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

PRESUBMIT.py

 # Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import json
 import os
@@ skipping 151 matching lines @@
 
   if len(files):
     return [output_api.PresubmitError(
         'Do not #include <iostream> in header files, since it inserts static ' +
         'initialization into every file including the header. Instead, ' +
         '#include <ostream>. See http://crbug.com/94794',
         files)]
   return []
 
 
+def _CheckNoUNIT_TESTInSourceFiles(input_api, output_api):
+  """Checks to make sure no source files use UNIT_TEST."""

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

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.)

+  problems = []
+  for f in input_api.AffectedFiles():
+    if not f.LocalPath().endswith(('.cc', '.mm')):

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

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...

+      continue
+
+    for line_num, line in f.ChangedContents():
+      if 'UNIT_TEST ' in line or line.endswith('UNIT_TEST'):

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

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.

+        problems.append('    %s:%d' % (f.LocalPath(), line_num))
+
+  if not problems:
+    return []
+  return [output_api.PresubmitPromptWarning('UNIT_TEST is only for headers.\n' +
+      '\n'.join(problems))]
+
+
 def _CheckNoFRIEND_TEST(input_api, output_api):
   """Make sure that gtest's FRIEND_TEST() macro is not used, the
   FRIEND_TEST_ALL_PREFIXES() macro from testsupport/gtest_prod_util.h should be
   used instead since that allows for FLAKY_, FAILS_ and DISABLED_ prefixes."""
   problems = []
 
   file_filter = lambda f: f.LocalPath().endswith(('.cc', '.h'))
   for f in input_api.AffectedFiles(file_filter=file_filter):
     for line_num, line in f.ChangedContents():
       if 'FRIEND_TEST(' in line:
@@ skipping 325 matching lines @@
   results.extend(input_api.canned_checks.CheckChangeHasNoTabs(
       input_api, output_api))
   results.extend(input_api.canned_checks.CheckChangeHasNoStrayWhitespace(
       input_api, output_api))
   results.extend(input_api.canned_checks.CheckAuthorizedAuthor(
       input_api, output_api))
   results.extend(input_api.canned_checks.CheckChangeTodoHasOwner(
       input_api, output_api))
   results.extend(_CheckNativeApiHeaderChanges(input_api, output_api))
   results.extend(_CheckNoIOStreamInHeaders(input_api, output_api))
+  results.extend(_CheckNoUNIT_TESTInSourceFiles(input_api, output_api))
   results.extend(_CheckNoFRIEND_TEST(input_api, output_api))
   results.extend(_CheckGnChanges(input_api, output_api))
   results.extend(_CheckUnwantedDependencies(input_api, output_api))
   results.extend(_CheckJSONParseErrors(input_api, output_api))
   results.extend(_RunPythonTests(input_api, output_api))
   return results
 
 
 def CheckChangeOnUpload(input_api, output_api):
   results = []
@@ skipping 12 matching lines @@
       input_api, output_api))
   results.extend(input_api.canned_checks.CheckChangeHasDescription(
       input_api, output_api))
   results.extend(_CheckChangeHasBugField(input_api, output_api))
   results.extend(input_api.canned_checks.CheckChangeHasTestField(
       input_api, output_api))
   results.extend(input_api.canned_checks.CheckTreeIsOpen(
       input_api, output_api,
       json_url='http://webrtc-status.appspot.com/current?format=json'))
   return results