PRESUBMIT: Add check for UNIT_TEST use in .cc files.

PRESUBMIT: Add check for UNIT_TEST use in .cc files.

Copy of Chromium's check in
https://cs.chromium.org/chromium/src/PRESUBMIT.py?rcl=22f522e10dd7a816ec45547fd35a6fa0356b3d21&l=416

BUG=None
NOTRY=True

[kjellander_webrtc, 2017-02-20 07:24:05]

kjellander@webrtc.org changed reviewers:
+ kwiberg@webrtc.org

[kwiberg-webrtc, 2017-02-20 08:44:46]

Good idea, but some nits.

And also, do we have any other preprocessor symbols that should be banned from
.cc files for the same reason?

https://codereview.webrtc.org/2703173002/diff/1/PRESUBMIT.py
File PRESUBMIT.py (right):

https://codereview.webrtc.org/2703173002/diff/1/PRESUBMIT.py#newcode173
PRESUBMIT.py:173: """Checks to make sure no source files use UNIT_TEST."""
Either this doc string or the error message below should probably explain why
UNIT_TEST must only be used in headers. (Because it's set by a whatsitsname gn
rule, it'll be set in a lot of headers without being set in their .cc files, so
any use in a .cc file is very very likely to be a bug.)

https://codereview.webrtc.org/2703173002/diff/1/PRESUBMIT.py#newcode176
PRESUBMIT.py:176: if not f.LocalPath().endswith(('.cc', '.mm')):
It would seem safer to have a whitelist of file types where UNIT_TEST is
allowed. Case in point: .c is missing from this list...

https://codereview.webrtc.org/2703173002/diff/1/PRESUBMIT.py#newcode180
PRESUBMIT.py:180: if 'UNIT_TEST ' in line or line.endswith('UNIT_TEST'):
Use re to search the line for "\bUNIT_TEST\b"? That way you won't catch
unrelated symbols whose only crime is a bad ending.

That is,

  unit_test_regexp = re.compile(r'\bUNIT_TEST\b')

first thing in the function, and

  if unit_test_regexp.search(line):

on this line.

[kjellander_webrtc, 2017-05-11 11:37:48]

hmm, now I don't remember why I even created this CL.
I cannot find anything by looking at the old Chromium commits either:
https://chromiumcodereview.appspot.com/10572054

I'll just close this instead.

[kjellander_webrtc, 2017-05-11 11:37:55]

Description was changed from

==========
PRESUBMIT: Add check for UNIT_TEST use in .cc files.

Copy of Chromium's check in
https://cs.chromium.org/chromium/src/PRESUBMIT.py?rcl=22f522e10dd7a816ec45547...

BUG=None
NOTRY=True
==========

to

==========
PRESUBMIT: Add check for UNIT_TEST use in .cc files.

Copy of Chromium's check in
https://cs.chromium.org/chromium/src/PRESUBMIT.py?rcl=22f522e10dd7a816ec45547...

BUG=None
NOTRY=True
==========

[kwiberg-webrtc, 2017-05-11 12:27:06]

On 2017/05/11 11:37:48, kjellander_webrtc wrote:
> hmm, now I don't remember why I even created this CL.
> I cannot find anything by looking at the old Chromium commits either:
> https://chromiumcodereview.appspot.com/10572054
> 
> I'll just close this instead.

IIRC, the preprocessor symbol UNIT_TEST is defined when compiling unit tests but
not otherwise, and it's not safe to make use of it in .cc files because... I
think it might be that UNIT_TEST is set only for the compilation units where we
compile *_unittest.cc. So in .cc files, UNIT_TEST is either always set or always
unset.