feat: add experimental virtual code cache for faster type-aware linting

Author: baseballyama

.gitignore

@@ -107,3 +107,6 @@ dist
 /lib
 /.nyc_output
 /coverage
+
+# svelte-eslint-parser virtual code cache
+.svelte-eslint-parser/

eslint.config.mjs

@@ -25,6 +25,7 @@ export default [
       "!.github",
       "explorer-v2/.svelte-kit",
       ".changeset/pre.json",
+      ".svelte-eslint-parser",
     ],
   },
   ...myPlugin.config({

package.json

@@ -62,14 +62,17 @@
     "eslint-scope": "^8.2.0",
     "eslint-visitor-keys": "^4.0.0",
     "espree": "^10.0.0",
+    "ignore": "^7.0.5",
     "postcss": "^8.4.49",
     "postcss-scss": "^4.0.9",
-    "postcss-selector-parser": "^7.0.0"
+    "postcss-selector-parser": "^7.0.0",
+    "proper-lockfile": "^4.1.2"
   },
   "devDependencies": {
     "@changesets/changelog-github": "^0.5.1",
     "@changesets/cli": "^2.29.7",
     "@changesets/get-release-plan": "^4.0.13",
+    "@eslint-community/eslint-plugin-eslint-comments": "4.3.0",
     "@ota-meshi/eslint-plugin": "^0.19.0",
     "@ota-meshi/test-snapshot": "^1.1.1",
     "@types/benchmark": "^2.1.5",
@@ -80,6 +83,7 @@
     "@types/estree": "^1.0.8",
     "@types/mocha": "^10.0.10",
     "@types/node": "^24.0.0",
+    "@types/proper-lockfile": "^4.1.4",
     "@types/semver": "^7.7.1",
     "@typescript-eslint/parser": "^8.46.1",
     "@typescript-eslint/scope-manager": "^8.46.1",
@@ -91,7 +95,6 @@
     "esbuild": "^0.27.0",
     "eslint": "^9.37.0",
     "eslint-config-prettier": "^10.1.8",
-    "eslint-plugin-eslint-comments": "^3.2.0",
     "eslint-plugin-jsdoc": "^62.0.0",
     "eslint-plugin-json-schema-validator": "^6.0.0",
     "eslint-plugin-jsonc": "^2.20.1",

pnpm-lock.yaml

@@ -57,6 +57,8 @@ import {
 } from "./svelte-parse-context.js";
 import type { SvelteConfig } from "../svelte-config/index.js";
 import { resolveSvelteConfigFromOption } from "../svelte-config/index.js";
+import { getVirtualCodeCacheManager } from "../virtual-code/index.js";
+import { initializeVirtualCodeCache } from "./virtual-code-initializer.js";
 
 export {
   StyleContext,
@@ -116,6 +118,21 @@ export function parseForESLint(code: string, options?: any): ParseResult {
   const svelteConfig = resolveSvelteConfigFromOption(options);
   const parserOptions = normalizeParserOptions(options);
 
+  // Initialize virtual code cache for TypeScript type-aware linting
+  // Only enabled when svelteFeatures.experimentalGenerateVirtualCodeCache is true
+  // Note: We only initialize the cache here; the actual tsconfig/filePath replacement
+  // happens in parseTypeScriptInSvelte to ensure we have a valid virtual file path
+  if (
+    parserOptions.svelteFeatures?.experimentalGenerateVirtualCodeCache &&
+    (parserOptions.projectService || parserOptions.project)
+  ) {
+    const cacheManager = getVirtualCodeCacheManager();
+
+    if (!cacheManager.isInitialized() && parserOptions.filePath) {
+      initializeVirtualCodeCache(parserOptions.filePath, parserOptions);
+    }
+  }
+
   if (
     parserOptions.filePath &&
     (parserOptions.filePath.endsWith(".svelte.js") ||

src/parser/index.ts

@@ -27,6 +27,11 @@ export type NormalizedParserOptions = {
     // If not configured this option, The parser will try to read the option from `compilerOptions.runes` from `svelte.config.js`.
     // If `parserOptions.svelteConfig` is not specified and the file cannot be parsed by static analysis, it will behave as `true`.
     runes?: boolean;
+    // Enable virtual code caching to speed up type-aware linting.
+    // When enabled, the parser generates virtual TypeScript files for all Svelte files
+    // in the project and creates a tsconfig that includes them.
+    // Default: false
+    experimentalGenerateVirtualCodeCache?: boolean;
   };
   loc: boolean;
   range: boolean;
@@ -36,6 +41,9 @@ export type NormalizedParserOptions = {
   eslintVisitorKeys: boolean;
   eslintScopeManager: boolean;
   filePath?: string;
+
+  // Internal use: tsconfig paths for import rewriting
+  __tsconfigPaths?: Record<string, string[]> | null;
 };
 
 /** Normalize parserOptions */

src/parser/parser-options.ts

@@ -15,7 +15,10 @@ import {
   sortedLastIndex,
 } from "../../../utils/index.js";
 import { parseScriptWithoutAnalyzeScope } from "../../script.js";
-import { VirtualTypeScriptContext } from "../context.js";
+import {
+  VirtualTypeScriptContext,
+  extractSvelteImportsFromAST,
+} from "../context.js";
 import type { TSESParseForESLintResult } from "../types.js";
 import type ESTree from "estree";
 import type { SvelteAttribute, SvelteHTMLElement } from "../../../ast/index.js";
@@ -99,6 +102,10 @@ export function analyzeTypeScriptInSvelte(
 
   ctx.appendOriginalToEnd();
 
+  // Extract .svelte imports from AST and compute their positions in virtual code
+  const svelteImportPaths = extractSvelteImportsFromAST(result.ast);
+  ctx.computeSvelteImportPositions(svelteImportPaths);
+
   return ctx;
 }
 /**
@@ -132,6 +139,10 @@ export function analyzeTypeScript(
 
   ctx.appendOriginalToEnd();
 
+  // Extract .svelte imports from AST and compute their positions in virtual code
+  const svelteImportPaths = extractSvelteImportsFromAST(result.ast);
+  ctx.computeSvelteImportPositions(svelteImportPaths);
+
   return ctx;
 }