Add presubmit check and automatic update script for ExtensionPermission enum.

tools/metrics/histograms/update_histogram_enum.py

Index: tools/metrics/histograms/update_histogram_enum.py
diff --git a/tools/metrics/histograms/update_histogram_enum.py b/tools/metrics/histograms/update_histogram_enum.py
new file mode 100644
index 0000000000000000000000000000000000000000..cd259dfcc7e3565b7548eb41ac63d5fc37b0ef67
--- /dev/null
+++ b/tools/metrics/histograms/update_histogram_enum.py
@@ -0,0 +1,130 @@
+# Copyright 2014 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.
+
+import logging
+import re
+import sys
+
+from xml.dom import minidom
+from diffutil import PromptUserToAcceptDiff
+from pretty_print import PrettyPrintNode
+
+class UserError(Exception):
+  def __init__(self, message):
+    Exception.__init__(self, message)
+
+  @property
+  def message(self):
+    return self.args[0]
+
+def Log(message):
+  logging.info(message)
+
+def ExtractRegexGroup(line, regex):
+  m = re.match(regex, line)
+  if m:
+    return m.group(1)
+  else:
+    return None
+
+def ReadHistogramValues(filename, start_marker, end_marker):

[Jeffrey Yasskin, 2014/03/10 20:53:23]

Set your --similarity low enough that `git cl upload` marks this as a copy. You
should be able to test with `git diff -C30% @{u}`.

+  '''Reads in values from |filename|, returning a list of (label, value) pairs
+  corresponding to the enum framed by |start_marker| and |end_marker|.
+  '''
+  # Read the file as a list of lines
+  with open(filename) as f:
+    content = f.readlines()
+
+  # Locate the enum definition and collect all entries in it
+  inside_enum = False # We haven't found the enum definition yet
+  result = []
+  for line in content:
+    line = line.strip()
+    if inside_enum:
+      # Exit condition: we reached last enum value
+      if re.match(end_marker, line):
+        inside_enum = False
+      else:
+        # Inside enum: generate new xml entry
+        label = ExtractRegexGroup(line.strip(), "^([\w]+)")
+        if label:
+          result.append((label, enum_value))
+          enum_value += 1
+    else:
+      if re.match(start_marker, line):
+        inside_enum = True
+        enum_value = 0 # Start at 'UNKNOWN'
+  return result
+
+def UpdateHistogramDefinitions(histogram_enum_name, source_enum_values,
+                               source_enum_path, document,
+                               labelTransformer):
+  '''Sets the children of <enum name=|histogram_enum_name| ...> node in
+  |document| to values generated from (label, value) pairs contained in
+  |source_enum_values|.
+
+  |labelTransformer| is a function used to transform labels from the
+  (label, value) pairs into a different format or style. Since label is
+  a string, defaulting labelTransformer to str() effectively does nothing.
+  '''
+  # Find ExtensionFunctions enum.
+  for enum_node in document.getElementsByTagName('enum'):
+    if enum_node.attributes['name'].value == histogram_enum_name:
+        histogram_enum_node = enum_node
+        break
+  else:
+    raise UserError('No {0} enum node found'.format(histogram_enum_name))
+
+  # Remove existing values.
+  while histogram_enum_node.hasChildNodes():
+    histogram_enum_node.removeChild(histogram_enum_node.lastChild)
+
+  # Add a "Generated from (...)" comment
+  comment = ' Generated from {0} '.format(source_enum_path)
+  histogram_enum_node.appendChild(document.createComment(comment))
+
+  # Add values generated from policy templates.
+  for (label, value) in source_enum_values:
+    node = document.createElement('int')
+    node.attributes['value'] = str(value)
+    node.attributes['label'] = labelTransformer(label)
+    histogram_enum_node.appendChild(node)
+
+def UpdateHistogramEnum(histogram_enum_name, source_enum_path,
+                        start_marker, end_marker, labelTransformer=str):
+  '''Updates |histogram_enum_name| enum in histograms.xml file with values
+  read from |source_enum_path|, where |start_marker| and |end_marker| indicate
+  the beginning and end of the source enum definition, respectively.
+
+  |labelTransformer| is a function whose usage is described in
+  UpdateHistogramDefinitions.
+  '''
+  HISTOGRAMS_PATH = 'histograms.xml'
+
+  if len(sys.argv) > 1:
+    print >>sys.stderr, 'No arguments expected!'
+    sys.stderr.write(__doc__)
+    sys.exit(1)
+
+  Log('Reading histogram enum definition from "{0}".'.format(source_enum_path))
+  source_enum_values = ReadHistogramValues(source_enum_path, start_marker,
+                                           end_marker)
+
+  Log('Reading existing histograms from "{0}".'.format(HISTOGRAMS_PATH))
+  with open(HISTOGRAMS_PATH, 'rb') as f:
+    histograms_doc = minidom.parse(f)
+    f.seek(0)
+    xml = f.read()
+
+  Log('Comparing histograms enum with new enum definition.')
+  UpdateHistogramDefinitions(histogram_enum_name, source_enum_values,
+      source_enum_path, histograms_doc, labelTransformer)
+
+  Log('Writing out new histograms file.')
+  new_xml = PrettyPrintNode(histograms_doc)
+  if PromptUserToAcceptDiff(xml, new_xml, 'Is the updated version acceptable?'):
+    with open(HISTOGRAMS_PATH, 'wb') as f:
+      f.write(new_xml)
+
+  Log('Done.')