[mojo-bindings] Support reuse of native enum classes

mojo/public/tools/bindings/pylib/mojom/parse/parser.py

 # Copyright 2014 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.
 
 """Generates a syntax tree from a Mojo IDL file."""
 
 import imp
 import os.path
 import sys
 
@@ skipping 316 matching lines @@
 
   def p_ordinal_2(self, p):
     """ordinal : ORDINAL"""
     value = int(p[1][1:])
     if value > _MAX_ORDINAL_VALUE:
       raise ParseError(self.filename, "Ordinal value %d too large:" % value,
                        lineno=p.lineno(1),
                        snippet=self._GetSnippet(p.lineno(1)))
     p[0] = ast.Ordinal(value, filename=self.filename, lineno=p.lineno(1))
 
-  def p_enum(self, p):
+  def p_enum_1(self, p):
     """enum : attribute_section ENUM NAME LBRACE nonempty_enum_value_list \
                   RBRACE SEMI
             | attribute_section ENUM NAME LBRACE nonempty_enum_value_list \
                   COMMA RBRACE SEMI"""
     p[0] = ast.Enum(p[3], p[1], p[5], filename=self.filename,
                     lineno=p.lineno(2))
 
+  def p_enum_2(self, p):
+    """enum : attribute_section ENUM NAME SEMI"""
+    p[0] = ast.Enum(p[3], p[1], None, filename=self.filename,
+                    lineno=p.lineno(2))
+
   def p_nonempty_enum_value_list_1(self, p):
     """nonempty_enum_value_list : enum_value"""
     p[0] = ast.EnumValueList(p[1])
 
   def p_nonempty_enum_value_list_2(self, p):
     """nonempty_enum_value_list : nonempty_enum_value_list COMMA enum_value"""
     p[0] = p[1]
     p[0].Append(p[3])
 
   def p_enum_value(self, p):
@@ skipping 64 matching lines @@
 
 def Parse(source, filename):
   lexer = Lexer(filename)
   parser = Parser(lexer, source, filename)
 
   lex.lex(object=lexer)
   yacc.yacc(module=parser, debug=0, write_tables=0)
 
   tree = yacc.parse(source)
   return tree