Add sass-parser support for variable declarations

lib/src/ast/sass/statement/stylesheet.dart

@@ -53,6 +53,11 @@ final class Stylesheet extends ParentStatement<List<Statement>> {
   @internal
   final List<ParseTimeWarning> parseTimeWarnings;
 
+  /// The set of (normalized) global variable names defined by this stylesheet
+  /// to the spans where they're defined.
+  @internal
+  final Map<String, FileSpan> globalVariables;
+
   Stylesheet(Iterable<Statement> children, FileSpan span)
       : this.internal(children, span, []);
 
@@ -62,8 +67,11 @@ final class Stylesheet extends ParentStatement<List<Statement>> {
   @internal
   Stylesheet.internal(Iterable<Statement> children, this.span,
       List<ParseTimeWarning> parseTimeWarnings,
-      {this.plainCss = false})
+      {this.plainCss = false, Map<String, FileSpan>? globalVariables})
       : parseTimeWarnings = UnmodifiableListView(parseTimeWarnings),
+        globalVariables = globalVariables == null
+            ? const {}
+            : Map.unmodifiable(globalVariables),
         super(List.unmodifiable(children)) {
     loop:
     for (var child in this.children) {

lib/src/parse/stylesheet.dart

@@ -61,13 +61,13 @@ abstract class StylesheetParser extends Parser {
   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.
+  /// current stylesheet to the spans where they're defined.
   ///
   /// These are collected at parse time because they affect the variables
   /// exposed by the module generated for this stylesheet, *even if they aren't
   /// evaluated*. This allows us to ensure that the stylesheet always exposes
   /// the same set of variable names no matter how it's evaluated.
-  final _globalVariables = <String, VariableDeclaration>{};
+  final _globalVariables = <String, FileSpan>{};
 
   /// Warnings discovered while parsing that should be emitted during
   /// evaluation once a proper logger is available.
@@ -100,15 +100,8 @@ abstract class StylesheetParser extends Parser {
       });
       scanner.expectDone();
 
-      /// Ensure that all global variable assignments produce a variable in this
-      /// stylesheet, even if they aren't evaluated. See sass/language#50.
-      statements.addAll(_globalVariables.values.map((declaration) =>
-          VariableDeclaration(declaration.name,
-              NullExpression(declaration.expression.span), declaration.span,
-              guarded: true)));
-
       return Stylesheet.internal(statements, scanner.spanFrom(start), warnings,
-          plainCss: plainCss);
+          plainCss: plainCss, globalVariables: _globalVariables);
     });
   }
 
@@ -288,7 +281,7 @@ abstract class StylesheetParser extends Parser {
         guarded: guarded,
         global: global,
         comment: precedingComment);
-    if (global) _globalVariables.putIfAbsent(name, () => declaration);
+    if (global) _globalVariables.putIfAbsent(name, () => declaration.span);
     return declaration;
   }
 

lib/src/visitor/async_evaluate.dart

@@ -1005,6 +1005,14 @@ final class _EvaluateVisitor
     for (var child in node.children) {
       await child.accept(this);
     }
+
+    // Make sure all global variables declared in a module always appear in the
+    // module's definition, even if their assignments aren't reached.
+    for (var (name, span) in node.globalVariables.pairs) {
+      visitVariableDeclaration(
+          VariableDeclaration(name, NullExpression(span), span, guarded: true));
+    }
+
     return null;
   }
 

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: e7260fedcd4f374ba517a93d038c3c53586c9622
+// Checksum: 396c8f169d95c601598b8c3be1f4b948ca22effa
 //
 // ignore_for_file: unused_import
 
@@ -1005,6 +1005,14 @@ final class _EvaluateVisitor
     for (var child in node.children) {
       child.accept(this);
     }
+
+    // Make sure all global variables declared in a module always appear in the
+    // module's definition, even if their assignments aren't reached.
+    for (var (name, span) in node.globalVariables.pairs) {
+      visitVariableDeclaration(
+          VariableDeclaration(name, NullExpression(span), span, guarded: true));
+    }
+
     return null;
   }
 

pkg/sass-parser/lib/index.ts

@@ -96,6 +96,11 @@ export {
   StatementType,
   StatementWithChildren,
 } from './src/statement';
+export {
+  VariableDeclaration,
+  VariableDeclarationProps,
+  VariableDeclarationRaws,
+} from './src/statement/variable-declaration';
 
 /** Options that can be passed to the Sass parsers to control their behavior. */
 export type SassParserOptions = Pick<postcss.ProcessOptions, 'from' | 'map'>;

pkg/sass-parser/lib/src/sass-internal.ts

@@ -180,6 +180,14 @@ declare namespace SassInternal {
     readonly configuration: ConfiguredVariable[];
   }
 
+  class VariableDeclaration extends Statement {
+    readonly namespace: string | null;
+    readonly name: string;
+    readonly expression: Expression;
+    readonly isGuarded: boolean;
+    readonly isGlobal: boolean;
+  }
+
   class ConfiguredVariable extends SassNode {
     readonly name: string;
     readonly expression: Expression;
@@ -238,6 +246,7 @@ export type Stylesheet = SassInternal.Stylesheet;
 export type StyleRule = SassInternal.StyleRule;
 export type SupportsRule = SassInternal.SupportsRule;
 export type UseRule = SassInternal.UseRule;
+export type VariableDeclaration = SassInternal.VariableDeclaration;
 export type ConfiguredVariable = SassInternal.ConfiguredVariable;
 export type Interpolation = SassInternal.Interpolation;
 export type Expression = SassInternal.Expression;
@@ -260,6 +269,7 @@ export interface StatementVisitorObject<T> {
   visitStyleRule(node: StyleRule): T;
   visitSupportsRule(node: SupportsRule): T;
   visitUseRule(node: UseRule): T;
+  visitVariableDeclaration(node: VariableDeclaration): T;
 }
 
 export interface ExpressionVisitorObject<T> {

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

@@ -0,0 +1,22 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`a variable declaration toJSON 1`] = `
+{
+  "expression": <"bar">,
+  "global": false,
+  "guarded": false,
+  "inputs": [
+    {
+      "css": "baz.$foo: "bar"",
+      "hasBOM": false,
+      "id": "<input css _____>",
+    },
+  ],
+  "namespace": "baz",
+  "raws": {},
+  "sassType": "variable-declaration",
+  "source": <1:1-1:16 in 0>,
+  "type": "decl",
+  "variableName": "foo",
+}
+`;

pkg/sass-parser/lib/src/statement/declaration-internal.d.ts

@@ -0,0 +1,77 @@
+// 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 * as postcss from 'postcss';
+
+import {Rule} from './rule';
+import {Root} from './root';
+import {AtRule, ChildNode, Comment, Declaration, NewNode} from '.';
+
+/**
+ * A fake intermediate class to convince TypeScript to use Sass types for
+ * various upstream methods.
+ *
+ * @hidden
+ */
+export class _Declaration<Props> extends postcss.Declaration {
+  // Override the PostCSS container types to constrain them to Sass types only.
+  // Unfortunately, there's no way to abstract this out, because anything
+  // mixin-like returns an intersection type which doesn't actually override
+  // parent methods. See microsoft/TypeScript#59394.
+
+  after(newNode: NewNode): this;
+  append(...nodes: NewNode[]): this;
+  assign(overrides: Partial<Props>): this;
+  before(newNode: NewNode): this;
+  cloneAfter(overrides?: Partial<Props>): this;
+  cloneBefore(overrides?: Partial<Props>): this;
+  each(
+    callback: (node: ChildNode, index: number) => false | void
+  ): false | undefined;
+  every(
+    condition: (node: ChildNode, index: number, nodes: ChildNode[]) => boolean
+  ): boolean;
+  insertAfter(oldNode: postcss.ChildNode | number, newNode: NewNode): this;
+  insertBefore(oldNode: postcss.ChildNode | number, newNode: NewNode): this;
+  next(): ChildNode | undefined;
+  prepend(...nodes: NewNode[]): this;
+  prev(): ChildNode | undefined;
+  replaceWith(...nodes: NewNode[]): this;
+  root(): Root;
+  some(
+    condition: (node: ChildNode, index: number, nodes: ChildNode[]) => boolean
+  ): boolean;
+  walk(
+    callback: (node: ChildNode, index: number) => false | void
+  ): false | undefined;
+  walkAtRules(
+    nameFilter: RegExp | string,
+    callback: (atRule: AtRule, index: number) => false | void
+  ): false | undefined;
+  walkAtRules(
+    callback: (atRule: AtRule, index: number) => false | void
+  ): false | undefined;
+  walkComments(
+    callback: (comment: Comment, indexed: number) => false | void
+  ): false | undefined;
+  walkComments(
+    callback: (comment: Comment, indexed: number) => false | void
+  ): false | undefined;
+  walkDecls(
+    propFilter: RegExp | string,
+    callback: (decl: Declaration, index: number) => false | void
+  ): false | undefined;
+  walkDecls(
+    callback: (decl: Declaration, index: number) => false | void
+  ): false | undefined;
+  walkRules(
+    selectorFilter: RegExp | string,
+    callback: (rule: Rule, index: number) => false | void
+  ): false | undefined;
+  walkRules(
+    callback: (rule: Rule, index: number) => false | void
+  ): false | undefined;
+  get first(): ChildNode | undefined;
+  get last(): ChildNode | undefined;
+}

pkg/sass-parser/lib/src/statement/declaration-internal.js

@@ -0,0 +1,5 @@
+// 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.
+
+exports._Declaration = require('postcss').Declaration;

pkg/sass-parser/lib/src/statement/index.ts

@@ -18,6 +18,10 @@ import {ForRule, ForRuleProps} from './for-rule';
 import {Root} from './root';
 import {Rule, RuleProps} from './rule';
 import {UseRule, UseRuleProps} from './use-rule';
+import {
+  VariableDeclaration,
+  VariableDeclarationProps,
+} from './variable-declaration';
 
 // TODO: Replace this with the corresponding Sass types once they're
 // implemented.
@@ -28,7 +32,7 @@ export {Declaration} from 'postcss';
  *
  * @category Statement
  */
-export type AnyStatement = Comment | Root | Rule | GenericAtRule;
+export type AnyStatement = Comment | Root | Rule | AtRule | VariableDeclaration;
 
 /**
  * Sass statement types.
@@ -49,7 +53,8 @@ export type StatementType =
   | 'for-rule'
   | 'error-rule'
   | 'use-rule'
-  | 'sass-comment';
+  | 'sass-comment'
+  | 'variable-declaration';
 
 /**
  * All Sass statements that are also at-rules.
@@ -78,7 +83,7 @@ export type Comment = CssComment | SassComment;
  *
  * @category Statement
  */
-export type ChildNode = Rule | AtRule | Comment;
+export type ChildNode = Rule | AtRule | Comment | VariableDeclaration;
 
 /**
  * The properties that can be used to construct {@link ChildNode}s.
@@ -97,7 +102,8 @@ export type ChildProps =
   | GenericAtRuleProps
   | RuleProps
   | SassCommentChildProps
-  | UseRuleProps;
+  | UseRuleProps
+  | VariableDeclarationProps;
 
 /**
  * The Sass eqivalent of PostCSS's `ContainerProps`.
@@ -185,6 +191,7 @@ const visitor = sassInternal.createStatementVisitor<Statement>({
     return rule;
   },
   visitUseRule: inner => new UseRule(undefined, inner),
+  visitVariableDeclaration: inner => new VariableDeclaration(undefined, inner),
 });
 
 /** Appends parsed versions of `internal`'s children to `container`. */
@@ -301,6 +308,8 @@ export function normalize(
       result.push(new SassComment(node));
     } else if ('useUrl' in node) {
       result.push(new UseRule(node));
+    } else if ('variableName' in node) {
+      result.push(new VariableDeclaration(node));
     } else {
       result.push(...postcssNormalizeAndConvertToSass(self, node, sample));
     }