typescript-eslint · ntdiary · Dec 17, 2025 · Dec 17, 2025 · Dec 17, 2025 · Dec 17, 2025
diff --git a/package.json b/package.json
@@ -74,6 +74,7 @@
     "@typescript-eslint/types": "workspace:^",
     "@typescript-eslint/typescript-estree": "workspace:^",
     "@typescript-eslint/utils": "workspace:^",
+    "@typescript/vfs": "^1.6.2",
     "@vitest/coverage-v8": "^3.1.3",
     "@vitest/eslint-plugin": "1.5.1",
     "console-fail-test": "^0.6.0",

diff --git a/packages/eslint-plugin/package.json b/packages/eslint-plugin/package.json
@@ -72,6 +72,7 @@
     "@types/natural-compare": "*",
     "@typescript-eslint/rule-schema-to-typescript-types": "8.50.0",
     "@typescript-eslint/rule-tester": "8.50.0",
+    "@typescript/vfs": "^1.6.2",
     "@vitest/coverage-v8": "^3.1.3",
     "ajv": "^6.12.6",
     "cross-fetch": "*",

diff --git a/packages/eslint-plugin/src/rules/consistent-type-exports.ts b/packages/eslint-plugin/src/rules/consistent-type-exports.ts
@@ -116,7 +116,7 @@ export default createRule<Options, MessageIds>({
           node.source.value,
           context.filename,
           services.program.getCompilerOptions(),
-          ts.sys,
+          services.host,
         );
         if (sourceModule.resolvedModule == null) {
           return;

diff --git a/packages/eslint-plugin/tests/rules/consistent-type-exports.test.ts b/packages/eslint-plugin/tests/rules/consistent-type-exports.test.ts
@@ -3,9 +3,65 @@ import { noFormat } from '@typescript-eslint/rule-tester';
 
 import rule from '../../src/rules/consistent-type-exports';
 import { createRuleTesterWithTypes } from '../RuleTester';
+import * as vfs from '../vfs';
+
+const sys = vfs.fixture`
+// @filename: /tsconfig.json
+{
+  "compilerOptions": {
+    "jsx": "preserve",
+    "target": "es5",
+    "module": "commonjs",
+    "strict": true,
+    "esModuleInterop": true,
+    "lib": ["es2015", "es2017", "esnext"],
+    "types": [],
+    "experimentalDecorators": true
+  },
+  "exclude": ["/lib*", "node_modules"]
+}
+// @filename: /consistent-type-exports/index.ts
+export type Type1 = 1;
+export type Type2 = 1;
+export const value1 = 2;
+export const value2 = 2;
+
+export class Class1 {}
+
+// @filename: /consistent-type-exports/type-only-exports.ts
+export type TypeFoo = 1;
+
+export interface InterfaceFoo {
+  foo: 'bar';
+}
+
+class LocalClass {}
+
+export type { LocalClass };
+
+// @filename: /consistent-type-exports/type-only-reexport.ts
+export * from './type-only-exports';
+
+export type * as typeOnlyExports from './type-only-exports';
+
+export type * from './index';
+
+export type * as indexExports from './index';
+
+export { Type1 as AliasedType1 } from './index';
+
+import { Class1 } from './index';
+
+export { type Class1 as AliasedClass1 };
+
+// @filename: /consistent-type-exports/value-reexport.ts
+export * from './index';
+`;
 
 const ruleTester = createRuleTesterWithTypes({
   project: './tsconfig.json',
+  sys,
+  tsconfigRootDir: '/',
 });
 
 ruleTester.run('consistent-type-exports', rule, {

diff --git a/packages/eslint-plugin/tests/rules/no-deprecated.test.ts b/packages/eslint-plugin/tests/rules/no-deprecated.test.ts
@@ -1,12 +1,88 @@
 import rule from '../../src/rules/no-deprecated';
-import { getFixturesRootDir, createRuleTesterWithTypes } from '../RuleTester';
+import { createRuleTesterWithTypes } from '../RuleTester';
+import * as vfs from '../vfs';
+
+const sys = vfs.fixture`
+// @filename: /tsconfig.json
+{
+  "compilerOptions": {
+    "jsx": "preserve",
+    "target": "es5",
+    "module": "commonjs",
+    "strict": true,
+    "esModuleInterop": true,
+    "lib": ["es2015", "es2017", "esnext"],
+    "types": ["node", "react"],
+    "experimentalDecorators": true
+  },
+  "exclude": ["/lib*", "node_modules"]
+}
 
-const rootDir = getFixturesRootDir();
+// @filename: /tsconfig.moduleresolution-node16.json
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "module": "node16",
+    "moduleResolution": "node16"
+  }
+}
+// @filename: /deprecated.ts
+/** @deprecated */
+export class DeprecatedClass {
+  /** @deprecated */
+  foo: string = '';
+}
+/** @deprecated */
+export const deprecatedVariable = 1;
+/** @deprecated */
+export function deprecatedFunction(): void {}
+class NormalClass {}
+const normalVariable = 1;
+function normalFunction(): void;
+function normalFunction(arg: string): void;
+function normalFunction(arg?: string): void {}
+function deprecatedFunctionWithOverloads(): void;
+/** @deprecated */
+function deprecatedFunctionWithOverloads(arg: string): void;
+function deprecatedFunctionWithOverloads(arg?: string): void {}
+export class ClassWithDeprecatedConstructor {
+  constructor();
+  /** @deprecated */
+  constructor(arg: string);
+  constructor(arg?: string) {}
+}
+export {
+  /** @deprecated */
+  NormalClass,
+  /** @deprecated */
+  normalVariable,
+  /** @deprecated */
+  normalFunction,
+  deprecatedFunctionWithOverloads,
+  /** @deprecated Reason */
+  deprecatedFunctionWithOverloads as reexportedDeprecatedFunctionWithOverloads,
+  /** @deprecated Reason */
+  ClassWithDeprecatedConstructor as ReexportedClassWithDeprecatedConstructor,
+};
+
+/** @deprecated Reason */
+export type T = { a: string };
+
+export type U = { b: string };
+
+/** @deprecated */
+export default {
+  foo: 1,
+};
+`;
+const rootDir = '/';
 const ruleTester = createRuleTesterWithTypes({
   ecmaFeatures: {
     jsx: true,
   },
   project: './tsconfig.json',
+  sys,
+  tsconfigRootDir: rootDir,
 });
 
 ruleTester.run('no-deprecated', rule, {
@@ -438,7 +514,7 @@ ruleTester.run('no-deprecated', rule, {
       `,
       languageOptions: {
         parserOptions: {
-          project: './tsconfig.moduleResolution-node16.json',
+          project: './tsconfig.moduleresolution-node16.json',
           projectService: false,
           tsconfigRootDir: rootDir,
         },
@@ -3333,7 +3409,7 @@ exists('/foo');
       ],
       languageOptions: {
         parserOptions: {
-          project: './tsconfig.moduleResolution-node16.json',
+          project: './tsconfig.moduleresolution-node16.json',
           projectService: false,
           tsconfigRootDir: rootDir,
         },

diff --git a/packages/eslint-plugin/tests/vfs.ts b/packages/eslint-plugin/tests/vfs.ts
@@ -0,0 +1,46 @@
+import type { System } from 'typescript';
+
+import {
+  addAllFilesFromFolder,
+  createDefaultMapFromNodeModules,
+  createSystem,
+} from '@typescript/vfs';
+import path from 'node:path';
+
+const fsMap: Map<string, string> = createDefaultMapFromNodeModules({});
+addAllFilesFromFolder(
+  fsMap,
+  path.join(__dirname, '../../../node_modules/@types'),
+);
+
+function parseVirtualFiles(code: string): [string, string][] {
+  const result: [string, string][] = [];
+
+  const lines = code.split(/\r?\n/);
+  const cmd = '// @filename: ';
+
+  let currentFileLines: string[] = [];
+  const files: [string, string[]][] = [];
+  for (const line of lines) {
+    if (line.startsWith(cmd)) {
+      currentFileLines = [];
+      files.push([line.slice(cmd.length).trim(), currentFileLines]);
+    } else {
+      currentFileLines.push(line);
+    }
+  }
+  for (const [fileName, fileLines] of files) {
+    result.push([fileName, fileLines.join('\n')]);
+  }
+  return result;
+}
+
+export function fixture(code: TemplateStringsArray, ...keys: string[]): System {
+  const files = parseVirtualFiles(String.raw(code, ...keys));
+  return {
+    ...createSystem(new Map([...fsMap, ...files])),
+    getExecutingFilePath: () => {
+      return '/';
+    },
+  };
+}
diff --git a/packages/parser/src/parser.ts b/packages/parser/src/parser.ts
@@ -129,6 +129,7 @@ export function parseForESLint(
     comment: true,
     loc: true,
     range: true,
+    sys: parserOptions.sys,
     tokens: true,
   } satisfies TSESTreeOptions;
 

diff --git a/packages/project-service/src/createProjectService.ts b/packages/project-service/src/createProjectService.ts
@@ -80,6 +80,7 @@ export interface CreateProjectServiceSettings {
 /**
  * Creates a new Project Service instance, as well as metadata on its creation.
  * @param settings Settings to create a new Project Service instance.
+ * @param sys An instance used for interacting with the file system.
  * @returns A new Project Service instance, as well as metadata on its creation.
  * @example
  * ```ts
@@ -90,11 +91,14 @@ export interface CreateProjectServiceSettings {
  * service.openClientFile('index.ts');
  * ```
  */
-export function createProjectService({
-  jsDocParsingMode,
-  options: optionsRaw = {},
-  tsconfigRootDir,
-}: CreateProjectServiceSettings = {}): ProjectServiceAndMetadata {
+export function createProjectService(
+  {
+    jsDocParsingMode,
+    options: optionsRaw = {},
+    tsconfigRootDir,
+  }: CreateProjectServiceSettings = {},
+  sys?: ts.System,
+): ProjectServiceAndMetadata {
   const options = {
     defaultProject: 'tsconfig.json',
     ...optionsRaw,
@@ -110,7 +114,7 @@ export function createProjectService({
   // there's a whole separate update pass in maybeInvalidateProgram at the bottom of getWatchProgramsForProjects
   // (this "goes nuclear on TypeScript")
   const system: ts.server.ServerHost = {
-    ...tsserver.sys,
+    ...(sys ?? tsserver.sys),
     clearImmediate,
     clearTimeout,
     setImmediate,

diff --git a/packages/rule-tester/src/RuleTester.ts b/packages/rule-tester/src/RuleTester.ts
@@ -321,6 +321,9 @@ export class RuleTester extends TestFramework {
           filename,
         );
       }
+      if (resolvedOptions.sys) {
+        return path.join(resolvedOptions.sys.getCurrentDirectory(), filename);
+      }
       return filename;
     };
     const normalizeTest = <
@@ -683,6 +686,9 @@ export class RuleTester extends TestFramework {
       );
       filename = item.filename;
     }
+    if (filename) {
+      config.languageOptions.parserOptions?.sys?.writeFile(filename, code);
+    }
 
     const prefixedRuleName = `${RULE_TESTER_PLUGIN_PREFIX}${ruleName}`;
 

diff --git a/packages/types/src/parser-options.ts b/packages/types/src/parser-options.ts
@@ -1,4 +1,4 @@
-import type { Program } from 'typescript';
+import type { Program, System } from 'typescript';
 
 import type { Lib } from './lib';
 
@@ -113,6 +113,7 @@ export interface ParserOptions {
   projectService?: boolean | ProjectServiceOptions;
   range?: boolean;
   sourceType?: SourceType | undefined;
+  sys?: System;
   tokens?: boolean;
   tsconfigRootDir?: string;
 

diff --git a/packages/typescript-estree/src/create-program/getWatchProgramsForProjects.ts b/packages/typescript-estree/src/create-program/getWatchProgramsForProjects.ts
@@ -251,7 +251,7 @@ function createWatchProgram(
   const watchCompilerHost = ts.createWatchCompilerHost(
     tsconfigPath,
     createDefaultCompilerOptionsFromExtra(parseSettings),
-    ts.sys,
+    parseSettings.sys ?? ts.sys,
     ts.createAbstractBuilder,
     diagnosticReporter,
     // TODO: file issue on TypeScript to suggest making optional?

diff --git a/packages/typescript-estree/src/createParserServices.ts b/packages/typescript-estree/src/createParserServices.ts
@@ -1,16 +1,18 @@
-import type * as ts from 'typescript';
+import * as ts from 'typescript';
 
 import type { ASTMaps } from './convert';
 import type { ParserServices } from './parser-options';
 
 export function createParserServices(
   astMaps: ASTMaps,
   program: ts.Program | null,
+  host?: ts.ModuleResolutionHost,
 ): ParserServices {
   if (!program) {
     return {
       emitDecoratorMetadata: undefined,
       experimentalDecorators: undefined,
+      host: null,
       isolatedDeclarations: undefined,
       program,
       // we always return the node maps because
@@ -24,6 +26,7 @@ export function createParserServices(
   const compilerOptions = program.getCompilerOptions();
 
   return {
+    host: host ?? ts.sys,
     program,
     // not set in the config is the same as off
     emitDecoratorMetadata: compilerOptions.emitDecoratorMetadata ?? false,