From dbf699a991ab18e0ceb57beff95f630c9ef82901 Mon Sep 17 00:00:00 2001
From: ConnorSkees <39542938+ConnorSkees@users.noreply.github.com>
Date: Thu, 2 Apr 2020 18:16:59 -0400
Subject: [PATCH] handle empty list separators in join

---
 src/builtin/list.rs | 10 ++++++----
 tests/list.rs       |  5 +++++
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/builtin/list.rs b/src/builtin/list.rs
index fa67373..2de3e5b 100644
--- a/src/builtin/list.rs
+++ b/src/builtin/list.rs
@@ -151,9 +151,9 @@ pub(crate) fn register(f: &mut HashMap<String, Builtin>) {
                 Value::List(v, sep, brackets) => (v, sep, brackets),
                 v => (vec![v], ListSeparator::Space, Brackets::None),
             };
-            let list2 = match arg!(args, 1, "list2") {
-                Value::List(v, ..) => v,
-                v => vec![v],
+            let (list2, sep2) = match arg!(args, 1, "list2") {
+                Value::List(v, sep, ..) => (v, sep),
+                v => (vec![v], ListSeparator::Space),
             };
             let sep = match arg!(
                 args,
@@ -164,6 +164,8 @@ pub(crate) fn register(f: &mut HashMap<String, Builtin>) {
                     "auto" => {
                         if list1.len() < 2 && list2.len() < 2 {
                             ListSeparator::Space
+                        } else if list1.is_empty() {
+                            sep2
                         } else {
                             sep1
                         }
@@ -174,7 +176,7 @@ pub(crate) fn register(f: &mut HashMap<String, Builtin>) {
                         return Err("$separator: Must be \"space\", \"comma\", or \"auto\".".into())
                     }
                 },
-                _ => return Err("$separator: Must be \"space\", \"comma\", or \"auto\".".into()),
+                v => return Err(format!("$separator: {} is not a string.", v).into()),
             };
 
             let brackets = match arg!(
diff --git a/tests/list.rs b/tests/list.rs
index 6f6ddaa..4d6387b 100644
--- a/tests/list.rs
+++ b/tests/list.rs
@@ -207,6 +207,11 @@ test!(
     "a {\n  color: join(a b, c, $bracketed: afhsihsdhsdkhsd);\n}\n",
     "a {\n  color: [a b c];\n}\n"
 );
+test!(
+    join_empty_first_takes_second_list_separator,
+    "a {\n  color: join((), (a, b, c));\n}\n",
+    "a {\n  color: a, b, c;\n}\n"
+);
 test!(bracketed_ident, "a {\n  color: [a];\n}\n");
 test!(bracketed_space_list, "a {\n  color: [a b];\n}\n");
 test!(bracketed_comma_list, "a {\n  color: [a, b];\n}\n");