Allow adjacent forward slashes in plain CSS expressions (#2190)

See sass/sass#3797

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## 1.72.0
 
+* Support adjacent `/`s without whitespace in between when parsing plain CSS
+  expressions.
+
 * Allow the Node.js `pkg:` importer to load Sass stylesheets for `package.json`
   `exports` field entries without extensions.
 

lib/src/parse/css.dart

@@ -32,7 +32,9 @@ class CssParser extends ScssParser {
 
   CssParser(super.contents, {super.url, super.logger});
 
-  void silentComment() {
+  bool silentComment() {
+    if (inExpression) return false;
+
     var start = scanner.state;
     super.silentComment();
     error("Silent comments aren't allowed in plain CSS.",

lib/src/parse/parser.dart

@@ -114,8 +114,7 @@ class Parser {
 
     switch (scanner.peekChar(1)) {
       case $slash:
-        silentComment();
-        return true;
+        return silentComment();
       case $asterisk:
         loudComment();
         return true;
@@ -135,12 +134,15 @@ class Parser {
   }
 
   /// Consumes and ignores a silent (Sass-style) comment.
+  ///
+  /// Returns whether the comment was consumed.
   @protected
-  void silentComment() {
+  bool silentComment() {
     scanner.expect("//");
     while (!scanner.isDone && !scanner.peekChar().isNewline) {
       scanner.readChar();
     }
+    return true;
   }
 
   /// Consumes and ignores a loud (CSS-style) comment.

lib/src/parse/stylesheet.dart

@@ -56,6 +56,11 @@ abstract class StylesheetParser extends Parser {
   /// Whether the parser is currently within a parenthesized expression.
   var _inParentheses = false;
 
+  /// Whether the parser is currently within an expression.
+  @protected
+  bool get inExpression => _inExpression;
+  var _inExpression = false;
+
   /// A map from all variable names that are assigned with `!global` in the
   /// current stylesheet to the nodes where they're defined.
   ///
@@ -1686,7 +1691,9 @@ abstract class StylesheetParser extends Parser {
     }
 
     var start = scanner.state;
+    var wasInExpression = _inExpression;
     var wasInParentheses = _inParentheses;
+    _inExpression = true;
 
     // We use the convention below of referring to nullable variables that are
     // shared across anonymous functions in this method with a trailing
@@ -2039,11 +2046,13 @@ abstract class StylesheetParser extends Parser {
       _inParentheses = wasInParentheses;
       var singleExpression = singleExpression_;
       if (singleExpression != null) commaExpressions.add(singleExpression);
+      _inExpression = wasInExpression;
       return ListExpression(commaExpressions, ListSeparator.comma,
           scanner.spanFrom(beforeBracket ?? start),
           brackets: bracketList);
     } else if (bracketList && spaceExpressions != null) {
       resolveOperations();
+      _inExpression = wasInExpression;
       return ListExpression(spaceExpressions..add(singleExpression_!),
           ListSeparator.space, scanner.spanFrom(beforeBracket!),
           brackets: true);
@@ -2054,6 +2063,7 @@ abstract class StylesheetParser extends Parser {
             ListSeparator.undecided, scanner.spanFrom(beforeBracket!),
             brackets: true);
       }
+      _inExpression = wasInExpression;
       return singleExpression_!;
     }
   }