Update the order of maps returned by map.deep-merge() (#1680)

Closes sass/sass#3092

CHANGELOG.md

@@ -1,4 +1,9 @@
-## 1.50.2
+## 1.51.0
+
+* **Potentially breaking change**: Change the order of maps returned by
+  `map.deep-merge()` to match those returned by `map.merge()`. All keys that
+  appeared in the first map will now be listed first in the same order they
+  appeared in that map, followed by any new keys added from the second map.
 
 * Improve the string output of some AST nodes in error messages.
 

lib/src/functions/map.dart

@@ -193,41 +193,28 @@ Value _modify(SassMap map, Iterable<Value> keys, Value modify(Value old),
 /// If both [map1] and [map2] have a map value associated with the same key,
 /// this recursively merges those maps as well.
 SassMap _deepMergeImpl(SassMap map1, SassMap map2) {
+  if (map1.contents.isEmpty) return map2;
   if (map2.contents.isEmpty) return map1;
 
-  // Avoid making a mutable copy of `map2` if it would totally overwrite `map1`
-  // anyway.
-  var mutable = false;
-  var result = map2.contents;
-  void _ensureMutable() {
-    if (mutable) return;
-    mutable = true;
-    result = Map.of(result);
-  }
+  var result = Map.of(map1.contents);
 
-  // Because values in `map2` take precedence over `map1`, we just check if any
-  // entries in `map1` don't have corresponding keys in `map2`, or if they're
-  // maps that need to be merged in their own right.
-  map1.contents.forEach((key, value) {
-    var resultValue = result[key];
-    if (resultValue == null) {
-      _ensureMutable();
+  map2.contents.forEach((key, value) {
+    var resultMap = result[key]?.tryMap();
+    if (resultMap == null) {
       result[key] = value;
     } else {
-      var resultMap = resultValue.tryMap();
       var valueMap = value.tryMap();
-
-      if (resultMap != null && valueMap != null) {
-        var merged = _deepMergeImpl(valueMap, resultMap);
+      if (valueMap != null) {
+        var merged = _deepMergeImpl(resultMap, valueMap);
         if (identical(merged, resultMap)) return;
-
-        _ensureMutable();
         result[key] = merged;
+      } else {
+        result[key] = value;
       }
     }
   });
 
-  return mutable ? SassMap(result) : map2;
+  return SassMap(result);
 }
 
 /// Like [new BuiltInCallable.function], but always sets the URL to `sass:map`.

pkg/sass_api/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.0.0-beta.43
+
+* No user-visible changes.
+
 ## 1.0.0-beta.42
 
 * No user-visible changes.

pkg/sass_api/pubspec.yaml

@@ -2,15 +2,15 @@ name: sass_api
 # Note: Every time we add a new Sass AST node, we need to bump the *major*
 # version because it's a breaking change for anyone who's implementing the
 # visitor interface(s).
-version: 1.0.0-beta.42
+version: 1.0.0-beta.43
 description: Additional APIs for Dart Sass.
 homepage: https://github.com/sass/dart-sass
 
 environment:
   sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
-  sass: 1.50.1
+  sass: 1.51.0
 
 dependency_overrides:
   sass: {path: ../..}

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.50.2-dev
+version: 1.51.0
 description: A Sass implementation in Dart.
 homepage: https://github.com/sass/dart-sass