Remove trailing Undefined arguments

2 files changed, 5 insertions, 3 deletions

diff --git a/scss/expression.py b/scss/expression.py
index 745ef2e..9194363 100644
--- a/scss/expression.py
+++ b/scss/expression.py
@@ -358,7 +358,9 @@ class ArgspecLiteral(Expression):
         # argpairs is a list of 2-tuples, parsed as though this were a function
         # call, so (variable name as string or None, default value as AST
         # node).
-        self.argpairs = argpairs
+        while argpairs and argpairs[-1] == (None, None):
+            argpairs = argpairs[:-1]
+        self.argpairs = tuple((var, Literal(Undefined()) if value is None else value) for var, value in argpairs)
 
     def iter_def_argspec(self):
         """Interpreting this literal as a function definition, yields pairs of
@@ -499,7 +501,7 @@ class SassExpression(Parser):
         v = [argspec_item]
         while self._peek(self.argspec_rsts) == '","':
             self._scan('","')
-            argspec_item = (None, Literal(Undefined()))
+            argspec_item = (None, None)
             if self._peek(self.argspec_rsts_) not in self.argspec_rsts:
                 argspec_item = self.argspec_item()
             v.append(argspec_item)
diff --git a/scss/src/grammar/grammar.g b/scss/src/grammar/grammar.g
index d2dbe6f..a65c6a5 100644
--- a/scss/src/grammar/grammar.g
+++ b/scss/src/grammar/grammar.g
@@ -40,7 +40,7 @@ parser SassExpression:
 
     rule argspec:       argspec_item                {{ v = [argspec_item] }}
                         (
-                            ","                     {{ argspec_item = (None, Literal(Undefined())) }}
+                            ","                     {{ argspec_item = (None, None) }}
                             [ argspec_item ]        {{ v.append(argspec_item) }}
                         )*                          {{ return ArgspecLiteral(v) }}