Add sass-parser support for the @use rule

lib/src/js/parser.dart

@@ -10,9 +10,12 @@ import 'package:path/path.dart' as p;
 import 'package:source_span/source_span.dart';
 
 import '../ast/sass.dart';
+import '../exception.dart';
+import '../parse/parser.dart';
 import '../syntax.dart';
 import '../util/nullable.dart';
 import '../util/span.dart';
+import '../util/string.dart';
 import '../visitor/interface/expression.dart';
 import '../visitor/interface/statement.dart';
 import 'reflection.dart';
@@ -24,10 +27,14 @@ import 'visitor/statement.dart';
 class ParserExports {
   external factory ParserExports(
       {required Function parse,
+      required Function parseIdentifier,
+      required Function toCssIdentifier,
       required Function createExpressionVisitor,
       required Function createStatementVisitor});
 
   external set parse(Function function);
+  external set parseIdentifier(Function function);
+  external set toCssIdentifier(Function function);
   external set createStatementVisitor(Function function);
   external set createExpressionVisitor(Function function);
 }
@@ -45,6 +52,8 @@ ParserExports loadParserExports() {
   _updateAstPrototypes();
   return ParserExports(
       parse: allowInterop(_parse),
+      parseIdentifier: allowInterop(_parseIdentifier),
+      toCssIdentifier: allowInterop(_toCssIdentifier),
       createExpressionVisitor: allowInterop(
           (JSExpressionVisitorObject inner) => JSExpressionVisitor(inner)),
       createStatementVisitor: allowInterop(
@@ -117,3 +126,18 @@ Stylesheet _parse(String css, String syntax, String? path) => Stylesheet.parse(
       _ => throw UnsupportedError('Unknown syntax "$syntax"')
     },
     url: path.andThen(p.toUri));
+
+/// A JavaScript-friendly method to parse an identifier to its semantic value.
+///
+/// Returns null if [identifier] isn't a valid identifier.
+String? _parseIdentifier(String identifier) {
+  try {
+    return Parser.parseIdentifier(identifier);
+  } on SassFormatException {
+    return null;
+  }
+}
+
+/// A JavaScript-friendly method to convert text to a valid CSS identifier with
+/// the same contents.
+String _toCssIdentifier(String text) => text.toCssIdentifier();

lib/src/util/character.dart

@@ -10,6 +10,11 @@ import 'package:charcode/charcode.dart';
 /// lowercase equivalents.
 const _asciiCaseBit = 0x20;
 
+/// The highest character allowed in CSS.
+///
+/// See https://drafts.csswg.org/css-syntax-3/#maximum-allowed-code-point
+const maxAllowedCharacter = 0x10FFFF;
+
 // Define these checks as extension getters so they can be used in pattern
 // matches.
 extension CharacterExtension on int {
@@ -35,6 +40,12 @@ extension CharacterExtension on int {
       // 0x36 == 0b110110.
       this >> 10 == 0x36;
 
+  /// Returns whether [character] is the end of a UTF-16 surrogate pair.
+  bool get isLowSurrogate =>
+      // A character is a high surrogate exactly if it matches 0b110111XXXXXXXXXX.
+      // 0x36 == 0b110111.
+      this >> 10 == 0x37;
+
   /// Returns whether [character] is a Unicode private-use code point in the Basic
   /// Multilingual Plane.
   ///

lib/src/util/string.dart

@@ -0,0 +1,108 @@
+// Copyright 2024 Google Inc. Use of this source code is governed by an
+// MIT-style license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+import 'package:charcode/charcode.dart';
+import 'package:string_scanner/string_scanner.dart';
+
+import 'character.dart';
+
+extension StringExtension on String {
+  /// Returns a minimally-escaped CSS identifiers whose contents evaluates to
+  /// [text].
+  ///
+  /// Throws a [FormatException] if [text] cannot be represented as a CSS
+  /// identifier (such as the empty string).
+  String toCssIdentifier() {
+    var buffer = StringBuffer();
+    var scanner = SpanScanner(this);
+
+    void writeEscape(int character) {
+      buffer.writeCharCode($backslash);
+      buffer.write(character.toRadixString(16));
+      if (scanner.peekChar() case int(isHex: true)) {
+        buffer.writeCharCode($space);
+      }
+    }
+
+    void consumeSurrogatePair(int character) {
+      if (scanner.peekChar(1) case null || int(isLowSurrogate: false)) {
+        scanner.error(
+            "An individual surrogates can't be represented as a CSS "
+            "identifier.",
+            length: 1);
+      } else if (character.isPrivateUseHighSurrogate) {
+        writeEscape(combineSurrogates(scanner.readChar(), scanner.readChar()));
+      } else {
+        buffer.writeCharCode(scanner.readChar());
+        buffer.writeCharCode(scanner.readChar());
+      }
+    }
+
+    var doubleDash = false;
+    if (scanner.scanChar($dash)) {
+      if (scanner.isDone) return '\\2d';
+
+      buffer.writeCharCode($dash);
+
+      if (scanner.scanChar($dash)) {
+        buffer.writeCharCode($dash);
+        doubleDash = true;
+      }
+    }
+
+    if (!doubleDash) {
+      switch (scanner.peekChar()) {
+        case null:
+          scanner.error(
+              "The empty string can't be represented as a CSS identifier.");
+
+        case 0:
+          scanner.error("The U+0000 can't be represented as a CSS identifier.");
+
+        case int character when character.isHighSurrogate:
+          consumeSurrogatePair(character);
+
+        case int(isLowSurrogate: true):
+          scanner.error(
+              "An individual surrogate can't be represented as a CSS "
+              "identifier.",
+              length: 1);
+
+        case int(isNameStart: true, isPrivateUseBMP: false):
+          buffer.writeCharCode(scanner.readChar());
+
+        case _:
+          writeEscape(scanner.readChar());
+      }
+    }
+
+    loop:
+    while (true) {
+      switch (scanner.peekChar()) {
+        case null:
+          break loop;
+
+        case 0:
+          scanner.error("The U+0000 can't be represented as a CSS identifier.");
+
+        case int character when character.isHighSurrogate:
+          consumeSurrogatePair(character);
+
+        case int(isLowSurrogate: true):
+          scanner.error(
+              "An individual surrogate can't be represented as a CSS "
+              "identifier.",
+              length: 1);
+
+        case int(isName: true, isPrivateUseBMP: false):
+          buffer.writeCharCode(scanner.readChar());
+
+        case _:
+          writeEscape(scanner.readChar());
+      }
+    }
+
+    return buffer.toString();
+  }
+}

lib/src/utils.dart

@@ -409,7 +409,7 @@ int consumeEscapedCharacter(StringScanner scanner) {
       if (scanner.peekChar().isWhitespace) scanner.readChar();
 
       return switch (value) {
-        0 || (>= 0xD800 && <= 0xDFFF) || >= 0x10FFFF => 0xFFFD,
+        0 || (>= 0xD800 && <= 0xDFFF) || >= maxAllowedCharacter => 0xFFFD,
         _ => value
       };
     case _:

pkg/sass-parser/CHANGELOG.md

@@ -2,6 +2,8 @@
 
 * Add `BooleanExpression` and `NumberExpression`.
 
+* Add support for parsing the `@use` rule.
+
 ## 0.4.0
 
 * **Breaking change:** Warnings are no longer emitted during parsing, so the

pkg/sass-parser/lib/index.ts

@@ -8,7 +8,20 @@ import {Root} from './src/statement/root';
 import * as sassInternal from './src/sass-internal';
 import {Stringifier} from './src/stringifier';
 
+export {
+  Configuration,
+  ConfigurationProps,
+  ConfigurationRaws,
+} from './src/configuration';
+export {
+  ConfiguredVariable,
+  ConfiguredVariableObjectProps,
+  ConfiguredVariableExpressionProps,
+  ConfiguredVariableProps,
+  ConfiguredVariableRaws,
+} from './src/configured-variable';
 export {AnyNode, Node, NodeProps, NodeType} from './src/node';
+export {RawWithValue} from './src/raw-with-value';
 export {
   AnyExpression,
   Expression,
@@ -71,6 +84,7 @@ export {
   SassCommentProps,
   SassCommentRaws,
 } from './src/statement/sass-comment';
+export {UseRule, UseRuleProps, UseRuleRaws} from './src/statement/use-rule';
 export {
   AnyStatement,
   AtRule,

pkg/sass-parser/lib/src/__snapshots__/configured-variable.test.ts.snap

@@ -0,0 +1,19 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`a configured variable toJSON 1`] = `
+{
+  "expression": <"qux">,
+  "guarded": false,
+  "inputs": [
+    {
+      "css": "@use "foo" with ($baz: "qux")",
+      "hasBOM": false,
+      "id": "<input css _____>",
+    },
+  ],
+  "raws": {},
+  "sassType": "configured-variable",
+  "source": <1:18-1:29 in 0>,
+  "variableName": "baz",
+}
+`;