Track original source spans for selectors (#1903)

Closes #1783

Author: nex3

CHANGELOG.md

@@ -5,6 +5,8 @@
 
 * Improve error messages for invalid CSS values passed to plain CSS functions.
 
+* Improve error messages involving selectors.
+
 ### Embedded Sass
 
 * Improve the performance of starting up a compilation.

lib/src/ast/css/media_query.dart

@@ -2,6 +2,7 @@
 // MIT-style license that can be found in the LICENSE file or at
 // https://opensource.org/licenses/MIT.
 
+import '../../interpolation_map.dart';
 import '../../logger.dart';
 import '../../parse/media_query.dart';
 import '../../utils.dart';
@@ -43,8 +44,10 @@ class CssMediaQuery {
   ///
   /// Throws a [SassFormatException] if parsing fails.
   static List<CssMediaQuery> parseList(String contents,
-          {Object? url, Logger? logger}) =>
-      MediaQueryParser(contents, url: url, logger: logger).parse();
+          {Object? url, Logger? logger, InterpolationMap? interpolationMap}) =>
+      MediaQueryParser(contents,
+              url: url, logger: logger, interpolationMap: interpolationMap)
+          .parse();
 
   /// Creates a media query specifies a type and, optionally, conditions.
   ///

lib/src/ast/css/modifiable.dart

@@ -12,4 +12,3 @@ export 'modifiable/node.dart';
 export 'modifiable/style_rule.dart';
 export 'modifiable/stylesheet.dart';
 export 'modifiable/supports_rule.dart';
-export 'modifiable/value.dart';

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

@@ -4,30 +4,35 @@
 
 import 'package:source_span/source_span.dart';
 
+import '../../../util/box.dart';
 import '../../../visitor/interface/modifiable_css.dart';
 import '../../selector.dart';
 import '../style_rule.dart';
 import 'node.dart';
-import 'value.dart';
 
 /// A modifiable version of [CssStyleRule] for use in the evaluation step.
 class ModifiableCssStyleRule extends ModifiableCssParentNode
     implements CssStyleRule {
-  final ModifiableCssValue<SelectorList> selector;
+  SelectorList get selector => _selector.value;
+
+  /// A reference to the modifiable selector list provided by the extension
+  /// store, which may update it over time as new extensions are applied.
+  final Box<SelectorList> _selector;
+
   final SelectorList originalSelector;
   final FileSpan span;
 
   /// Creates a new [ModifiableCssStyleRule].
   ///
-  /// If [originalSelector] isn't passed, it defaults to [selector.value].
-  ModifiableCssStyleRule(this.selector, this.span,
+  /// If [originalSelector] isn't passed, it defaults to [_selector.value].
+  ModifiableCssStyleRule(this._selector, this.span,
       {SelectorList? originalSelector})
-      : originalSelector = originalSelector ?? selector.value;
+      : originalSelector = originalSelector ?? _selector.value;
 
   T accept<T>(ModifiableCssVisitor<T> visitor) =>
       visitor.visitCssStyleRule(this);
 
   ModifiableCssStyleRule copyWithoutChildren() =>
-      ModifiableCssStyleRule(selector, span,
+      ModifiableCssStyleRule(_selector, span,
           originalSelector: originalSelector);
 }

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

@@ -82,7 +82,7 @@ class _IsInvisibleVisitor with EveryCssVisitor {
 
   bool visitCssStyleRule(CssStyleRule rule) =>
       (includeBogus
-          ? rule.selector.value.isInvisible
-          : rule.selector.value.isInvisibleOtherThanBogusCombinators) ||
+          ? rule.selector.isInvisible
+          : rule.selector.isInvisibleOtherThanBogusCombinators) ||
       super.visitCssStyleRule(rule);
 }

lib/src/ast/css/node.dart

@@ -5,7 +5,6 @@
 import '../../visitor/interface/css.dart';
 import '../selector.dart';
 import 'node.dart';
-import 'value.dart';
 
 /// A plain CSS style rule.
 ///
@@ -14,7 +13,7 @@ import 'value.dart';
 /// contain placeholder selectors.
 abstract class CssStyleRule extends CssParentNode {
   /// The selector for this rule.
-  CssValue<SelectorList> get selector;
+  SelectorList get selector;
 
   /// The selector for this rule, before any extensions were applied.
   SelectorList get originalSelector;

lib/src/ast/css/style_rule.dart

@@ -9,7 +9,7 @@ import '../node.dart';
 /// A value in a plain CSS tree.
 ///
 /// This is used to associate a span with a value that doesn't otherwise track
-/// its span.
+/// its span. It has value equality semantics.
 class CssValue<T extends Object> implements AstNode {
   /// The value.
   final T value;
@@ -19,5 +19,10 @@ class CssValue<T extends Object> implements AstNode {
 
   CssValue(this.value, this.span);
 
+  bool operator ==(Object other) =>
+      other is CssValue<T> && other.value == value;
+
+  int get hashCode => value.hashCode;
+
   String toString() => value.toString();
 }

lib/src/ast/css/value.dart

@@ -6,6 +6,7 @@ import 'package:meta/meta.dart';
 import 'package:collection/collection.dart';
 
 import '../../exception.dart';
+import '../../interpolation_map.dart';
 import '../../logger.dart';
 import '../../parse/at_root_query.dart';
 import '../css.dart';
@@ -53,8 +54,12 @@ class AtRootQuery {
   ///
   /// If passed, [url] is the name of the file from which [contents] comes.
   ///
+  /// If passed, [interpolationMap] maps the text of [contents] back to the
+  /// original location of the selector in the source file.
+  ///
   /// Throws a [SassFormatException] if parsing fails.
-  factory AtRootQuery.parse(String contents, {Object? url, Logger? logger}) =>
+  factory AtRootQuery.parse(String contents,
+          {Object? url, Logger? logger, InterpolationMap? interpolationMap}) =>
       AtRootQueryParser(contents, url: url, logger: logger).parse();
 
   /// Returns whether [this] excludes [node].

lib/src/ast/sass/at_root_query.dart

@@ -3,12 +3,14 @@
 // https://opensource.org/licenses/MIT.
 
 import 'package:meta/meta.dart';
+import 'package:source_span/source_span.dart';
 
 import '../evaluation_context.dart';
 import '../exception.dart';
 import '../visitor/any_selector.dart';
 import '../visitor/interface/selector.dart';
 import '../visitor/serialize.dart';
+import 'node.dart';
 import 'selector/complex.dart';
 import 'selector/list.dart';
 import 'selector/placeholder.dart';
@@ -38,7 +40,7 @@ export 'selector/universal.dart';
 /// Selectors have structural equality semantics.
 ///
 /// {@category AST}
-abstract class Selector {
+abstract class Selector implements AstNode {
   /// Whether this selector, and complex selectors containing it, should not be
   /// emitted.
   ///
@@ -76,10 +78,14 @@ abstract class Selector {
   @internal
   bool get isUseless => accept(const _IsUselessVisitor());
 
+  final FileSpan span;
+
+  Selector(this.span);
+
   /// Prints a warning if [this] is a bogus selector.
   ///
   /// This may only be called from within a custom Sass function. This will
-  /// throw a [SassScriptException] in Dart Sass 2.0.0.
+  /// throw a [SassException] in Dart Sass 2.0.0.
   void assertNotBogus({String? name}) {
     if (!isBogus) return;
     warn(