JSON Schema Compiler supports functions as PropertyTypes.

tools/json_schema_compiler/cc_generator.py

Index: tools/json_schema_compiler/cc_generator.py
diff --git a/tools/json_schema_compiler/cc_generator.py b/tools/json_schema_compiler/cc_generator.py
index 8cea17b588af55ed93f5df205ca5076d9bf6080d..6cb2b5f87afb8469631e0e42a3fad967295d0774 100644
--- a/tools/json_schema_compiler/cc_generator.py
+++ b/tools/json_schema_compiler/cc_generator.py
@@ -152,6 +152,7 @@ class CCGenerator(object):
             t == PropertyType.CHOICES or
             t == PropertyType.ENUM or
             t == PropertyType.OBJECT or
+            t == PropertyType.FUNCTION or
             t == PropertyType.REF or
             t == PropertyType.STRING):
         # TODO(miket): It would be nice to initialize CHOICES and ENUM, but we
@@ -215,13 +216,21 @@ class CCGenerator(object):
     value_var = prop.unix_name + '_value'
     c.Append('base::Value* %(value_var)s = NULL;')
     if prop.optional:
-      (c.Sblock(
-          'if (%(src)s->GetWithoutPathExpansion("%(key)s", &%(value_var)s)) {'
+      if prop.type_ == PropertyType.FUNCTION:

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

Comment why you're only generating for optional.

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

the empty dict solved a lot of problems, so a lot of these comments will no
longer be relevant. 

On 2012/07/25 01:32:33, kalman wrote:

+        # For functions, we only want to check the presence, we are not actually
+        # getting a value

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

nit: fullstop

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

Done.

+        (c.Sblock('%s->has_%s = '
+              '%s->GetWithoutPathExpansion("%s", &%s);' %

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

just use HasKey, don't need to Get it too.

+                  (dst, prop.unix_name, src, prop.name, value_var))
+        )
+      else:
+        (c.Sblock(
+            'if (%(src)s->GetWithoutPathExpansion("%(key)s", &%(value_var)s)) {'
+          )
+          .Concat(self._GeneratePopulatePropertyFromValue(
+              prop, value_var, dst, 'false'))
+          .Eblock('}')
         )
-        .Concat(self._GeneratePopulatePropertyFromValue(
-            prop, value_var, dst, 'false'))
-        .Eblock('}')
-      )
     else:
       (c.Append(
           'if (!%(src)s->GetWithoutPathExpansion("%(key)s", &%(value_var)s))')
@@ -250,7 +259,7 @@ class CCGenerator(object):
       if prop.type_ == PropertyType.ADDITIONAL_PROPERTIES:
         c.Append('value->MergeDictionary(&%s);' % prop.unix_name)
       else:
-        if prop.optional:
+        if prop.optional and not prop.type_ == PropertyType.FUNCTION:

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

nit: assign this condition to a local variable and read it here and below.

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

Done.

           if prop.type_ == PropertyType.ENUM:
             c.Sblock('if (%s != %s)' %
                 (prop.unix_name,
@@ -264,7 +273,7 @@ class CCGenerator(object):
         c.Append('value->SetWithoutPathExpansion("%s", %s);' % (
             prop.name,
             self._CreateValueFromProperty(prop, 'this->' + prop.unix_name)))
-        if prop.optional:
+        if prop.optional and not prop.type_ == PropertyType.FUNCTION:
           c.Eblock();
     (c.Append()
       .Append('return value.Pass();')
@@ -318,6 +327,8 @@ class CCGenerator(object):
       return '%s.DeepCopy()' % var
     elif prop.type_ == PropertyType.ENUM:
       return 'CreateEnumValue(%s).release()' % var
+    elif prop.type_ == PropertyType.FUNCTION:

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

Hm, well, for consistency with the way that functions come in from the renderer,
this should return an empty object (i.e. empty DictionaryValue).

I just spent a while looking through how onclick even arrives at the browser in
the first place, and it looks like a bit of a fluke; in V8ValueConverterImpl it
just happens that functions get serialised to an empty object in json; and
that's how they're going to come into json-schema-compiler.

I'm tempted to just ignore going back from has_foo to a value, but you never
know; that might surprise somebody at some point. So let's just make it
seriialize to an empty object.

(Add comment to that effect btw)

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

Done.

+      return 'base::Value::CreateBooleanValue(this->has_%s)' % prop.unix_name
     elif prop.type_ == PropertyType.BINARY:
       if prop.optional:
         vardot = var + '->'
@@ -469,6 +480,8 @@ class CCGenerator(object):
               'if (!%(ctype)s::Populate(*dictionary, &%(dst)s->%(name)s))')
           .Append('  return %(failure_value)s;')
         )
+    elif prop.type_ == PropertyType.FUNCTION:
+      c.Append('%s->has_%s = true;' % (dst, prop.unix_name))

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

comment plz, the stuff about the renderer I said in the comment above.

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

Done.

     elif prop.type_ == PropertyType.ANY:
       if prop.optional:
         c.Append('%(dst)s->%(name)s.reset(new ' + any_helper.ANY_CLASS + '());')