Deprecate duplicate !global and !default declarations (#1931)

See #604
See sass/sass#2607

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.62.0
+
+* Deprecate the use of multiple `!global` or `!default` flags on the same
+  variable. This deprecation is named `duplicate-var-flags`.
+
 ## 1.61.0
 
 * **Potentially breaking change:** Drop support for End-of-Life Node.js 12.

lib/src/deprecation.dart

@@ -54,6 +54,11 @@ enum Deprecation {
       deprecatedIn: '1.56.0',
       description: 'Passing invalid units to built-in functions.'),
 
+  duplicateVariableFlags('duplicate-var-flags',
+      deprecatedIn: '1.62.0',
+      description:
+          'Using !default or !global multiple times for one variable.'),
+
   /// Deprecation for `@import` rules.
   import.future('import', description: '@import rules.'),
 

lib/src/parse/stylesheet.dart

@@ -230,11 +230,25 @@ abstract class StylesheetParser extends Parser {
     while (scanner.scanChar($exclamation)) {
       var flag = identifier();
       if (flag == 'default') {
+        if (guarded) {
+          logger.warnForDeprecation(
+              Deprecation.duplicateVariableFlags,
+              '!default should only be written once for each variable.\n'
+              'This will be an error in Dart Sass 2.0.0.',
+              span: scanner.spanFrom(flagStart));
+        }
+
         guarded = true;
       } else if (flag == 'global') {
         if (namespace != null) {
           error("!global isn't allowed for variables in other modules.",
               scanner.spanFrom(flagStart));
+        } else if (global) {
+          logger.warnForDeprecation(
+              Deprecation.duplicateVariableFlags,
+              '!global should only be written once for each variable.\n'
+              'This will be an error in Dart Sass 2.0.0.',
+              span: scanner.spanFrom(flagStart));
         }
 
         global = true;

pkg/sass_api/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 6.3.0
+
+* No user-visible changes.
+
 ## 6.2.0
 
 * 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: 6.2.0
+version: 6.3.0-dev
 description: Additional APIs for Dart Sass.
 homepage: https://github.com/sass/dart-sass
 
 environment:
   sdk: ">=2.17.0 <3.0.0"
 
 dependencies:
-  sass: 1.61.0
+  sass: 1.62.0
 
 dev_dependencies:
   dartdoc: ^5.0.0

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.61.0
+version: 1.62.0-dev
 description: A Sass implementation in Dart.
 homepage: https://github.com/sass/dart-sass