Fix Issue pallets#100, tailing commas in macros args

This change will allow trailing commas in macro definitions, and in
calls to macros.

jinja2/parser.py

@@ -308,6 +308,8 @@ def parse_signature(self, node):
         while self.stream.current.type != 'rparen':
             if args:
                 self.stream.expect('comma')
+            if self.stream.current.type == 'rparen':
+                break
             arg = self.parse_assign_target(name_only=True)
             arg.set_ctx('param')
             if self.stream.skip_if('assign'):

jinja2/testsuite/core_tags.py

@@ -226,6 +226,12 @@ def test_arguments(self):
 {{ m() }}|{{ m('a') }}|{{ m('a', 'b') }}|{{ m(1, 2, 3) }}''')
         assert tmpl.render() == '||c|d|a||c|d|a|b|c|d|1|2|3|d'
 
+    def test_trailing_comma(self):
+        tmpl = self.env.from_string('''\
+{% macro m(a, b,) %}{{ a }}|{{ b }}{% endmacro %}
+{{ m(1,2,) }}''')
+        assert tmpl.render() == '1|2'
+
     def test_varargs(self):
         tmpl = self.env.from_string('''\
 {% macro test() %}{{ varargs|join('|') }}{% endmacro %}\