JSON Schema Compiler supports functions as PropertyTypes.

tools/json_schema_compiler/model.py

 # Copyright (c) 2012 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 os.path
 import re
 
 class ParseException(Exception):
   """Thrown when data in the model is invalid.
@@ skipping 194 matching lines @@
             from_json=from_json,
             from_client=from_client)
         self.type_ = PropertyType.ARRAY
       elif json_type == 'object':
         self.type_ = PropertyType.OBJECT
         # These members are read when this OBJECT Property is used as a Type
         type_ = Type(self, self.name, json)
         # self.properties will already have some value from |_AddProperties|.
         self.properties.update(type_.properties)
         self.functions = type_.functions
+      elif json_type == 'function':
+        self.type_ = PropertyType.FUNCTION
       elif json_type == 'binary':
         self.type_ = PropertyType.BINARY
       else:
         raise ParseException(self, 'type ' + json_type + ' not recognized')
     elif 'choices' in json:
       if not json['choices'] or len(json['choices']) == 0:
         raise ParseException(self, 'Choices has no choices')
       self.choices = {}
       self.type_ = PropertyType.CHOICES
       for choice_json in json['choices']:
@@ skipping 61 matching lines @@
 
   INTEGER = _Info(True, "INTEGER")
   DOUBLE = _Info(True, "DOUBLE")
   BOOLEAN = _Info(True, "BOOLEAN")
   STRING = _Info(True, "STRING")
   ENUM = _Info(False, "ENUM")
   ARRAY = _Info(False, "ARRAY")
   REF = _Info(False, "REF")
   CHOICES = _Info(False, "CHOICES")
   OBJECT = _Info(False, "OBJECT")
+  FUNCTION = _Info(False, "FUNCTION")
   BINARY = _Info(False, "BINARY")
   ANY = _Info(False, "ANY")
   ADDITIONAL_PROPERTIES = _Info(False, "ADDITIONAL_PROPERTIES")
 
 def UnixName(name):
   """Returns the unix_style name for a given lowerCamelCase string.
   """
   # First replace any lowerUpper patterns with lower_Upper.
   s1 = re.sub('([a-z])([A-Z])', r'\1_\2', name)
   # Now replace any ACMEWidgets patterns with ACME_Widgets
@@ skipping 37 matching lines @@
   for event_json in json.get('events', []):
     event = Function(model, event_json, from_client=True)
     model.events[event.name] = event
 
 def _AddProperties(model, json, from_json=False, from_client=False):
   """Adds model.Property objects to |model| contained in the 'properties' field
   of |json|.
   """
   model.properties = {}
   for name, property_json in json.get('properties', {}).items():
-    # TODO(calamity): support functions (callbacks) as properties.  The model
-    # doesn't support it yet because the h/cc generators don't -- this is
-    # because we'd need to hook it into a base::Callback or something.
-    #
-    # However, pragmatically it's not necessary to support them anyway, since
-    # the instances of functions-on-properties in the extension APIs are all
-    # handled in pure Javascript on the render process (and .: never reach
-    # C++ let alone the browser).
-    if property_json.get('type') == 'function':
-      continue
     model.properties[name] = Property(
         model,
         name,
         property_json,
         from_json=from_json,
         from_client=from_client)