svndiff.py: fix --add-new for JSON-format expectations

tools/svndiff.py

 #!/usr/bin/python
 '''
 Copyright 2012 Google Inc.
 
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 '''
 
 '''
 Generates a visual diff of all pending changes in the local SVN checkout.
@@ skipping 78 matching lines @@
     for try_path in possible_paths:
         if os.path.isfile(try_path):
             return try_path
     raise Exception('cannot find skdiff in paths %s; maybe you need to '
                     'specify the %s option or build skdiff?' % (
                         possible_paths, OPTION_PATH_TO_SKDIFF))
 
 def _DownloadUrlToFile(source_url, dest_path):
     """Download source_url, and save its contents to dest_path.
     Raises an exception if there were any problems."""
-    reader = urllib2.urlopen(source_url)
-    writer = open(dest_path, 'wb')
-    writer.write(reader.read())
-    writer.close()
+    try:
+        reader = urllib2.urlopen(source_url)
+        writer = open(dest_path, 'wb')
+        writer.write(reader.read())
+        writer.close()
+    except BaseException as e:
+        raise Exception(
+            '%s: unable to download source_url %s to dest_path %s' % (
+                e, source_url, dest_path))
 
 def _CreateGSUrl(imagename, hash_type, hash_digest):
     """Return the HTTP URL we can use to download this particular version of
     the actually-generated GM image with this imagename.
 
     imagename: name of the test image, e.g. 'perlinnoise_msaa4.png'
     hash_type: string indicating the hash type used to generate hash_digest,
                e.g. gm_json.JSONKEY_HASHTYPE_BITMAP_64BITMD5
     hash_digest: the hash digest of the image to retrieve
     """
     return gm_json.CreateGmActualUrl(
         test_name=IMAGE_FILENAME_RE.match(imagename).group(1),
         hash_type=hash_type,
         hash_digest=hash_digest)
 
 def _CallJsonDiff(old_json_path, new_json_path,
                   old_flattened_dir, new_flattened_dir,
                   filename_prefix):
     """Using jsondiff.py, write the images that differ between two GM
     expectations summary files (old and new) into old_flattened_dir and
     new_flattened_dir.
 
     filename_prefix: prefix to prepend to filenames of all images we write
         into the flattened directories
     """
     json_differ = jsondiff.GMDiffer()
     diff_dict = json_differ.GenerateDiffDict(oldfile=old_json_path,
                                              newfile=new_json_path)
+    print 'Downloading %d before-and-after image pairs...' % len(diff_dict)
     for (imagename, results) in diff_dict.iteritems():
-        old_checksum = results['old']
-        new_checksum = results['new']
         # TODO(epoger): Currently, this assumes that all images have been
         # checksummed using gm_json.JSONKEY_HASHTYPE_BITMAP_64BITMD5
-        old_image_url = _CreateGSUrl(
-            imagename=imagename,
-            hash_type=gm_json.JSONKEY_HASHTYPE_BITMAP_64BITMD5,
-            hash_digest=old_checksum)
-        new_image_url = _CreateGSUrl(
-            imagename=imagename,
-            hash_type=gm_json.JSONKEY_HASHTYPE_BITMAP_64BITMD5,
-            hash_digest=new_checksum)
-        _DownloadUrlToFile(
-            source_url=old_image_url,
-            dest_path=os.path.join(old_flattened_dir,
-                                   filename_prefix + imagename))
-        _DownloadUrlToFile(
-            source_url=new_image_url,
-            dest_path=os.path.join(new_flattened_dir,
-                                   filename_prefix + imagename))
+
+        old_checksum = results['old']
+        if old_checksum:
+            old_image_url = _CreateGSUrl(
+                imagename=imagename,
+                hash_type=gm_json.JSONKEY_HASHTYPE_BITMAP_64BITMD5,
+                hash_digest=old_checksum)
+            _DownloadUrlToFile(
+                source_url=old_image_url,
+                dest_path=os.path.join(old_flattened_dir,
+                                       filename_prefix + imagename))
+
+        new_checksum = results['new']
+        if new_checksum:
+            new_image_url = _CreateGSUrl(
+                imagename=imagename,
+                hash_type=gm_json.JSONKEY_HASHTYPE_BITMAP_64BITMD5,
+                hash_digest=new_checksum)
+            _DownloadUrlToFile(
+                source_url=new_image_url,
+                dest_path=os.path.join(new_flattened_dir,
+                                       filename_prefix + imagename))
 
 def SvnDiff(path_to_skdiff, dest_dir, source_dir):
     """Generates a visual diff of all pending changes in source_dir.
 
     @param path_to_skdiff
     @param dest_dir existing directory within which to write results
     @param source_dir
     """
     # Validate parameters, filling in default values if necessary and possible.
     path_to_skdiff = os.path.abspath(FindPathToSkDiff(path_to_skdiff))
@@ skipping 33 matching lines @@
                           new_json_path=modified_file_path,
                           old_flattened_dir=original_flattened_dir,
                           new_flattened_dir=modified_flattened_dir,
                           filename_prefix=platform_prefix)
             os.remove(original_file_path)
         else:
             dest_filename = re.sub(os.sep, '__', modified_file_path)
             # If the file had STATUS_DELETED, it won't exist anymore...
             if os.path.isfile(modified_file_path):
                 shutil.copyfile(modified_file_path,
-                                os.path.join(modified_flattened_dir, dest_filename))
+                                os.path.join(modified_flattened_dir,
+                                             dest_filename))
             svn_repo.ExportBaseVersionOfFile(
                 modified_file_path,
                 os.path.join(original_flattened_dir, dest_filename))
 
     # Run skdiff: compare original_flattened_dir against modified_flattened_dir
     RunCommand('%s %s %s %s' % (path_to_skdiff, original_flattened_dir,
                                 modified_flattened_dir, diff_dir))
     print '\nskdiff results are ready in file://%s/index.html' % diff_dir
 
 def RaiseUsageException():
@@ skipping 20 matching lines @@
                       action='store', type='string', default=None,
                       help='path to already-built skdiff tool; if not set, '
                       'will search for it in typical directories near this '
                       'script')
     parser.add_option(OPTION_SOURCE_DIR,
                       action='store', type='string', default='.',
                       help='root directory within which to compare all ' +
                       'files; defaults to "%default"')
     (options, args) = parser.parse_args()
     Main(options, args)