Correctly preserve commas in append().

2 files changed, 5 insertions, 1 deletions

diff --git a/scss/functions/core.py b/scss/functions/core.py
index 422b505..9a68cc8 100644
--- a/scss/functions/core.py
+++ b/scss/functions/core.py
@@ -474,8 +474,9 @@ CORE_LIBRARY.add(Number.wrap_python_function(math.floor), 'floor', 1)
 
 def __parse_separator(separator, default_from=None):
     if separator is None:
-        return None
+        separator = 'auto'
     separator = String.unquoted(separator).value
+
     if separator == 'comma':
         return True
     elif separator == 'space':
diff --git a/scss/tests/functions/test_core.py b/scss/tests/functions/test_core.py
index d6a8ed0..4b1e906 100644
--- a/scss/tests/functions/test_core.py
+++ b/scss/tests/functions/test_core.py
@@ -322,6 +322,9 @@ def test_append(calc):
     assert calc('append(10px, 20px, comma)') == calc('10px, 20px')
     assert calc('append((blue, red), green, space)') == calc('blue red green')
 
+    # TODO need to test for commas here
+    assert calc('append((a, b), c)') == calc('a, b, c')
+
 
 def test_zip(calc):
     # Examples from the Ruby docs