Support empty custom properties

See sass/sass#4078

Author: nex3

CHANGELOG.md

@@ -1,4 +1,6 @@
-## 1.88.1-dev
+## 1.89.0
+
+* Allow custom properties with empty values (such as `--var:;`).
 
 * Fix a bug when calculating source spans for interpolations.
 

lib/src/parse/stylesheet.dart

@@ -412,7 +412,9 @@ abstract class StylesheetParser extends Parser {
     var name = nameBuffer.interpolation(scanner.spanFrom(start, beforeColon));
     if (name.initialPlain.startsWith('--')) {
       var value = StringExpression(
-        _interpolatedDeclarationValue(silentComments: false),
+        atEndOfStatement()
+            ? Interpolation(const [], const [], scanner.emptySpan)
+            : _interpolatedDeclarationValue(silentComments: false),
       );
       expectStatementSeparator("custom property");
       return Declaration(name, value, scanner.spanFrom(start));

lib/src/visitor/async_evaluate.dart

@@ -1371,9 +1371,12 @@ final class _EvaluateVisitor
 
     if (node.value case var expression?) {
       var value = await expression.accept(this);
-      // If the value is an empty list, preserve it, because converting it to CSS
-      // will throw an error that we want the user to see.
-      if (!value.isBlank || _isEmptyList(value)) {
+      if (!value.isBlank ||
+          // If the value is an empty list, preserve it, because converting it
+          // to CSS will throw an error that we want the user to see.
+          _isEmptyList(value) ||
+          // Custom properties are allowed to have empty values, per spec.
+          name.value.startsWith('--')) {
         _parent.addChild(
           ModifiableCssDeclaration(
             name,
@@ -1386,11 +1389,6 @@ final class _EvaluateVisitor
                 _sourceMap ? node.value.andThen(_expressionNode)?.span : null,
           ),
         );
-      } else if (name.value.startsWith('--')) {
-        throw _exception(
-          "Custom property values may not be empty.",
-          expression.span,
-        );
       }
     }
 

lib/src/visitor/evaluate.dart

@@ -5,7 +5,7 @@
 // DO NOT EDIT. This file was generated from async_evaluate.dart.
 // See tool/grind/synchronize.dart for details.
 //
-// Checksum: 607745b48d0737b3be112d0a8753dd87492fcc31
+// Checksum: 1dbe29b392b2eb2990a731741299fd2feea5491a
 //
 // ignore_for_file: unused_import
 
@@ -1379,9 +1379,12 @@ final class _EvaluateVisitor
 
     if (node.value case var expression?) {
       var value = expression.accept(this);
-      // If the value is an empty list, preserve it, because converting it to CSS
-      // will throw an error that we want the user to see.
-      if (!value.isBlank || _isEmptyList(value)) {
+      if (!value.isBlank ||
+          // If the value is an empty list, preserve it, because converting it
+          // to CSS will throw an error that we want the user to see.
+          _isEmptyList(value) ||
+          // Custom properties are allowed to have empty values, per spec.
+          name.value.startsWith('--')) {
         _parent.addChild(
           ModifiableCssDeclaration(
             name,
@@ -1394,11 +1397,6 @@ final class _EvaluateVisitor
                 _sourceMap ? node.value.andThen(_expressionNode)?.span : null,
           ),
         );
-      } else if (name.value.startsWith('--')) {
-        throw _exception(
-          "Custom property values may not be empty.",
-          expression.span,
-        );
       }
     }
 

pkg/sass-parser/CHANGELOG.md

@@ -1,4 +1,4 @@
-## 0.4.21-dev
+## 0.4.21
 
 * No user-visible changes.
 

pkg/sass-parser/package.json

@@ -1,6 +1,6 @@
 {
   "name": "sass-parser",
-  "version": "0.4.21-dev",
+  "version": "0.4.21",
   "description": "A PostCSS-compatible wrapper of the official Sass parser",
   "repository": "sass/sass",
   "author": "Google Inc.",

pkg/sass_api/CHANGELOG.md

@@ -1,4 +1,4 @@
-## 15.5.1-dev
+## 15.6.0
 
 * 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: 15.5.1-dev
+version: 15.6.0
 description: Additional APIs for Dart Sass.
 homepage: https://github.com/sass/dart-sass
 
 environment:
   sdk: ">=3.6.0 <4.0.0"
 
 dependencies:
-  sass: 1.88.1
+  sass: 1.89.0
 
 dev_dependencies:
   dartdoc: ^8.0.14

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.88.1-dev
+version: 1.89.0
 description: A Sass implementation in Dart.
 homepage: https://github.com/sass/dart-sass