> > >>>> >
> >> > >>>> > On Thu, Oct 22, 2015 at 3:13 PM, Maximilian Michels <
> >> [hidden email]
> >> > >
> >> > >>>> > wrote:
> >> > >>>> >
> >> > >>>> > > I think we have to document all these classes. Code Style
> >> doesn't
> >> > come
> >> > >>>> > > for free :)
> >> > >>>> > >
> >> > >>>> > > On Thu, Oct 22, 2015 at 3:09 PM, Fabian Hueske <
> >> [hidden email]
> >> > >
> >> > >>>> > wrote:
> >> > >>>> > > > Any ideas how to deal with the mandatory JavaDoc rule for
> >> > existing
> >> > >>>> > code?
> >> > >>>> > > > Just adding empty headers to make the checkstyle pass or
> >> start a
> >> > >>>> > serious
> >> > >>>> > > > effort to add the missing docs?
> >> > >>>> > > >
> >> > >>>> > > > 2015-10-21 13:31 GMT+02:00 Matthias J. Sax <
> [hidden email]
> >> >:
> >> > >>>> > > >
> >> > >>>> > > >> Agreed. That's the reason why I am in favor of using
> vanilla
> >> > Google
> >> > >>>> > code
> >> > >>>> > > >> style.
> >> > >>>> > > >>
> >> > >>>> > > >> On 10/21/2015 12:31 PM, Stephan Ewen wrote:
> >> > >>>> > > >> > We started out originally with mixed tab/spaces, but it
> >> > ended up
> >> > >>>> > with
> >> > >>>> > > >> > people mixing spaces and tabs arbitrarily, and there is
> >> > little way
> >> > >>>> > to
> >> > >>>> > > >> > enforce Matthias' specific suggestion via checkstyle.
> >> > >>>> > > >> > That's why we dropped spaces alltogether...
> >> > >>>> > > >> >
> >> > >>>> > > >> > On Wed, Oct 21, 2015 at 12:03 PM, Gyula Fóra <
> >> > >>>> [hidden email]>
> >> > >>>> > > >> wrote:
> >> > >>>> > > >> >
> >> > >>>> > > >> >> I think the nice thing about a common codestyle is that
> >> > everyone
> >> > >>>> > can
> >> > >>>> > > set
> >> > >>>> > > >> >> the template in the IDE and use the formatting
> commands.
> >> > >>>> > > >> >>
> >> > >>>> > > >> >> Matthias's suggestion makes this practically
> impossible so
> >> > -1 for
> >> > >>>> > > mixed
> >> > >>>> > > >> >> tabs/spaces from my side.
> >> > >>>> > > >> >>
> >> > >>>> > > >> >> Matthias J. Sax <[hidden email]> ezt írta (időpont:
> >> > 2015. okt.
> >> > >>>> > > 21.,
> >> > >>>> > > >> Sze,
> >> > >>>> > > >> >> 11:46):
> >> > >>>> > > >> >>
> >> > >>>> > > >> >>> I actually like tabs a lot, however, in a "mixed"
> style
> >> > together
> >> > >>>> > > with
> >> > >>>> > > >> >>> spaces. Example:
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>>         myVar.callMethod(param1, // many more
> >> > >>>> > > >> >>>         .................paramX); // the dots mark
> space
> >> > >>>> indention
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>> indenting "paramX" with tabs does not give nice
> aliment.
> >> > Not
> >> > >>>> sure
> >> > >>>> > if
> >> > >>>> > > >> >>> this would be a feasible compromise to keeps tabs in
> >> > general,
> >> > >>>> but
> >> > >>>> > > use
> >> > >>>> > > >> >>> space for cases as above.
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>> If this in no feasible compromise, I would prefer
> space
> >> to
> >> > get
> >> > >>>> the
> >> > >>>> > > >> >>> correct indention in examples as above. Even if this
> >> > result in a
> >> > >>>> > > >> >>> complete reformatting of the whole code.
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>> Why this? Everybody can set this in it's IDE/editor as
> >> > he/she
> >> > >>>> > > wishes...
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>>>> If we keep tabs, we will have to specify the line
> >> length
> >> > >>>> > relative
> >> > >>>> > > to
> >> > >>>> > > >> a
> >> > >>>> > > >> >>> tab
> >> > >>>> > > >> >>>>> size (like 4).
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>> -Matthias
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>> On 10/21/2015 11:06 AM, Ufuk Celebi wrote:
> >> > >>>> > > >> >>>> To summarize up to this point:
> >> > >>>> > > >> >>>>
> >> > >>>> > > >> >>>> - All are in favour of Google check style (with the
> >> > following
> >> > >>>> > > possible
> >> > >>>> > > >> >>>> exceptions)
> >> > >>>> > > >> >>>> - Proposed exceptions so far:
> >> > >>>> > > >> >>>>   * Specific line length 100 vs. 120 characters
> >> > >>>> > > >> >>>>   * Keep tabs instead converting to spaces (this
> would
> >> > >>>> translate
> >> > >>>> > to
> >> > >>>> > > >> >>>> skipping/coming up with some indentation rules as
> well)
> >> > >>>> > > >> >>>>
> >> > >>>> > > >> >>>> If we keep tabs, we will have to specify the line
> length
> >> > >>>> relative
> >> > >>>> > > to a
> >> > >>>> > > >> >>> tab
> >> > >>>> > > >> >>>> size (like 4).
> >> > >>>> > > >> >>>>
> >> > >>>> > > >> >>>> Let’s keep the discussion going a little longer. I
> think
> >> > it has
> >> > >>>> > > >> >> proceeded
> >> > >>>> > > >> >>>> in a very reasonable manner so far. Thanks for this!
> >> > >>>> > > >> >>>>
> >> > >>>> > > >> >>>> – Ufuk
> >> > >>>> > > >> >>>>
> >> > >>>> > > >> >>>> On Wed, Oct 21, 2015 at 10:29 AM, Fabian Hueske <
> >> > >>>> > [hidden email]
> >> > >>>> > > >
> >> > >>>> > > >> >>> wrote:
> >> > >>>> > > >> >>>>
> >> > >>>> > > >> >>>>> Thanks Max for checking the modifications by the
> Google
> >> > code
> >> > >>>> > > style.
> >> > >>>> > > >> >>>>> It is very good to know, that the impact on the code
> >> base
> >> > >>>> would
> >> > >>>> > > not
> >> > >>>> > > >> be
> >> > >>>> > > >> >>> too
> >> > >>>> > > >> >>>>> massive. If the Google code style would have touched
> >> > almost
> >> > >>>> > every
> >> > >>>> > > >> >> line,
> >> > >>>> > > >> >>> I
> >> > >>>> > > >> >>>>> would have been in favor of converting to spaces.
> >> > However,
> >> > >>>> your
> >> > >>>> > > >> >>> assessment
> >> > >>>> > > >> >>>>> is a strong argument to continue with tabs, IMO.
> >> > >>>> > > >> >>>>>
> >> > >>>> > > >> >>>>> Regarding the line length limit, I personally find
> 100
> >> > chars
> >> > >>>> too
> >> > >>>> > > >> >> narrow
> >> > >>>> > > >> >>> but
> >> > >>>> > > >> >>>>> would be +1 for having a limit.
> >> > >>>> > > >> >>>>>
> >> > >>>> > > >> >>>>> +1 for discussing the Scala style in a separate
> thread.
> >> > >>>> > > >> >>>>>
> >> > >>>> > > >> >>>>> Fabian
> >> > >>>> > > >> >>>>>
> >> > >>>> > > >> >>>>> 2015-10-20 18:12 GMT+02:00 Maximilian Michels <
> >> > [hidden email]
> >> > >>>> >:
> >> > >>>> > > >> >>>>>
> >> > >>>> > > >> >>>>>> I'm a little less excited about this. You might
> not be
> >> > aware
> >> > >>>> > but,
> >> > >>>> > > >> for
> >> > >>>> > > >> >>>>>> a large portion of the source code, we already
> follow
> >> > the
> >> > >>>> > Google
> >> > >>>> > > >> >> style
> >> > >>>> > > >> >>>>>> guide. The main changes will be tabs->spaces and
> >> 80/100
> >> > >>>> > > characters
> >> > >>>> > > >> >>>>>> line limit.
> >> > >>>> > > >> >>>>>>
> >> > >>>> > > >> >>>>>> Out of curiosity, I ran the official Google Style
> >> > Checkstyle
> >> > >>>> > > >> >>>>>> configuration to confirm my suspicion:
> >> > >>>> > > >> >>>>>>
> >> > >>>> > > >> >>>>>>
> >> > >>>> > > >> >>>>>
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>
> >> > >>>> > > >>
> >> > >>>> > >
> >> > >>>> >
> >> > >>>>
> >> >
> >>
> https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml
> >> > >>>> > > >> >>>>>> The changes are very little if we turn off line
> length
> >> > limit
> >> > >>>> > and
> >> > >>>> > > >> >>>>>> tabs-to-spaces conversion.
> >> > >>>> > > >> >>>>>>
> >> > >>>> > > >> >>>>>> There are some things I really like about the
> Google
> >> > style,
> >> > >>>> > e.g.
> >> > >>>> > > >> >> every
> >> > >>>> > > >> >>>>>> class has to have a JavaDoc and spaces after
> keywords
> >> > (can't
> >> > >>>> > > stand
> >> > >>>> > > >> if
> >> > >>>> > > >> >>>>>> there aren't any). I'm not sure if we should change
> >> > tabs to
> >> > >>>> > > spaces,
> >> > >>>> > > >> >>>>>> because it means touching almost every single line
> of
> >> > code.
> >> > >>>> > > However,
> >> > >>>> > > >> >>>>>> if we keep the tabs, we cannot make use of the
> >> different
> >> > >>>> > > indention
> >> > >>>> > > >> >> for
> >> > >>>> > > >> >>>>>> case statements or wrapped lines...maybe that's a
> >> > compromise
> >> > >>>> we
> >> > >>>> > > can
> >> > >>>> > > >> >>>>>> live with.
> >> > >>>> > > >> >>>>>>
> >> > >>>> > > >> >>>>>> If we introduce the Google Style for Java, will we
> >> also
> >> > >>>> impose
> >> > >>>> > a
> >> > >>>> > > >> >>>>>> stricter style check for Scala? IMHO the line
> length
> >> is
> >> > the
> >> > >>>> > > >> strictest
> >> > >>>> > > >> >>>>>> part of the Scala Checkstyle.
> >> > >>>> > > >> >>>>>>
> >> > >>>> > > >> >>>>>>
> >> > >>>> > > >> >>>>>> On Tue, Oct 20, 2015 at 4:14 PM, Henry Saputra <
> >> > >>>> > > >> >>> [hidden email]>
> >> > >>>> > > >> >>>>>> wrote:
> >> > >>>> > > >> >>>>>>> 1) yes. Been dancing this issue for a while. Let's
> >> > pull the
> >> > >>>> > > >> trigger.
> >> > >>>> > > >> >>>>> Did
> >> > >>>> > > >> >>>>>>> the exercise with Tachyon while back and did help
> >> > >>>> readability
> >> > >>>> > > and
> >> > >>>> > > >> >>>>>>> homogeneity of code.
> >> > >>>> > > >> >>>>>>>
> >> > >>>> > > >> >>>>>>> 2) +1 for Google Java style with documented
> >> exceptions
> >> > and
> >> > >>>> > > >> >> explanation
> >> > >>>> > > >> >>>>> on
> >> > >>>> > > >> >>>>>>> why.
> >> > >>>> > > >> >>>>>>>
> >> > >>>> > > >> >>>>>>> On Tuesday, October 20, 2015, Ufuk Celebi <
> >> > [hidden email]>
> >> > >>>> > > wrote:
> >> > >>>> > > >> >>>>>>>
> >> > >>>> > > >> >>>>>>>> DISCLAIMER: This is not my personal idea, but a
> >> > community
> >> > >>>> > > >> >> discussion
> >> > >>>> > > >> >>>>>> from
> >> > >>>> > > >> >>>>>>>> some time ago. Don't kill the messenger.
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> In March we were discussing issues with
> >> heterogeneity
> >> > of
> >> > >>>> the
> >> > >>>> > > code
> >> > >>>> > > >> >>> [1].
> >> > >>>> > > >> >>>>>> The
> >> > >>>> > > >> >>>>>>>> summary is that we had a consensus to enforce a
> >> > stricter
> >> > >>>> code
> >> > >>>> > > >> style
> >> > >>>> > > >> >>> on
> >> > >>>> > > >> >>>>>> our
> >> > >>>> > > >> >>>>>>>> Java code base in order to make it easier to
> switch
> >> > between
> >> > >>>> > > >> >> projects
> >> > >>>> > > >> >>>>>> and to
> >> > >>>> > > >> >>>>>>>> have clear rules for new contributions. The main
> >> > proposal
> >> > >>>> in
> >> > >>>> > > the
> >> > >>>> > > >> >> last
> >> > >>>> > > >> >>>>>>>> discussion was to go with Google's Java code
> style.
> >> > Not all
> >> > >>>> > > were
> >> > >>>> > > >> >>> fully
> >> > >>>> > > >> >>>>>>>> satisfied with this, but still everyone agreed on
> >> > some kind
> >> > >>>> > of
> >> > >>>> > > >> >> style.
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> I think the upcoming 0.10 release is a good
> point to
> >> > >>>> finally
> >> > >>>> > go
> >> > >>>> > > >> >>>>> through
> >> > >>>> > > >> >>>>>>>> with these changes (right after the
> >> > release/branch-off).
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> I propose to go with Google's Java code style
> [2] as
> >> > >>>> proposed
> >> > >>>> > > >> >>> earlier.
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> PROs:
> >> > >>>> > > >> >>>>>>>> - Clear style guide available
> >> > >>>> > > >> >>>>>>>> - Tooling like checkstyle rules, IDE plugins
> already
> >> > >>>> > available
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> CONs:
> >> > >>>> > > >> >>>>>>>> - Fully breaks our current style
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> The main problem with this will be open pull
> >> requests,
> >> > >>>> which
> >> > >>>> > > will
> >> > >>>> > > >> >> be
> >> > >>>> > > >> >>>>>> harder
> >> > >>>> > > >> >>>>>>>> to merge after all the changes. On the other
> hand,
> >> > should
> >> > >>>> > pull
> >> > >>>> > > >> >>>>> requests
> >> > >>>> > > >> >>>>>>>> that have been open for a long time block this?
> Most
> >> > of the
> >> > >>>> > > >> >> important
> >> > >>>> > > >> >>>>>>>> changes will be merged for the release anyways. I
> >> > think in
> >> > >>>> > the
> >> > >>>> > > >> long
> >> > >>>> > > >> >>>>> run
> >> > >>>> > > >> >>>>>> we
> >> > >>>> > > >> >>>>>>>> will gain more than we loose by this (more
> >> homogenous
> >> > code,
> >> > >>>> > > clear
> >> > >>>> > > >> >>>>>> rules).
> >> > >>>> > > >> >>>>>>>> And it is questionable whether we will ever be
> able
> >> > to do
> >> > >>>> > such
> >> > >>>> > > a
> >> > >>>> > > >> >>>>> change
> >> > >>>> > > >> >>>>>> in
> >> > >>>> > > >> >>>>>>>> the future if we cannot do it now. The project
> will
> >> > most
> >> > >>>> > likely
> >> > >>>> > > >> >> grow
> >> > >>>> > > >> >>>>> and
> >> > >>>> > > >> >>>>>>>> attract more contributors, at which point it
> will be
> >> > even
> >> > >>>> > > harder
> >> > >>>> > > >> to
> >> > >>>> > > >> >>>>> do.
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> Please make sure to answer the following points
> in
> >> the
> >> > >>>> > > discussion:
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> 1) Are you (still) in favour of enforcing
> stricter
> >> > rules on
> >> > >>>> > the
> >> > >>>> > > >> >> Java
> >> > >>>> > > >> >>>>>>>> codebase?
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> 2) If yes, would you be OK with the Google's Java
> >> code
> >> > >>>> style?
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> – Ufuk
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> [1]
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>
> >> > >>>> > > >> >>>>>
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>
> >> > >>>> > > >>
> >> > >>>> > >
> >> > >>>> >
> >> > >>>>
> >> >
> >>
> http://mail-archives.apache.org/mod_mbox/flink-dev/201503.mbox/%3cCANC1h_voN0B5omNWZxcHTyzwHAKeGhbZVQUyK7S9o2A36b891Q@...%3e
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>>> [2]
> >> > https://google.github.io/styleguide/javaguide.html
> >> > >>>> > > >> >>>>>>>>
> >> > >>>> > > >> >>>>>>
> >> > >>>> > > >> >>>>>
> >> > >>>> > > >> >>>>
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>>
> >> > >>>> > > >> >>
> >> > >>>> > > >> >
> >> > >>>> > > >>
> >> > >>>> > > >>
> >> > >>>> > >
> >> > >>>> >
> >> > >>>>
> >> >
> >>
>

[Matthias J. Sax-2]

Thanks for the summary Fabian.

Maybe we should have kind of a vote about this. No classical Apache vote
though, but voting for different options (so only +1), and the option
with the highest score wins? (Not sure if this is possible to do...)

About spaced vs. tabs:
> "AFAIR, nobody said to have a personal preferences of tabs over spaces."

I think this is wrong. If I am correct, Till and myself would prefer
spaces (but non of us is super strict about this -- we could both live
with tabs too).

-Matthias

On 11/02/2015 12:14 PM, Fabian Hueske wrote:

> OK, I'll try to summarize the discussion so far (please correct me if I got
> something wrong):
>
> Everybody is in favor of adding a stricter code style based on the Google
> Java code style.
> Main points of discussion are:
> 1) Line length
> 2) JavaDocs
> 3) Tabs vs. Spaces
>
> -- Line length
> Issue:
> Google code style demands 80 or 100 chars line length limit.
> Some people find this too narrow.
>
> Discussion so far:
> Nobody objected against a limit of 120 chars, AFAIR.
>
> -- JavaDocs
> Issue:
> Google code style says "At the *minimum*, Javadoc is present for every
> public class, and every public or protected member of such a class, with a
> few exceptions noted below." Exceptions are self-explanatory methods like
> getters and setters and overwritten method.
> Significant parts of the Flink code base do not comply with this
> requirement. It would be a huge effort to add the corresponding code
> documentation.
>
> Discussion so far:
> Disable JavaDoc checks when adding the code style and opening JIRAs for
> adding JavaDocs on a per Maven module level (with potentially subissues)
> with target dates. Once a module complies to the rule, the JavaDoc check is
> enabled in the checkstyle.
>
> -- Tabs vs. Spaces
> Issue:
> The Google code style requires two spaces for indention. The Java code base
> of Flink uses tabs. Moving from tabs to spaces would touch every line of
> Java code and therefore might make the tracking of changes in the past much
> harder.
> Max provided some numbers for applying the Google code style on the current
> code base: The style checker found 28k violations (possibly multiple ones
> per LOC) on 121k LOC of Java code in 1601 out of 3251 Java classes. So
> Google code style without spaces would touch every second file and about
> every 4th line of code. The question I have, would it be easier to track
> history with a commit that touches 1/2 (or 1/4) of the code base compared
> to one that touches everything.
>
> Discussion so far:
> AFAIR, nobody said to have a personal preferences of tabs over spaces.
> However, some people raised concerns that the implied changes of moving the
> code base from tabs to spaces would be too massive and the "benefits" would
> not justify the "cost" of the change.
> I think, this is the main point of discussion, right now.
>
> If we want to come to a conclusion, we should not let this discussion fall
> asleep (as happened a few times in the past).
>
> Does anybody NOT agree with the "solutions" for line length and JavaDocs,
> i.e., 120 chars and "lazy" adding of JavaDocs with JIRA tracking, or has
> another proposal?
> How can we resolve the Tabs vs. Spaces discussion?
>
> Cheers, Fabian
>
>
>
> 2015-10-30 18:16 GMT+01:00 Maximilian Michels <[hidden email]>:
>
>> I looked up if the Checkstyle plugin would also support tabs with a
>> fixed line length. Indeed, this is possible because a tab can be
>> mapped to a fixed number of spaces.
>>
>> I've modified the default Google Style Checkstyle file. I changed the
>> indention to tabs (2 spaces) and increased the line length to 120:
>> https://gist.github.com/mxm/2ca4ef7702667c167d10
>>
>> The scan of the entire Flink project resulted in 27,992 items in 1601
>> files. This is roughly corresponds to the number of lines we would
>> have to touch to comply with the style rules. Note that, one line may
>> contain multiple items. A lot of the items are import statements.
>>
>> Next, I tried running the vanilla Google Style Checkstyle file over
>> the entire code base but my IntelliJ crashed. Using Maven, I wasn't
>> able to get a total result displayed but I'm assuming it would be
>> almost all lines of Flink code that had a violation due to tabs.
>>
>> On Mon, Oct 26, 2015 at 6:56 PM, Suneel Marthi <[hidden email]>
>> wrote:
>>> 2 spaces is the convention that's followed on Mahout and Oryx.
>>>
>>> On Mon, Oct 26, 2015 at 1:42 PM, Till Rohrmann <[hidden email]>
>> wrote:
>>>
>>>> Concerning question 2 Tabs vs. Spaces, in case of spaces we would have
>> to
>>>> decide on the number of spaces, too. The Google Java style says to use
>> a 2
>>>> space indentation, which is in my opinion sufficient to distinguish
>>>> different indentations levels from each other. Furthermore, it would
>> save
>>>> some space.
>>>>
>>>> I would not vote -1 if we keep tabs.
>>>>
>>>>
>>>>
>>>> On Sat, Oct 24, 2015 at 8:33 PM, Henry Saputra <[hidden email]
>>>
>>>> wrote:
>>>>
>>>>> +1 for adding restriction for Javadoc at least at the header of public
>>>>> classes and methods.
>>>>>
>>>>> We did the exercise in Twill and seemed to work pretty well.
>>>>>
>>>>> On Fri, Oct 23, 2015 at 1:34 AM, Maximilian Michels <[hidden email]>
>>>>> wrote:
>>>>>> I don't think lazily adding comments will work. However, I'm fine
>> with
>>>>>> adding all the checkstyle rules one module at a time (with a jira
>>>>>> issue to keep track of the modules already converted). It's not
>> going
>>>>>> to happen that we lazily add comments because that's the reason why
>>>>>> comments are missing in the first place...
>>>>>>
>>>>>> On Fri, Oct 23, 2015 at 12:05 AM, Henry Saputra <
>>>> [hidden email]>
>>>>> wrote:
>>>>>>> Could we make certain rules to give warning instead of error?
>>>>>>>
>>>>>>> This would allow us to cherry-pick certain rules we would like
>> people
>>>>>>> to follow but not strictly enforced.
>>>>>>>
>>>>>>> - Henry
>>>>>>>
>>>>>>> On Thu, Oct 22, 2015 at 9:20 AM, Stephan Ewen <[hidden email]>
>>>> wrote:
>>>>>>>> I don't think a "let add comments to everything" effort gives us
>> good
>>>>>>>> comments, actually. It just gives us checkmark comments that make
>> the
>>>>> rules
>>>>>>>> pass.
>>>>>>>>
>>>>>>>> On Thu, Oct 22, 2015 at 3:29 PM, Fabian Hueske <[hidden email]
>>>
>>>>> wrote:
>>>>>>>>
>>>>>>>>> Sure, I don't expect it to be free.
>>>>>>>>> But everybody should be aware of the cost of adding this code
>> style,
>>>>> i.e.,
>>>>>>>>> spending a huge amount of time on reformatting and documenting
>> code.
>>>>>>>>>
>>>>>>>>> Alternatively, we could drop the JavaDocs rule and make the
>>>> transition
>>>>>>>>> significantly cheaper.
>>>>>>>>>
>>>>>>>>> 2015-10-22 15:24 GMT+02:00 Till Rohrmann <[hidden email]>:
>>>>>>>>>
>>>>>>>>>> There ain’t no such thing as a free lunch and code style.
>>>>>>>>>>
>>>>>>>>>> On Thu, Oct 22, 2015 at 3:13 PM, Maximilian Michels <
>>>> [hidden email]
>>>>>>
>>>>>>>>>> wrote:
>>>>>>>>>>
>>>>>>>>>>> I think we have to document all these classes. Code Style
>>>> doesn't
>>>>> come
>>>>>>>>>>> for free :)
>>>>>>>>>>>
>>>>>>>>>>> On Thu, Oct 22, 2015 at 3:09 PM, Fabian Hueske <
>>>> [hidden email]
>>>>>>
>>>>>>>>>> wrote:
>>>>>>>>>>>> Any ideas how to deal with the mandatory JavaDoc rule for
>>>>> existing
>>>>>>>>>> code?
>>>>>>>>>>>> Just adding empty headers to make the checkstyle pass or
>>>> start a
>>>>>>>>>> serious
>>>>>>>>>>>> effort to add the missing docs?
>>>>>>>>>>>>
>>>>>>>>>>>> 2015-10-21 13:31 GMT+02:00 Matthias J. Sax <
>> [hidden email]
>>>>> :
>>>>>>>>>>>>
>>>>>>>>>>>>> Agreed. That's the reason why I am in favor of using
>> vanilla
>>>>> Google
>>>>>>>>>> code
>>>>>>>>>>>>> style.
>>>>>>>>>>>>>
>>>>>>>>>>>>> On 10/21/2015 12:31 PM, Stephan Ewen wrote:
>>>>>>>>>>>>>> We started out originally with mixed tab/spaces, but it
>>>>> ended up
>>>>>>>>>> with
>>>>>>>>>>>>>> people mixing spaces and tabs arbitrarily, and there is
>>>>> little way
>>>>>>>>>> to
>>>>>>>>>>>>>> enforce Matthias' specific suggestion via checkstyle.
>>>>>>>>>>>>>> That's why we dropped spaces alltogether...
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 12:03 PM, Gyula Fóra <
>>>>>>>>> [hidden email]>
>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> I think the nice thing about a common codestyle is that
>>>>> everyone
>>>>>>>>>> can
>>>>>>>>>>> set
>>>>>>>>>>>>>>> the template in the IDE and use the formatting
>> commands.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Matthias's suggestion makes this practically
>> impossible so
>>>>> -1 for
>>>>>>>>>>> mixed
>>>>>>>>>>>>>>> tabs/spaces from my side.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Matthias J. Sax <[hidden email]> ezt írta (időpont:
>>>>> 2015. okt.
>>>>>>>>>>> 21.,
>>>>>>>>>>>>> Sze,
>>>>>>>>>>>>>>> 11:46):
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> I actually like tabs a lot, however, in a "mixed"
>> style
>>>>> together
>>>>>>>>>>> with
>>>>>>>>>>>>>>>> spaces. Example:
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>         myVar.callMethod(param1, // many more
>>>>>>>>>>>>>>>>         .................paramX); // the dots mark
>> space
>>>>>>>>> indention
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> indenting "paramX" with tabs does not give nice
>> aliment.
>>>>> Not
>>>>>>>>> sure
>>>>>>>>>> if
>>>>>>>>>>>>>>>> this would be a feasible compromise to keeps tabs in
>>>>> general,
>>>>>>>>> but
>>>>>>>>>>> use
>>>>>>>>>>>>>>>> space for cases as above.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> If this in no feasible compromise, I would prefer
>> space
>>>> to
>>>>> get
>>>>>>>>> the
>>>>>>>>>>>>>>>> correct indention in examples as above. Even if this
>>>>> result in a
>>>>>>>>>>>>>>>> complete reformatting of the whole code.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Why this? Everybody can set this in it's IDE/editor as
>>>>> he/she
>>>>>>>>>>> wishes...
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
>>>> length
>>>>>>>>>> relative
>>>>>>>>>>> to
>>>>>>>>>>>>> a
>>>>>>>>>>>>>>>> tab
>>>>>>>>>>>>>>>>>> size (like 4).
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> -Matthias
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> On 10/21/2015 11:06 AM, Ufuk Celebi wrote:
>>>>>>>>>>>>>>>>> To summarize up to this point:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> - All are in favour of Google check style (with the
>>>>> following
>>>>>>>>>>> possible
>>>>>>>>>>>>>>>>> exceptions)
>>>>>>>>>>>>>>>>> - Proposed exceptions so far:
>>>>>>>>>>>>>>>>>   * Specific line length 100 vs. 120 characters
>>>>>>>>>>>>>>>>>   * Keep tabs instead converting to spaces (this
>> would
>>>>>>>>> translate
>>>>>>>>>> to
>>>>>>>>>>>>>>>>> skipping/coming up with some indentation rules as
>> well)
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
>> length
>>>>>>>>> relative
>>>>>>>>>>> to a
>>>>>>>>>>>>>>>> tab
>>>>>>>>>>>>>>>>> size (like 4).
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Let’s keep the discussion going a little longer. I
>> think
>>>>> it has
>>>>>>>>>>>>>>> proceeded
>>>>>>>>>>>>>>>>> in a very reasonable manner so far. Thanks for this!
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> – Ufuk
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 10:29 AM, Fabian Hueske <
>>>>>>>>>> [hidden email]
>>>>>>>>>>>>
>>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Thanks Max for checking the modifications by the
>> Google
>>>>> code
>>>>>>>>>>> style.
>>>>>>>>>>>>>>>>>> It is very good to know, that the impact on the code
>>>> base
>>>>>>>>> would
>>>>>>>>>>> not
>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>> too
>>>>>>>>>>>>>>>>>> massive. If the Google code style would have touched
>>>>> almost
>>>>>>>>>> every
>>>>>>>>>>>>>>> line,
>>>>>>>>>>>>>>>> I
>>>>>>>>>>>>>>>>>> would have been in favor of converting to spaces.
>>>>> However,
>>>>>>>>> your
>>>>>>>>>>>>>>>> assessment
>>>>>>>>>>>>>>>>>> is a strong argument to continue with tabs, IMO.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Regarding the line length limit, I personally find
>> 100
>>>>> chars
>>>>>>>>> too
>>>>>>>>>>>>>>> narrow
>>>>>>>>>>>>>>>> but
>>>>>>>>>>>>>>>>>> would be +1 for having a limit.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> +1 for discussing the Scala style in a separate
>> thread.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Fabian
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> 2015-10-20 18:12 GMT+02:00 Maximilian Michels <
>>>>> [hidden email]
>>>>>>>>>> :
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> I'm a little less excited about this. You might
>> not be
>>>>> aware
>>>>>>>>>> but,
>>>>>>>>>>>>> for
>>>>>>>>>>>>>>>>>>> a large portion of the source code, we already
>> follow
>>>>> the
>>>>>>>>>> Google
>>>>>>>>>>>>>>> style
>>>>>>>>>>>>>>>>>>> guide. The main changes will be tabs->spaces and
>>>> 80/100
>>>>>>>>>>> characters
>>>>>>>>>>>>>>>>>>> line limit.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Out of curiosity, I ran the official Google Style
>>>>> Checkstyle
>>>>>>>>>>>>>>>>>>> configuration to confirm my suspicion:
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>
>>>>
>> https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml
>>>>>>>>>>>>>>>>>>> The changes are very little if we turn off line
>> length
>>>>> limit
>>>>>>>>>> and
>>>>>>>>>>>>>>>>>>> tabs-to-spaces conversion.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> There are some things I really like about the
>> Google
>>>>> style,
>>>>>>>>>> e.g.
>>>>>>>>>>>>>>> every
>>>>>>>>>>>>>>>>>>> class has to have a JavaDoc and spaces after
>> keywords
>>>>> (can't
>>>>>>>>>>> stand
>>>>>>>>>>>>> if
>>>>>>>>>>>>>>>>>>> there aren't any). I'm not sure if we should change
>>>>> tabs to
>>>>>>>>>>> spaces,
>>>>>>>>>>>>>>>>>>> because it means touching almost every single line
>> of
>>>>> code.
>>>>>>>>>>> However,
>>>>>>>>>>>>>>>>>>> if we keep the tabs, we cannot make use of the
>>>> different
>>>>>>>>>>> indention
>>>>>>>>>>>>>>> for
>>>>>>>>>>>>>>>>>>> case statements or wrapped lines...maybe that's a
>>>>> compromise
>>>>>>>>> we
>>>>>>>>>>> can
>>>>>>>>>>>>>>>>>>> live with.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> If we introduce the Google Style for Java, will we
>>>> also
>>>>>>>>> impose
>>>>>>>>>> a
>>>>>>>>>>>>>>>>>>> stricter style check for Scala? IMHO the line
>> length
>>>> is
>>>>> the
>>>>>>>>>>>>> strictest
>>>>>>>>>>>>>>>>>>> part of the Scala Checkstyle.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> On Tue, Oct 20, 2015 at 4:14 PM, Henry Saputra <
>>>>>>>>>>>>>>>> [hidden email]>
>>>>>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>>> 1) yes. Been dancing this issue for a while. Let's
>>>>> pull the
>>>>>>>>>>>>> trigger.
>>>>>>>>>>>>>>>>>> Did
>>>>>>>>>>>>>>>>>>>> the exercise with Tachyon while back and did help
>>>>>>>>> readability
>>>>>>>>>>> and
>>>>>>>>>>>>>>>>>>>> homogeneity of code.
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> 2) +1 for Google Java style with documented
>>>> exceptions
>>>>> and
>>>>>>>>>>>>>>> explanation
>>>>>>>>>>>>>>>>>> on
>>>>>>>>>>>>>>>>>>>> why.
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> On Tuesday, October 20, 2015, Ufuk Celebi <
>>>>> [hidden email]>
>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> DISCLAIMER: This is not my personal idea, but a
>>>>> community
>>>>>>>>>>>>>>> discussion
>>>>>>>>>>>>>>>>>>> from
>>>>>>>>>>>>>>>>>>>>> some time ago. Don't kill the messenger.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> In March we were discussing issues with
>>>> heterogeneity
>>>>> of
>>>>>>>>> the
>>>>>>>>>>> code
>>>>>>>>>>>>>>>> [1].
>>>>>>>>>>>>>>>>>>> The
>>>>>>>>>>>>>>>>>>>>> summary is that we had a consensus to enforce a
>>>>> stricter
>>>>>>>>> code
>>>>>>>>>>>>> style
>>>>>>>>>>>>>>>> on
>>>>>>>>>>>>>>>>>>> our
>>>>>>>>>>>>>>>>>>>>> Java code base in order to make it easier to
>> switch
>>>>> between
>>>>>>>>>>>>>>> projects
>>>>>>>>>>>>>>>>>>> and to
>>>>>>>>>>>>>>>>>>>>> have clear rules for new contributions. The main
>>>>> proposal
>>>>>>>>> in
>>>>>>>>>>> the
>>>>>>>>>>>>>>> last
>>>>>>>>>>>>>>>>>>>>> discussion was to go with Google's Java code
>> style.
>>>>> Not all
>>>>>>>>>>> were
>>>>>>>>>>>>>>>> fully
>>>>>>>>>>>>>>>>>>>>> satisfied with this, but still everyone agreed on
>>>>> some kind
>>>>>>>>>> of
>>>>>>>>>>>>>>> style.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> I think the upcoming 0.10 release is a good
>> point to
>>>>>>>>> finally
>>>>>>>>>> go
>>>>>>>>>>>>>>>>>> through
>>>>>>>>>>>>>>>>>>>>> with these changes (right after the
>>>>> release/branch-off).
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> I propose to go with Google's Java code style
>> [2] as
>>>>>>>>> proposed
>>>>>>>>>>>>>>>> earlier.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> PROs:
>>>>>>>>>>>>>>>>>>>>> - Clear style guide available
>>>>>>>>>>>>>>>>>>>>> - Tooling like checkstyle rules, IDE plugins
>> already
>>>>>>>>>> available
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> CONs:
>>>>>>>>>>>>>>>>>>>>> - Fully breaks our current style
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> The main problem with this will be open pull
>>>> requests,
>>>>>>>>> which
>>>>>>>>>>> will
>>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>>> harder
>>>>>>>>>>>>>>>>>>>>> to merge after all the changes. On the other
>> hand,
>>>>> should
>>>>>>>>>> pull
>>>>>>>>>>>>>>>>>> requests
>>>>>>>>>>>>>>>>>>>>> that have been open for a long time block this?
>> Most
>>>>> of the
>>>>>>>>>>>>>>> important
>>>>>>>>>>>>>>>>>>>>> changes will be merged for the release anyways. I
>>>>> think in
>>>>>>>>>> the
>>>>>>>>>>>>> long
>>>>>>>>>>>>>>>>>> run
>>>>>>>>>>>>>>>>>>> we
>>>>>>>>>>>>>>>>>>>>> will gain more than we loose by this (more
>>>> homogenous
>>>>> code,
>>>>>>>>>>> clear
>>>>>>>>>>>>>>>>>>> rules).
>>>>>>>>>>>>>>>>>>>>> And it is questionable whether we will ever be
>> able
>>>>> to do
>>>>>>>>>> such
>>>>>>>>>>> a
>>>>>>>>>>>>>>>>>> change
>>>>>>>>>>>>>>>>>>> in
>>>>>>>>>>>>>>>>>>>>> the future if we cannot do it now. The project
>> will
>>>>> most
>>>>>>>>>> likely
>>>>>>>>>>>>>>> grow
>>>>>>>>>>>>>>>>>> and
>>>>>>>>>>>>>>>>>>>>> attract more contributors, at which point it
>> will be
>>>>> even
>>>>>>>>>>> harder
>>>>>>>>>>>>> to
>>>>>>>>>>>>>>>>>> do.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Please make sure to answer the following points
>> in
>>>> the
>>>>>>>>>>> discussion:
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> 1) Are you (still) in favour of enforcing
>> stricter
>>>>> rules on
>>>>>>>>>> the
>>>>>>>>>>>>>>> Java
>>>>>>>>>>>>>>>>>>>>> codebase?
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> 2) If yes, would you be OK with the Google's Java
>>>> code
>>>>>>>>> style?
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> – Ufuk
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> [1]
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>
>>>>
>> http://mail-archives.apache.org/mod_mbox/flink-dev/201503.mbox/%3cCANC1h_voN0B5omNWZxcHTyzwHAKeGhbZVQUyK7S9o2A36b891Q@...%3e
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> [2]
>>>>> https://google.github.io/styleguide/javaguide.html
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>
>>>>
>>
>

[Stephan Ewen]

I think by now virtually everyone prefers spaces if it came for free, so it
is a matter of making an educated decision about the cost/benefit tradeoffs.

What are the benefits of spaces in the style other than people liking the
looks of space-formatted code better (aesthetics, schmaesthetics ;-) )


On Mon, Nov 2, 2015 at 5:38 AM, Matthias J. Sax <[hidden email]> wrote:

> Thanks for the summary Fabian.
>
> Maybe we should have kind of a vote about this. No classical Apache vote
> though, but voting for different options (so only +1), and the option
> with the highest score wins? (Not sure if this is possible to do...)
>
> About spaced vs. tabs:
> > "AFAIR, nobody said to have a personal preferences of tabs over spaces."
>
> I think this is wrong. If I am correct, Till and myself would prefer
> spaces (but non of us is super strict about this -- we could both live
> with tabs too).
>
> -Matthias
>
> On 11/02/2015 12:14 PM, Fabian Hueske wrote:
> > OK, I'll try to summarize the discussion so far (please correct me if I
> got
> > something wrong):
> >
> > Everybody is in favor of adding a stricter code style based on the Google
> > Java code style.
> > Main points of discussion are:
> > 1) Line length
> > 2) JavaDocs
> > 3) Tabs vs. Spaces
> >
> > -- Line length
> > Issue:
> > Google code style demands 80 or 100 chars line length limit.
> > Some people find this too narrow.
> >
> > Discussion so far:
> > Nobody objected against a limit of 120 chars, AFAIR.
> >
> > -- JavaDocs
> > Issue:
> > Google code style says "At the *minimum*, Javadoc is present for every
> > public class, and every public or protected member of such a class, with
> a
> > few exceptions noted below." Exceptions are self-explanatory methods like
> > getters and setters and overwritten method.
> > Significant parts of the Flink code base do not comply with this
> > requirement. It would be a huge effort to add the corresponding code
> > documentation.
> >
> > Discussion so far:
> > Disable JavaDoc checks when adding the code style and opening JIRAs for
> > adding JavaDocs on a per Maven module level (with potentially subissues)
> > with target dates. Once a module complies to the rule, the JavaDoc check
> is
> > enabled in the checkstyle.
> >
> > -- Tabs vs. Spaces
> > Issue:
> > The Google code style requires two spaces for indention. The Java code
> base
> > of Flink uses tabs. Moving from tabs to spaces would touch every line of
> > Java code and therefore might make the tracking of changes in the past
> much
> > harder.
> > Max provided some numbers for applying the Google code style on the
> current
> > code base: The style checker found 28k violations (possibly multiple ones
> > per LOC) on 121k LOC of Java code in 1601 out of 3251 Java classes. So
> > Google code style without spaces would touch every second file and about
> > every 4th line of code. The question I have, would it be easier to track
> > history with a commit that touches 1/2 (or 1/4) of the code base compared
> > to one that touches everything.
> >
> > Discussion so far:
> > AFAIR, nobody said to have a personal preferences of tabs over spaces.
> > However, some people raised concerns that the implied changes of moving
> the
> > code base from tabs to spaces would be too massive and the "benefits"
> would
> > not justify the "cost" of the change.
> > I think, this is the main point of discussion, right now.
> >
> > If we want to come to a conclusion, we should not let this discussion
> fall
> > asleep (as happened a few times in the past).
> >
> > Does anybody NOT agree with the "solutions" for line length and JavaDocs,
> > i.e., 120 chars and "lazy" adding of JavaDocs with JIRA tracking, or has
> > another proposal?
> > How can we resolve the Tabs vs. Spaces discussion?
> >
> > Cheers, Fabian
> >
> >
> >
> > 2015-10-30 18:16 GMT+01:00 Maximilian Michels <[hidden email]>:
> >
> >> I looked up if the Checkstyle plugin would also support tabs with a
> >> fixed line length. Indeed, this is possible because a tab can be
> >> mapped to a fixed number of spaces.
> >>
> >> I've modified the default Google Style Checkstyle file. I changed the
> >> indention to tabs (2 spaces) and increased the line length to 120:
> >> https://gist.github.com/mxm/2ca4ef7702667c167d10
> >>
> >> The scan of the entire Flink project resulted in 27,992 items in 1601
> >> files. This is roughly corresponds to the number of lines we would
> >> have to touch to comply with the style rules. Note that, one line may
> >> contain multiple items. A lot of the items are import statements.
> >>
> >> Next, I tried running the vanilla Google Style Checkstyle file over
> >> the entire code base but my IntelliJ crashed. Using Maven, I wasn't
> >> able to get a total result displayed but I'm assuming it would be
> >> almost all lines of Flink code that had a violation due to tabs.
> >>
> >> On Mon, Oct 26, 2015 at 6:56 PM, Suneel Marthi <[hidden email]
> >
> >> wrote:
> >>> 2 spaces is the convention that's followed on Mahout and Oryx.
> >>>
> >>> On Mon, Oct 26, 2015 at 1:42 PM, Till Rohrmann <[hidden email]>
> >> wrote:
> >>>
> >>>> Concerning question 2 Tabs vs. Spaces, in case of spaces we would have
> >> to
> >>>> decide on the number of spaces, too. The Google Java style says to use
> >> a 2
> >>>> space indentation, which is in my opinion sufficient to distinguish
> >>>> different indentations levels from each other. Furthermore, it would
> >> save
> >>>> some space.
> >>>>
> >>>> I would not vote -1 if we keep tabs.
> >>>>
> >>>>
> >>>>
> >>>> On Sat, Oct 24, 2015 at 8:33 PM, Henry Saputra <
> [hidden email]
> >>>
> >>>> wrote:
> >>>>
> >>>>> +1 for adding restriction for Javadoc at least at the header of
> public
> >>>>> classes and methods.
> >>>>>
> >>>>> We did the exercise in Twill and seemed to work pretty well.
> >>>>>
> >>>>> On Fri, Oct 23, 2015 at 1:34 AM, Maximilian Michels <[hidden email]>
> >>>>> wrote:
> >>>>>> I don't think lazily adding comments will work. However, I'm fine
> >> with
> >>>>>> adding all the checkstyle rules one module at a time (with a jira
> >>>>>> issue to keep track of the modules already converted). It's not
> >> going
> >>>>>> to happen that we lazily add comments because that's the reason why
> >>>>>> comments are missing in the first place...
> >>>>>>
> >>>>>> On Fri, Oct 23, 2015 at 12:05 AM, Henry Saputra <
> >>>> [hidden email]>
> >>>>> wrote:
> >>>>>>> Could we make certain rules to give warning instead of error?
> >>>>>>>
> >>>>>>> This would allow us to cherry-pick certain rules we would like
> >> people
> >>>>>>> to follow but not strictly enforced.
> >>>>>>>
> >>>>>>> - Henry
> >>>>>>>
> >>>>>>> On Thu, Oct 22, 2015 at 9:20 AM, Stephan Ewen <[hidden email]>
> >>>> wrote:
> >>>>>>>> I don't think a "let add comments to everything" effort gives us
> >> good
> >>>>>>>> comments, actually. It just gives us checkmark comments that make
> >> the
> >>>>> rules
> >>>>>>>> pass.
> >>>>>>>>
> >>>>>>>> On Thu, Oct 22, 2015 at 3:29 PM, Fabian Hueske <[hidden email]
> >>>
> >>>>> wrote:
> >>>>>>>>
> >>>>>>>>> Sure, I don't expect it to be free.
> >>>>>>>>> But everybody should be aware of the cost of adding this code
> >> style,
> >>>>> i.e.,
> >>>>>>>>> spending a huge amount of time on reformatting and documenting
> >> code.
> >>>>>>>>>
> >>>>>>>>> Alternatively, we could drop the JavaDocs rule and make the
> >>>> transition
> >>>>>>>>> significantly cheaper.
> >>>>>>>>>
> >>>>>>>>> 2015-10-22 15:24 GMT+02:00 Till Rohrmann <[hidden email]>:
> >>>>>>>>>
> >>>>>>>>>> There ain’t no such thing as a free lunch and code style.
> >>>>>>>>>>
> >>>>>>>>>> On Thu, Oct 22, 2015 at 3:13 PM, Maximilian Michels <
> >>>> [hidden email]
> >>>>>>
> >>>>>>>>>> wrote:
> >>>>>>>>>>
> >>>>>>>>>>> I think we have to document all these classes. Code Style
> >>>> doesn't
> >>>>> come
> >>>>>>>>>>> for free :)
> >>>>>>>>>>>
> >>>>>>>>>>> On Thu, Oct 22, 2015 at 3:09 PM, Fabian Hueske <
> >>>> [hidden email]
> >>>>>>
> >>>>>>>>>> wrote:
> >>>>>>>>>>>> Any ideas how to deal with the mandatory JavaDoc rule for
> >>>>> existing
> >>>>>>>>>> code?
> >>>>>>>>>>>> Just adding empty headers to make the checkstyle pass or
> >>>> start a
> >>>>>>>>>> serious
> >>>>>>>>>>>> effort to add the missing docs?
> >>>>>>>>>>>>
> >>>>>>>>>>>> 2015-10-21 13:31 GMT+02:00 Matthias J. Sax <
> >> [hidden email]
> >>>>> :
> >>>>>>>>>>>>
> >>>>>>>>>>>>> Agreed. That's the reason why I am in favor of using
> >> vanilla
> >>>>> Google
> >>>>>>>>>> code
> >>>>>>>>>>>>> style.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> On 10/21/2015 12:31 PM, Stephan Ewen wrote:
> >>>>>>>>>>>>>> We started out originally with mixed tab/spaces, but it
> >>>>> ended up
> >>>>>>>>>> with
> >>>>>>>>>>>>>> people mixing spaces and tabs arbitrarily, and there is
> >>>>> little way
> >>>>>>>>>> to
> >>>>>>>>>>>>>> enforce Matthias' specific suggestion via checkstyle.
> >>>>>>>>>>>>>> That's why we dropped spaces alltogether...
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 12:03 PM, Gyula Fóra <
> >>>>>>>>> [hidden email]>
> >>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> I think the nice thing about a common codestyle is that
> >>>>> everyone
> >>>>>>>>>> can
> >>>>>>>>>>> set
> >>>>>>>>>>>>>>> the template in the IDE and use the formatting
> >> commands.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Matthias's suggestion makes this practically
> >> impossible so
> >>>>> -1 for
> >>>>>>>>>>> mixed
> >>>>>>>>>>>>>>> tabs/spaces from my side.
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> Matthias J. Sax <[hidden email]> ezt írta (időpont:
> >>>>> 2015. okt.
> >>>>>>>>>>> 21.,
> >>>>>>>>>>>>> Sze,
> >>>>>>>>>>>>>>> 11:46):
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> I actually like tabs a lot, however, in a "mixed"
> >> style
> >>>>> together
> >>>>>>>>>>> with
> >>>>>>>>>>>>>>>> spaces. Example:
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>         myVar.callMethod(param1, // many more
> >>>>>>>>>>>>>>>>         .................paramX); // the dots mark
> >> space
> >>>>>>>>> indention
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> indenting "paramX" with tabs does not give nice
> >> aliment.
> >>>>> Not
> >>>>>>>>> sure
> >>>>>>>>>> if
> >>>>>>>>>>>>>>>> this would be a feasible compromise to keeps tabs in
> >>>>> general,
> >>>>>>>>> but
> >>>>>>>>>>> use
> >>>>>>>>>>>>>>>> space for cases as above.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> If this in no feasible compromise, I would prefer
> >> space
> >>>> to
> >>>>> get
> >>>>>>>>> the
> >>>>>>>>>>>>>>>> correct indention in examples as above. Even if this
> >>>>> result in a
> >>>>>>>>>>>>>>>> complete reformatting of the whole code.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Why this? Everybody can set this in it's IDE/editor as
> >>>>> he/she
> >>>>>>>>>>> wishes...
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
> >>>> length
> >>>>>>>>>> relative
> >>>>>>>>>>> to
> >>>>>>>>>>>>> a
> >>>>>>>>>>>>>>>> tab
> >>>>>>>>>>>>>>>>>> size (like 4).
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> -Matthias
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> On 10/21/2015 11:06 AM, Ufuk Celebi wrote:
> >>>>>>>>>>>>>>>>> To summarize up to this point:
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> - All are in favour of Google check style (with the
> >>>>> following
> >>>>>>>>>>> possible
> >>>>>>>>>>>>>>>>> exceptions)
> >>>>>>>>>>>>>>>>> - Proposed exceptions so far:
> >>>>>>>>>>>>>>>>>   * Specific line length 100 vs. 120 characters
> >>>>>>>>>>>>>>>>>   * Keep tabs instead converting to spaces (this
> >> would
> >>>>>>>>> translate
> >>>>>>>>>> to
> >>>>>>>>>>>>>>>>> skipping/coming up with some indentation rules as
> >> well)
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
> >> length
> >>>>>>>>> relative
> >>>>>>>>>>> to a
> >>>>>>>>>>>>>>>> tab
> >>>>>>>>>>>>>>>>> size (like 4).
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> Let’s keep the discussion going a little longer. I
> >> think
> >>>>> it has
> >>>>>>>>>>>>>>> proceeded
> >>>>>>>>>>>>>>>>> in a very reasonable manner so far. Thanks for this!
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> – Ufuk
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 10:29 AM, Fabian Hueske <
> >>>>>>>>>> [hidden email]
> >>>>>>>>>>>>
> >>>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Thanks Max for checking the modifications by the
> >> Google
> >>>>> code
> >>>>>>>>>>> style.
> >>>>>>>>>>>>>>>>>> It is very good to know, that the impact on the code
> >>>> base
> >>>>>>>>> would
> >>>>>>>>>>> not
> >>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>> too
> >>>>>>>>>>>>>>>>>> massive. If the Google code style would have touched
> >>>>> almost
> >>>>>>>>>> every
> >>>>>>>>>>>>>>> line,
> >>>>>>>>>>>>>>>> I
> >>>>>>>>>>>>>>>>>> would have been in favor of converting to spaces.
> >>>>> However,
> >>>>>>>>> your
> >>>>>>>>>>>>>>>> assessment
> >>>>>>>>>>>>>>>>>> is a strong argument to continue with tabs, IMO.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Regarding the line length limit, I personally find
> >> 100
> >>>>> chars
> >>>>>>>>> too
> >>>>>>>>>>>>>>> narrow
> >>>>>>>>>>>>>>>> but
> >>>>>>>>>>>>>>>>>> would be +1 for having a limit.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> +1 for discussing the Scala style in a separate
> >> thread.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Fabian
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> 2015-10-20 18:12 GMT+02:00 Maximilian Michels <
> >>>>> [hidden email]
> >>>>>>>>>> :
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> I'm a little less excited about this. You might
> >> not be
> >>>>> aware
> >>>>>>>>>> but,
> >>>>>>>>>>>>> for
> >>>>>>>>>>>>>>>>>>> a large portion of the source code, we already
> >> follow
> >>>>> the
> >>>>>>>>>> Google
> >>>>>>>>>>>>>>> style
> >>>>>>>>>>>>>>>>>>> guide. The main changes will be tabs->spaces and
> >>>> 80/100
> >>>>>>>>>>> characters
> >>>>>>>>>>>>>>>>>>> line limit.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Out of curiosity, I ran the official Google Style
> >>>>> Checkstyle
> >>>>>>>>>>>>>>>>>>> configuration to confirm my suspicion:
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>
> >>>>
> >>
> https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml
> >>>>>>>>>>>>>>>>>>> The changes are very little if we turn off line
> >> length
> >>>>> limit
> >>>>>>>>>> and
> >>>>>>>>>>>>>>>>>>> tabs-to-spaces conversion.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> There are some things I really like about the
> >> Google
> >>>>> style,
> >>>>>>>>>> e.g.
> >>>>>>>>>>>>>>> every
> >>>>>>>>>>>>>>>>>>> class has to have a JavaDoc and spaces after
> >> keywords
> >>>>> (can't
> >>>>>>>>>>> stand
> >>>>>>>>>>>>> if
> >>>>>>>>>>>>>>>>>>> there aren't any). I'm not sure if we should change
> >>>>> tabs to
> >>>>>>>>>>> spaces,
> >>>>>>>>>>>>>>>>>>> because it means touching almost every single line
> >> of
> >>>>> code.
> >>>>>>>>>>> However,
> >>>>>>>>>>>>>>>>>>> if we keep the tabs, we cannot make use of the
> >>>> different
> >>>>>>>>>>> indention
> >>>>>>>>>>>>>>> for
> >>>>>>>>>>>>>>>>>>> case statements or wrapped lines...maybe that's a
> >>>>> compromise
> >>>>>>>>> we
> >>>>>>>>>>> can
> >>>>>>>>>>>>>>>>>>> live with.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> If we introduce the Google Style for Java, will we
> >>>> also
> >>>>>>>>> impose
> >>>>>>>>>> a
> >>>>>>>>>>>>>>>>>>> stricter style check for Scala? IMHO the line
> >> length
> >>>> is
> >>>>> the
> >>>>>>>>>>>>> strictest
> >>>>>>>>>>>>>>>>>>> part of the Scala Checkstyle.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> On Tue, Oct 20, 2015 at 4:14 PM, Henry Saputra <
> >>>>>>>>>>>>>>>> [hidden email]>
> >>>>>>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>>> 1) yes. Been dancing this issue for a while. Let's
> >>>>> pull the
> >>>>>>>>>>>>> trigger.
> >>>>>>>>>>>>>>>>>> Did
> >>>>>>>>>>>>>>>>>>>> the exercise with Tachyon while back and did help
> >>>>>>>>> readability
> >>>>>>>>>>> and
> >>>>>>>>>>>>>>>>>>>> homogeneity of code.
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> 2) +1 for Google Java style with documented
> >>>> exceptions
> >>>>> and
> >>>>>>>>>>>>>>> explanation
> >>>>>>>>>>>>>>>>>> on
> >>>>>>>>>>>>>>>>>>>> why.
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> On Tuesday, October 20, 2015, Ufuk Celebi <
> >>>>> [hidden email]>
> >>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> DISCLAIMER: This is not my personal idea, but a
> >>>>> community
> >>>>>>>>>>>>>>> discussion
> >>>>>>>>>>>>>>>>>>> from
> >>>>>>>>>>>>>>>>>>>>> some time ago. Don't kill the messenger.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> In March we were discussing issues with
> >>>> heterogeneity
> >>>>> of
> >>>>>>>>> the
> >>>>>>>>>>> code
> >>>>>>>>>>>>>>>> [1].
> >>>>>>>>>>>>>>>>>>> The
> >>>>>>>>>>>>>>>>>>>>> summary is that we had a consensus to enforce a
> >>>>> stricter
> >>>>>>>>> code
> >>>>>>>>>>>>> style
> >>>>>>>>>>>>>>>> on
> >>>>>>>>>>>>>>>>>>> our
> >>>>>>>>>>>>>>>>>>>>> Java code base in order to make it easier to
> >> switch
> >>>>> between
> >>>>>>>>>>>>>>> projects
> >>>>>>>>>>>>>>>>>>> and to
> >>>>>>>>>>>>>>>>>>>>> have clear rules for new contributions. The main
> >>>>> proposal
> >>>>>>>>> in
> >>>>>>>>>>> the
> >>>>>>>>>>>>>>> last
> >>>>>>>>>>>>>>>>>>>>> discussion was to go with Google's Java code
> >> style.
> >>>>> Not all
> >>>>>>>>>>> were
> >>>>>>>>>>>>>>>> fully
> >>>>>>>>>>>>>>>>>>>>> satisfied with this, but still everyone agreed on
> >>>>> some kind
> >>>>>>>>>> of
> >>>>>>>>>>>>>>> style.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> I think the upcoming 0.10 release is a good
> >> point to
> >>>>>>>>> finally
> >>>>>>>>>> go
> >>>>>>>>>>>>>>>>>> through
> >>>>>>>>>>>>>>>>>>>>> with these changes (right after the
> >>>>> release/branch-off).
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> I propose to go with Google's Java code style
> >> [2] as
> >>>>>>>>> proposed
> >>>>>>>>>>>>>>>> earlier.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> PROs:
> >>>>>>>>>>>>>>>>>>>>> - Clear style guide available
> >>>>>>>>>>>>>>>>>>>>> - Tooling like checkstyle rules, IDE plugins
> >> already
> >>>>>>>>>> available
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> CONs:
> >>>>>>>>>>>>>>>>>>>>> - Fully breaks our current style
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> The main problem with this will be open pull
> >>>> requests,
> >>>>>>>>> which
> >>>>>>>>>>> will
> >>>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>>> harder
> >>>>>>>>>>>>>>>>>>>>> to merge after all the changes. On the other
> >> hand,
> >>>>> should
> >>>>>>>>>> pull
> >>>>>>>>>>>>>>>>>> requests
> >>>>>>>>>>>>>>>>>>>>> that have been open for a long time block this?
> >> Most
> >>>>> of the
> >>>>>>>>>>>>>>> important
> >>>>>>>>>>>>>>>>>>>>> changes will be merged for the release anyways. I
> >>>>> think in
> >>>>>>>>>> the
> >>>>>>>>>>>>> long
> >>>>>>>>>>>>>>>>>> run
> >>>>>>>>>>>>>>>>>>> we
> >>>>>>>>>>>>>>>>>>>>> will gain more than we loose by this (more
> >>>> homogenous
> >>>>> code,
> >>>>>>>>>>> clear
> >>>>>>>>>>>>>>>>>>> rules).
> >>>>>>>>>>>>>>>>>>>>> And it is questionable whether we will ever be
> >> able
> >>>>> to do
> >>>>>>>>>> such
> >>>>>>>>>>> a
> >>>>>>>>>>>>>>>>>> change
> >>>>>>>>>>>>>>>>>>> in
> >>>>>>>>>>>>>>>>>>>>> the future if we cannot do it now. The project
> >> will
> >>>>> most
> >>>>>>>>>> likely
> >>>>>>>>>>>>>>> grow
> >>>>>>>>>>>>>>>>>> and
> >>>>>>>>>>>>>>>>>>>>> attract more contributors, at which point it
> >> will be
> >>>>> even
> >>>>>>>>>>> harder
> >>>>>>>>>>>>> to
> >>>>>>>>>>>>>>>>>> do.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Please make sure to answer the following points
> >> in
> >>>> the
> >>>>>>>>>>> discussion:
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> 1) Are you (still) in favour of enforcing
> >> stricter
> >>>>> rules on
> >>>>>>>>>> the
> >>>>>>>>>>>>>>> Java
> >>>>>>>>>>>>>>>>>>>>> codebase?
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> 2) If yes, would you be OK with the Google's Java
> >>>> code
> >>>>>>>>> style?
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> – Ufuk
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> [1]
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>
> >>>>
> >>
> http://mail-archives.apache.org/mod_mbox/flink-dev/201503.mbox/%3cCANC1h_voN0B5omNWZxcHTyzwHAKeGhbZVQUyK7S9o2A36b891Q@...%3e
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> [2]
> >>>>> https://google.github.io/styleguide/javaguide.html
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>
> >>>>>>>>>>
> >>>>>>>>>
> >>>>>
> >>>>
> >>
> >
>
>

[Fabian Hueske-2]

I don't see other benefits except maybe being closer to the vanilla Google
style.

2015-11-02 20:46 GMT+01:00 Stephan Ewen <[hidden email]>:

> I think by now virtually everyone prefers spaces if it came for free, so it
> is a matter of making an educated decision about the cost/benefit
> tradeoffs.
>
> What are the benefits of spaces in the style other than people liking the
> looks of space-formatted code better (aesthetics, schmaesthetics ;-) )
>
>
> On Mon, Nov 2, 2015 at 5:38 AM, Matthias J. Sax <[hidden email]> wrote:
>
> > Thanks for the summary Fabian.
> >
> > Maybe we should have kind of a vote about this. No classical Apache vote
> > though, but voting for different options (so only +1), and the option
> > with the highest score wins? (Not sure if this is possible to do...)
> >
> > About spaced vs. tabs:
> > > "AFAIR, nobody said to have a personal preferences of tabs over
> spaces."
> >
> > I think this is wrong. If I am correct, Till and myself would prefer
> > spaces (but non of us is super strict about this -- we could both live
> > with tabs too).
> >
> > -Matthias
> >
> > On 11/02/2015 12:14 PM, Fabian Hueske wrote:
> > > OK, I'll try to summarize the discussion so far (please correct me if I
> > got
> > > something wrong):
> > >
> > > Everybody is in favor of adding a stricter code style based on the
> Google
> > > Java code style.
> > > Main points of discussion are:
> > > 1) Line length
> > > 2) JavaDocs
> > > 3) Tabs vs. Spaces
> > >
> > > -- Line length
> > > Issue:
> > > Google code style demands 80 or 100 chars line length limit.
> > > Some people find this too narrow.
> > >
> > > Discussion so far:
> > > Nobody objected against a limit of 120 chars, AFAIR.
> > >
> > > -- JavaDocs
> > > Issue:
> > > Google code style says "At the *minimum*, Javadoc is present for every
> > > public class, and every public or protected member of such a class,
> with
> > a
> > > few exceptions noted below." Exceptions are self-explanatory methods
> like
> > > getters and setters and overwritten method.
> > > Significant parts of the Flink code base do not comply with this
> > > requirement. It would be a huge effort to add the corresponding code
> > > documentation.
> > >
> > > Discussion so far:
> > > Disable JavaDoc checks when adding the code style and opening JIRAs for
> > > adding JavaDocs on a per Maven module level (with potentially
> subissues)
> > > with target dates. Once a module complies to the rule, the JavaDoc
> check
> > is
> > > enabled in the checkstyle.
> > >
> > > -- Tabs vs. Spaces
> > > Issue:
> > > The Google code style requires two spaces for indention. The Java code
> > base
> > > of Flink uses tabs. Moving from tabs to spaces would touch every line
> of
> > > Java code and therefore might make the tracking of changes in the past
> > much
> > > harder.
> > > Max provided some numbers for applying the Google code style on the
> > current
> > > code base: The style checker found 28k violations (possibly multiple
> ones
> > > per LOC) on 121k LOC of Java code in 1601 out of 3251 Java classes. So
> > > Google code style without spaces would touch every second file and
> about
> > > every 4th line of code. The question I have, would it be easier to
> track
> > > history with a commit that touches 1/2 (or 1/4) of the code base
> compared
> > > to one that touches everything.
> > >
> > > Discussion so far:
> > > AFAIR, nobody said to have a personal preferences of tabs over spaces.
> > > However, some people raised concerns that the implied changes of moving
> > the
> > > code base from tabs to spaces would be too massive and the "benefits"
> > would
> > > not justify the "cost" of the change.
> > > I think, this is the main point of discussion, right now.
> > >
> > > If we want to come to a conclusion, we should not let this discussion
> > fall
> > > asleep (as happened a few times in the past).
> > >
> > > Does anybody NOT agree with the "solutions" for line length and
> JavaDocs,
> > > i.e., 120 chars and "lazy" adding of JavaDocs with JIRA tracking, or
> has
> > > another proposal?
> > > How can we resolve the Tabs vs. Spaces discussion?
> > >
> > > Cheers, Fabian
> > >
> > >
> > >
> > > 2015-10-30 18:16 GMT+01:00 Maximilian Michels <[hidden email]>:
> > >
> > >> I looked up if the Checkstyle plugin would also support tabs with a
> > >> fixed line length. Indeed, this is possible because a tab can be
> > >> mapped to a fixed number of spaces.
> > >>
> > >> I've modified the default Google Style Checkstyle file. I changed the
> > >> indention to tabs (2 spaces) and increased the line length to 120:
> > >> https://gist.github.com/mxm/2ca4ef7702667c167d10
> > >>
> > >> The scan of the entire Flink project resulted in 27,992 items in 1601
> > >> files. This is roughly corresponds to the number of lines we would
> > >> have to touch to comply with the style rules. Note that, one line may
> > >> contain multiple items. A lot of the items are import statements.
> > >>
> > >> Next, I tried running the vanilla Google Style Checkstyle file over
> > >> the entire code base but my IntelliJ crashed. Using Maven, I wasn't
> > >> able to get a total result displayed but I'm assuming it would be
> > >> almost all lines of Flink code that had a violation due to tabs.
> > >>
> > >> On Mon, Oct 26, 2015 at 6:56 PM, Suneel Marthi <
> [hidden email]
> > >
> > >> wrote:
> > >>> 2 spaces is the convention that's followed on Mahout and Oryx.
> > >>>
> > >>> On Mon, Oct 26, 2015 at 1:42 PM, Till Rohrmann <[hidden email]
> >
> > >> wrote:
> > >>>
> > >>>> Concerning question 2 Tabs vs. Spaces, in case of spaces we would
> have
> > >> to
> > >>>> decide on the number of spaces, too. The Google Java style says to
> use
> > >> a 2
> > >>>> space indentation, which is in my opinion sufficient to distinguish
> > >>>> different indentations levels from each other. Furthermore, it would
> > >> save
> > >>>> some space.
> > >>>>
> > >>>> I would not vote -1 if we keep tabs.
> > >>>>
> > >>>>
> > >>>>
> > >>>> On Sat, Oct 24, 2015 at 8:33 PM, Henry Saputra <
> > [hidden email]
> > >>>
> > >>>> wrote:
> > >>>>
> > >>>>> +1 for adding restriction for Javadoc at least at the header of
> > public
> > >>>>> classes and methods.
> > >>>>>
> > >>>>> We did the exercise in Twill and seemed to work pretty well.
> > >>>>>
> > >>>>> On Fri, Oct 23, 2015 at 1:34 AM, Maximilian Michels <
> [hidden email]>
> > >>>>> wrote:
> > >>>>>> I don't think lazily adding comments will work. However, I'm fine
> > >> with
> > >>>>>> adding all the checkstyle rules one module at a time (with a jira
> > >>>>>> issue to keep track of the modules already converted). It's not
> > >> going
> > >>>>>> to happen that we lazily add comments because that's the reason
> why
> > >>>>>> comments are missing in the first place...
> > >>>>>>
> > >>>>>> On Fri, Oct 23, 2015 at 12:05 AM, Henry Saputra <
> > >>>> [hidden email]>
> > >>>>> wrote:
> > >>>>>>> Could we make certain rules to give warning instead of error?
> > >>>>>>>
> > >>>>>>> This would allow us to cherry-pick certain rules we would like
> > >> people
> > >>>>>>> to follow but not strictly enforced.
> > >>>>>>>
> > >>>>>>> - Henry
> > >>>>>>>
> > >>>>>>> On Thu, Oct 22, 2015 at 9:20 AM, Stephan Ewen <[hidden email]>
> > >>>> wrote:
> > >>>>>>>> I don't think a "let add comments to everything" effort gives us
> > >> good
> > >>>>>>>> comments, actually. It just gives us checkmark comments that
> make
> > >> the
> > >>>>> rules
> > >>>>>>>> pass.
> > >>>>>>>>
> > >>>>>>>> On Thu, Oct 22, 2015 at 3:29 PM, Fabian Hueske <
> [hidden email]
> > >>>
> > >>>>> wrote:
> > >>>>>>>>
> > >>>>>>>>> Sure, I don't expect it to be free.
> > >>>>>>>>> But everybody should be aware of the cost of adding this code
> > >> style,
> > >>>>> i.e.,
> > >>>>>>>>> spending a huge amount of time on reformatting and documenting
> > >> code.
> > >>>>>>>>>
> > >>>>>>>>> Alternatively, we could drop the JavaDocs rule and make the
> > >>>> transition
> > >>>>>>>>> significantly cheaper.
> > >>>>>>>>>
> > >>>>>>>>> 2015-10-22 15:24 GMT+02:00 Till Rohrmann <[hidden email]
> >:
> > >>>>>>>>>
> > >>>>>>>>>> There ain’t no such thing as a free lunch and code style.
> > >>>>>>>>>>
> > >>>>>>>>>> On Thu, Oct 22, 2015 at 3:13 PM, Maximilian Michels <
> > >>>> [hidden email]
> > >>>>>>
> > >>>>>>>>>> wrote:
> > >>>>>>>>>>
> > >>>>>>>>>>> I think we have to document all these classes. Code Style
> > >>>> doesn't
> > >>>>> come
> > >>>>>>>>>>> for free :)
> > >>>>>>>>>>>
> > >>>>>>>>>>> On Thu, Oct 22, 2015 at 3:09 PM, Fabian Hueske <
> > >>>> [hidden email]
> > >>>>>>
> > >>>>>>>>>> wrote:
> > >>>>>>>>>>>> Any ideas how to deal with the mandatory JavaDoc rule for
> > >>>>> existing
> > >>>>>>>>>> code?
> > >>>>>>>>>>>> Just adding empty headers to make the checkstyle pass or
> > >>>> start a
> > >>>>>>>>>> serious
> > >>>>>>>>>>>> effort to add the missing docs?
> > >>>>>>>>>>>>
> > >>>>>>>>>>>> 2015-10-21 13:31 GMT+02:00 Matthias J. Sax <
> > >> [hidden email]
> > >>>>> :
> > >>>>>>>>>>>>
> > >>>>>>>>>>>>> Agreed. That's the reason why I am in favor of using
> > >> vanilla
> > >>>>> Google
> > >>>>>>>>>> code
> > >>>>>>>>>>>>> style.
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>> On 10/21/2015 12:31 PM, Stephan Ewen wrote:
> > >>>>>>>>>>>>>> We started out originally with mixed tab/spaces, but it
> > >>>>> ended up
> > >>>>>>>>>> with
> > >>>>>>>>>>>>>> people mixing spaces and tabs arbitrarily, and there is
> > >>>>> little way
> > >>>>>>>>>> to
> > >>>>>>>>>>>>>> enforce Matthias' specific suggestion via checkstyle.
> > >>>>>>>>>>>>>> That's why we dropped spaces alltogether...
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 12:03 PM, Gyula Fóra <
> > >>>>>>>>> [hidden email]>
> > >>>>>>>>>>>>> wrote:
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> I think the nice thing about a common codestyle is that
> > >>>>> everyone
> > >>>>>>>>>> can
> > >>>>>>>>>>> set
> > >>>>>>>>>>>>>>> the template in the IDE and use the formatting
> > >> commands.
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> Matthias's suggestion makes this practically
> > >> impossible so
> > >>>>> -1 for
> > >>>>>>>>>>> mixed
> > >>>>>>>>>>>>>>> tabs/spaces from my side.
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>> Matthias J. Sax <[hidden email]> ezt írta (időpont:
> > >>>>> 2015. okt.
> > >>>>>>>>>>> 21.,
> > >>>>>>>>>>>>> Sze,
> > >>>>>>>>>>>>>>> 11:46):
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> I actually like tabs a lot, however, in a "mixed"
> > >> style
> > >>>>> together
> > >>>>>>>>>>> with
> > >>>>>>>>>>>>>>>> spaces. Example:
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>         myVar.callMethod(param1, // many more
> > >>>>>>>>>>>>>>>>         .................paramX); // the dots mark
> > >> space
> > >>>>>>>>> indention
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> indenting "paramX" with tabs does not give nice
> > >> aliment.
> > >>>>> Not
> > >>>>>>>>> sure
> > >>>>>>>>>> if
> > >>>>>>>>>>>>>>>> this would be a feasible compromise to keeps tabs in
> > >>>>> general,
> > >>>>>>>>> but
> > >>>>>>>>>>> use
> > >>>>>>>>>>>>>>>> space for cases as above.
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> If this in no feasible compromise, I would prefer
> > >> space
> > >>>> to
> > >>>>> get
> > >>>>>>>>> the
> > >>>>>>>>>>>>>>>> correct indention in examples as above. Even if this
> > >>>>> result in a
> > >>>>>>>>>>>>>>>> complete reformatting of the whole code.
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> Why this? Everybody can set this in it's IDE/editor as
> > >>>>> he/she
> > >>>>>>>>>>> wishes...
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
> > >>>> length
> > >>>>>>>>>> relative
> > >>>>>>>>>>> to
> > >>>>>>>>>>>>> a
> > >>>>>>>>>>>>>>>> tab
> > >>>>>>>>>>>>>>>>>> size (like 4).
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> -Matthias
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> On 10/21/2015 11:06 AM, Ufuk Celebi wrote:
> > >>>>>>>>>>>>>>>>> To summarize up to this point:
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> - All are in favour of Google check style (with the
> > >>>>> following
> > >>>>>>>>>>> possible
> > >>>>>>>>>>>>>>>>> exceptions)
> > >>>>>>>>>>>>>>>>> - Proposed exceptions so far:
> > >>>>>>>>>>>>>>>>>   * Specific line length 100 vs. 120 characters
> > >>>>>>>>>>>>>>>>>   * Keep tabs instead converting to spaces (this
> > >> would
> > >>>>>>>>> translate
> > >>>>>>>>>> to
> > >>>>>>>>>>>>>>>>> skipping/coming up with some indentation rules as
> > >> well)
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
> > >> length
> > >>>>>>>>> relative
> > >>>>>>>>>>> to a
> > >>>>>>>>>>>>>>>> tab
> > >>>>>>>>>>>>>>>>> size (like 4).
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> Let’s keep the discussion going a little longer. I
> > >> think
> > >>>>> it has
> > >>>>>>>>>>>>>>> proceeded
> > >>>>>>>>>>>>>>>>> in a very reasonable manner so far. Thanks for this!
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> – Ufuk
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 10:29 AM, Fabian Hueske <
> > >>>>>>>>>> [hidden email]
> > >>>>>>>>>>>>
> > >>>>>>>>>>>>>>>> wrote:
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> Thanks Max for checking the modifications by the
> > >> Google
> > >>>>> code
> > >>>>>>>>>>> style.
> > >>>>>>>>>>>>>>>>>> It is very good to know, that the impact on the code
> > >>>> base
> > >>>>>>>>> would
> > >>>>>>>>>>> not
> > >>>>>>>>>>>>> be
> > >>>>>>>>>>>>>>>> too
> > >>>>>>>>>>>>>>>>>> massive. If the Google code style would have touched
> > >>>>> almost
> > >>>>>>>>>> every
> > >>>>>>>>>>>>>>> line,
> > >>>>>>>>>>>>>>>> I
> > >>>>>>>>>>>>>>>>>> would have been in favor of converting to spaces.
> > >>>>> However,
> > >>>>>>>>> your
> > >>>>>>>>>>>>>>>> assessment
> > >>>>>>>>>>>>>>>>>> is a strong argument to continue with tabs, IMO.
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> Regarding the line length limit, I personally find
> > >> 100
> > >>>>> chars
> > >>>>>>>>> too
> > >>>>>>>>>>>>>>> narrow
> > >>>>>>>>>>>>>>>> but
> > >>>>>>>>>>>>>>>>>> would be +1 for having a limit.
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> +1 for discussing the Scala style in a separate
> > >> thread.
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> Fabian
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>> 2015-10-20 18:12 GMT+02:00 Maximilian Michels <
> > >>>>> [hidden email]
> > >>>>>>>>>> :
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>> I'm a little less excited about this. You might
> > >> not be
> > >>>>> aware
> > >>>>>>>>>> but,
> > >>>>>>>>>>>>> for
> > >>>>>>>>>>>>>>>>>>> a large portion of the source code, we already
> > >> follow
> > >>>>> the
> > >>>>>>>>>> Google
> > >>>>>>>>>>>>>>> style
> > >>>>>>>>>>>>>>>>>>> guide. The main changes will be tabs->spaces and
> > >>>> 80/100
> > >>>>>>>>>>> characters
> > >>>>>>>>>>>>>>>>>>> line limit.
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>> Out of curiosity, I ran the official Google Style
> > >>>>> Checkstyle
> > >>>>>>>>>>>>>>>>>>> configuration to confirm my suspicion:
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>
> > >>>>>>>>>>
> > >>>>>>>>>
> > >>>>>
> > >>>>
> > >>
> >
> https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml
> > >>>>>>>>>>>>>>>>>>> The changes are very little if we turn off line
> > >> length
> > >>>>> limit
> > >>>>>>>>>> and
> > >>>>>>>>>>>>>>>>>>> tabs-to-spaces conversion.
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>> There are some things I really like about the
> > >> Google
> > >>>>> style,
> > >>>>>>>>>> e.g.
> > >>>>>>>>>>>>>>> every
> > >>>>>>>>>>>>>>>>>>> class has to have a JavaDoc and spaces after
> > >> keywords
> > >>>>> (can't
> > >>>>>>>>>>> stand
> > >>>>>>>>>>>>> if
> > >>>>>>>>>>>>>>>>>>> there aren't any). I'm not sure if we should change
> > >>>>> tabs to
> > >>>>>>>>>>> spaces,
> > >>>>>>>>>>>>>>>>>>> because it means touching almost every single line
> > >> of
> > >>>>> code.
> > >>>>>>>>>>> However,
> > >>>>>>>>>>>>>>>>>>> if we keep the tabs, we cannot make use of the
> > >>>> different
> > >>>>>>>>>>> indention
> > >>>>>>>>>>>>>>> for
> > >>>>>>>>>>>>>>>>>>> case statements or wrapped lines...maybe that's a
> > >>>>> compromise
> > >>>>>>>>> we
> > >>>>>>>>>>> can
> > >>>>>>>>>>>>>>>>>>> live with.
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>> If we introduce the Google Style for Java, will we
> > >>>> also
> > >>>>>>>>> impose
> > >>>>>>>>>> a
> > >>>>>>>>>>>>>>>>>>> stricter style check for Scala? IMHO the line
> > >> length
> > >>>> is
> > >>>>> the
> > >>>>>>>>>>>>> strictest
> > >>>>>>>>>>>>>>>>>>> part of the Scala Checkstyle.
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>> On Tue, Oct 20, 2015 at 4:14 PM, Henry Saputra <
> > >>>>>>>>>>>>>>>> [hidden email]>
> > >>>>>>>>>>>>>>>>>>> wrote:
> > >>>>>>>>>>>>>>>>>>>> 1) yes. Been dancing this issue for a while. Let's
> > >>>>> pull the
> > >>>>>>>>>>>>> trigger.
> > >>>>>>>>>>>>>>>>>> Did
> > >>>>>>>>>>>>>>>>>>>> the exercise with Tachyon while back and did help
> > >>>>>>>>> readability
> > >>>>>>>>>>> and
> > >>>>>>>>>>>>>>>>>>>> homogeneity of code.
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> 2) +1 for Google Java style with documented
> > >>>> exceptions
> > >>>>> and
> > >>>>>>>>>>>>>>> explanation
> > >>>>>>>>>>>>>>>>>> on
> > >>>>>>>>>>>>>>>>>>>> why.
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>> On Tuesday, October 20, 2015, Ufuk Celebi <
> > >>>>> [hidden email]>
> > >>>>>>>>>>> wrote:
> > >>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> DISCLAIMER: This is not my personal idea, but a
> > >>>>> community
> > >>>>>>>>>>>>>>> discussion
> > >>>>>>>>>>>>>>>>>>> from
> > >>>>>>>>>>>>>>>>>>>>> some time ago. Don't kill the messenger.
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> In March we were discussing issues with
> > >>>> heterogeneity
> > >>>>> of
> > >>>>>>>>> the
> > >>>>>>>>>>> code
> > >>>>>>>>>>>>>>>> [1].
> > >>>>>>>>>>>>>>>>>>> The
> > >>>>>>>>>>>>>>>>>>>>> summary is that we had a consensus to enforce a
> > >>>>> stricter
> > >>>>>>>>> code
> > >>>>>>>>>>>>> style
> > >>>>>>>>>>>>>>>> on
> > >>>>>>>>>>>>>>>>>>> our
> > >>>>>>>>>>>>>>>>>>>>> Java code base in order to make it easier to
> > >> switch
> > >>>>> between
> > >>>>>>>>>>>>>>> projects
> > >>>>>>>>>>>>>>>>>>> and to
> > >>>>>>>>>>>>>>>>>>>>> have clear rules for new contributions. The main
> > >>>>> proposal
> > >>>>>>>>> in
> > >>>>>>>>>>> the
> > >>>>>>>>>>>>>>> last
> > >>>>>>>>>>>>>>>>>>>>> discussion was to go with Google's Java code
> > >> style.
> > >>>>> Not all
> > >>>>>>>>>>> were
> > >>>>>>>>>>>>>>>> fully
> > >>>>>>>>>>>>>>>>>>>>> satisfied with this, but still everyone agreed on
> > >>>>> some kind
> > >>>>>>>>>> of
> > >>>>>>>>>>>>>>> style.
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> I think the upcoming 0.10 release is a good
> > >> point to
> > >>>>>>>>> finally
> > >>>>>>>>>> go
> > >>>>>>>>>>>>>>>>>> through
> > >>>>>>>>>>>>>>>>>>>>> with these changes (right after the
> > >>>>> release/branch-off).
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> I propose to go with Google's Java code style
> > >> [2] as
> > >>>>>>>>> proposed
> > >>>>>>>>>>>>>>>> earlier.
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> PROs:
> > >>>>>>>>>>>>>>>>>>>>> - Clear style guide available
> > >>>>>>>>>>>>>>>>>>>>> - Tooling like checkstyle rules, IDE plugins
> > >> already
> > >>>>>>>>>> available
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> CONs:
> > >>>>>>>>>>>>>>>>>>>>> - Fully breaks our current style
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> The main problem with this will be open pull
> > >>>> requests,
> > >>>>>>>>> which
> > >>>>>>>>>>> will
> > >>>>>>>>>>>>>>> be
> > >>>>>>>>>>>>>>>>>>> harder
> > >>>>>>>>>>>>>>>>>>>>> to merge after all the changes. On the other
> > >> hand,
> > >>>>> should
> > >>>>>>>>>> pull
> > >>>>>>>>>>>>>>>>>> requests
> > >>>>>>>>>>>>>>>>>>>>> that have been open for a long time block this?
> > >> Most
> > >>>>> of the
> > >>>>>>>>>>>>>>> important
> > >>>>>>>>>>>>>>>>>>>>> changes will be merged for the release anyways. I
> > >>>>> think in
> > >>>>>>>>>> the
> > >>>>>>>>>>>>> long
> > >>>>>>>>>>>>>>>>>> run
> > >>>>>>>>>>>>>>>>>>> we
> > >>>>>>>>>>>>>>>>>>>>> will gain more than we loose by this (more
> > >>>> homogenous
> > >>>>> code,
> > >>>>>>>>>>> clear
> > >>>>>>>>>>>>>>>>>>> rules).
> > >>>>>>>>>>>>>>>>>>>>> And it is questionable whether we will ever be
> > >> able
> > >>>>> to do
> > >>>>>>>>>> such
> > >>>>>>>>>>> a
> > >>>>>>>>>>>>>>>>>> change
> > >>>>>>>>>>>>>>>>>>> in
> > >>>>>>>>>>>>>>>>>>>>> the future if we cannot do it now. The project
> > >> will
> > >>>>> most
> > >>>>>>>>>> likely
> > >>>>>>>>>>>>>>> grow
> > >>>>>>>>>>>>>>>>>> and
> > >>>>>>>>>>>>>>>>>>>>> attract more contributors, at which point it
> > >> will be
> > >>>>> even
> > >>>>>>>>>>> harder
> > >>>>>>>>>>>>> to
> > >>>>>>>>>>>>>>>>>> do.
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> Please make sure to answer the following points
> > >> in
> > >>>> the
> > >>>>>>>>>>> discussion:
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> 1) Are you (still) in favour of enforcing
> > >> stricter
> > >>>>> rules on
> > >>>>>>>>>> the
> > >>>>>>>>>>>>>>> Java
> > >>>>>>>>>>>>>>>>>>>>> codebase?
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> 2) If yes, would you be OK with the Google's Java
> > >>>> code
> > >>>>>>>>> style?
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> – Ufuk
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> [1]
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>
> > >>>>>>>>>>
> > >>>>>>>>>
> > >>>>>
> > >>>>
> > >>
> >
> http://mail-archives.apache.org/mod_mbox/flink-dev/201503.mbox/%3cCANC1h_voN0B5omNWZxcHTyzwHAKeGhbZVQUyK7S9o2A36b891Q@...%3e
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>>> [2]
> > >>>>> https://google.github.io/styleguide/javaguide.html
> > >>>>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>>
> > >>>>>>>>>>>>>>
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>>>
> > >>>>>>>>>>>
> > >>>>>>>>>>
> > >>>>>>>>>
> > >>>>>
> > >>>>
> > >>
> > >
> >
> >
>

[Ufuk Celebi-2]

Minor thing in favour of spaces: Reviewability on GitHub is improved (they use 8 spaces for tabs and line length of 120, which often results in too long lines).

> On 09 Nov 2015, at 13:53, Fabian Hueske <[hidden email]> wrote:
>
> I don't see other benefits except maybe being closer to the vanilla Google
> style.
>
> 2015-11-02 20:46 GMT+01:00 Stephan Ewen <[hidden email]>:
>
>> I think by now virtually everyone prefers spaces if it came for free, so it
>> is a matter of making an educated decision about the cost/benefit
>> tradeoffs.
>>
>> What are the benefits of spaces in the style other than people liking the
>> looks of space-formatted code better (aesthetics, schmaesthetics ;-) )
>>
>>
>> On Mon, Nov 2, 2015 at 5:38 AM, Matthias J. Sax <[hidden email]> wrote:
>>
>>> Thanks for the summary Fabian.
>>>
>>> Maybe we should have kind of a vote about this. No classical Apache vote
>>> though, but voting for different options (so only +1), and the option
>>> with the highest score wins? (Not sure if this is possible to do...)
>>>
>>> About spaced vs. tabs:
>>>> "AFAIR, nobody said to have a personal preferences of tabs over
>> spaces."
>>>
>>> I think this is wrong. If I am correct, Till and myself would prefer
>>> spaces (but non of us is super strict about this -- we could both live
>>> with tabs too).
>>>
>>> -Matthias
>>>
>>> On 11/02/2015 12:14 PM, Fabian Hueske wrote:
>>>> OK, I'll try to summarize the discussion so far (please correct me if I
>>> got
>>>> something wrong):
>>>>
>>>> Everybody is in favor of adding a stricter code style based on the
>> Google
>>>> Java code style.
>>>> Main points of discussion are:
>>>> 1) Line length
>>>> 2) JavaDocs
>>>> 3) Tabs vs. Spaces
>>>>
>>>> -- Line length
>>>> Issue:
>>>> Google code style demands 80 or 100 chars line length limit.
>>>> Some people find this too narrow.
>>>>
>>>> Discussion so far:
>>>> Nobody objected against a limit of 120 chars, AFAIR.
>>>>
>>>> -- JavaDocs
>>>> Issue:
>>>> Google code style says "At the *minimum*, Javadoc is present for every
>>>> public class, and every public or protected member of such a class,
>> with
>>> a
>>>> few exceptions noted below." Exceptions are self-explanatory methods
>> like
>>>> getters and setters and overwritten method.
>>>> Significant parts of the Flink code base do not comply with this
>>>> requirement. It would be a huge effort to add the corresponding code
>>>> documentation.
>>>>
>>>> Discussion so far:
>>>> Disable JavaDoc checks when adding the code style and opening JIRAs for
>>>> adding JavaDocs on a per Maven module level (with potentially
>> subissues)
>>>> with target dates. Once a module complies to the rule, the JavaDoc
>> check
>>> is
>>>> enabled in the checkstyle.
>>>>
>>>> -- Tabs vs. Spaces
>>>> Issue:
>>>> The Google code style requires two spaces for indention. The Java code
>>> base
>>>> of Flink uses tabs. Moving from tabs to spaces would touch every line
>> of
>>>> Java code and therefore might make the tracking of changes in the past
>>> much
>>>> harder.
>>>> Max provided some numbers for applying the Google code style on the
>>> current
>>>> code base: The style checker found 28k violations (possibly multiple
>> ones
>>>> per LOC) on 121k LOC of Java code in 1601 out of 3251 Java classes. So
>>>> Google code style without spaces would touch every second file and
>> about
>>>> every 4th line of code. The question I have, would it be easier to
>> track
>>>> history with a commit that touches 1/2 (or 1/4) of the code base
>> compared
>>>> to one that touches everything.
>>>>
>>>> Discussion so far:
>>>> AFAIR, nobody said to have a personal preferences of tabs over spaces.
>>>> However, some people raised concerns that the implied changes of moving
>>> the
>>>> code base from tabs to spaces would be too massive and the "benefits"
>>> would
>>>> not justify the "cost" of the change.
>>>> I think, this is the main point of discussion, right now.
>>>>
>>>> If we want to come to a conclusion, we should not let this discussion
>>> fall
>>>> asleep (as happened a few times in the past).
>>>>
>>>> Does anybody NOT agree with the "solutions" for line length and
>> JavaDocs,
>>>> i.e., 120 chars and "lazy" adding of JavaDocs with JIRA tracking, or
>> has
>>>> another proposal?
>>>> How can we resolve the Tabs vs. Spaces discussion?
>>>>
>>>> Cheers, Fabian
>>>>
>>>>
>>>>
>>>> 2015-10-30 18:16 GMT+01:00 Maximilian Michels <[hidden email]>:
>>>>
>>>>> I looked up if the Checkstyle plugin would also support tabs with a
>>>>> fixed line length. Indeed, this is possible because a tab can be
>>>>> mapped to a fixed number of spaces.
>>>>>
>>>>> I've modified the default Google Style Checkstyle file. I changed the
>>>>> indention to tabs (2 spaces) and increased the line length to 120:
>>>>> https://gist.github.com/mxm/2ca4ef7702667c167d10
>>>>>
>>>>> The scan of the entire Flink project resulted in 27,992 items in 1601
>>>>> files. This is roughly corresponds to the number of lines we would
>>>>> have to touch to comply with the style rules. Note that, one line may
>>>>> contain multiple items. A lot of the items are import statements.
>>>>>
>>>>> Next, I tried running the vanilla Google Style Checkstyle file over
>>>>> the entire code base but my IntelliJ crashed. Using Maven, I wasn't
>>>>> able to get a total result displayed but I'm assuming it would be
>>>>> almost all lines of Flink code that had a violation due to tabs.
>>>>>
>>>>> On Mon, Oct 26, 2015 at 6:56 PM, Suneel Marthi <
>> [hidden email]
>>>>
>>>>> wrote:
>>>>>> 2 spaces is the convention that's followed on Mahout and Oryx.
>>>>>>
>>>>>> On Mon, Oct 26, 2015 at 1:42 PM, Till Rohrmann <[hidden email]
>>>
>>>>> wrote:
>>>>>>
>>>>>>> Concerning question 2 Tabs vs. Spaces, in case of spaces we would
>> have
>>>>> to
>>>>>>> decide on the number of spaces, too. The Google Java style says to
>> use
>>>>> a 2
>>>>>>> space indentation, which is in my opinion sufficient to distinguish
>>>>>>> different indentations levels from each other. Furthermore, it would
>>>>> save
>>>>>>> some space.
>>>>>>>
>>>>>>> I would not vote -1 if we keep tabs.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Sat, Oct 24, 2015 at 8:33 PM, Henry Saputra <
>>> [hidden email]
>>>>>>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> +1 for adding restriction for Javadoc at least at the header of
>>> public
>>>>>>>> classes and methods.
>>>>>>>>
>>>>>>>> We did the exercise in Twill and seemed to work pretty well.
>>>>>>>>
>>>>>>>> On Fri, Oct 23, 2015 at 1:34 AM, Maximilian Michels <
>> [hidden email]>
>>>>>>>> wrote:
>>>>>>>>> I don't think lazily adding comments will work. However, I'm fine
>>>>> with
>>>>>>>>> adding all the checkstyle rules one module at a time (with a jira
>>>>>>>>> issue to keep track of the modules already converted). It's not
>>>>> going
>>>>>>>>> to happen that we lazily add comments because that's the reason
>> why
>>>>>>>>> comments are missing in the first place...
>>>>>>>>>
>>>>>>>>> On Fri, Oct 23, 2015 at 12:05 AM, Henry Saputra <
>>>>>>> [hidden email]>
>>>>>>>> wrote:
>>>>>>>>>> Could we make certain rules to give warning instead of error?
>>>>>>>>>>
>>>>>>>>>> This would allow us to cherry-pick certain rules we would like
>>>>> people
>>>>>>>>>> to follow but not strictly enforced.
>>>>>>>>>>
>>>>>>>>>> - Henry
>>>>>>>>>>
>>>>>>>>>> On Thu, Oct 22, 2015 at 9:20 AM, Stephan Ewen <[hidden email]>
>>>>>>> wrote:
>>>>>>>>>>> I don't think a "let add comments to everything" effort gives us
>>>>> good
>>>>>>>>>>> comments, actually. It just gives us checkmark comments that
>> make
>>>>> the
>>>>>>>> rules
>>>>>>>>>>> pass.
>>>>>>>>>>>
>>>>>>>>>>> On Thu, Oct 22, 2015 at 3:29 PM, Fabian Hueske <
>> [hidden email]
>>>>>>
>>>>>>>> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> Sure, I don't expect it to be free.
>>>>>>>>>>>> But everybody should be aware of the cost of adding this code
>>>>> style,
>>>>>>>> i.e.,
>>>>>>>>>>>> spending a huge amount of time on reformatting and documenting
>>>>> code.
>>>>>>>>>>>>
>>>>>>>>>>>> Alternatively, we could drop the JavaDocs rule and make the
>>>>>>> transition
>>>>>>>>>>>> significantly cheaper.
>>>>>>>>>>>>
>>>>>>>>>>>> 2015-10-22 15:24 GMT+02:00 Till Rohrmann <[hidden email]
>>> :
>>>>>>>>>>>>
>>>>>>>>>>>>> There ain’t no such thing as a free lunch and code style.
>>>>>>>>>>>>>
>>>>>>>>>>>>> On Thu, Oct 22, 2015 at 3:13 PM, Maximilian Michels <
>>>>>>> [hidden email]
>>>>>>>>>
>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>
>>>>>>>>>>>>>> I think we have to document all these classes. Code Style
>>>>>>> doesn't
>>>>>>>> come
>>>>>>>>>>>>>> for free :)
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> On Thu, Oct 22, 2015 at 3:09 PM, Fabian Hueske <
>>>>>>> [hidden email]
>>>>>>>>>
>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>> Any ideas how to deal with the mandatory JavaDoc rule for
>>>>>>>> existing
>>>>>>>>>>>>> code?
>>>>>>>>>>>>>>> Just adding empty headers to make the checkstyle pass or
>>>>>>> start a
>>>>>>>>>>>>> serious
>>>>>>>>>>>>>>> effort to add the missing docs?
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 2015-10-21 13:31 GMT+02:00 Matthias J. Sax <
>>>>> [hidden email]
>>>>>>>> :
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Agreed. That's the reason why I am in favor of using
>>>>> vanilla
>>>>>>>> Google
>>>>>>>>>>>>> code
>>>>>>>>>>>>>>>> style.
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> On 10/21/2015 12:31 PM, Stephan Ewen wrote:
>>>>>>>>>>>>>>>>> We started out originally with mixed tab/spaces, but it
>>>>>>>> ended up
>>>>>>>>>>>>> with
>>>>>>>>>>>>>>>>> people mixing spaces and tabs arbitrarily, and there is
>>>>>>>> little way
>>>>>>>>>>>>> to
>>>>>>>>>>>>>>>>> enforce Matthias' specific suggestion via checkstyle.
>>>>>>>>>>>>>>>>> That's why we dropped spaces alltogether...
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 12:03 PM, Gyula Fóra <
>>>>>>>>>>>> [hidden email]>
>>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> I think the nice thing about a common codestyle is that
>>>>>>>> everyone
>>>>>>>>>>>>> can
>>>>>>>>>>>>>> set
>>>>>>>>>>>>>>>>>> the template in the IDE and use the formatting
>>>>> commands.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Matthias's suggestion makes this practically
>>>>> impossible so
>>>>>>>> -1 for
>>>>>>>>>>>>>> mixed
>>>>>>>>>>>>>>>>>> tabs/spaces from my side.
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>> Matthias J. Sax <[hidden email]> ezt írta (időpont:
>>>>>>>> 2015. okt.
>>>>>>>>>>>>>> 21.,
>>>>>>>>>>>>>>>> Sze,
>>>>>>>>>>>>>>>>>> 11:46):
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> I actually like tabs a lot, however, in a "mixed"
>>>>> style
>>>>>>>> together
>>>>>>>>>>>>>> with
>>>>>>>>>>>>>>>>>>> spaces. Example:
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>        myVar.callMethod(param1, // many more
>>>>>>>>>>>>>>>>>>>        .................paramX); // the dots mark
>>>>> space
>>>>>>>>>>>> indention
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> indenting "paramX" with tabs does not give nice
>>>>> aliment.
>>>>>>>> Not
>>>>>>>>>>>> sure
>>>>>>>>>>>>> if
>>>>>>>>>>>>>>>>>>> this would be a feasible compromise to keeps tabs in
>>>>>>>> general,
>>>>>>>>>>>> but
>>>>>>>>>>>>>> use
>>>>>>>>>>>>>>>>>>> space for cases as above.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> If this in no feasible compromise, I would prefer
>>>>> space
>>>>>>> to
>>>>>>>> get
>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>>>> correct indention in examples as above. Even if this
>>>>>>>> result in a
>>>>>>>>>>>>>>>>>>> complete reformatting of the whole code.
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> Why this? Everybody can set this in it's IDE/editor as
>>>>>>>> he/she
>>>>>>>>>>>>>> wishes...
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
>>>>>>> length
>>>>>>>>>>>>> relative
>>>>>>>>>>>>>> to
>>>>>>>>>>>>>>>> a
>>>>>>>>>>>>>>>>>>> tab
>>>>>>>>>>>>>>>>>>>>> size (like 4).
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> -Matthias
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> On 10/21/2015 11:06 AM, Ufuk Celebi wrote:
>>>>>>>>>>>>>>>>>>>> To summarize up to this point:
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> - All are in favour of Google check style (with the
>>>>>>>> following
>>>>>>>>>>>>>> possible
>>>>>>>>>>>>>>>>>>>> exceptions)
>>>>>>>>>>>>>>>>>>>> - Proposed exceptions so far:
>>>>>>>>>>>>>>>>>>>>  * Specific line length 100 vs. 120 characters
>>>>>>>>>>>>>>>>>>>>  * Keep tabs instead converting to spaces (this
>>>>> would
>>>>>>>>>>>> translate
>>>>>>>>>>>>> to
>>>>>>>>>>>>>>>>>>>> skipping/coming up with some indentation rules as
>>>>> well)
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
>>>>> length
>>>>>>>>>>>> relative
>>>>>>>>>>>>>> to a
>>>>>>>>>>>>>>>>>>> tab
>>>>>>>>>>>>>>>>>>>> size (like 4).
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> Let’s keep the discussion going a little longer. I
>>>>> think
>>>>>>>> it has
>>>>>>>>>>>>>>>>>> proceeded
>>>>>>>>>>>>>>>>>>>> in a very reasonable manner so far. Thanks for this!
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> – Ufuk
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 10:29 AM, Fabian Hueske <
>>>>>>>>>>>>> [hidden email]
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Thanks Max for checking the modifications by the
>>>>> Google
>>>>>>>> code
>>>>>>>>>>>>>> style.
>>>>>>>>>>>>>>>>>>>>> It is very good to know, that the impact on the code
>>>>>>> base
>>>>>>>>>>>> would
>>>>>>>>>>>>>> not
>>>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>>> too
>>>>>>>>>>>>>>>>>>>>> massive. If the Google code style would have touched
>>>>>>>> almost
>>>>>>>>>>>>> every
>>>>>>>>>>>>>>>>>> line,
>>>>>>>>>>>>>>>>>>> I
>>>>>>>>>>>>>>>>>>>>> would have been in favor of converting to spaces.
>>>>>>>> However,
>>>>>>>>>>>> your
>>>>>>>>>>>>>>>>>>> assessment
>>>>>>>>>>>>>>>>>>>>> is a strong argument to continue with tabs, IMO.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Regarding the line length limit, I personally find
>>>>> 100
>>>>>>>> chars
>>>>>>>>>>>> too
>>>>>>>>>>>>>>>>>> narrow
>>>>>>>>>>>>>>>>>>> but
>>>>>>>>>>>>>>>>>>>>> would be +1 for having a limit.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> +1 for discussing the Scala style in a separate
>>>>> thread.
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> Fabian
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>> 2015-10-20 18:12 GMT+02:00 Maximilian Michels <
>>>>>>>> [hidden email]
>>>>>>>>>>>>> :
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> I'm a little less excited about this. You might
>>>>> not be
>>>>>>>> aware
>>>>>>>>>>>>> but,
>>>>>>>>>>>>>>>> for
>>>>>>>>>>>>>>>>>>>>>> a large portion of the source code, we already
>>>>> follow
>>>>>>>> the
>>>>>>>>>>>>> Google
>>>>>>>>>>>>>>>>>> style
>>>>>>>>>>>>>>>>>>>>>> guide. The main changes will be tabs->spaces and
>>>>>>> 80/100
>>>>>>>>>>>>>> characters
>>>>>>>>>>>>>>>>>>>>>> line limit.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> Out of curiosity, I ran the official Google Style
>>>>>>>> Checkstyle
>>>>>>>>>>>>>>>>>>>>>> configuration to confirm my suspicion:
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>
>>>
>> https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml
>>>>>>>>>>>>>>>>>>>>>> The changes are very little if we turn off line
>>>>> length
>>>>>>>> limit
>>>>>>>>>>>>> and
>>>>>>>>>>>>>>>>>>>>>> tabs-to-spaces conversion.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> There are some things I really like about the
>>>>> Google
>>>>>>>> style,
>>>>>>>>>>>>> e.g.
>>>>>>>>>>>>>>>>>> every
>>>>>>>>>>>>>>>>>>>>>> class has to have a JavaDoc and spaces after
>>>>> keywords
>>>>>>>> (can't
>>>>>>>>>>>>>> stand
>>>>>>>>>>>>>>>> if
>>>>>>>>>>>>>>>>>>>>>> there aren't any). I'm not sure if we should change
>>>>>>>> tabs to
>>>>>>>>>>>>>> spaces,
>>>>>>>>>>>>>>>>>>>>>> because it means touching almost every single line
>>>>> of
>>>>>>>> code.
>>>>>>>>>>>>>> However,
>>>>>>>>>>>>>>>>>>>>>> if we keep the tabs, we cannot make use of the
>>>>>>> different
>>>>>>>>>>>>>> indention
>>>>>>>>>>>>>>>>>> for
>>>>>>>>>>>>>>>>>>>>>> case statements or wrapped lines...maybe that's a
>>>>>>>> compromise
>>>>>>>>>>>> we
>>>>>>>>>>>>>> can
>>>>>>>>>>>>>>>>>>>>>> live with.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> If we introduce the Google Style for Java, will we
>>>>>>> also
>>>>>>>>>>>> impose
>>>>>>>>>>>>> a
>>>>>>>>>>>>>>>>>>>>>> stricter style check for Scala? IMHO the line
>>>>> length
>>>>>>> is
>>>>>>>> the
>>>>>>>>>>>>>>>> strictest
>>>>>>>>>>>>>>>>>>>>>> part of the Scala Checkstyle.
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>> On Tue, Oct 20, 2015 at 4:14 PM, Henry Saputra <
>>>>>>>>>>>>>>>>>>> [hidden email]>
>>>>>>>>>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>>>>>> 1) yes. Been dancing this issue for a while. Let's
>>>>>>>> pull the
>>>>>>>>>>>>>>>> trigger.
>>>>>>>>>>>>>>>>>>>>> Did
>>>>>>>>>>>>>>>>>>>>>>> the exercise with Tachyon while back and did help
>>>>>>>>>>>> readability
>>>>>>>>>>>>>> and
>>>>>>>>>>>>>>>>>>>>>>> homogeneity of code.
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> 2) +1 for Google Java style with documented
>>>>>>> exceptions
>>>>>>>> and
>>>>>>>>>>>>>>>>>> explanation
>>>>>>>>>>>>>>>>>>>>> on
>>>>>>>>>>>>>>>>>>>>>>> why.
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>> On Tuesday, October 20, 2015, Ufuk Celebi <
>>>>>>>> [hidden email]>
>>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> DISCLAIMER: This is not my personal idea, but a
>>>>>>>> community
>>>>>>>>>>>>>>>>>> discussion
>>>>>>>>>>>>>>>>>>>>>> from
>>>>>>>>>>>>>>>>>>>>>>>> some time ago. Don't kill the messenger.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> In March we were discussing issues with
>>>>>>> heterogeneity
>>>>>>>> of
>>>>>>>>>>>> the
>>>>>>>>>>>>>> code
>>>>>>>>>>>>>>>>>>> [1].
>>>>>>>>>>>>>>>>>>>>>> The
>>>>>>>>>>>>>>>>>>>>>>>> summary is that we had a consensus to enforce a
>>>>>>>> stricter
>>>>>>>>>>>> code
>>>>>>>>>>>>>>>> style
>>>>>>>>>>>>>>>>>>> on
>>>>>>>>>>>>>>>>>>>>>> our
>>>>>>>>>>>>>>>>>>>>>>>> Java code base in order to make it easier to
>>>>> switch
>>>>>>>> between
>>>>>>>>>>>>>>>>>> projects
>>>>>>>>>>>>>>>>>>>>>> and to
>>>>>>>>>>>>>>>>>>>>>>>> have clear rules for new contributions. The main
>>>>>>>> proposal
>>>>>>>>>>>> in
>>>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>>> last
>>>>>>>>>>>>>>>>>>>>>>>> discussion was to go with Google's Java code
>>>>> style.
>>>>>>>> Not all
>>>>>>>>>>>>>> were
>>>>>>>>>>>>>>>>>>> fully
>>>>>>>>>>>>>>>>>>>>>>>> satisfied with this, but still everyone agreed on
>>>>>>>> some kind
>>>>>>>>>>>>> of
>>>>>>>>>>>>>>>>>> style.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> I think the upcoming 0.10 release is a good
>>>>> point to
>>>>>>>>>>>> finally
>>>>>>>>>>>>> go
>>>>>>>>>>>>>>>>>>>>> through
>>>>>>>>>>>>>>>>>>>>>>>> with these changes (right after the
>>>>>>>> release/branch-off).
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> I propose to go with Google's Java code style
>>>>> [2] as
>>>>>>>>>>>> proposed
>>>>>>>>>>>>>>>>>>> earlier.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> PROs:
>>>>>>>>>>>>>>>>>>>>>>>> - Clear style guide available
>>>>>>>>>>>>>>>>>>>>>>>> - Tooling like checkstyle rules, IDE plugins
>>>>> already
>>>>>>>>>>>>> available
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> CONs:
>>>>>>>>>>>>>>>>>>>>>>>> - Fully breaks our current style
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> The main problem with this will be open pull
>>>>>>> requests,
>>>>>>>>>>>> which
>>>>>>>>>>>>>> will
>>>>>>>>>>>>>>>>>> be
>>>>>>>>>>>>>>>>>>>>>> harder
>>>>>>>>>>>>>>>>>>>>>>>> to merge after all the changes. On the other
>>>>> hand,
>>>>>>>> should
>>>>>>>>>>>>> pull
>>>>>>>>>>>>>>>>>>>>> requests
>>>>>>>>>>>>>>>>>>>>>>>> that have been open for a long time block this?
>>>>> Most
>>>>>>>> of the
>>>>>>>>>>>>>>>>>> important
>>>>>>>>>>>>>>>>>>>>>>>> changes will be merged for the release anyways. I
>>>>>>>> think in
>>>>>>>>>>>>> the
>>>>>>>>>>>>>>>> long
>>>>>>>>>>>>>>>>>>>>> run
>>>>>>>>>>>>>>>>>>>>>> we
>>>>>>>>>>>>>>>>>>>>>>>> will gain more than we loose by this (more
>>>>>>> homogenous
>>>>>>>> code,
>>>>>>>>>>>>>> clear
>>>>>>>>>>>>>>>>>>>>>> rules).
>>>>>>>>>>>>>>>>>>>>>>>> And it is questionable whether we will ever be
>>>>> able
>>>>>>>> to do
>>>>>>>>>>>>> such
>>>>>>>>>>>>>> a
>>>>>>>>>>>>>>>>>>>>> change
>>>>>>>>>>>>>>>>>>>>>> in
>>>>>>>>>>>>>>>>>>>>>>>> the future if we cannot do it now. The project
>>>>> will
>>>>>>>> most
>>>>>>>>>>>>> likely
>>>>>>>>>>>>>>>>>> grow
>>>>>>>>>>>>>>>>>>>>> and
>>>>>>>>>>>>>>>>>>>>>>>> attract more contributors, at which point it
>>>>> will be
>>>>>>>> even
>>>>>>>>>>>>>> harder
>>>>>>>>>>>>>>>> to
>>>>>>>>>>>>>>>>>>>>> do.
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> Please make sure to answer the following points
>>>>> in
>>>>>>> the
>>>>>>>>>>>>>> discussion:
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> 1) Are you (still) in favour of enforcing
>>>>> stricter
>>>>>>>> rules on
>>>>>>>>>>>>> the
>>>>>>>>>>>>>>>>>> Java
>>>>>>>>>>>>>>>>>>>>>>>> codebase?
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> 2) If yes, would you be OK with the Google's Java
>>>>>>> code
>>>>>>>>>>>> style?
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> – Ufuk
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> [1]
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>
>>>
>> http://mail-archives.apache.org/mod_mbox/flink-dev/201503.mbox/%3cCANC1h_voN0B5omNWZxcHTyzwHAKeGhbZVQUyK7S9o2A36b891Q@...%3e
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>> [2]
>>>>>>>> https://google.github.io/styleguide/javaguide.html
>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>
>>>>
>>>
>>>
>>

[aalexandrov]

I wouldn't stop with GitHub - the main benefit for spaces is that the code
looks the same on all viewers because it does not depend on a user-specific
parameter (the size of the tab).

2015-11-09 14:02 GMT+01:00 Ufuk Celebi <[hidden email]>:

> Minor thing in favour of spaces: Reviewability on GitHub is improved (they
> use 8 spaces for tabs and line length of 120, which often results in too
> long lines).
>
> > On 09 Nov 2015, at 13:53, Fabian Hueske <[hidden email]> wrote:
> >
> > I don't see other benefits except maybe being closer to the vanilla
> Google
> > style.
> >
> > 2015-11-02 20:46 GMT+01:00 Stephan Ewen <[hidden email]>:
> >
> >> I think by now virtually everyone prefers spaces if it came for free,
> so it
> >> is a matter of making an educated decision about the cost/benefit
> >> tradeoffs.
> >>
> >> What are the benefits of spaces in the style other than people liking
> the
> >> looks of space-formatted code better (aesthetics, schmaesthetics ;-) )
> >>
> >>
> >> On Mon, Nov 2, 2015 at 5:38 AM, Matthias J. Sax <[hidden email]>
> wrote:
> >>
> >>> Thanks for the summary Fabian.
> >>>
> >>> Maybe we should have kind of a vote about this. No classical Apache
> vote
> >>> though, but voting for different options (so only +1), and the option
> >>> with the highest score wins? (Not sure if this is possible to do...)
> >>>
> >>> About spaced vs. tabs:
> >>>> "AFAIR, nobody said to have a personal preferences of tabs over
> >> spaces."
> >>>
> >>> I think this is wrong. If I am correct, Till and myself would prefer
> >>> spaces (but non of us is super strict about this -- we could both live
> >>> with tabs too).
> >>>
> >>> -Matthias
> >>>
> >>> On 11/02/2015 12:14 PM, Fabian Hueske wrote:
> >>>> OK, I'll try to summarize the discussion so far (please correct me if
> I
> >>> got
> >>>> something wrong):
> >>>>
> >>>> Everybody is in favor of adding a stricter code style based on the
> >> Google
> >>>> Java code style.
> >>>> Main points of discussion are:
> >>>> 1) Line length
> >>>> 2) JavaDocs
> >>>> 3) Tabs vs. Spaces
> >>>>
> >>>> -- Line length
> >>>> Issue:
> >>>> Google code style demands 80 or 100 chars line length limit.
> >>>> Some people find this too narrow.
> >>>>
> >>>> Discussion so far:
> >>>> Nobody objected against a limit of 120 chars, AFAIR.
> >>>>
> >>>> -- JavaDocs
> >>>> Issue:
> >>>> Google code style says "At the *minimum*, Javadoc is present for every
> >>>> public class, and every public or protected member of such a class,
> >> with
> >>> a
> >>>> few exceptions noted below." Exceptions are self-explanatory methods
> >> like
> >>>> getters and setters and overwritten method.
> >>>> Significant parts of the Flink code base do not comply with this
> >>>> requirement. It would be a huge effort to add the corresponding code
> >>>> documentation.
> >>>>
> >>>> Discussion so far:
> >>>> Disable JavaDoc checks when adding the code style and opening JIRAs
> for
> >>>> adding JavaDocs on a per Maven module level (with potentially
> >> subissues)
> >>>> with target dates. Once a module complies to the rule, the JavaDoc
> >> check
> >>> is
> >>>> enabled in the checkstyle.
> >>>>
> >>>> -- Tabs vs. Spaces
> >>>> Issue:
> >>>> The Google code style requires two spaces for indention. The Java code
> >>> base
> >>>> of Flink uses tabs. Moving from tabs to spaces would touch every line
> >> of
> >>>> Java code and therefore might make the tracking of changes in the past
> >>> much
> >>>> harder.
> >>>> Max provided some numbers for applying the Google code style on the
> >>> current
> >>>> code base: The style checker found 28k violations (possibly multiple
> >> ones
> >>>> per LOC) on 121k LOC of Java code in 1601 out of 3251 Java classes. So
> >>>> Google code style without spaces would touch every second file and
> >> about
> >>>> every 4th line of code. The question I have, would it be easier to
> >> track
> >>>> history with a commit that touches 1/2 (or 1/4) of the code base
> >> compared
> >>>> to one that touches everything.
> >>>>
> >>>> Discussion so far:
> >>>> AFAIR, nobody said to have a personal preferences of tabs over spaces.
> >>>> However, some people raised concerns that the implied changes of
> moving
> >>> the
> >>>> code base from tabs to spaces would be too massive and the "benefits"
> >>> would
> >>>> not justify the "cost" of the change.
> >>>> I think, this is the main point of discussion, right now.
> >>>>
> >>>> If we want to come to a conclusion, we should not let this discussion
> >>> fall
> >>>> asleep (as happened a few times in the past).
> >>>>
> >>>> Does anybody NOT agree with the "solutions" for line length and
> >> JavaDocs,
> >>>> i.e., 120 chars and "lazy" adding of JavaDocs with JIRA tracking, or
> >> has
> >>>> another proposal?
> >>>> How can we resolve the Tabs vs. Spaces discussion?
> >>>>
> >>>> Cheers, Fabian
> >>>>
> >>>>
> >>>>
> >>>> 2015-10-30 18:16 GMT+01:00 Maximilian Michels <[hidden email]>:
> >>>>
> >>>>> I looked up if the Checkstyle plugin would also support tabs with a
> >>>>> fixed line length. Indeed, this is possible because a tab can be
> >>>>> mapped to a fixed number of spaces.
> >>>>>
> >>>>> I've modified the default Google Style Checkstyle file. I changed the
> >>>>> indention to tabs (2 spaces) and increased the line length to 120:
> >>>>> https://gist.github.com/mxm/2ca4ef7702667c167d10
> >>>>>
> >>>>> The scan of the entire Flink project resulted in 27,992 items in 1601
> >>>>> files. This is roughly corresponds to the number of lines we would
> >>>>> have to touch to comply with the style rules. Note that, one line may
> >>>>> contain multiple items. A lot of the items are import statements.
> >>>>>
> >>>>> Next, I tried running the vanilla Google Style Checkstyle file over
> >>>>> the entire code base but my IntelliJ crashed. Using Maven, I wasn't
> >>>>> able to get a total result displayed but I'm assuming it would be
> >>>>> almost all lines of Flink code that had a violation due to tabs.
> >>>>>
> >>>>> On Mon, Oct 26, 2015 at 6:56 PM, Suneel Marthi <
> >> [hidden email]
> >>>>
> >>>>> wrote:
> >>>>>> 2 spaces is the convention that's followed on Mahout and Oryx.
> >>>>>>
> >>>>>> On Mon, Oct 26, 2015 at 1:42 PM, Till Rohrmann <
> [hidden email]
> >>>
> >>>>> wrote:
> >>>>>>
> >>>>>>> Concerning question 2 Tabs vs. Spaces, in case of spaces we would
> >> have
> >>>>> to
> >>>>>>> decide on the number of spaces, too. The Google Java style says to
> >> use
> >>>>> a 2
> >>>>>>> space indentation, which is in my opinion sufficient to distinguish
> >>>>>>> different indentations levels from each other. Furthermore, it
> would
> >>>>> save
> >>>>>>> some space.
> >>>>>>>
> >>>>>>> I would not vote -1 if we keep tabs.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> On Sat, Oct 24, 2015 at 8:33 PM, Henry Saputra <
> >>> [hidden email]
> >>>>>>
> >>>>>>> wrote:
> >>>>>>>
> >>>>>>>> +1 for adding restriction for Javadoc at least at the header of
> >>> public
> >>>>>>>> classes and methods.
> >>>>>>>>
> >>>>>>>> We did the exercise in Twill and seemed to work pretty well.
> >>>>>>>>
> >>>>>>>> On Fri, Oct 23, 2015 at 1:34 AM, Maximilian Michels <
> >> [hidden email]>
> >>>>>>>> wrote:
> >>>>>>>>> I don't think lazily adding comments will work. However, I'm fine
> >>>>> with
> >>>>>>>>> adding all the checkstyle rules one module at a time (with a jira
> >>>>>>>>> issue to keep track of the modules already converted). It's not
> >>>>> going
> >>>>>>>>> to happen that we lazily add comments because that's the reason
> >> why
> >>>>>>>>> comments are missing in the first place...
> >>>>>>>>>
> >>>>>>>>> On Fri, Oct 23, 2015 at 12:05 AM, Henry Saputra <
> >>>>>>> [hidden email]>
> >>>>>>>> wrote:
> >>>>>>>>>> Could we make certain rules to give warning instead of error?
> >>>>>>>>>>
> >>>>>>>>>> This would allow us to cherry-pick certain rules we would like
> >>>>> people
> >>>>>>>>>> to follow but not strictly enforced.
> >>>>>>>>>>
> >>>>>>>>>> - Henry
> >>>>>>>>>>
> >>>>>>>>>> On Thu, Oct 22, 2015 at 9:20 AM, Stephan Ewen <[hidden email]
> >
> >>>>>>> wrote:
> >>>>>>>>>>> I don't think a "let add comments to everything" effort gives
> us
> >>>>> good
> >>>>>>>>>>> comments, actually. It just gives us checkmark comments that
> >> make
> >>>>> the
> >>>>>>>> rules
> >>>>>>>>>>> pass.
> >>>>>>>>>>>
> >>>>>>>>>>> On Thu, Oct 22, 2015 at 3:29 PM, Fabian Hueske <
> >> [hidden email]
> >>>>>>
> >>>>>>>> wrote:
> >>>>>>>>>>>
> >>>>>>>>>>>> Sure, I don't expect it to be free.
> >>>>>>>>>>>> But everybody should be aware of the cost of adding this code
> >>>>> style,
> >>>>>>>> i.e.,
> >>>>>>>>>>>> spending a huge amount of time on reformatting and documenting
> >>>>> code.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Alternatively, we could drop the JavaDocs rule and make the
> >>>>>>> transition
> >>>>>>>>>>>> significantly cheaper.
> >>>>>>>>>>>>
> >>>>>>>>>>>> 2015-10-22 15:24 GMT+02:00 Till Rohrmann <
> [hidden email]
> >>> :
> >>>>>>>>>>>>
> >>>>>>>>>>>>> There ain’t no such thing as a free lunch and code style.
> >>>>>>>>>>>>>
> >>>>>>>>>>>>> On Thu, Oct 22, 2015 at 3:13 PM, Maximilian Michels <
> >>>>>>> [hidden email]
> >>>>>>>>>
> >>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>
> >>>>>>>>>>>>>> I think we have to document all these classes. Code Style
> >>>>>>> doesn't
> >>>>>>>> come
> >>>>>>>>>>>>>> for free :)
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>> On Thu, Oct 22, 2015 at 3:09 PM, Fabian Hueske <
> >>>>>>> [hidden email]
> >>>>>>>>>
> >>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>> Any ideas how to deal with the mandatory JavaDoc rule for
> >>>>>>>> existing
> >>>>>>>>>>>>> code?
> >>>>>>>>>>>>>>> Just adding empty headers to make the checkstyle pass or
> >>>>>>> start a
> >>>>>>>>>>>>> serious
> >>>>>>>>>>>>>>> effort to add the missing docs?
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>> 2015-10-21 13:31 GMT+02:00 Matthias J. Sax <
> >>>>> [hidden email]
> >>>>>>>> :
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> Agreed. That's the reason why I am in favor of using
> >>>>> vanilla
> >>>>>>>> Google
> >>>>>>>>>>>>> code
> >>>>>>>>>>>>>>>> style.
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>> On 10/21/2015 12:31 PM, Stephan Ewen wrote:
> >>>>>>>>>>>>>>>>> We started out originally with mixed tab/spaces, but it
> >>>>>>>> ended up
> >>>>>>>>>>>>> with
> >>>>>>>>>>>>>>>>> people mixing spaces and tabs arbitrarily, and there is
> >>>>>>>> little way
> >>>>>>>>>>>>> to
> >>>>>>>>>>>>>>>>> enforce Matthias' specific suggestion via checkstyle.
> >>>>>>>>>>>>>>>>> That's why we dropped spaces alltogether...
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 12:03 PM, Gyula Fóra <
> >>>>>>>>>>>> [hidden email]>
> >>>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> I think the nice thing about a common codestyle is that
> >>>>>>>> everyone
> >>>>>>>>>>>>> can
> >>>>>>>>>>>>>> set
> >>>>>>>>>>>>>>>>>> the template in the IDE and use the formatting
> >>>>> commands.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Matthias's suggestion makes this practically
> >>>>> impossible so
> >>>>>>>> -1 for
> >>>>>>>>>>>>>> mixed
> >>>>>>>>>>>>>>>>>> tabs/spaces from my side.
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>> Matthias J. Sax <[hidden email]> ezt írta (időpont:
> >>>>>>>> 2015. okt.
> >>>>>>>>>>>>>> 21.,
> >>>>>>>>>>>>>>>> Sze,
> >>>>>>>>>>>>>>>>>> 11:46):
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> I actually like tabs a lot, however, in a "mixed"
> >>>>> style
> >>>>>>>> together
> >>>>>>>>>>>>>> with
> >>>>>>>>>>>>>>>>>>> spaces. Example:
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>        myVar.callMethod(param1, // many more
> >>>>>>>>>>>>>>>>>>>        .................paramX); // the dots mark
> >>>>> space
> >>>>>>>>>>>> indention
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> indenting "paramX" with tabs does not give nice
> >>>>> aliment.
> >>>>>>>> Not
> >>>>>>>>>>>> sure
> >>>>>>>>>>>>> if
> >>>>>>>>>>>>>>>>>>> this would be a feasible compromise to keeps tabs in
> >>>>>>>> general,
> >>>>>>>>>>>> but
> >>>>>>>>>>>>>> use
> >>>>>>>>>>>>>>>>>>> space for cases as above.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> If this in no feasible compromise, I would prefer
> >>>>> space
> >>>>>>> to
> >>>>>>>> get
> >>>>>>>>>>>> the
> >>>>>>>>>>>>>>>>>>> correct indention in examples as above. Even if this
> >>>>>>>> result in a
> >>>>>>>>>>>>>>>>>>> complete reformatting of the whole code.
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> Why this? Everybody can set this in it's IDE/editor as
> >>>>>>>> he/she
> >>>>>>>>>>>>>> wishes...
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
> >>>>>>> length
> >>>>>>>>>>>>> relative
> >>>>>>>>>>>>>> to
> >>>>>>>>>>>>>>>> a
> >>>>>>>>>>>>>>>>>>> tab
> >>>>>>>>>>>>>>>>>>>>> size (like 4).
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> -Matthias
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> On 10/21/2015 11:06 AM, Ufuk Celebi wrote:
> >>>>>>>>>>>>>>>>>>>> To summarize up to this point:
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> - All are in favour of Google check style (with the
> >>>>>>>> following
> >>>>>>>>>>>>>> possible
> >>>>>>>>>>>>>>>>>>>> exceptions)
> >>>>>>>>>>>>>>>>>>>> - Proposed exceptions so far:
> >>>>>>>>>>>>>>>>>>>>  * Specific line length 100 vs. 120 characters
> >>>>>>>>>>>>>>>>>>>>  * Keep tabs instead converting to spaces (this
> >>>>> would
> >>>>>>>>>>>> translate
> >>>>>>>>>>>>> to
> >>>>>>>>>>>>>>>>>>>> skipping/coming up with some indentation rules as
> >>>>> well)
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
> >>>>> length
> >>>>>>>>>>>> relative
> >>>>>>>>>>>>>> to a
> >>>>>>>>>>>>>>>>>>> tab
> >>>>>>>>>>>>>>>>>>>> size (like 4).
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> Let’s keep the discussion going a little longer. I
> >>>>> think
> >>>>>>>> it has
> >>>>>>>>>>>>>>>>>> proceeded
> >>>>>>>>>>>>>>>>>>>> in a very reasonable manner so far. Thanks for this!
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> – Ufuk
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 10:29 AM, Fabian Hueske <
> >>>>>>>>>>>>> [hidden email]
> >>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Thanks Max for checking the modifications by the
> >>>>> Google
> >>>>>>>> code
> >>>>>>>>>>>>>> style.
> >>>>>>>>>>>>>>>>>>>>> It is very good to know, that the impact on the code
> >>>>>>> base
> >>>>>>>>>>>> would
> >>>>>>>>>>>>>> not
> >>>>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>>> too
> >>>>>>>>>>>>>>>>>>>>> massive. If the Google code style would have touched
> >>>>>>>> almost
> >>>>>>>>>>>>> every
> >>>>>>>>>>>>>>>>>> line,
> >>>>>>>>>>>>>>>>>>> I
> >>>>>>>>>>>>>>>>>>>>> would have been in favor of converting to spaces.
> >>>>>>>> However,
> >>>>>>>>>>>> your
> >>>>>>>>>>>>>>>>>>> assessment
> >>>>>>>>>>>>>>>>>>>>> is a strong argument to continue with tabs, IMO.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Regarding the line length limit, I personally find
> >>>>> 100
> >>>>>>>> chars
> >>>>>>>>>>>> too
> >>>>>>>>>>>>>>>>>> narrow
> >>>>>>>>>>>>>>>>>>> but
> >>>>>>>>>>>>>>>>>>>>> would be +1 for having a limit.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> +1 for discussing the Scala style in a separate
> >>>>> thread.
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> Fabian
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>> 2015-10-20 18:12 GMT+02:00 Maximilian Michels <
> >>>>>>>> [hidden email]
> >>>>>>>>>>>>> :
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> I'm a little less excited about this. You might
> >>>>> not be
> >>>>>>>> aware
> >>>>>>>>>>>>> but,
> >>>>>>>>>>>>>>>> for
> >>>>>>>>>>>>>>>>>>>>>> a large portion of the source code, we already
> >>>>> follow
> >>>>>>>> the
> >>>>>>>>>>>>> Google
> >>>>>>>>>>>>>>>>>> style
> >>>>>>>>>>>>>>>>>>>>>> guide. The main changes will be tabs->spaces and
> >>>>>>> 80/100
> >>>>>>>>>>>>>> characters
> >>>>>>>>>>>>>>>>>>>>>> line limit.
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> Out of curiosity, I ran the official Google Style
> >>>>>>>> Checkstyle
> >>>>>>>>>>>>>>>>>>>>>> configuration to confirm my suspicion:
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>
> >>>
> >>
> https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml
> >>>>>>>>>>>>>>>>>>>>>> The changes are very little if we turn off line
> >>>>> length
> >>>>>>>> limit
> >>>>>>>>>>>>> and
> >>>>>>>>>>>>>>>>>>>>>> tabs-to-spaces conversion.
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> There are some things I really like about the
> >>>>> Google
> >>>>>>>> style,
> >>>>>>>>>>>>> e.g.
> >>>>>>>>>>>>>>>>>> every
> >>>>>>>>>>>>>>>>>>>>>> class has to have a JavaDoc and spaces after
> >>>>> keywords
> >>>>>>>> (can't
> >>>>>>>>>>>>>> stand
> >>>>>>>>>>>>>>>> if
> >>>>>>>>>>>>>>>>>>>>>> there aren't any). I'm not sure if we should change
> >>>>>>>> tabs to
> >>>>>>>>>>>>>> spaces,
> >>>>>>>>>>>>>>>>>>>>>> because it means touching almost every single line
> >>>>> of
> >>>>>>>> code.
> >>>>>>>>>>>>>> However,
> >>>>>>>>>>>>>>>>>>>>>> if we keep the tabs, we cannot make use of the
> >>>>>>> different
> >>>>>>>>>>>>>> indention
> >>>>>>>>>>>>>>>>>> for
> >>>>>>>>>>>>>>>>>>>>>> case statements or wrapped lines...maybe that's a
> >>>>>>>> compromise
> >>>>>>>>>>>> we
> >>>>>>>>>>>>>> can
> >>>>>>>>>>>>>>>>>>>>>> live with.
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> If we introduce the Google Style for Java, will we
> >>>>>>> also
> >>>>>>>>>>>> impose
> >>>>>>>>>>>>> a
> >>>>>>>>>>>>>>>>>>>>>> stricter style check for Scala? IMHO the line
> >>>>> length
> >>>>>>> is
> >>>>>>>> the
> >>>>>>>>>>>>>>>> strictest
> >>>>>>>>>>>>>>>>>>>>>> part of the Scala Checkstyle.
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>> On Tue, Oct 20, 2015 at 4:14 PM, Henry Saputra <
> >>>>>>>>>>>>>>>>>>> [hidden email]>
> >>>>>>>>>>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>>>>>> 1) yes. Been dancing this issue for a while. Let's
> >>>>>>>> pull the
> >>>>>>>>>>>>>>>> trigger.
> >>>>>>>>>>>>>>>>>>>>> Did
> >>>>>>>>>>>>>>>>>>>>>>> the exercise with Tachyon while back and did help
> >>>>>>>>>>>> readability
> >>>>>>>>>>>>>> and
> >>>>>>>>>>>>>>>>>>>>>>> homogeneity of code.
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>> 2) +1 for Google Java style with documented
> >>>>>>> exceptions
> >>>>>>>> and
> >>>>>>>>>>>>>>>>>> explanation
> >>>>>>>>>>>>>>>>>>>>> on
> >>>>>>>>>>>>>>>>>>>>>>> why.
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>> On Tuesday, October 20, 2015, Ufuk Celebi <
> >>>>>>>> [hidden email]>
> >>>>>>>>>>>>>> wrote:
> >>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> DISCLAIMER: This is not my personal idea, but a
> >>>>>>>> community
> >>>>>>>>>>>>>>>>>> discussion
> >>>>>>>>>>>>>>>>>>>>>> from
> >>>>>>>>>>>>>>>>>>>>>>>> some time ago. Don't kill the messenger.
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> In March we were discussing issues with
> >>>>>>> heterogeneity
> >>>>>>>> of
> >>>>>>>>>>>> the
> >>>>>>>>>>>>>> code
> >>>>>>>>>>>>>>>>>>> [1].
> >>>>>>>>>>>>>>>>>>>>>> The
> >>>>>>>>>>>>>>>>>>>>>>>> summary is that we had a consensus to enforce a
> >>>>>>>> stricter
> >>>>>>>>>>>> code
> >>>>>>>>>>>>>>>> style
> >>>>>>>>>>>>>>>>>>> on
> >>>>>>>>>>>>>>>>>>>>>> our
> >>>>>>>>>>>>>>>>>>>>>>>> Java code base in order to make it easier to
> >>>>> switch
> >>>>>>>> between
> >>>>>>>>>>>>>>>>>> projects
> >>>>>>>>>>>>>>>>>>>>>> and to
> >>>>>>>>>>>>>>>>>>>>>>>> have clear rules for new contributions. The main
> >>>>>>>> proposal
> >>>>>>>>>>>> in
> >>>>>>>>>>>>>> the
> >>>>>>>>>>>>>>>>>> last
> >>>>>>>>>>>>>>>>>>>>>>>> discussion was to go with Google's Java code
> >>>>> style.
> >>>>>>>> Not all
> >>>>>>>>>>>>>> were
> >>>>>>>>>>>>>>>>>>> fully
> >>>>>>>>>>>>>>>>>>>>>>>> satisfied with this, but still everyone agreed on
> >>>>>>>> some kind
> >>>>>>>>>>>>> of
> >>>>>>>>>>>>>>>>>> style.
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> I think the upcoming 0.10 release is a good
> >>>>> point to
> >>>>>>>>>>>> finally
> >>>>>>>>>>>>> go
> >>>>>>>>>>>>>>>>>>>>> through
> >>>>>>>>>>>>>>>>>>>>>>>> with these changes (right after the
> >>>>>>>> release/branch-off).
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> I propose to go with Google's Java code style
> >>>>> [2] as
> >>>>>>>>>>>> proposed
> >>>>>>>>>>>>>>>>>>> earlier.
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> PROs:
> >>>>>>>>>>>>>>>>>>>>>>>> - Clear style guide available
> >>>>>>>>>>>>>>>>>>>>>>>> - Tooling like checkstyle rules, IDE plugins
> >>>>> already
> >>>>>>>>>>>>> available
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> CONs:
> >>>>>>>>>>>>>>>>>>>>>>>> - Fully breaks our current style
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> The main problem with this will be open pull
> >>>>>>> requests,
> >>>>>>>>>>>> which
> >>>>>>>>>>>>>> will
> >>>>>>>>>>>>>>>>>> be
> >>>>>>>>>>>>>>>>>>>>>> harder
> >>>>>>>>>>>>>>>>>>>>>>>> to merge after all the changes. On the other
> >>>>> hand,
> >>>>>>>> should
> >>>>>>>>>>>>> pull
> >>>>>>>>>>>>>>>>>>>>> requests
> >>>>>>>>>>>>>>>>>>>>>>>> that have been open for a long time block this?
> >>>>> Most
> >>>>>>>> of the
> >>>>>>>>>>>>>>>>>> important
> >>>>>>>>>>>>>>>>>>>>>>>> changes will be merged for the release anyways. I
> >>>>>>>> think in
> >>>>>>>>>>>>> the
> >>>>>>>>>>>>>>>> long
> >>>>>>>>>>>>>>>>>>>>> run
> >>>>>>>>>>>>>>>>>>>>>> we
> >>>>>>>>>>>>>>>>>>>>>>>> will gain more than we loose by this (more
> >>>>>>> homogenous
> >>>>>>>> code,
> >>>>>>>>>>>>>> clear
> >>>>>>>>>>>>>>>>>>>>>> rules).
> >>>>>>>>>>>>>>>>>>>>>>>> And it is questionable whether we will ever be
> >>>>> able
> >>>>>>>> to do
> >>>>>>>>>>>>> such
> >>>>>>>>>>>>>> a
> >>>>>>>>>>>>>>>>>>>>> change
> >>>>>>>>>>>>>>>>>>>>>> in
> >>>>>>>>>>>>>>>>>>>>>>>> the future if we cannot do it now. The project
> >>>>> will
> >>>>>>>> most
> >>>>>>>>>>>>> likely
> >>>>>>>>>>>>>>>>>> grow
> >>>>>>>>>>>>>>>>>>>>> and
> >>>>>>>>>>>>>>>>>>>>>>>> attract more contributors, at which point it
> >>>>> will be
> >>>>>>>> even
> >>>>>>>>>>>>>> harder
> >>>>>>>>>>>>>>>> to
> >>>>>>>>>>>>>>>>>>>>> do.
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> Please make sure to answer the following points
> >>>>> in
> >>>>>>> the
> >>>>>>>>>>>>>> discussion:
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> 1) Are you (still) in favour of enforcing
> >>>>> stricter
> >>>>>>>> rules on
> >>>>>>>>>>>>> the
> >>>>>>>>>>>>>>>>>> Java
> >>>>>>>>>>>>>>>>>>>>>>>> codebase?
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> 2) If yes, would you be OK with the Google's Java
> >>>>>>> code
> >>>>>>>>>>>> style?
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> – Ufuk
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> [1]
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>
> >>>
> >>
> http://mail-archives.apache.org/mod_mbox/flink-dev/201503.mbox/%3cCANC1h_voN0B5omNWZxcHTyzwHAKeGhbZVQUyK7S9o2A36b891Q@...%3e
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>>> [2]
> >>>>>>>> https://google.github.io/styleguide/javaguide.html
> >>>>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>>>
> >>>>>>>>>>>>>>
> >>>>>>>>>>>>>
> >>>>>>>>>>>>
> >>>>>>>>
> >>>>>>>
> >>>>>
> >>>>
> >>>
> >>>
> >>
>
>

[mxm]

Thanks for wrapping up the discussion, Fabian!

The tab size is adjustable in all the viewers I know of, e.g. DataSet
with tab size of 2 on GitHub:
https://github.com/apache/flink/blob/master/flink-java/src/main/java/org/apache/flink/api/java/DataSet.java?ts=2
You can even even use "less -x2 Sourcefile.java" to adjust the tab
size. Generally, developers should know about these things, so I don't
think tabs are a real issue.

The more important consideration in the tabs vs spaces debate seems to
be the preservation of the most recent Git line history. Spaces
destroy the most recent line history entirely. Tabs let us at least
keep parts of the most recent line history. If we care about that, we
should keep tabs.

On Tue, Nov 10, 2015 at 1:39 AM, Alexander Alexandrov
<[hidden email]> wrote:

> I wouldn't stop with GitHub - the main benefit for spaces is that the code
> looks the same on all viewers because it does not depend on a user-specific
> parameter (the size of the tab).
>
> 2015-11-09 14:02 GMT+01:00 Ufuk Celebi <[hidden email]>:
>
>> Minor thing in favour of spaces: Reviewability on GitHub is improved (they
>> use 8 spaces for tabs and line length of 120, which often results in too
>> long lines).
>>
>> > On 09 Nov 2015, at 13:53, Fabian Hueske <[hidden email]> wrote:
>> >
>> > I don't see other benefits except maybe being closer to the vanilla
>> Google
>> > style.
>> >
>> > 2015-11-02 20:46 GMT+01:00 Stephan Ewen <[hidden email]>:
>> >
>> >> I think by now virtually everyone prefers spaces if it came for free,
>> so it
>> >> is a matter of making an educated decision about the cost/benefit
>> >> tradeoffs.
>> >>
>> >> What are the benefits of spaces in the style other than people liking
>> the
>> >> looks of space-formatted code better (aesthetics, schmaesthetics ;-) )
>> >>
>> >>
>> >> On Mon, Nov 2, 2015 at 5:38 AM, Matthias J. Sax <[hidden email]>
>> wrote:
>> >>
>> >>> Thanks for the summary Fabian.
>> >>>
>> >>> Maybe we should have kind of a vote about this. No classical Apache
>> vote
>> >>> though, but voting for different options (so only +1), and the option
>> >>> with the highest score wins? (Not sure if this is possible to do...)
>> >>>
>> >>> About spaced vs. tabs:
>> >>>> "AFAIR, nobody said to have a personal preferences of tabs over
>> >> spaces."
>> >>>
>> >>> I think this is wrong. If I am correct, Till and myself would prefer
>> >>> spaces (but non of us is super strict about this -- we could both live
>> >>> with tabs too).
>> >>>
>> >>> -Matthias
>> >>>
>> >>> On 11/02/2015 12:14 PM, Fabian Hueske wrote:
>> >>>> OK, I'll try to summarize the discussion so far (please correct me if
>> I
>> >>> got
>> >>>> something wrong):
>> >>>>
>> >>>> Everybody is in favor of adding a stricter code style based on the
>> >> Google
>> >>>> Java code style.
>> >>>> Main points of discussion are:
>> >>>> 1) Line length
>> >>>> 2) JavaDocs
>> >>>> 3) Tabs vs. Spaces
>> >>>>
>> >>>> -- Line length
>> >>>> Issue:
>> >>>> Google code style demands 80 or 100 chars line length limit.
>> >>>> Some people find this too narrow.
>> >>>>
>> >>>> Discussion so far:
>> >>>> Nobody objected against a limit of 120 chars, AFAIR.
>> >>>>
>> >>>> -- JavaDocs
>> >>>> Issue:
>> >>>> Google code style says "At the *minimum*, Javadoc is present for every
>> >>>> public class, and every public or protected member of such a class,
>> >> with
>> >>> a
>> >>>> few exceptions noted below." Exceptions are self-explanatory methods
>> >> like
>> >>>> getters and setters and overwritten method.
>> >>>> Significant parts of the Flink code base do not comply with this
>> >>>> requirement. It would be a huge effort to add the corresponding code
>> >>>> documentation.
>> >>>>
>> >>>> Discussion so far:
>> >>>> Disable JavaDoc checks when adding the code style and opening JIRAs
>> for
>> >>>> adding JavaDocs on a per Maven module level (with potentially
>> >> subissues)
>> >>>> with target dates. Once a module complies to the rule, the JavaDoc
>> >> check
>> >>> is
>> >>>> enabled in the checkstyle.
>> >>>>
>> >>>> -- Tabs vs. Spaces
>> >>>> Issue:
>> >>>> The Google code style requires two spaces for indention. The Java code
>> >>> base
>> >>>> of Flink uses tabs. Moving from tabs to spaces would touch every line
>> >> of
>> >>>> Java code and therefore might make the tracking of changes in the past
>> >>> much
>> >>>> harder.
>> >>>> Max provided some numbers for applying the Google code style on the
>> >>> current
>> >>>> code base: The style checker found 28k violations (possibly multiple
>> >> ones
>> >>>> per LOC) on 121k LOC of Java code in 1601 out of 3251 Java classes. So
>> >>>> Google code style without spaces would touch every second file and
>> >> about
>> >>>> every 4th line of code. The question I have, would it be easier to
>> >> track
>> >>>> history with a commit that touches 1/2 (or 1/4) of the code base
>> >> compared
>> >>>> to one that touches everything.
>> >>>>
>> >>>> Discussion so far:
>> >>>> AFAIR, nobody said to have a personal preferences of tabs over spaces.
>> >>>> However, some people raised concerns that the implied changes of
>> moving
>> >>> the
>> >>>> code base from tabs to spaces would be too massive and the "benefits"
>> >>> would
>> >>>> not justify the "cost" of the change.
>> >>>> I think, this is the main point of discussion, right now.
>> >>>>
>> >>>> If we want to come to a conclusion, we should not let this discussion
>> >>> fall
>> >>>> asleep (as happened a few times in the past).
>> >>>>
>> >>>> Does anybody NOT agree with the "solutions" for line length and
>> >> JavaDocs,
>> >>>> i.e., 120 chars and "lazy" adding of JavaDocs with JIRA tracking, or
>> >> has
>> >>>> another proposal?
>> >>>> How can we resolve the Tabs vs. Spaces discussion?
>> >>>>
>> >>>> Cheers, Fabian
>> >>>>
>> >>>>
>> >>>>
>> >>>> 2015-10-30 18:16 GMT+01:00 Maximilian Michels <[hidden email]>:
>> >>>>
>> >>>>> I looked up if the Checkstyle plugin would also support tabs with a
>> >>>>> fixed line length. Indeed, this is possible because a tab can be
>> >>>>> mapped to a fixed number of spaces.
>> >>>>>
>> >>>>> I've modified the default Google Style Checkstyle file. I changed the
>> >>>>> indention to tabs (2 spaces) and increased the line length to 120:
>> >>>>> https://gist.github.com/mxm/2ca4ef7702667c167d10
>> >>>>>
>> >>>>> The scan of the entire Flink project resulted in 27,992 items in 1601
>> >>>>> files. This is roughly corresponds to the number of lines we would
>> >>>>> have to touch to comply with the style rules. Note that, one line may
>> >>>>> contain multiple items. A lot of the items are import statements.
>> >>>>>
>> >>>>> Next, I tried running the vanilla Google Style Checkstyle file over
>> >>>>> the entire code base but my IntelliJ crashed. Using Maven, I wasn't
>> >>>>> able to get a total result displayed but I'm assuming it would be
>> >>>>> almost all lines of Flink code that had a violation due to tabs.
>> >>>>>
>> >>>>> On Mon, Oct 26, 2015 at 6:56 PM, Suneel Marthi <
>> >> [hidden email]
>> >>>>
>> >>>>> wrote:
>> >>>>>> 2 spaces is the convention that's followed on Mahout and Oryx.
>> >>>>>>
>> >>>>>> On Mon, Oct 26, 2015 at 1:42 PM, Till Rohrmann <
>> [hidden email]
>> >>>
>> >>>>> wrote:
>> >>>>>>
>> >>>>>>> Concerning question 2 Tabs vs. Spaces, in case of spaces we would
>> >> have
>> >>>>> to
>> >>>>>>> decide on the number of spaces, too. The Google Java style says to
>> >> use
>> >>>>> a 2
>> >>>>>>> space indentation, which is in my opinion sufficient to distinguish
>> >>>>>>> different indentations levels from each other. Furthermore, it
>> would
>> >>>>> save
>> >>>>>>> some space.
>> >>>>>>>
>> >>>>>>> I would not vote -1 if we keep tabs.
>> >>>>>>>
>> >>>>>>>
>> >>>>>>>
>> >>>>>>> On Sat, Oct 24, 2015 at 8:33 PM, Henry Saputra <
>> >>> [hidden email]
>> >>>>>>
>> >>>>>>> wrote:
>> >>>>>>>
>> >>>>>>>> +1 for adding restriction for Javadoc at least at the header of
>> >>> public
>> >>>>>>>> classes and methods.
>> >>>>>>>>
>> >>>>>>>> We did the exercise in Twill and seemed to work pretty well.
>> >>>>>>>>
>> >>>>>>>> On Fri, Oct 23, 2015 at 1:34 AM, Maximilian Michels <
>> >> [hidden email]>
>> >>>>>>>> wrote:
>> >>>>>>>>> I don't think lazily adding comments will work. However, I'm fine
>> >>>>> with
>> >>>>>>>>> adding all the checkstyle rules one module at a time (with a jira
>> >>>>>>>>> issue to keep track of the modules already converted). It's not
>> >>>>> going
>> >>>>>>>>> to happen that we lazily add comments because that's the reason
>> >> why
>> >>>>>>>>> comments are missing in the first place...
>> >>>>>>>>>
>> >>>>>>>>> On Fri, Oct 23, 2015 at 12:05 AM, Henry Saputra <
>> >>>>>>> [hidden email]>
>> >>>>>>>> wrote:
>> >>>>>>>>>> Could we make certain rules to give warning instead of error?
>> >>>>>>>>>>
>> >>>>>>>>>> This would allow us to cherry-pick certain rules we would like
>> >>>>> people
>> >>>>>>>>>> to follow but not strictly enforced.
>> >>>>>>>>>>
>> >>>>>>>>>> - Henry
>> >>>>>>>>>>
>> >>>>>>>>>> On Thu, Oct 22, 2015 at 9:20 AM, Stephan Ewen <[hidden email]
>> >
>> >>>>>>> wrote:
>> >>>>>>>>>>> I don't think a "let add comments to everything" effort gives
>> us
>> >>>>> good
>> >>>>>>>>>>> comments, actually. It just gives us checkmark comments that
>> >> make
>> >>>>> the
>> >>>>>>>> rules
>> >>>>>>>>>>> pass.
>> >>>>>>>>>>>
>> >>>>>>>>>>> On Thu, Oct 22, 2015 at 3:29 PM, Fabian Hueske <
>> >> [hidden email]
>> >>>>>>
>> >>>>>>>> wrote:
>> >>>>>>>>>>>
>> >>>>>>>>>>>> Sure, I don't expect it to be free.
>> >>>>>>>>>>>> But everybody should be aware of the cost of adding this code
>> >>>>> style,
>> >>>>>>>> i.e.,
>> >>>>>>>>>>>> spending a huge amount of time on reformatting and documenting
>> >>>>> code.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> Alternatively, we could drop the JavaDocs rule and make the
>> >>>>>>> transition
>> >>>>>>>>>>>> significantly cheaper.
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> 2015-10-22 15:24 GMT+02:00 Till Rohrmann <
>> [hidden email]
>> >>> :
>> >>>>>>>>>>>>
>> >>>>>>>>>>>>> There ain’t no such thing as a free lunch and code style.
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>> On Thu, Oct 22, 2015 at 3:13 PM, Maximilian Michels <
>> >>>>>>> [hidden email]
>> >>>>>>>>>
>> >>>>>>>>>>>>> wrote:
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>>> I think we have to document all these classes. Code Style
>> >>>>>>> doesn't
>> >>>>>>>> come
>> >>>>>>>>>>>>>> for free :)
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>> On Thu, Oct 22, 2015 at 3:09 PM, Fabian Hueske <
>> >>>>>>> [hidden email]
>> >>>>>>>>>
>> >>>>>>>>>>>>> wrote:
>> >>>>>>>>>>>>>>> Any ideas how to deal with the mandatory JavaDoc rule for
>> >>>>>>>> existing
>> >>>>>>>>>>>>> code?
>> >>>>>>>>>>>>>>> Just adding empty headers to make the checkstyle pass or
>> >>>>>>> start a
>> >>>>>>>>>>>>> serious
>> >>>>>>>>>>>>>>> effort to add the missing docs?
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>> 2015-10-21 13:31 GMT+02:00 Matthias J. Sax <
>> >>>>> [hidden email]
>> >>>>>>>> :
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> Agreed. That's the reason why I am in favor of using
>> >>>>> vanilla
>> >>>>>>>> Google
>> >>>>>>>>>>>>> code
>> >>>>>>>>>>>>>>>> style.
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>> On 10/21/2015 12:31 PM, Stephan Ewen wrote:
>> >>>>>>>>>>>>>>>>> We started out originally with mixed tab/spaces, but it
>> >>>>>>>> ended up
>> >>>>>>>>>>>>> with
>> >>>>>>>>>>>>>>>>> people mixing spaces and tabs arbitrarily, and there is
>> >>>>>>>> little way
>> >>>>>>>>>>>>> to
>> >>>>>>>>>>>>>>>>> enforce Matthias' specific suggestion via checkstyle.
>> >>>>>>>>>>>>>>>>> That's why we dropped spaces alltogether...
>> >>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 12:03 PM, Gyula Fóra <
>> >>>>>>>>>>>> [hidden email]>
>> >>>>>>>>>>>>>>>> wrote:
>> >>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>> I think the nice thing about a common codestyle is that
>> >>>>>>>> everyone
>> >>>>>>>>>>>>> can
>> >>>>>>>>>>>>>> set
>> >>>>>>>>>>>>>>>>>> the template in the IDE and use the formatting
>> >>>>> commands.
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>> Matthias's suggestion makes this practically
>> >>>>> impossible so
>> >>>>>>>> -1 for
>> >>>>>>>>>>>>>> mixed
>> >>>>>>>>>>>>>>>>>> tabs/spaces from my side.
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>> Matthias J. Sax <[hidden email]> ezt írta (időpont:
>> >>>>>>>> 2015. okt.
>> >>>>>>>>>>>>>> 21.,
>> >>>>>>>>>>>>>>>> Sze,
>> >>>>>>>>>>>>>>>>>> 11:46):
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> I actually like tabs a lot, however, in a "mixed"
>> >>>>> style
>> >>>>>>>> together
>> >>>>>>>>>>>>>> with
>> >>>>>>>>>>>>>>>>>>> spaces. Example:
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>        myVar.callMethod(param1, // many more
>> >>>>>>>>>>>>>>>>>>>        .................paramX); // the dots mark
>> >>>>> space
>> >>>>>>>>>>>> indention
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> indenting "paramX" with tabs does not give nice
>> >>>>> aliment.
>> >>>>>>>> Not
>> >>>>>>>>>>>> sure
>> >>>>>>>>>>>>> if
>> >>>>>>>>>>>>>>>>>>> this would be a feasible compromise to keeps tabs in
>> >>>>>>>> general,
>> >>>>>>>>>>>> but
>> >>>>>>>>>>>>>> use
>> >>>>>>>>>>>>>>>>>>> space for cases as above.
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> If this in no feasible compromise, I would prefer
>> >>>>> space
>> >>>>>>> to
>> >>>>>>>> get
>> >>>>>>>>>>>> the
>> >>>>>>>>>>>>>>>>>>> correct indention in examples as above. Even if this
>> >>>>>>>> result in a
>> >>>>>>>>>>>>>>>>>>> complete reformatting of the whole code.
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> Why this? Everybody can set this in it's IDE/editor as
>> >>>>>>>> he/she
>> >>>>>>>>>>>>>> wishes...
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
>> >>>>>>> length
>> >>>>>>>>>>>>> relative
>> >>>>>>>>>>>>>> to
>> >>>>>>>>>>>>>>>> a
>> >>>>>>>>>>>>>>>>>>> tab
>> >>>>>>>>>>>>>>>>>>>>> size (like 4).
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> -Matthias
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> On 10/21/2015 11:06 AM, Ufuk Celebi wrote:
>> >>>>>>>>>>>>>>>>>>>> To summarize up to this point:
>> >>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>> - All are in favour of Google check style (with the
>> >>>>>>>> following
>> >>>>>>>>>>>>>> possible
>> >>>>>>>>>>>>>>>>>>>> exceptions)
>> >>>>>>>>>>>>>>>>>>>> - Proposed exceptions so far:
>> >>>>>>>>>>>>>>>>>>>>  * Specific line length 100 vs. 120 characters
>> >>>>>>>>>>>>>>>>>>>>  * Keep tabs instead converting to spaces (this
>> >>>>> would
>> >>>>>>>>>>>> translate
>> >>>>>>>>>>>>> to
>> >>>>>>>>>>>>>>>>>>>> skipping/coming up with some indentation rules as
>> >>>>> well)
>> >>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>> If we keep tabs, we will have to specify the line
>> >>>>> length
>> >>>>>>>>>>>> relative
>> >>>>>>>>>>>>>> to a
>> >>>>>>>>>>>>>>>>>>> tab
>> >>>>>>>>>>>>>>>>>>>> size (like 4).
>> >>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>> Let’s keep the discussion going a little longer. I
>> >>>>> think
>> >>>>>>>> it has
>> >>>>>>>>>>>>>>>>>> proceeded
>> >>>>>>>>>>>>>>>>>>>> in a very reasonable manner so far. Thanks for this!
>> >>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>> – Ufuk
>> >>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>> On Wed, Oct 21, 2015 at 10:29 AM, Fabian Hueske <
>> >>>>>>>>>>>>> [hidden email]
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>> wrote:
>> >>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>> Thanks Max for checking the modifications by the
>> >>>>> Google
>> >>>>>>>> code
>> >>>>>>>>>>>>>> style.
>> >>>>>>>>>>>>>>>>>>>>> It is very good to know, that the impact on the code
>> >>>>>>> base
>> >>>>>>>>>>>> would
>> >>>>>>>>>>>>>> not
>> >>>>>>>>>>>>>>>> be
>> >>>>>>>>>>>>>>>>>>> too
>> >>>>>>>>>>>>>>>>>>>>> massive. If the Google code style would have touched
>> >>>>>>>> almost
>> >>>>>>>>>>>>> every
>> >>>>>>>>>>>>>>>>>> line,
>> >>>>>>>>>>>>>>>>>>> I
>> >>>>>>>>>>>>>>>>>>>>> would have been in favor of converting to spaces.
>> >>>>>>>> However,
>> >>>>>>>>>>>> your
>> >>>>>>>>>>>>>>>>>>> assessment
>> >>>>>>>>>>>>>>>>>>>>> is a strong argument to continue with tabs, IMO.
>> >>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>> Regarding the line length limit, I personally find
>> >>>>> 100
>> >>>>>>>> chars
>> >>>>>>>>>>>> too
>> >>>>>>>>>>>>>>>>>> narrow
>> >>>>>>>>>>>>>>>>>>> but
>> >>>>>>>>>>>>>>>>>>>>> would be +1 for having a limit.
>> >>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>> +1 for discussing the Scala style in a separate
>> >>>>> thread.
>> >>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>> Fabian
>> >>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>> 2015-10-20 18:12 GMT+02:00 Maximilian Michels <
>> >>>>>>>> [hidden email]
>> >>>>>>>>>>>>> :
>> >>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>> I'm a little less excited about this. You might
>> >>>>> not be
>> >>>>>>>> aware
>> >>>>>>>>>>>>> but,
>> >>>>>>>>>>>>>>>> for
>> >>>>>>>>>>>>>>>>>>>>>> a large portion of the source code, we already
>> >>>>> follow
>> >>>>>>>> the
>> >>>>>>>>>>>>> Google
>> >>>>>>>>>>>>>>>>>> style
>> >>>>>>>>>>>>>>>>>>>>>> guide. The main changes will be tabs->spaces and
>> >>>>>>> 80/100
>> >>>>>>>>>>>>>> characters
>> >>>>>>>>>>>>>>>>>>>>>> line limit.
>> >>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>> Out of curiosity, I ran the official Google Style
>> >>>>>>>> Checkstyle
>> >>>>>>>>>>>>>>>>>>>>>> configuration to confirm my suspicion:
>> >>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>
>> >>>>>>>
>> >>>>>
>> >>>
>> >>
>> https://github.com/checkstyle/checkstyle/blob/master/src/main/resources/google_checks.xml
>> >>>>>>>>>>>>>>>>>>>>>> The changes are very little if we turn off line
>> >>>>> length
>> >>>>>>>> limit
>> >>>>>>>>>>>>> and
>> >>>>>>>>>>>>>>>>>>>>>> tabs-to-spaces conversion.
>> >>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>> There are some things I really like about the
>> >>>>> Google
>> >>>>>>>> style,
>> >>>>>>>>>>>>> e.g.
>> >>>>>>>>>>>>>>>>>> every
>> >>>>>>>>>>>>>>>>>>>>>> class has to have a JavaDoc and spaces after
>> >>>>> keywords
>> >>>>>>>> (can't
>> >>>>>>>>>>>>>> stand
>> >>>>>>>>>>>>>>>> if
>> >>>>>>>>>>>>>>>>>>>>>> there aren't any). I'm not sure if we should change
>> >>>>>>>> tabs to
>> >>>>>>>>>>>>>> spaces,
>> >>>>>>>>>>>>>>>>>>>>>> because it means touching almost every single line
>> >>>>> of
>> >>>>>>>> code.
>> >>>>>>>>>>>>>> However,
>> >>>>>>>>>>>>>>>>>>>>>> if we keep the tabs, we cannot make use of the
>> >>>>>>> different
>> >>>>>>>>>>>>>> indention
>> >>>>>>>>>>>>>>>>>> for
>> >>>>>>>>>>>>>>>>>>>>>> case statements or wrapped lines...maybe that's a
>> >>>>>>>> compromise
>> >>>>>>>>>>>> we
>> >>>>>>>>>>>>>> can
>> >>>>>>>>>>>>>>>>>>>>>> live with.
>> >>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>> If we introduce the Google Style for Java, will we
>> >>>>>>> also
>> >>>>>>>>>>>> impose
>> >>>>>>>>>>>>> a
>> >>>>>>>>>>>>>>>>>>>>>> stricter style check for Scala? IMHO the line
>> >>>>> length
>> >>>>>>> is
>> >>>>>>>> the
>> >>>>>>>>>>>>>>>> strictest
>> >>>>>>>>>>>>>>>>>>>>>> part of the Scala Checkstyle.
>> >>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>> On Tue, Oct 20, 2015 at 4:14 PM, Henry Saputra <
>> >>>>>>>>>>>>>>>>>>> [hidden email]>
>> >>>>>>>>>>>>>>>>>>>>>> wrote:
>> >>>>>>>>>>>>>>>>>>>>>>> 1) yes. Been dancing this issue for a while. Let's
>> >>>>>>>> pull the
>> >>>>>>>>>>>>>>>> trigger.
>> >>>>>>>>>>>>>>>>>>>>> Did
>> >>>>>>>>>>>>>>>>>>>>>>> the exercise with Tachyon while back and did help
>> >>>>>>>>>>>> readability
>> >>>>>>>>>>>>>> and
>> >>>>>>>>>>>>>>>>>>>>>>> homogeneity of code.
>> >>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>> 2) +1 for Google Java style with documented
>> >>>>>>> exceptions
>> >>>>>>>> and
>> >>>>>>>>>>>>>>>>>> explanation
>> >>>>>>>>>>>>>>>>>>>>> on
>> >>>>>>>>>>>>>>>>>>>>>>> why.
>> >>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>> On Tuesday, October 20, 2015, Ufuk Celebi <
>> >>>>>>>> [hidden email]>
>> >>>>>>>>>>>>>> wrote:
>> >>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> DISCLAIMER: This is not my personal idea, but a
>> >>>>>>>> community
>> >>>>>>>>>>>>>>>>>> discussion
>> >>>>>>>>>>>>>>>>>>>>>> from
>> >>>>>>>>>>>>>>>>>>>>>>>> some time ago. Don't kill the messenger.
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> In March we were discussing issues with
>> >>>>>>> heterogeneity
>> >>>>>>>> of
>> >>>>>>>>>>>> the
>> >>>>>>>>>>>>>> code
>> >>>>>>>>>>>>>>>>>>> [1].
>> >>>>>>>>>>>>>>>>>>>>>> The
>> >>>>>>>>>>>>>>>>>>>>>>>> summary is that we had a consensus to enforce a
>> >>>>>>>> stricter
>> >>>>>>>>>>>> code
>> >>>>>>>>>>>>>>>> style
>> >>>>>>>>>>>>>>>>>>> on
>> >>>>>>>>>>>>>>>>>>>>>> our
>> >>>>>>>>>>>>>>>>>>>>>>>> Java code base in order to make it easier to
>> >>>>> switch
>> >>>>>>>> between
>> >>>>>>>>>>>>>>>>>> projects
>> >>>>>>>>>>>>>>>>>>>>>> and to
>> >>>>>>>>>>>>>>>>>>>>>>>> have clear rules for new contributions. The main
>> >>>>>>>> proposal
>> >>>>>>>>>>>> in
>> >>>>>>>>>>>>>> the
>> >>>>>>>>>>>>>>>>>> last
>> >>>>>>>>>>>>>>>>>>>>>>>> discussion was to go with Google's Java code
>> >>>>> style.
>> >>>>>>>> Not all
>> >>>>>>>>>>>>>> were
>> >>>>>>>>>>>>>>>>>>> fully
>> >>>>>>>>>>>>>>>>>>>>>>>> satisfied with this, but still everyone agreed on
>> >>>>>>>> some kind
>> >>>>>>>>>>>>> of
>> >>>>>>>>>>>>>>>>>> style.
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> I think the upcoming 0.10 release is a good
>> >>>>> point to
>> >>>>>>>>>>>> finally
>> >>>>>>>>>>>>> go
>> >>>>>>>>>>>>>>>>>>>>> through
>> >>>>>>>>>>>>>>>>>>>>>>>> with these changes (right after the
>> >>>>>>>> release/branch-off).
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> I propose to go with Google's Java code style
>> >>>>> [2] as
>> >>>>>>>>>>>> proposed
>> >>>>>>>>>>>>>>>>>>> earlier.
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> PROs:
>> >>>>>>>>>>>>>>>>>>>>>>>> - Clear style guide available
>> >>>>>>>>>>>>>>>>>>>>>>>> - Tooling like checkstyle rules, IDE plugins
>> >>>>> already
>> >>>>>>>>>>>>> available
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> CONs:
>> >>>>>>>>>>>>>>>>>>>>>>>> - Fully breaks our current style
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> The main problem with this will be open pull
>> >>>>>>> requests,
>> >>>>>>>>>>>> which
>> >>>>>>>>>>>>>> will
>> >>>>>>>>>>>>>>>>>> be
>> >>>>>>>>>>>>>>>>>>>>>> harder
>> >>>>>>>>>>>>>>>>>>>>>>>> to merge after all the changes. On the other
>> >>>>> hand,
>> >>>>>>>> should
>> >>>>>>>>>>>>> pull
>> >>>>>>>>>>>>>>>>>>>>> requests
>> >>>>>>>>>>>>>>>>>>>>>>>> that have been open for a long time block this?
>> >>>>> Most
>> >>>>>>>> of the
>> >>>>>>>>>>>>>>>>>> important
>> >>>>>>>>>>>>>>>>>>>>>>>> changes will be merged for the release anyways. I
>> >>>>>>>> think in
>> >>>>>>>>>>>>> the
>> >>>>>>>>>>>>>>>> long
>> >>>>>>>>>>>>>>>>>>>>> run
>> >>>>>>>>>>>>>>>>>>>>>> we
>> >>>>>>>>>>>>>>>>>>>>>>>> will gain more than we loose by this (more
>> >>>>>>> homogenous
>> >>>>>>>> code,
>> >>>>>>>>>>>>>> clear
>> >>>>>>>>>>>>>>>>>>>>>> rules).
>> >>>>>>>>>>>>>>>>>>>>>>>> And it is questionable whether we will ever be
>> >>>>> able
>> >>>>>>>> to do
>> >>>>>>>>>>>>> such
>> >>>>>>>>>>>>>> a
>> >>>>>>>>>>>>>>>>>>>>> change
>> >>>>>>>>>>>>>>>>>>>>>> in
>> >>>>>>>>>>>>>>>>>>>>>>>> the future if we cannot do it now. The project
>> >>>>> will
>> >>>>>>>> most
>> >>>>>>>>>>>>> likely
>> >>>>>>>>>>>>>>>>>> grow
>> >>>>>>>>>>>>>>>>>>>>> and
>> >>>>>>>>>>>>>>>>>>>>>>>> attract more contributors, at which point it
>> >>>>> will be
>> >>>>>>>> even
>> >>>>>>>>>>>>>> harder
>> >>>>>>>>>>>>>>>> to
>> >>>>>>>>>>>>>>>>>>>>> do.
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> Please make sure to answer the following points
>> >>>>> in
>> >>>>>>> the
>> >>>>>>>>>>>>>> discussion:
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> 1) Are you (still) in favour of enforcing
>> >>>>> stricter
>> >>>>>>>> rules on
>> >>>>>>>>>>>>> the
>> >>>>>>>>>>>>>>>>>> Java
>> >>>>>>>>>>>>>>>>>>>>>>>> codebase?
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> 2) If yes, would you be OK with the Google's Java
>> >>>>>>> code
>> >>>>>>>>>>>> style?
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> – Ufuk
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> [1]
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>
>> >>>>>>>
>> >>>>>
>> >>>
>> >>
>> http://mail-archives.apache.org/mod_mbox/flink-dev/201503.mbox/%3cCANC1h_voN0B5omNWZxcHTyzwHAKeGhbZVQUyK7S9o2A36b891Q@...%3e
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>>> [2]
>> >>>>>>>> https://google.github.io/styleguide/javaguide.html
>> >>>>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>
>> >>>>>>>
>> >>>>>
>> >>>>
>> >>>
>> >>>
>> >>
>>
>>