JSON Schema Compiler supports functions as PropertyTypes.

tools/json_schema_compiler/h_generator.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.
 
 from code import Code
 from model import PropertyType
 import cpp_util
 import schema_util
 
 class HGenerator(object):
@@ skipping 138 matching lines @@
     """
     c = Code()
     # Generate the enums needed for any fields with "choices"
     for prop in props:
       if prop.type_ == PropertyType.CHOICES:
         enum_name = self._cpp_type_generator.GetChoicesEnumType(prop)
         c.Append('%s %s_type;' % (enum_name, prop.unix_name))
         c.Append()
 
     for prop in self._cpp_type_generator.ExpandParams(props):
-      if prop.description:
+      if prop.type_ == PropertyType.FUNCTION and prop.optional:
+        c.Comment('Determines whether the given optional function was passed '
+                  'as a parameter.')

[not at google - send to devlin, 2012/07/25 01:32:33]

include the function name here, and include the overall comment either way if
there is one?

[chebert, 2012/07/25 18:38:30]

Done.

+      elif prop.description:
         c.Comment(prop.description)
-      c.Append('%s %s;' % (
-          self._cpp_type_generator.GetType(prop, wrap_optional=True),
-          prop.unix_name))
+      if prop.type_ == PropertyType.FUNCTION:
+        c.Append('bool has_%s;' % prop.unix_name)

[not at google - send to devlin, 2012/07/25 01:32:33]

i think you only want this if it's optional too.

[chebert, 2012/07/25 18:38:30]

Done.

+      else:
+        c.Append('%s %s;' % (
+            self._cpp_type_generator.GetType(prop, wrap_optional=True),
+            prop.unix_name))
       c.Append()
     return c
 
   def _GenerateType(self, type_):
     """Generates a struct for a type.
     """
     classname = cpp_util.Classname(schema_util.StripSchemaNamespace(type_.name))
     c = Code()
 
     if type_.functions:
@@ skipping 170 matching lines @@
 
   def _GenerateFunctionResults(self, callback):
     """Generates namespace for passing a function's result back.
     """
     c = Code()
     (c.Sblock('namespace Results {')
         .Concat(self._GenerateCreateCallbackArguments(callback))
       .Eblock('};')
     )
     return c