Open-source histograms.xml, starting with Autofill histograms.

tools/metrics/histograms/diffutil.py

+# Copyright 2013 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.
+
+"""Utility functions for prompting user if changes automatically applied to some
+user-managed files are correct.
+"""
+
+import logging
+import os
+import webbrowser
+
+from difflib import HtmlDiff
+from tempfile import NamedTemporaryFile
+
+
+def PromptUserToAcceptDiff(old_text, new_text, prompt):
+  """Displays a difference in two strings (old and new file contents) to the
+  user and asks whether the new version is acceptable.
+
+  Args:
+    old_text: A string containing old file contents.
+    new_text: A string containing new file contents.
+    prompt: Text that should be displayed to the user, asking whether the new
+            file contents should be accepted.
+
+  Returns:
+    True is user accepted the changes or there were no changes, False otherwise.
+  """
+  logging.info('Computing diff...')
+  if old_text == new_text:
+    logging.info('No changes detected')
+    return True
+  html_diff = HtmlDiff(wrapcolumn=80).make_file(
+      old_text.splitlines(), new_text.splitlines(), fromdesc='Original',
+      todesc='Updated', context=True, numlines=5)
+  temp = NamedTemporaryFile(suffix='.html', delete=False)
+  try:
+    temp.write(html_diff)
+    temp.close()  # Close the file so the browser process can access it.
+    webbrowser.open('file://' + temp.name)
+    print prompt
+    response = raw_input('(Y/n): ').strip().lower()
+  finally:
+    temp.close()  # May be called on already closed file.
+    os.remove(temp.name)
+  return response == 'y' or response == ''