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

cc/PRESUBMIT.py

Index: cc/PRESUBMIT.py
diff --git a/cc/PRESUBMIT.py b/cc/PRESUBMIT.py
index bcf71ef0d52800f862be518a40f0bce2be1d7709..051a3eef28ec35bc3bba0392b24a302023ce1b4f 100644
--- a/cc/PRESUBMIT.py
+++ b/cc/PRESUBMIT.py
@@ -76,9 +76,16 @@ def CheckStdAbs(input_api, output_api,
       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 = []