rebaseline_server: use new intermediate JSON format

gm/rebaseline_server/imagepair.py

 #!/usr/bin/python
 
 """
 Copyright 2014 Google Inc.
 
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 
 ImagePair class (see class docstring for details)
 """
 
 import posixpath
 
 # Keys used within ImagePair dictionary representations.
+# NOTE: Keep these in sync with static/constants.js
 KEY__DIFFERENCE_DATA = 'differenceData'
 KEY__EXPECTATIONS_DATA = 'expectations'
 KEY__EXTRA_COLUMN_VALUES = 'extraColumns'
 KEY__IMAGE_A_URL = 'imageAUrl'
 KEY__IMAGE_B_URL = 'imageBUrl'
 KEY__IS_DIFFERENT = 'isDifferent'
 
 
 class ImagePair(object):
   """Describes a pair of images, pixel difference info, and optional metadata.
   """
 
   def __init__(self, image_diff_db,
                base_url, imageA_relative_url, imageB_relative_url,
                expectations=None, extra_columns=None):
     """
     Args:
       image_diff_db: ImageDiffDB instance we use to generate/store image diffs
       base_url: base of all image URLs
-      imageA_relative_url: URL pointing at an image, relative to base_url
-      imageB_relative_url: URL pointing at an image, relative to base_url
+      imageA_relative_url: string; URL pointing at an image, relative to
+          base_url; or None, if this image is missing
+      imageB_relative_url: string; URL pointing at an image, relative to
+          base_url; or None, if this image is missing
       expectations: optional dictionary containing expectations-specific
           metadata (ignore-failure, bug numbers, etc.)
       extra_columns: optional dictionary containing more metadata (test name,
           builder name, etc.)
     """
     self.base_url = base_url
     self.imageA_relative_url = imageA_relative_url
     self.imageB_relative_url = imageB_relative_url
     self.expectations_dict = expectations
     self.extra_columns_dict = extra_columns
-    if imageA_relative_url == imageB_relative_url:
+    if not imageA_relative_url or not imageB_relative_url:
+      self.diff_record = None
+    elif imageA_relative_url == imageB_relative_url:
       self.diff_record = None
     else:
       # TODO(epoger): Rather than blocking until image_diff_db can read in
       # the image pair and generate diffs, it would be better to do it
       # asynchronously: tell image_diff_db to download a bunch of file pairs,
       # and only block later if we're still waiting for diff_records to come
       # back.
       image_diff_db.add_image_pair(
           expected_image_locator=imageA_relative_url,
           expected_image_url=posixpath.join(base_url, imageA_relative_url),
@@ skipping 15 matching lines @@
     if self.expectations_dict:
       asdict[KEY__EXPECTATIONS_DATA] = self.expectations_dict
     if self.extra_columns_dict:
       asdict[KEY__EXTRA_COLUMN_VALUES] = self.extra_columns_dict
     if self.diff_record and (self.diff_record.get_num_pixels_differing() > 0):
       asdict[KEY__IS_DIFFERENT] = True
       asdict[KEY__DIFFERENCE_DATA] = self.diff_record.as_dict()
     else:
       asdict[KEY__IS_DIFFERENT] = False
     return asdict