JSON Schema Compiler supports functions as PropertyTypes.

tools/json_schema_compiler/h_generator.py

Index: tools/json_schema_compiler/h_generator.py
diff --git a/tools/json_schema_compiler/h_generator.py b/tools/json_schema_compiler/h_generator.py
index ba7c5ca133a27b4a4ebc5e87089b5a77071a143c..67f1d264b01c99c9d80ca862c276fe02d4cc87dc 100644
--- a/tools/json_schema_compiler/h_generator.py
+++ b/tools/json_schema_compiler/h_generator.py
@@ -156,11 +156,17 @@ class HGenerator(object):
         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