rebaseline_server: use new intermediate JSON format

gm/gm_json.py

 #!/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.
 
 """Schema of the JSON summary file written out by the GM tool.
 
 This must be kept in sync with the kJsonKey_ constants in gm_expectations.cpp !
 """
 
 __author__ = 'Elliot Poger'
 
 
 # system-level imports
 import io
 import json
 import os
+import re
 
 
 # Key strings used in GM results JSON files (both expected-results.json and
 # actual-results.json).
 #
 # These constants must be kept in sync with the kJsonKey_ constants in
 # gm_expectations.cpp !
 
 
 JSONKEY_ACTUALRESULTS = 'actual-results'
@@ skipping 58 matching lines @@
 
 # Root directory where buildbots store skimage actual results json files.
 SKIMAGE_ACTUALS_BASE_URL = (
     'http://chromium-skia-gm.commondatastorage.googleapis.com/skimage/actuals')
 # Root directory inside trunk where skimage expectations are stored.
 SKIMAGE_EXPECTATIONS_ROOT = os.path.join('expectations', 'skimage')
 
 # Pattern used to assemble each image's filename
 IMAGE_FILENAME_PATTERN = '(.+)_(.+)\.png'  # matches (testname, config)
 
+# Pattern used to create image URLs, relative to some base URL.
+GM_RELATIVE_URL_FORMATTER = '%s/%s/%s.png' # pass in (hash_type, test_name,
+                                           #          hash_digest)

[epoger, 2014/02/26 04:38:14]

As I recall, the Python style guide recommends against custom spacing like this.

If you have a better format to suggest, please let me know.  I would be happy
for this code to be both readable AND style-guide-compliant!

+GM_RELATIVE_URL_PATTERN = '(.+)/(.+)/(.+).png' # matches (hash_type, test_name,
+                                               #          hash_digest)
+GM_RELATIVE_URL_RE = re.compile(GM_RELATIVE_URL_PATTERN)
+
+
 def CreateGmActualUrl(test_name, hash_type, hash_digest,
                       gm_actuals_root_url=GM_ACTUALS_ROOT_HTTP_URL):
   """Return the URL we can use to download a particular version of
   the actually-generated image for this particular GM test.
 
   test_name: name of the test, e.g. 'perlinnoise'
   hash_type: string indicating the hash type used to generate hash_digest,
              e.g. JSONKEY_HASHTYPE_BITMAP_64BITMD5
   hash_digest: the hash digest of the image to retrieve
   gm_actuals_root_url: root url where actual images are stored
   """
-  # TODO(epoger): Maybe use url_or_path.join() so that, for testing, this can
-  # return either a URL or a local filepath?
-  return '%s/%s/%s/%s.png' % (gm_actuals_root_url, hash_type, test_name,
-                              hash_digest)
+  return '%s/%s' % (gm_actuals_root_url, CreateGmRelativeUrl(
+      test_name=test_name, hash_type=hash_type, hash_digest=hash_digest))
+
+def CreateGmRelativeUrl(test_name, hash_type, hash_digest):
+  """Returns a relative URL pointing at a test result's image.
+
+  Returns the URL we can use to download a particular version of
+  the actually-generated image for this particular GM test,
+  relative to the URL root.
+
+  Args:
+    test_name: name of the test, e.g. 'perlinnoise'
+    hash_type: string indicating the hash type used to generate hash_digest,
+               e.g. JSONKEY_HASHTYPE_BITMAP_64BITMD5
+    hash_digest: the hash digest of the image to retrieve
+  """
+  return GM_RELATIVE_URL_FORMATTER % (hash_type, test_name, hash_digest)
+
+def SplitGmRelativeUrl(url):
+  """Splits the relative URL into (test_name, hash_type, hash_digest) tuple.
+
+  This is the inverse of CreateGmRelativeUrl().
+
+  Args:
+    url: a URL generated with CreateGmRelativeUrl().
+
+  Returns: (test_name, hash_type, hash_digest) tuple.
+  """
+  hash_type, test_name, hash_digest = GM_RELATIVE_URL_RE.match(url).groups()
+  return (test_name, hash_type, hash_digest)
 
 def LoadFromString(file_contents):
   """Loads the JSON summary written out by the GM tool.
      Returns a dictionary keyed by the values listed as JSONKEY_ constants
      above."""
   # TODO(epoger): we should add a version number to the JSON file to ensure
   # that the writer and reader agree on the schema (raising an exception
   # otherwise).
   json_dict = json.loads(file_contents)
   return json_dict
 
 def LoadFromFile(file_path):
   """Loads the JSON summary written out by the GM tool.
      Returns a dictionary keyed by the values listed as JSONKEY_ constants
      above."""
   file_contents = open(file_path, 'r').read()
   return LoadFromString(file_contents)
 
 def WriteToFile(json_dict, file_path):
   """Writes the JSON summary in json_dict out to file_path.
 
   The file is written Unix-style (each line ends with just LF, not CRLF);
   see https://code.google.com/p/skia/issues/detail?id=1815 for reasons."""
   with io.open(file_path, mode='w', newline='', encoding='utf-8') as outfile:
     outfile.write(unicode(json.dumps(json_dict, outfile, sort_keys=True,
                                      indent=2)))