support arg to map-merge

src/builtin/functions/map.rs

@@ -1,3 +1,5 @@
+use std::mem;
+
 use super::{Builtin, GlobalFunctionMap};
 
 use crate::{
@@ -87,7 +89,12 @@ pub(crate) fn map_values(mut args: CallArgs, parser: &mut Parser<'_>) -> SassRes
 }
 
 pub(crate) fn map_merge(mut args: CallArgs, parser: &mut Parser<'_>) -> SassResult<Value> {
-    args.max_args(2)?;
+    if args.len() == 1 {
+        return Err(("Expected $args to contain a key.", args.span()).into());
+    }
+
+    let last_position = args.len().saturating_sub(1);
+
     let mut map1 = match args.get_err(0, "map1")? {
         Value::Map(m) => m,
         Value::List(v, ..) if v.is_empty() => SassMap::new(),
@@ -100,7 +107,8 @@ pub(crate) fn map_merge(mut args: CallArgs, parser: &mut Parser<'_>) -> SassResu
                 .into())
         }
     };
-    let map2 = match args.get_err(1, "map2")? {
+
+    let mut map2 = match args.get_err(last_position, "map2")? {
         Value::Map(m) => m,
         Value::List(v, ..) if v.is_empty() => SassMap::new(),
         Value::ArgList(v) if v.is_empty() => SassMap::new(),
@@ -112,7 +120,28 @@ pub(crate) fn map_merge(mut args: CallArgs, parser: &mut Parser<'_>) -> SassResu
                 .into())
         }
     };
-    map1.merge(map2);
+
+    let mut keys = args.get_variadic()?;
+
+    if keys.is_empty() {
+        map1.merge(map2);
+    } else {
+        while let Some(key) = keys.pop() {
+            let mut new_map = SassMap::new();
+            new_map.insert(key.node, Value::Map(mem::take(&mut map2)));
+            map2 = new_map;
+        }
+
+        for (key, value) in map2 {
+            // if they are two maps sharing a key, merge the keys
+            if let (Some(Value::Map(map1)), Value::Map(map2)) = (map1.get_mut(&key), &value) {
+                map1.merge(map2.clone());
+            } else {
+                map1.insert(key, value);
+            }
+        }
+    }
+
     Ok(Value::Map(map1))
 }
 

src/lib.rs

@@ -43,7 +43,7 @@ grass input.scss
     // it is sometimes useful to break up `impl`s
     clippy::multiple_inherent_impl,
     // filter isn't fallible
-    clippy::filter_map,
+    clippy::manual_filter_map,
     clippy::else_if_without_else,
     clippy::new_ret_no_self,
     renamed_and_removed_lints,

src/value/map.rs

@@ -6,7 +6,7 @@ use crate::{
     value::Value,
 };
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Default)]
 pub(crate) struct SassMap(Vec<(Value, Value)>);
 
 impl PartialEq for SassMap {
@@ -51,6 +51,16 @@ impl SassMap {
         Ok(None)
     }
 
+    pub fn get_mut(&mut self, key: &Value) -> Option<&mut Value> {
+        for (k, v) in &mut self.0 {
+            if k == key {
+                return Some(v);
+            }
+        }
+
+        None
+    }
+
     pub fn remove(&mut self, key: &Value) {
         self.0.retain(|(ref k, ..)| k.not_equals(key));
     }

tests/map.rs

@@ -95,6 +95,31 @@ test!(
     "a {\n  color: inspect(map-merge((c: d, e: f), (c: 1, e: 2)));\n}\n",
     "a {\n  color: (c: 1, e: 2);\n}\n"
 );
+test!(
+    map_merge_nested_empty,
+    "a {b: inspect(map-merge((c: ()), c, ()))}",
+    "a {\n  b: (c: ());\n}\n"
+);
+test!(
+    map_merge_nested_overlapping_keys,
+    "a {b: inspect(map-merge((c: (d: e, f: g, h: i)), c, (j: 1, f: 2, k: 3)))}",
+    "a {\n  b: (c: (d: e, f: 2, h: i, j: 1, k: 3));\n}\n"
+);
+test!(
+    map_merge_nested_intermediate_is_not_map,
+    "a {b: inspect(map-merge((c: 1), c, d, (e: f)))}",
+    "a {\n  b: (c: (d: (e: f)));\n}\n"
+);
+test!(
+    map_merge_nested_leaf_is_not_map,
+    "a {b: inspect(map-merge((c: 1), c, (d: e)))}",
+    "a {\n  b: (c: (d: e));\n}\n"
+);
+test!(
+    map_merge_nested_multiple_keys,
+    "a {b: inspect(map-merge((c: (d: (e: (f: (g: h))))), c, d, e, f, (g: 1)))}",
+    "a {\n  b: (c: (d: (e: (f: (g: 1)))));\n}\n"
+);
 error!(
     map_merge_map1_non_map,
     "a {\n  color: map-merge(foo, (a: b));\n}\n", "Error: $map1: foo is not a map."