Allow NOLINT to skip the std::abs PRESUBMIT check.

cc/PRESUBMIT.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Top-level presubmit script for cc.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts for
 details on the presubmit API built into gcl.
 """
 
@@ skipping 58 matching lines @@
   missing_std_prefix_files = []
 
   for f in input_api.AffectedSourceFiles(source_file_filter):
     contents = input_api.ReadFile(f, 'rb')
     if re.search(r"using std::f?abs;", contents):
       using_std_abs_files.append(f.LocalPath())
     if re.search(r"\bfabsf?\(", contents):
       found_fabs_files.append(f.LocalPath());
     # The following regular expression in words says:
     # "if there is no 'std::' behind an 'abs(' or 'absf(',
-    # or if there is no 'std::' behind a 'fabs(' or 'fabsf(',
+    # OR if there is no 'std::' behind a 'fabs(' or 'fabsf(',
+    # AND if there's no '// NOLINT' on the same line of code,
     # then it's a match."
-    if re.search(r"((?<!std::)(\babsf?\()|(?<!std::)(\bfabsf?\())", contents):
+    # Note that \ characters have to be escaped since these
+    # are not explicitly defined as regexes.
+    no_abs = "((?<!std::)(\\babsf?\\()"
+    no_fabs = "(?<!std::)(\\bfabsf?\\())"
+    no_nolint = "(?![^\\n]*// NOLINT)"

[enne (OOO), 2013/09/05 01:00:40]

Maybe \s+ instead of the space in NOLINT?

+    expression = re.compile("%s|%s%s" % (no_abs, no_fabs, no_nolint))

[enne (OOO), 2013/09/05 01:00:40]

If you're going to put an | outside of the strings, can you also put the
surrounding parentheses too?  It took me a second to realize there wasn't a typo
in the strings or the final regular expression.

If you didn't know, you can do implicit line continuation in Python using
parentheses if you wanted to keep this all in one statement.

+    if expression.search(contents):
       missing_std_prefix_files.append(f.LocalPath())
 
   result = []
   if using_std_abs_files:
     result.append(output_api.PresubmitError(
         'These files have "using std::abs" which is not permitted.',
         items=using_std_abs_files))
   if found_fabs_files:
     result.append(output_api.PresubmitError(
         'std::abs() should be used instead of std::fabs() for consistency.',
@@ skipping 92 matching lines @@
   results += CheckSpamLogging(input_api, output_api, black_list=CC_PERF_TEST)
   results += CheckPassByValue(input_api, output_api)
   results += CheckChangeLintsClean(input_api, output_api)
   results += CheckTodos(input_api, output_api)
   return results
 
 def GetPreferredTrySlaves(project, change):
   return [
     'linux_layout_rel',
     ]