Add gm/confirm_no_failures_in_json.py

gm/confirm_no_failures_in_json.py

Index: gm/confirm_no_failures_in_json.py
===================================================================
--- gm/confirm_no_failures_in_json.py	(revision 0)
+++ gm/confirm_no_failures_in_json.py	(revision 0)
@@ -0,0 +1,47 @@
+#!/usr/bin/env python
+# Copyright (c) 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 to confirm that a JSON summary written by GM contains no failures.
+
+Usage:
+  python confirm_no_failures_in_json.py <filename>
+"""
+
+__author__ = 'Elliot Poger'
+
+
+import json
+import sys
+
+
+# These constants must be kept in sync with the kJsonKey_ constants in
+# gm_expectations.cpp !
+JSONKEY_ACTUALRESULTS = 'actual-results'
+JSONKEY_ACTUALRESULTS_FAILED = 'failed'
+
+# This is the same indent level as used by jsoncpp, just for consistency.
+JSON_INDENTLEVEL = 3
+
+
+def Assert(filepath):
+  """Raises an exception if the JSON summary at filepath contains any failed
+  tests, or if we were unable to read the JSON summary."""
+  failed_tests = GetFailedTests(filepath)
+  if failed_tests:
+    raise Exception('JSON file %s contained these test failures...\n%s' % (
+        filepath, json.dumps(failed_tests, indent=JSON_INDENTLEVEL)))
+
+
+def GetFailedTests(filepath):
+  """Returns the dictionary of failed tests from the JSON file at filepath."""
+  json_dict = json.load(open(filepath))
+  actual_results = json_dict[JSONKEY_ACTUALRESULTS]
+  return actual_results[JSONKEY_ACTUALRESULTS_FAILED]
+
+
+if '__main__' == __name__:
+  if len(sys.argv) != 2:
+    raise Exception('usage: %s <input-json-filepath>' % sys.argv[0])
+  Assert(sys.argv[1])