BuildBucket recipe module can expose properties.

scripts/slave/recipe_modules/chromite/api.py

 # Copyright 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.
 
 import cgi
 import re
 
 from recipe_engine import recipe_api
 
 
@@ skipping 52 matching lines @@
   def get_config_defaults(self):
     defaults = {
         'CBB_CONFIG': self.m.properties.get('cbb_config'),
         'CBB_BRANCH': self.m.properties.get('cbb_branch'),
         'CBB_DEBUG': self.m.properties.get('cbb_debug') is not None,
         'CBB_CLOBBER': 'clobber' in self.m.properties,
     }
     if 'buildnumber' in self.m.properties:
       defaults['CBB_BUILD_NUMBER'] = int(self.m.properties['buildnumber'])
 
-    if 'buildbucket' in self.m.properties:
-      buildbucket_json = self.m.json.loads(self.m.properties.get('buildbucket'))
-      defaults['CBB_BUILDBUCKET_ID'] = buildbucket_json['build']['id']
+    buildbucket_props = self.m.buildbucket.properties
+    if buildbucket_props:
+      defaults['CBB_BUILDBUCKET_ID'] = buildbucket_props['build']['id']
 
     return defaults
 
   def _load_config_dump(self):
     if not self._cached_config:
       config_path = self.m.path.join(self.chromite_path,
                                      'cbuildbot', 'config_dump.json')
       step_result = self.m.json.read('read chromite config', config_path,
                                      add_json_log=False)
       self._cached_config = step_result.json.output
@@ skipping 276 matching lines @@
       cbb_args.extend(['--master-build-id', self.c.cbb.build_id])
 
     # Add custom args, if there are any.
     cbb_args.extend(args)
 
     # Run cbuildbot.
     return self.cbuildbot(str('cbuildbot [%s]' % (self.c.cbb.config,)),
                           self.c.cbb.config,
                           args=cbb_args,
                           cwd=self.m.path['slave_build'])