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

PRESUBMIT.py

Index: PRESUBMIT.py
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index 3405ef9116fcd9e654af577ba49538e08ca945d3..119060c61b183839fa7f5ccbf829b71b24325e71 100755
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -169,6 +169,23 @@ def _CheckNoIOStreamInHeaders(input_api, output_api):
   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
@@ -514,6 +531,7 @@ def _CommonChecks(input_api, output_api):
       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))