swarmbucket: allow overriding config

appengine/cr-buildbucket/swarming/swarmingcfg.py

 # Copyright 2014 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 copy
 import json
 import re
 
 from components.config import validation
 
 from proto import project_config_pb2
 
 
 DIMENSION_KEY_RGX = re.compile(r'^[a-zA-Z\_\-]+$')
-NO_PROPERTY = object()
 
 
 def read_properties(recipe):
   """Parses build properties from the recipe message.
 
   Expects the message to be valid.
 
   Uses NO_PROPERTY for empty values.
   """
   result = dict(p.split(':', 1) for p in recipe.properties)
   for p in recipe.properties_j:
     k, v = p.split(':', 1)
-    if not v:
-      parsed = NO_PROPERTY
-    else:
-      parsed = json.loads(v)
+    parsed = json.loads(v)
     result[k] = parsed
   return result
 
 
 def merge_recipe(r1, r2):
   """Merges Recipe message r2 into r1.
 
   Expects messages to be valid.
 
   All properties are converted to properties_j.
   """
   props = read_properties(r1)
   props.update(read_properties(r2))
 
   r1.MergeFrom(r2)
   r1.properties[:] = []
   r1.properties_j[:] = [
     '%s:%s' % (k, json.dumps(v))
     for k, v in sorted(props.iteritems())
-    if v is not NO_PROPERTY
+    if v is not None
   ]
 
 
 def merge_dimensions(d1, d2):
   """Merges dimensions. Values in d2 overwrite values in d1.
 
   Expects dimensions to be valid.
 
   If a dimensions value in d2 is empty, it is excluded from the result.
   """
@@ skipping 101 matching lines @@
         keys.add(key)
 
   for i, p in enumerate(properties_j):
     with ctx.prefix('properties_j #%d: ', i + 1):
       if ':' not in p:
         ctx.error('does not have colon')
       else:
         key, value = p.split(':', 1)
         validate_key(key)
         keys.add(key)
-        if value:
-          try:
-            json.loads(value)
-          except ValueError as ex:
-            ctx.error(ex)
+        try:
+          json.loads(value)
+        except ValueError as ex:
+          ctx.error(ex)
 
 
 def validate_builder_cfg(builder, ctx, final=True):
   """Validates a Builder message.
 
   If final is False, does not validate for completeness.
   """
   if final and not builder.name:
     ctx.error('name unspecified')
 
@@ skipping 41 matching lines @@
         # Do no try to merge invalid configs.
         continue
 
       merged = copy.deepcopy(swarming.builder_defaults)
       merge_builder(merged, b)
       validate_builder_cfg(merged, ctx)
 
 
 def has_pool_dimension(dimensions):
   return any(d.startswith('pool:') for d in dimensions)