Convert Sass to Dart 3 style (#2038)

bin/sass.dart

@@ -4,7 +4,6 @@
 
 import 'dart:isolate';
 
-import 'package:collection/collection.dart';
 import 'package:path/path.dart' as p;
 import 'package:stack_trace/stack_trace.dart';
 import 'package:term_glyph/term_glyph.dart' as term_glyph;
@@ -19,6 +18,7 @@ import 'package:sass/src/io.dart';
 import 'package:sass/src/io.dart' as io;
 import 'package:sass/src/logger/deprecation_handling.dart';
 import 'package:sass/src/stylesheet_graph.dart';
+import 'package:sass/src/util/map.dart';
 import 'package:sass/src/utils.dart';
 import 'package:sass/src/embedded/executable.dart'
     // Never load the embedded protocol when compiling to JS.
@@ -47,8 +47,8 @@ Future<void> main(List<String> args) async {
     io.printError(buffer);
   }
 
-  if (args.firstOrNull == '--embedded') {
-    embedded.main(args.sublist(1));
+  if (args case ['--embedded', ...var rest]) {
+    embedded.main(rest);
     return;
   }
 
@@ -84,25 +84,14 @@ Future<void> main(List<String> args) async {
       return;
     }
 
-    for (var source in options.sourcesToDestinations.keys) {
-      var destination = options.sourcesToDestinations[source];
+    for (var (source, destination) in options.sourcesToDestinations.pairs) {
       try {
         await compileStylesheet(options, graph, source, destination,
             ifModified: options.update);
       } on SassException catch (error, stackTrace) {
-        // This is an immediately-invoked function expression to work around
-        // dart-lang/sdk#33400.
-        () {
-          try {
-            if (destination != null &&
-                // dart-lang/sdk#45348
-                !options!.emitErrorCss) {
-              deleteFile(destination);
-            }
-          } on FileSystemException {
-            // If the file doesn't exist, that's fine.
-          }
-        }();
+        if (destination != null && !options.emitErrorCss) {
+          _tryDelete(destination);
+        }
 
         printError(error.toString(color: options.color),
             options.trace ? getTrace(error) ?? stackTrace : null);
@@ -134,9 +123,9 @@ Future<void> main(List<String> args) async {
     exitCode = 64;
   } catch (error, stackTrace) {
     var buffer = StringBuffer();
-    if (options != null && options.color) buffer.write('\u001b[31m\u001b[1m');
+    if (options?.color ?? false) buffer.write('\u001b[31m\u001b[1m');
     buffer.write('Unexpected exception:');
-    if (options != null && options.color) buffer.write('\u001b[0m');
+    if (options?.color ?? false) buffer.write('\u001b[0m');
     buffer.writeln();
     buffer.writeln(error);
 
@@ -165,3 +154,14 @@ Future<String> _loadVersion() async {
       .split(" ")
       .last;
 }
+
+/// Delete [path] if it exists and do nothing otherwise.
+///
+/// This is a separate function to work around dart-lang/sdk#53082.
+void _tryDelete(String path) {
+  try {
+    deleteFile(path);
+  } on FileSystemException {
+    // If the file doesn't exist, that's fine.
+  }
+}

lib/src/ast/css/at_rule.dart

@@ -2,12 +2,11 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
-import '../../visitor/interface/css.dart';
 import 'node.dart';
 import 'value.dart';
 
 /// An unknown plain CSS at-rule.
-abstract class CssAtRule extends CssParentNode {
+abstract interface class CssAtRule implements CssParentNode {
   /// The name of this rule.
   CssValue<String> get name;
 
@@ -19,6 +18,4 @@ abstract class CssAtRule extends CssParentNode {
   /// This implies `children.isEmpty`, but the reverse is not true—for a rule
   /// like `@foo {}`, [children] is empty but [isChildless] is `false`.
   bool get isChildless;
-
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssAtRule(this);
 }

lib/src/ast/css/comment.dart

@@ -2,19 +2,16 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
-import '../../visitor/interface/css.dart';
 import 'node.dart';
 
 /// A plain CSS comment.
 ///
 /// This is always a multi-line comment.
-abstract class CssComment extends CssNode {
+abstract interface class CssComment implements CssNode {
   /// The contents of this comment, including `/*` and `*/`.
   String get text;
 
   /// Whether this comment starts with `/*!` and so should be preserved even in
   /// compressed mode.
   bool get isPreserved;
-
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssComment(this);
 }

lib/src/ast/css/declaration.dart

@@ -5,12 +5,11 @@
 import 'package:source_span/source_span.dart';
 
 import '../../value.dart';
-import '../../visitor/interface/css.dart';
 import 'node.dart';
 import 'value.dart';
 
 /// A plain CSS declaration (that is, a `name: value` pair).
-abstract class CssDeclaration extends CssNode {
+abstract interface class CssDeclaration implements CssNode {
   /// The name of this declaration.
   CssValue<String> get name;
 
@@ -34,6 +33,4 @@ abstract class CssDeclaration extends CssNode {
   /// If this is `true`, [isCustomProperty] will also be `true` and [value] will
   /// contain a [SassString].
   bool get parsedAsCustomProperty;
-
-  T accept<T>(CssVisitor<T> visitor);
 }

lib/src/ast/css/import.dart

@@ -2,19 +2,16 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
-import '../../visitor/interface/css.dart';
 import 'node.dart';
 import 'value.dart';
 
 /// A plain CSS `@import`.
-abstract class CssImport extends CssNode {
+abstract interface class CssImport implements CssNode {
   /// The URL being imported.
   ///
   /// This includes quotes.
   CssValue<String> get url;
 
   /// The modifiers (such as media or supports queries) attached to this import.
   CssValue<String>? get modifiers;
-
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssImport(this);
 }

lib/src/ast/css/keyframe_block.dart

@@ -2,16 +2,13 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
-import '../../visitor/interface/css.dart';
 import 'node.dart';
 import 'value.dart';
 
 /// A block within a `@keyframes` rule.
 ///
 /// For example, `10% {opacity: 0.5}`.
-abstract class CssKeyframeBlock extends CssParentNode {
+abstract interface class CssKeyframeBlock implements CssParentNode {
   /// The selector for this block.
   CssValue<List<String>> get selector;
-
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssKeyframeBlock(this);
 }

lib/src/ast/css/media_query.dart

@@ -8,7 +8,7 @@ import '../../parse/media_query.dart';
 import '../../utils.dart';
 
 /// A plain CSS media query, as used in `@media` and `@import`.
-class CssMediaQuery {
+final class CssMediaQuery {
   /// The modifier, probably either "not" or "only".
   ///
   /// This may be `null` if no modifier is in use.
@@ -197,25 +197,21 @@ class CssMediaQuery {
 ///
 /// This is either the singleton values [empty] or [unrepresentable], or an
 /// instance of [MediaQuerySuccessfulMergeResult].
-abstract class MediaQueryMergeResult {
+sealed class MediaQueryMergeResult {
   /// A singleton value indicating that there are no contexts that match both
   /// input queries.
-  static const empty = _SingletonCssMediaQueryMergeResult("empty");
+  static const empty = _SingletonCssMediaQueryMergeResult.empty;
 
   /// A singleton value indicating that the contexts that match both input
   /// queries can't be represented by a Level 3 media query.
   static const unrepresentable =
-      _SingletonCssMediaQueryMergeResult("unrepresentable");
+      _SingletonCssMediaQueryMergeResult.unrepresentable;
 }
 
 /// The subclass [MediaQueryMergeResult] that represents singleton enum values.
-class _SingletonCssMediaQueryMergeResult implements MediaQueryMergeResult {
-  /// The name of the result type.
-  final String _name;
-
-  const _SingletonCssMediaQueryMergeResult(this._name);
-
-  String toString() => _name;
+enum _SingletonCssMediaQueryMergeResult implements MediaQueryMergeResult {
+  empty,
+  unrepresentable;
 }
 
 /// A successful result of [CssMediaQuery.merge].

lib/src/ast/css/media_rule.dart

@@ -2,16 +2,13 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
-import '../../visitor/interface/css.dart';
 import 'media_query.dart';
 import 'node.dart';
 
 /// A plain CSS `@media` rule.
-abstract class CssMediaRule extends CssParentNode {
+abstract interface class CssMediaRule implements CssParentNode {
   /// The queries for this rule.
   ///
   /// This is never empty.
   List<CssMediaQuery> get queries;
-
-  T accept<T>(CssVisitor<T> visitor) => visitor.visitCssMediaRule(this);
 }

lib/src/ast/css/modifiable/at_rule.dart

@@ -10,7 +10,8 @@ import '../value.dart';
 import 'node.dart';
 
 /// A modifiable version of [CssAtRule] for use in the evaluation step.
-class ModifiableCssAtRule extends ModifiableCssParentNode implements CssAtRule {
+final class ModifiableCssAtRule extends ModifiableCssParentNode
+    implements CssAtRule {
   final CssValue<String> name;
   final CssValue<String>? value;
   final bool isChildless;

lib/src/ast/css/modifiable/comment.dart

@@ -10,7 +10,8 @@ import '../comment.dart';
 import 'node.dart';
 
 /// A modifiable version of [CssComment] for use in the evaluation step.
-class ModifiableCssComment extends ModifiableCssNode implements CssComment {
+final class ModifiableCssComment extends ModifiableCssNode
+    implements CssComment {
   final String text;
   final FileSpan span;
 

lib/src/ast/css/modifiable/declaration.dart

@@ -11,7 +11,7 @@ import '../value.dart';
 import 'node.dart';
 
 /// A modifiable version of [CssDeclaration] for use in the evaluation step.
-class ModifiableCssDeclaration extends ModifiableCssNode
+final class ModifiableCssDeclaration extends ModifiableCssNode
     implements CssDeclaration {
   final CssValue<String> name;
   final CssValue<Value> value;

lib/src/ast/css/modifiable/import.dart

@@ -10,7 +10,7 @@ import '../value.dart';
 import 'node.dart';
 
 /// A modifiable version of [CssImport] for use in the evaluation step.
-class ModifiableCssImport extends ModifiableCssNode implements CssImport {
+final class ModifiableCssImport extends ModifiableCssNode implements CssImport {
   /// The URL being imported.
   ///
   /// This includes quotes.

lib/src/ast/css/modifiable/keyframe_block.dart

@@ -11,7 +11,7 @@ import '../value.dart';
 import 'node.dart';
 
 /// A modifiable version of [CssKeyframeBlock] for use in the evaluation step.
-class ModifiableCssKeyframeBlock extends ModifiableCssParentNode
+final class ModifiableCssKeyframeBlock extends ModifiableCssParentNode
     implements CssKeyframeBlock {
   final CssValue<List<String>> selector;
   final FileSpan span;

lib/src/ast/css/modifiable/media_rule.dart

@@ -11,7 +11,7 @@ import '../media_rule.dart';
 import 'node.dart';
 
 /// A modifiable version of [CssMediaRule] for use in the evaluation step.
-class ModifiableCssMediaRule extends ModifiableCssParentNode
+final class ModifiableCssMediaRule extends ModifiableCssParentNode
     implements CssMediaRule {
   final List<CssMediaQuery> queries;
   final FileSpan span;

lib/src/ast/css/modifiable/node.dart

@@ -12,7 +12,7 @@ import '../node.dart';
 /// Almost all CSS nodes are the modifiable classes under the covers. However,
 /// modification should only be done within the evaluation step, so the
 /// unmodifiable types are used elsewhere to enforce that constraint.
-abstract class ModifiableCssNode extends CssNode {
+abstract base class ModifiableCssNode extends CssNode {
   /// The node that contains this, or `null` for the root [CssStylesheet] node.
   ModifiableCssParentNode? get parent => _parent;
   ModifiableCssParentNode? _parent;
@@ -43,16 +43,15 @@ abstract class ModifiableCssNode extends CssNode {
     }
 
     parent._children.removeAt(_indexInParent!);
-    for (var i = _indexInParent!; i < parent._children.length; i++) {
-      var child = parent._children[i];
+    for (var child in parent._children.skip(_indexInParent!)) {
       child._indexInParent = child._indexInParent! - 1;
     }
     _parent = null;
   }
 }
 
 /// A modifiable version of [CssParentNode] for use in the evaluation step.
-abstract class ModifiableCssParentNode extends ModifiableCssNode
+abstract base class ModifiableCssParentNode extends ModifiableCssNode
     implements CssParentNode {
   final List<ModifiableCssNode> children;
   final List<ModifiableCssNode> _children;

lib/src/ast/css/modifiable/style_rule.dart

@@ -11,7 +11,7 @@ import '../style_rule.dart';
 import 'node.dart';
 
 /// A modifiable version of [CssStyleRule] for use in the evaluation step.
-class ModifiableCssStyleRule extends ModifiableCssParentNode
+final class ModifiableCssStyleRule extends ModifiableCssParentNode
     implements CssStyleRule {
   SelectorList get selector => _selector.value;
 

lib/src/ast/css/modifiable/stylesheet.dart

@@ -9,7 +9,7 @@ import '../stylesheet.dart';
 import 'node.dart';
 
 /// A modifiable version of [CssStylesheet] for use in the evaluation step.
-class ModifiableCssStylesheet extends ModifiableCssParentNode
+final class ModifiableCssStylesheet extends ModifiableCssParentNode
     implements CssStylesheet {
   final FileSpan span;
 

lib/src/ast/css/modifiable/supports_rule.dart

@@ -10,7 +10,7 @@ import '../value.dart';
 import 'node.dart';
 
 /// A modifiable version of [CssSupportsRule] for use in the evaluation step.
-class ModifiableCssSupportsRule extends ModifiableCssParentNode
+final class ModifiableCssSupportsRule extends ModifiableCssParentNode
     implements CssSupportsRule {
   final CssValue<String> condition;
   final FileSpan span;

lib/src/ast/css/node.dart

@@ -13,7 +13,8 @@ import 'comment.dart';
 import 'style_rule.dart';
 
 /// A statement in a plain CSS syntax tree.
-abstract class CssNode extends AstNode {
+@sealed
+abstract class CssNode implements AstNode {
   /// Whether this was generated from the last node in a nested Sass tree that
   /// got flattened during evaluation.
   bool get isGroupEnd;
@@ -43,12 +44,13 @@ abstract class CssNode extends AstNode {
   bool get isInvisibleHidingComments => accept(
       const _IsInvisibleVisitor(includeBogus: true, includeComments: true));
 
-  String toString() => serialize(this, inspect: true).css;
+  String toString() => serialize(this, inspect: true).$1;
 }
 
 // NOTE: New at-rule implementations should add themselves to [AtRootRule]'s
 // exclude logic.
 /// A [CssNode] that can have child statements.
+@sealed
 abstract class CssParentNode extends CssNode {
   /// The child statements of this node.
   List<CssNode> get children;