[mojo] Add mojom parser support for native-only structs

mojo/public/tools/bindings/pylib/mojom/generate/data.py

 # Copyright 2013 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.
 
 # TODO(vtl): "data" is a pretty vague name. Rename it?
 
 import copy
 
 import module as mojom
 
@@ skipping 191 matching lines @@
     # TODO(yzshen): EnumToData() and ConstantToData() are missing.
     istr(2, 'enums'): [],
     istr(3, 'constants'): []
   }
   AddOptional(data, istr(4, 'attributes'), struct.attributes)
   return data
 
 def StructFromData(module, data):
   struct = mojom.Struct(module=module)
   struct.name = data['name']
+  struct.native_only = data['native_only']
   struct.spec = 'x:' + module.namespace + '.' + struct.name
   module.kinds[struct.spec] = struct
-  struct.enums = map(lambda enum:
-      EnumFromData(module, enum, struct), data['enums'])
-  struct.constants = map(lambda constant:
-      ConstantFromData(module, constant, struct), data['constants'])
-  # Stash fields data here temporarily.
-  struct.fields_data = data['fields']
+  if struct.native_only:
+    struct.enums = []
+    struct.constants = []
+    struct.fields_data = []
+  else:
+    struct.enums = map(lambda enum:
+        EnumFromData(module, enum, struct), data['enums'])
+    struct.constants = map(lambda constant:
+        ConstantFromData(module, constant, struct), data['constants'])
+    # Stash fields data here temporarily.
+    struct.fields_data = data['fields']
   struct.attributes = data.get('attributes')
+
+  # Enforce that a [native=True] attribute is set to make native-only struct
+  # declarations more explicit.
+  if struct.native_only:
+    if not struct.attributes or not struct.attributes.get('native', False):
+      raise Exception("Native-only struct declarations must include a " +
+                      "native=True attribute.")
+
   return struct
 
 def UnionToData(union):
   data = {
     istr(0, 'name'): union.name,
     istr(1, 'fields'): map(FieldToData, union.fields)
   }
   AddOptional(data, istr(2, 'attributes'), union.attributes)
   return data
 
@@ skipping 248 matching lines @@
 
 def OrderedModuleFromData(data):
   module = ModuleFromData(data)
   for interface in module.interfaces:
     next_ordinal = 0
     for method in interface.methods:
       if method.ordinal is None:
         method.ordinal = next_ordinal
       next_ordinal = method.ordinal + 1
   return module