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From Vincent Hennebert <vhenneb...@gmail.com>
Subject Checkstyle, Reloaded
Date Fri, 03 Feb 2012 17:45:09 GMT
Hi All,

it is well-known that people are not happy with the Checkstyle file we
have in FOP. And there’s no point enforcing the application of
Checkstyle rules if we don’t agree with them in the first place.

I’ve finally taken on me to create a new Checkstyle file that follows
modern development practices. I’ve been testing it on my own projects
for a few months now and I’m happy with it, so I’d like to share it with
the community. The idea is that once we’ve reached consensus on the
Checkstyle rules we want to apply, we could set up a no warning policy
and enforce it by running Checkstyle in CI.

I’m also taking this as an opportunity to propose that we adopt a common
Checkstyle policy to all the sub-projects of XML Graphics. So once we’ve
agreed on a set of rules we would apply them to FOP and XGC immediately,
and eventually also to Batik, and keep them in sync.

We would also apply the rules to the test files as well as the main
code. Tests are as important as the actual code and there is no reason
why they shouldn’t be checked.

It is likely that the current code will not be compliant with the new
rules. However, most of them are really just about the syntax, so
I believe it should be fairly straightforward to make the code at least
90% compliant just by applying Eclipse’s command-line code formatter.

Please find the Checkstyle file attached. It is based on Checkstyle 5.5
and basically follows Sun’s recommendations for Java styling with a few
adaptations. What’s noteworthy is the following:

• Removed checks for Javadoc. What we want is quality Javadoc, and that
  is not something that Checkstyle can check. Having Javadoc checks is
  counter-productive as it forces us to put {@inheritDoc} everywhere, or
  to create truly useless doc like the following:
   * Returns the thing.
   * @return the thing
  public Thing getThing() {
      return thing;
  This is just clutter really. I think it should be left to peer review
  to check whether a Javadoc comment is properly written, or whether the
  lack thereof is justified. There’s an excellent blog entry from
  Torsten Curdt about this:
• Removed check for file and method lengths. I don’t think it makes
  sense to define a maximum size for files and methods. Sometimes
  a 10-line method is way too big, sometimes it makes sense to have it
  reach 20 lines. Same for files: it’s ok to reach 1000 lines if the
  class contains several inner classes. If it doesn’t, then it’s
  probably too big. I don’t think there is any definite figure we can
  agree on and blindly follow, so I think sizes should be left to peer
• However, I left the check for maximum line length because unreasonably
  long lines make the code hard to follow. I increased it to 110
  though to follow the evolution of monitor sizes. But as Peter
  suggested me, we probably want to keep it low in order to make
  side-by-side comparison easy.
• I added a check for the order of imports; this is to reduce noise in
  diffs when committing. I think most of us have configured their IDE to
  automatically organise imports when saving changes to a file. This is
  a great feature because it allows to keep the list of imports
  up-to-date. But in order to avoid constant back and forth changes when
  different committers change the same file, I think it makes sense that
  we all have the same configuration. I modeled this list after
  Jeremias’ one, that I progressively inferred from his commits.

Please let me know what you think. I’m inclined to follow lazy consensus
on this, and apply the proposed changes if nobody has objected within
2 weeks. If anybody feels that a formal vote is necessary, feel free to
say so.


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