Mojo: Mojom: Disallow trailing commas in parameter lists.

mojo/public/tools/bindings/pylib/mojom_tests/parse/parser_unittest.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.
 
 import imp
 import os.path
 import sys
 import unittest
 
 # Disable lint check for finding modules:
@@ skipping 625 matching lines @@
             'MyInterface',
             None,
             [('METHOD',
               'MyMethod',
               [ast.Parameter('string', 'a', ast.Ordinal(None))],
               ast.Ordinal(None),
               [ast.Parameter('int32', 'a', ast.Ordinal(None)),
                ast.Parameter('bool', 'b', ast.Ordinal(None))])])])]
     self.assertEquals(parser.Parse(source3, "my_file.mojom"), expected3)
 
+  def testInvalidMethods(self):
+    """Tests that invalid method declarations are correctly detected."""
+
+    # No trailing commas.
+    source1 = """\
+        interface MyInterface {
+          MyMethod(string a,);
+        };
+        """
+    with self.assertRaisesRegexp(
+        parser.ParseError,
+        r"^my_file\.mojom:2: Error: Unexpected '\)':\n"
+            r" *MyMethod\(string a,\);$"):
+      parser.Parse(source1, "my_file.mojom")
+
+    # No leading commas.
+    source2 = """\
+        interface MyInterface {
+          MyMethod(, string a);
+        };
+        """
+    with self.assertRaisesRegexp(
+        parser.ParseError,
+        r"^my_file\.mojom:2: Error: Unexpected ',':\n"
+            r" *MyMethod\(, string a\);$"):
+      parser.Parse(source2, "my_file.mojom")
+
 if __name__ == "__main__":
   unittest.main()