do not strip whitespace before comma in psuedo selector

src/parse/mod.rs

@@ -319,6 +319,7 @@ impl<'a> Parser<'a> {
 
         let mut found_curly = false;
 
+        // we resolve interpolation and strip comments
         while let Some(tok) = self.toks.next() {
             span = span.merge(tok.pos());
             match tok.kind {
@@ -330,16 +331,6 @@ impl<'a> Parser<'a> {
                         string.push('#');
                     }
                 }
-                ',' => {
-                    while let Some(c) = string.pop() {
-                        if c == ' ' || c == ',' {
-                            continue;
-                        }
-                        string.push(c);
-                        string.push(',');
-                        break;
-                    }
-                }
                 '/' => {
                     if self.toks.peek().is_none() {
                         return Err(("Expected selector.", tok.pos()).into());

tests/selectors.rs

@@ -668,6 +668,11 @@ test!(
     "a, // 1\nb,\nc {\n    color: red;\n}\n",
     "a,\nb,\nc {\n  color: red;\n}\n"
 );
+test!(
+    spaces_are_preserved_before_comma_in_pseudo_arg,
+    ":a(a , b) {\n  color: &;\n}\n",
+    ":a(a , b) {\n  color: :a(a , b);\n}\n"
+);
 error!(
     a_n_plus_b_n_invalid_odd,
     ":nth-child(ofdd) {\n  color: &;\n}\n", "Error: Expected \"odd\"."