Implement builtin function list-separator()

src/builtin/list.rs

@@ -3,6 +3,7 @@ use std::collections::HashMap;
 use num_traits::cast::ToPrimitive;
 
 use super::Builtin;
+use crate::common::{ListSeparator, QuoteKind};
 use crate::unit::Unit;
 use crate::value::{Number, Value};
 
@@ -55,4 +56,18 @@ pub(crate) fn register(f: &mut HashMap<String, Builtin>) {
             }
         }),
     );
+    f.insert(
+        "list-separator".to_owned(),
+        Box::new(|args, _| {
+            max_args!(args, 1);
+            Ok(Value::Ident(
+                match arg!(args, 0, "list") {
+                    Value::List(_, sep) => sep.name(),
+                    _ => ListSeparator::Space.name(),
+                }
+                .to_owned(),
+                QuoteKind::None,
+            ))
+        }),
+    );
 }

src/common.rs

@@ -382,8 +382,6 @@ impl ListSeparator {
         }
     }
 
-    // Used in currently unimplemented builtin function
-    #[allow(dead_code)]
     pub fn name(self) -> &'static str {
         match self {
             Self::Space => "space",

tests/list.rs

@@ -33,3 +33,25 @@ test!(
     "a {\n  color: nth((a, b, c), 3);\n}\n",
     "a {\n  color: c;\n}\n"
 );
+test!(
+    list_separator_space_separated,
+    "a {\n  color: list-separator(a b c);\n}\n",
+    "a {\n  color: space;\n}\n"
+);
+test!(
+    list_separator_foo,
+    "a {\n  color: list-separator(foo);\n}\n",
+    "a {\n  color: space;\n}\n"
+);
+test!(
+    list_separator_comma_separated,
+    "a {\n  color: list-separator((a, b, c));\n}\n",
+    "a {\n  color: comma;\n}\n"
+);
+// blocked on better parsing of comma separated lists with
+// space separated lists inside
+// test!(
+//     list_separator_comma_separated_with_space,
+//     "a {\n  color: list-separator(((a b, c d)));\n}\n",
+//     "a {\n  color: comma;\n}\n"
+// );