Fixed Root.parent type

Author: marekdedic

src/ast/style.ts

@@ -1,5 +1,6 @@
-import type { Node, ChildProps, Container } from "postcss";
+import type { Node, ChildProps, Container, Root } from "postcss";
 import type { Locations } from "./common";
+import type { SvelteStyleElement } from "./html";
 
 type ESLintCompatiblePostCSSContainer<
   PostCSSNode extends Node,
@@ -64,10 +65,12 @@ type ESLintCompatiblePostCSSContainer<
 };
 
 export type ESLintCompatiblePostCSSNode<PostCSSNode extends Node> =
+  // The following hack makes the `type` property work for type narrowing, see microsoft/TypeScript#53887.
   PostCSSNode extends any
     ? Locations &
         Omit<
           PostCSSNode,
+          | "parent"
           | "type"
           | "each"
           | "every"
@@ -85,5 +88,12 @@ export type ESLintCompatiblePostCSSNode<PostCSSNode extends Node> =
           type: `SvelteStyle-${PostCSSNode["type"]}`;
         } & (PostCSSNode extends Container<infer Child>
           ? ESLintCompatiblePostCSSContainer<PostCSSNode, Child>
-          : unknown)
+          : unknown) &
+        (PostCSSNode extends Root
+          ? {
+              parent: SvelteStyleElement;
+            }
+          : {
+              parent: PostCSSNode["parent"];
+            })
     : never;

src/parser/converts/root.ts

@@ -11,7 +11,7 @@ import type { Context } from "../../context";
 import { convertChildren, extractElementTags } from "./element";
 import { convertAttributeTokens } from "./attr";
 import type { Scope } from "eslint-scope";
-import type { Document, Node, Parser, Root } from "postcss";
+import type { Node, Parser, Root } from "postcss";
 import postcss from "postcss";
 import { parse as SCSSparse } from "postcss-scss";
 import type { ESLintCompatiblePostCSSNode } from "../../ast/style";
@@ -149,15 +149,19 @@ export function convertSvelteRoot(
         style.body = parseFn(styleCode, {
           from: ctx.parserOptions.filePath,
         }) as unknown as ESLintCompatiblePostCSSNode<Root>;
-        convertPostCSSNodeToESLintNode(style.body, style.loc, contentRange);
+        convertPostCSSNodeToESLintNode<Root>(
+          style.body,
+          style.loc,
+          contentRange
+        );
         // Fix Root loc
         style.body.loc.start.column += style.startTag.loc.end.column;
         style.body.loc.end.column -=
           style.endTag.loc.end.column - style.endTag.loc.start.column;
         style.body?.walk((node) =>
           convertPostCSSNodeToESLintNode(node, style.loc, contentRange)
         );
-        style.body.parent = style as unknown as Document;
+        style.body.parent = style;
         delete style.body.source?.input.file;
       }
       ctx.addToken("HTMLText", contentRange);