blob: 65d65515107fd7b043b8560f0a95b14081f5a29d [file] [log] [blame]
# Copyright 2016 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.
"""A utility function to do text diffs of expected and actual web test results."""
import difflib
import six
def unified_diff(expected_text, actual_text, expected_filename,
actual_filename):
"""Returns a string containing the diff of the two text strings
in 'unified diff' format.
"""
# The filenames show up in the diff output, make sure they're
# raw bytes and not unicode, so that they don't trigger join()
# trying to decode the input.
if six.PY2:
expected_filename = six.ensure_binary(expected_filename)
actual_filename = six.ensure_binary(actual_filename)
diff = difflib.unified_diff(expected_text.splitlines(True),
actual_text.splitlines(True),
expected_filename, actual_filename)
return ''.join(_diff_fixup(diff))
def _diff_fixup(diff):
# The diff generated by the difflib is incorrect if one of the files
# does not have a newline at the end of the file and it is present in
# the diff. Relevant Python issue: http://bugs.python.org/issue2142
for line in diff:
yield line
if not line.endswith('\n'):
yield '\n\\ No newline at end of file\n'