Mojo: Mojom: Disallow trailing commas in parameter lists.

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

Index: mojo/public/tools/bindings/pylib/mojom/parse/parser.py
diff --git a/mojo/public/tools/bindings/pylib/mojom/parse/parser.py b/mojo/public/tools/bindings/pylib/mojom/parse/parser.py
index 0bd6094500ca770ec956f442c51bddff40d03d22..35ca5c790c8e0f698abc1dc8e19fef2bbbd20995 100644
--- a/mojo/public/tools/bindings/pylib/mojom/parse/parser.py
+++ b/mojo/public/tools/bindings/pylib/mojom/parse/parser.py
@@ -177,16 +177,22 @@ class Parser(object):
     """method : NAME ordinal LPAREN parameter_list RPAREN response SEMI"""
     p[0] = ('METHOD', p[1], p[4], p[2], p[6])
 
-  def p_parameter_list(self, p):
-    """parameter_list : parameter
-                      | parameter COMMA parameter_list
-                      | """
-    if len(p) == 1:
-      p[0] = []
-    elif len(p) == 2:
-      p[0] = [p[1]]
-    else:
-      p[0] = [p[1]] + p[3]
+  def p_parameter_list_1(self, p):

[jamesr, 2014/07/02 22:03:01]

do _1 / _2 have any particular meaning? i'd expect naively for this to mean
"with one parameter" and "with two parameters" but that clearly isn't the case.
can we name these something else?

+    """parameter_list : """
+    p[0] = []
+
+  def p_parameter_list_2(self, p):
+    """parameter_list : nonempty_parameter_list"""
+    p[0] = p[1]
+
+  def p_nonempty_parameter_list_1(self, p):
+    """nonempty_parameter_list : parameter"""
+    p[0] = [p[1]]
+
+  def p_nonempty_parameter_list_2(self, p):
+    """nonempty_parameter_list : nonempty_parameter_list COMMA parameter"""
+    p[0] = p[1]
+    p[0].append(p[3])
 
   def p_parameter(self, p):
     """parameter : typename NAME ordinal"""