Deprecate the feature-exists function (#2235)

Co-authored-by: Natalie Weizenbaum <nweiz@google.com>

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## 1.78.0
 
+* The `meta.feature-exists` function is now deprecated. This deprecation is
+  named `feature-exists`.
+
 * Fix a crash when using `@at-root` without any queries or children in the
   indented syntax.
 

lib/src/deprecation.dart

@@ -15,7 +15,7 @@ enum Deprecation {
   // DO NOT EDIT. This section was generated from the language repo.
   // See tool/grind/generate_deprecations.dart for details.
   //
-  // Checksum: 309e4f1f008f08379b824ab6094e13df2e18e187
+  // Checksum: dd5c6aa0f1431fa9fc88bb71a96f832adbc165f5
 
   /// Deprecation for passing a string directly to meta.call().
   callString('call-string',
@@ -95,6 +95,10 @@ enum Deprecation {
       deprecatedIn: '1.77.7',
       description: 'Declarations after or between nested rules.'),
 
+  /// Deprecation for meta.feature-exists
+  featureExists('feature-exists',
+      deprecatedIn: '1.78.0', description: 'meta.feature-exists'),
+
   /// Deprecation for @import rules.
   import.future('import', description: '@import rules.'),
 

lib/src/functions/meta.dart

@@ -8,6 +8,8 @@ import 'package:collection/collection.dart';
 
 import '../ast/sass/statement/mixin_rule.dart';
 import '../callable.dart';
+import '../deprecation.dart';
+import '../evaluation_context.dart';
 import '../util/map.dart';
 import '../value.dart';
 
@@ -26,6 +28,10 @@ final global = UnmodifiableListView([
   // evaluator, because they need access to context that's only available at
   // runtime.
   _function("feature-exists", r"$feature", (arguments) {
+    warnForDeprecation(
+        "The feature-exists() function is deprecated.\n\n"
+        "More info: https://sass-lang.com/d/feature-exists",
+        Deprecation.featureExists);
     var feature = arguments[0].assertString("feature");
     return SassBoolean(_features.contains(feature.text));
   }),