Modify presubmit checks to work on changed lines only.

presubmit_support.py

Index: presubmit_support.py
diff --git a/presubmit_support.py b/presubmit_support.py
index 049438d7500eef415ab988178adf54fe3e9ca22d..3365cd089ace959c6ad2edd42a493db8210852ca 100755
--- a/presubmit_support.py
+++ b/presubmit_support.py
@@ -86,11 +86,9 @@ def PromptYesNo(input_stream, output_stream, prompt):
 def _RightHandSideLinesImpl(affected_files):
   """Implements RightHandSideLines for InputApi and GclChange."""
   for af in affected_files:
-    lines = af.NewContents()
-    line_number = 0
+    lines = af.ChangedContents()
     for line in lines:
-      line_number += 1
-      yield (af, line_number, line)
+      yield (af, line[0], line[1])
 
 
 class OutputApi(object):
@@ -481,6 +479,27 @@ class AffectedFile(object):
     """
     raise NotImplementedError()  # Implement if/when needed.
 
+  def ChangedContents(self):
+    # Return a list of tuples (line number, line text) of all new lines in the

[M-A Ruel, 2011/02/09 18:30:26]

I think it should be a docstring.

"""Returns a list of ...

[vb, 2011/02/09 18:54:11]

Done.

+    # file. This relies on the scm diff output describing each changed code
+    # section with a line of the form
+    #
+    # ^@@ <old line num>,<old size> <new line num>,<new size> @@$
+    #
+    new_lines = []
+    line_num = 0
+    diff_text = self.GenerateScmDiff()
+    for line in diff_text.splitlines():

[M-A Ruel, 2011/02/09 18:30:26]

You didn't merge lines 491 and 492. You prefer to keep that on two lines? I
don't mind much but I don't think this data needs a named variable.

[vb, 2011/02/09 18:54:11]

good point, it was a leftover of previous code, now refactored. 

+      m = re.match(r'^@@ [0-9\,\+\-]+ \+([0-9]+)\,[0-9]+ @@', line)
+      if m:
+        line_num = int(m.groups(1)[0])
+        continue
+      if re.search(r'^\+[^\+]', line):

[M-A Ruel, 2011/02/09 18:30:26]

Actually, this regexp is wrong:

what if the line was empty, e.g. there's no character on this line, I don't
think this regexp will trigger. Can you confirm?

[vb, 2011/02/09 18:54:11]

Yes, a good catch. Did away with regexp here, I think it is even better readable
this way. And we don't care about the '^---' case , because it would be followed
by a @@ line and reset the line counter anyways.

+        new_lines.append((line_num, line[1:]))
+      if not re.search(r'^\-[^\-]', line):
+        line_num += 1
+    return new_lines
+
   def __str__(self):
     return self.LocalPath()
 
@@ -532,6 +551,8 @@ class SvnAffectedFile(AffectedFile):
         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.AbsoluteLocalPath())
 
 class GitAffectedFile(AffectedFile):
   """Representation of a file in a change out of a git checkout."""
@@ -577,6 +598,10 @@ class GitAffectedFile(AffectedFile):
         self._is_text_file = os.path.isfile(self.AbsoluteLocalPath())
     return self._is_text_file
 
+  def GenerateScmDiff(self):
+    return scm.GIT.GenerateDiff(
+      os.path.dirname(self.AbsoluteLocalPath()),
+      files=[os.path.basename(self.AbsoluteLocalPath()),])
 
 class Change(object):
   """Describe a change.