Revert the core of #2255 (#2511)

This was causing serious performance issues in places where `@extend`
was used heavily with a large number of extenders.

Closes #2504

Author: nex3

CHANGELOG.md

@@ -1,7 +1,11 @@
-## 1.84.1-dev
+## 1.85.0-dev
 
 * No user-visible changes.
 
+* No longer fully trim redundant selectors generated by `@extend`. This caused
+  unacceptable performance issues for certain heavy users of `@extend`. We'll
+  try to find a more performant way to accomplish it in the future.
+
 ## 1.84.0
 
 * Allow newlines in whitespace in the indented syntax.

lib/src/extend/extension_store.dart

@@ -901,6 +901,13 @@ class ExtensionStore {
   // document, and thus should never be trimmed.
   List<ComplexSelector> _trim(List<ComplexSelector> selectors,
       bool isOriginal(ComplexSelector complex)) {
+    // Avoid truly horrific quadratic behavior.
+    //
+    // TODO(nweiz): I think there may be a way to get perfect trimming without
+    // going quadratic by building some sort of trie-like data structure that
+    // can be used to look up superselectors.
+    if (selectors.length > 100) return selectors;
+
     // This is n² on the sequences, but only comparing between separate
     // sequences should limit the quadratic behavior. We iterate from last to
     // first and reverse the result so that, if two selectors are identical, we

pkg/sass_api/CHANGELOG.md

@@ -1,4 +1,4 @@
-## 15.1.1-dev
+## 15.2.0-dev
 
 * 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: 15.1.1-dev
+version: 15.2.0-dev
 description: Additional APIs for Dart Sass.
 homepage: https://github.com/sass/dart-sass
 
 environment:
   sdk: ">=3.3.0 <4.0.0"
 
 dependencies:
-  sass: 1.84.1
+  sass: 1.85.0
 
 dev_dependencies:
   dartdoc: ^8.0.14

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.84.1-dev
+version: 1.85.0-dev
 description: A Sass implementation in Dart.
 homepage: https://github.com/sass/dart-sass