presubmit checks: skip computing the diff if possible

presubmit_canned_checks.py

Index: presubmit_canned_checks.py
===================================================================
--- presubmit_canned_checks.py	(revision 82663)
+++ presubmit_canned_checks.py	(working copy)
@@ -67,12 +67,14 @@
 
 def CheckDoNotSubmitInFiles(input_api, output_api):
   """Checks that the user didn't add 'DO NOT ' + 'SUBMIT' to any files."""
+  # We want to check every text file, not just source files.
+  file_filter = lambda x : x
   keyword = 'DO NOT ' + 'SUBMIT'
-  # We want to check every text files, not just source files.
-  for f, line_num, line in input_api.RightHandSideLines(lambda x: x):
-    if keyword in line:
-      text = 'Found ' + keyword + ' in %s, line %s' % (f.LocalPath(), line_num)
-      return [output_api.PresubmitError(text)]
+  errors = _FindNewViolationsOfRule(lambda line : keyword not in line,
+                                    input_api, file_filter)
+  text = '\n'.join('Found %s in %s' % (keyword, loc) for loc in errors)
+  if text:
+    return [output_api.PresubmitError(text)]
   return []
 
 
@@ -213,6 +215,42 @@
   return outputs
 
 
+def _ReportErrorFileAndLine(filename, line_num, line):
+  """Default error formatter for _FindNewViolationsOfRule."""
+  return '%s, line %s' % (filename, line_num)
+
+
+def _FindNewViolationsOfRule(callable_rule, input_api, source_file_filter=None,
+                             error_formatter=_ReportErrorFileAndLine):
+  """Find all newly introduced violations of a per-line rule (a callable).
+
+  Arguments:
+    callable_rule: a callable taking a line of input and returning True
+      if the rule is satisfied and False if there was a problem.
+    input_api: object to enumerate the affected files.
+    source_file_filter: a filter to be passed to the input api.
+    error_formatter: a callable taking (filename, line_number, line) and
+      returning a formatted error string.
+
+  Returns:
+    A list of the newly-introduced violations reported by the rule.
+  """
+  errors = []
+  for f in input_api.AffectedFiles(source_file_filter, include_deletes=False):
+    # For speed, we do two passes, checking first the full file.  Shelling out
+    # to the SCM to determine the changed region can be quite expensive on
+    # Win32.  Assuming that most files will be kept problem-free, we can
+    # skip the SCM operations most of the time.
+    if all(callable_rule(line) for line in f.NewContents()):
+      continue  # No violation found in full text: can skip considering diff.
+
+    for line_num, line in f.ChangedContents():
+      if not callable_rule(line):
+        errors.append(error_formatter(f.LocalPath(), line_num, line))
+
+  return errors
+
+
 def CheckChangeHasNoTabs(input_api, output_api, source_file_filter=None):
   """Checks that there are no tab characters in any of the text files to be
   submitted.
@@ -225,10 +263,10 @@
     return (not input_api.os_path.basename(affected_file.LocalPath()) in
                 ('Makefile', 'makefile') and
             source_file_filter(affected_file))
-  tabs = []
-  for f, line_num, line in input_api.RightHandSideLines(filter_more):
-    if '\t' in line:
-      tabs.append('%s, line %s' % (f.LocalPath(), line_num))
+
+  tabs = _FindNewViolationsOfRule(lambda line : '\t' not in line,
+                                  input_api, filter_more)
+
   if tabs:
     return [output_api.PresubmitPromptWarning('Found a tab character in:',
                                               long_text='\n'.join(tabs))]
@@ -239,21 +277,19 @@
   """Checks that the user didn't add TODO(name) without an owner."""
 
   unowned_todo = input_api.re.compile('TO' + 'DO[^(]')
-  for f, line_num, line in input_api.RightHandSideLines(source_file_filter):
-    if unowned_todo.search(line):
-      text = ('Found TO' + 'DO with no owner in %s, line %s' %
-              (f.LocalPath(), line_num))
-      return [output_api.PresubmitPromptWarning(text)]
+  errors = _FindNewViolationsOfRule(lambda x : not unowned_todo.search(x),
+                                    input_api, source_file_filter)
+  errors = ['Found TO' + 'DO with no owner in ' + x for x in errors]
+  if errors:
+    return [output_api.PresubmitPromptWarning('\n'.join(errors))]
   return []
 
 
 def CheckChangeHasNoStrayWhitespace(input_api, output_api,
                                     source_file_filter=None):
   """Checks that there is no stray whitespace at source lines end."""
-  errors = []
-  for f, line_num, line in input_api.RightHandSideLines(source_file_filter):
-    if line.rstrip() != line:
-      errors.append('%s, line %s' % (f.LocalPath(), line_num))
+  errors = _FindNewViolationsOfRule(lambda line : line.rstrip() == line,
+                                    input_api, source_file_filter)
   if errors:
     return [output_api.PresubmitPromptWarning(
         'Found line ending with white spaces in:',
@@ -265,28 +301,23 @@
   """Checks that there aren't any lines longer than maxlen characters in any of
   the text files to be submitted.
   """
-  bad = []
-  for f, line_num, line in input_api.RightHandSideLines(source_file_filter):
+  def no_long_lines(line):
     # Allow lines with http://, https:// and #define/#pragma/#include/#if/#endif
     # to exceed the maxlen rule.
-    if (len(line) > maxlen and
-        not 'http://' in line and
-        not 'https://' in line and
-        not line.startswith('#define') and
-        not line.startswith('#include') and
-        not line.startswith('#import') and
-        not line.startswith('#pragma') and
-        not line.startswith('#if') and
-        not line.startswith('#endif')):
-      bad.append(
-          '%s, line %s, %s chars' %
-          (f.LocalPath(), line_num, len(line)))
-      if len(bad) == 5:  # Just show the first 5 errors.
-        break
+    return (len(line) <= maxlen or
+            any((url in line) for url in ('http://', 'https://')) or
+            line.startswith(('#define', '#include', '#import', '#pragma',
+                             '#if', '#endif')))
 
-  if bad:
+  def format_error(filename, line_num, line):
+    return '%s, line %s, %s chars' % (filename, line_num, len(line))
+
+  errors = _FindNewViolationsOfRule(no_long_lines, input_api,
+                                    source_file_filter,
+                                    error_formatter=format_error)
+  if errors:
     msg = 'Found lines longer than %s characters (first 5 shown).' % maxlen
-    return [output_api.PresubmitPromptWarning(msg, items=bad)]
+    return [output_api.PresubmitPromptWarning(msg, items=errors[:5])]
   else:
     return []
 
@@ -880,24 +911,45 @@
   text_files = lambda x: input_api.FilterSourceFile(x, black_list=black_list,
                                                     white_list=white_list)
 
+
+  snapshot_memory = []
+  def snapshot(msg):
+    """Measures & prints performance warning if a rule is running slow."""
+    dt2 = input_api.time.clock()
+    if snapshot_memory:
+      delta_ms = int(1000*(dt2 - snapshot_memory[0]))
+      if delta_ms > 500:
+        print "  %s took a long time: %dms" % (snapshot_memory[1], delta_ms)
+    snapshot_memory[:] = (dt2, msg)
+
   if owners_check:
+    snapshot("checking owners")
     results.extend(input_api.canned_checks.CheckOwners(
         input_api, output_api, source_file_filter=sources))
 
+  snapshot("checking long lines")
   results.extend(input_api.canned_checks.CheckLongLines(
       input_api, output_api, source_file_filter=sources))
+  snapshot( "checking tabs")
   results.extend(input_api.canned_checks.CheckChangeHasNoTabs(
       input_api, output_api, source_file_filter=sources))
+  snapshot( "checking stray whitespace")
   results.extend(input_api.canned_checks.CheckChangeHasNoStrayWhitespace(
       input_api, output_api, source_file_filter=sources))
+  snapshot("checking eol style")
   results.extend(input_api.canned_checks.CheckChangeSvnEolStyle(
       input_api, output_api, source_file_filter=text_files))
+  snapshot("checking svn mime types")
   results.extend(input_api.canned_checks.CheckSvnForCommonMimeTypes(
       input_api, output_api))
+  snapshot("checking license")
   results.extend(input_api.canned_checks.CheckLicense(
       input_api, output_api, license_header, source_file_filter=sources))
+  snapshot("checking nsobjects")
   results.extend(_CheckConstNSObject(
       input_api, output_api, source_file_filter=sources))
+  snapshot("checking singletons")
   results.extend(_CheckSingletonInHeaders(
       input_api, output_api, source_file_filter=sources))
+  snapshot("done")
   return results