Cache diff to speed up when the diff is processed multiple times

presubmit_support.py

 #!/usr/bin/env python
 # Copyright (c) 2011 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.
 
 """Enables directory-specific presubmit checks to run at upload and/or commit.
 """
 
 __version__ = '1.6.1'
 
@@ skipping 540 matching lines @@
 
 class SvnAffectedFile(AffectedFile):
   """Representation of a file in a change out of a Subversion checkout."""
   # Method 'NNN' is abstract in class 'NNN' but is not overridden
   # pylint: disable=W0223
 
   def __init__(self, *args, **kwargs):
     AffectedFile.__init__(self, *args, **kwargs)
     self._server_path = None
     self._is_text_file = None
+    self._diff = None
 
   def ServerPath(self):
     if self._server_path is None:
       self._server_path = scm.SVN.CaptureLocalInfo(
           [self.LocalPath()], self._local_root).get('URL', '')
     return self._server_path
 
   def IsDirectory(self):
     if self._is_directory is None:
       path = self.AbsoluteLocalPath()
@@ skipping 20 matching lines @@
         self._is_text_file = False
       elif self.IsDirectory():
         self._is_text_file = False
       else:
         mime_type = scm.SVN.GetFileProperty(
             self.LocalPath(), 'svn:mime-type', self._local_root)
         self._is_text_file = (not mime_type or mime_type.startswith('text/'))
     return self._is_text_file
 
   def GenerateScmDiff(self):
-    return scm.SVN.GenerateDiff(
-        [self.LocalPath()], self._local_root, False, None)
+    if self._diff is None:
+      self._diff = scm.SVN.GenerateDiff(
+          [self.LocalPath()], self._local_root, False, None)
+    return self._diff
 
 
 class GitAffectedFile(AffectedFile):
   """Representation of a file in a change out of a git checkout."""
   # Method 'NNN' is abstract in class 'NNN' but is not overridden
   # pylint: disable=W0223
 
   def __init__(self, *args, **kwargs):
     AffectedFile.__init__(self, *args, **kwargs)
     self._server_path = None
     self._is_text_file = None
+    self._diff = None
 
   def ServerPath(self):
     if self._server_path is None:
       raise NotImplementedError('TODO(maruel) Implement.')
     return self._server_path
 
   def IsDirectory(self):
     if self._is_directory is None:
       path = self.AbsoluteLocalPath()
       if os.path.exists(path):
@@ skipping 14 matching lines @@
       if self.Action() == 'D':
         # A deleted file is not a text file.
         self._is_text_file = False
       elif self.IsDirectory():
         self._is_text_file = False
       else:
         self._is_text_file = os.path.isfile(self.AbsoluteLocalPath())
     return self._is_text_file
 
   def GenerateScmDiff(self):
-    return scm.GIT.GenerateDiff(self._local_root, files=[self.LocalPath(),])
+    if self._diff is None:
+      self._diff = scm.GIT.GenerateDiff(
+          self._local_root, files=[self.LocalPath(),])
+    return self._diff
 
 
 class Change(object):
   """Describe a change.
 
   Used directly by the presubmit scripts to query the current change being
   tested.
 
   Instance members:
     tags: Dictionnary of KEY=VALUE pairs found in the change description.
@@ skipping 599 matching lines @@
   except PresubmitFailure, e:
     print >> sys.stderr, e
     print >> sys.stderr, 'Maybe your depot_tools is out of date?'
     print >> sys.stderr, 'If all fails, contact maruel@'
     return 2
 
 
 if __name__ == '__main__':
   fix_encoding.fix_encoding()
   sys.exit(Main(None))