Changes to improve multiprocessing PRESUBMIT support in Windows

presubmit_canned_checks.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.
 
 """Generic presubmit checks that can be reused by other presubmit checks."""
 
 import os as _os
 _HERE = _os.path.dirname(_os.path.abspath(__file__))
 
 # Justifications for each filter:
@@ skipping 753 matching lines @@
 
   input_api.logging.info('Running pylint on %d files', len(files))
   input_api.logging.debug('Running pylint on: %s', files)
   # Copy the system path to the environment so pylint can find the right
   # imports.
   env = input_api.environ.copy()
   import sys
   env['PYTHONPATH'] = input_api.os_path.pathsep.join(
       extra_paths_list + sys.path).encode('utf8')
 
-  def GetPylintCmd(files, extra, parallel):
+  def GetPylintCmd(flist, extra, parallel):
     # Windows needs help running python files so we explicitly specify
     # the interpreter to use. It also has limitations on the size of
     # the command-line, so we pass arguments via a pipe.
     cmd = [input_api.python_executable,
            input_api.os_path.join(_HERE, 'third_party', 'pylint.py'),
            '--args-on-stdin']
-    if len(files) == 1:
-      description = files[0]
+    if len(flist) == 1:
+      description = flist[0]
     else:
-      description = '%s files' % len(files)
+      description = '%s files' % len(flist)
 
+    args = extra_args[:]
     if extra:
-      cmd.extend(extra)
+      args.extend(extra)
       description += ' using %s' % (extra,)
     if parallel:
-      cmd.append('--jobs=%s' % input_api.cpu_count)
+      args.append('--jobs=%s' % input_api.cpu_count)
       description += ' on %d cores' % input_api.cpu_count
 
     return input_api.Command(
         name='Pylint (%s)' % description,
         cmd=cmd,
-        kwargs={'env': env, 'stdin': '\n'.join(files + extra_args)},
+        kwargs={'env': env, 'stdin': '\n'.join(args + flist)},
         message=error_type)
 
   # Always run pylint and pass it all the py files at once.
   # Passing py files one at time is slower and can produce
   # different results.  input_api.verbose used to be used
   # to enable this behaviour but differing behaviour in
   # verbose mode is not desirable.
   # Leave this unreachable code in here so users can make
   # a quick local edit to diagnose pylint issues more
   # easily.
   if True:
     # pylint's cycle detection doesn't work in parallel, so spawn a second,
     # single-threaded job for just that check.
-    return [
-      GetPylintCmd(files, ["--disable=cyclic-import"], True),
-      GetPylintCmd(files, ["--disable=all", "--enable=cyclic-import"], False)
-    ]
+
+    # Some PRESUBMITs explicitly mention cycle detection.
+    if not any('R0401' in a or 'cyclic-import' in a for a in extra_args):
+      return [
+        GetPylintCmd(files, ["--disable=cyclic-import"], True),
+        GetPylintCmd(files, ["--disable=all", "--enable=cyclic-import"], False)
+      ]
+    else:
+      return [ GetPylintCmd(files, [], True) ]
+
   else:
-    return map(lambda x: GetPylintCmd([x], extra_args, 1), files)
+    return map(lambda x: GetPylintCmd([x], [], 1), files)
 
 
 def RunPylint(input_api, *args, **kwargs):
   """Legacy presubmit function.
 
   For better performance, get all tests and then pass to
   input_api.RunTests.
   """
   return input_api.RunTests(GetPylint(input_api, *args, **kwargs), False)
 
@@ skipping 316 matching lines @@
   for f in affected_files:
     cmd = ['gn', 'format', '--dry-run', f.AbsoluteLocalPath()]
     rc = gn.main(cmd)
     if rc == 2:
       warnings.append(output_api.PresubmitPromptWarning(
           '%s requires formatting. Please run `gn format --in-place %s`.' % (
               f.AbsoluteLocalPath(), f.LocalPath())))
   # It's just a warning, so ignore other types of failures assuming they'll be
   # caught elsewhere.
   return warnings