nrwl · FrozenPandaz · Jun 2, 2026 · May 28, 2026 · May 28, 2026 · May 28, 2026
@@ -1,11 +1,18 @@
 import { joinPathFragments, output, type ExecutorContext } from '@nx/devkit';
-import { assertSupportedInstalledPackageVersion } from '@nx/devkit/internal';
+import {
+  assertSupportedInstalledPackageVersion,
+  getInstalledPackageVersion,
+} from '@nx/devkit/internal';
 import type { ESLint } from 'eslint';
 import { mkdirSync, writeFileSync } from 'fs';
 import { interpolate } from 'nx/src/tasks-runner/utils';
 import { dirname, posix, relative, resolve } from 'path';
+import { major } from 'semver';
 import { findFlatConfigFile, findOldConfigFile } from '../../utils/config-file';
-import { warnEslintExecutorDeprecation } from '../../utils/deprecation';
+import {
+  warnEslintExecutorDeprecation,
+  warnEslintV8Deprecation,
+} from '../../utils/deprecation';
 import { minSupportedEslintVersion } from '../../utils/versions';
 import type { Schema } from './schema';
 import { resolveAndInstantiateESLint } from './utility/eslint-utils';
@@ -69,6 +76,11 @@ export default async function run(
 
   assertSupportedInstalledPackageVersion('eslint', minSupportedEslintVersion);
 
+  const installedEslintVersion = getInstalledPackageVersion('eslint');
+  if (installedEslintVersion && major(installedEslintVersion) === 8) {
+    warnEslintV8Deprecation();
+  }
+
   if (printConfig) {
     try {
       const fileConfig = await eslint.calculateConfigForFile(printConfig);

@@ -41,12 +41,15 @@ export const rule = ESLintUtils.RuleCreator(() => __filename)({
 `;
 
 exports[`@nx/eslint:workspace-rule --dir should support creating the rule in a nested directory 2`] = `
-"import { TSESLint } from '@typescript-eslint/utils';
+"import { RuleTester } from '@typescript-eslint/rule-tester';
+import type { RuleTesterConfig } from '@typescript-eslint/rule-tester';
 import { rule, RULE_NAME } from './another-rule';
 
-const ruleTester = new TSESLint.RuleTester({
-  parser: require.resolve('@typescript-eslint/parser'),
-});
+const ruleTester = new RuleTester({
+  languageOptions: {
+    parser: require('@typescript-eslint/parser'),
+  },
+} as RuleTesterConfig);
 
 ruleTester.run(RULE_NAME, rule, {
   valid: [\`const example = true;\`],
@@ -96,12 +99,15 @@ export const rule = ESLintUtils.RuleCreator(() => __filename)({
 `;
 
 exports[`@nx/eslint:workspace-rule --dir should support creating the rule in a nested directory with multiple levels of nesting 2`] = `
-"import { TSESLint } from '@typescript-eslint/utils';
+"import { RuleTester } from '@typescript-eslint/rule-tester';
+import type { RuleTesterConfig } from '@typescript-eslint/rule-tester';
 import { rule, RULE_NAME } from './one-more-rule';
 
-const ruleTester = new TSESLint.RuleTester({
-  parser: require.resolve('@typescript-eslint/parser'),
-});
+const ruleTester = new RuleTester({
+  languageOptions: {
+    parser: require('@typescript-eslint/parser'),
+  },
+} as RuleTesterConfig);
 
 ruleTester.run(RULE_NAME, rule, {
   valid: [\`const example = true;\`],
@@ -151,12 +157,15 @@ export const rule = ESLintUtils.RuleCreator(() => __filename)({
 `;
 
 exports[`@nx/eslint:workspace-rule should generate the required files 2`] = `
-"import { TSESLint } from '@typescript-eslint/utils';
+"import { RuleTester } from '@typescript-eslint/rule-tester';
+import type { RuleTesterConfig } from '@typescript-eslint/rule-tester';
 import { rule, RULE_NAME } from './my-rule';
 
-const ruleTester = new TSESLint.RuleTester({
-  parser: require.resolve('@typescript-eslint/parser'),
-});
+const ruleTester = new RuleTester({
+  languageOptions: {
+    parser: require('@typescript-eslint/parser'),
+  },
+} as RuleTesterConfig);
 
 ruleTester.run(RULE_NAME, rule, {
   valid: [\`const example = true;\`],

@@ -1,4 +1,4 @@
-<% if (flatConfig) { %>import { RuleTester } from '@typescript-eslint/rule-tester';
+<% if (useFlatRuleTester) { %>import { RuleTester } from '@typescript-eslint/rule-tester';
 import type { RuleTesterConfig } from '@typescript-eslint/rule-tester';
 import { rule, RULE_NAME } from './<%= name %>';
 

@@ -1,6 +1,6 @@
 import 'nx/src/internal-testing-utils/mock-project-graph';
 
-import { Tree } from '@nx/devkit';
+import { readJson, Tree, updateJson } from '@nx/devkit';
 import { createTreeWithEmptyWorkspace } from '@nx/devkit/testing';
 import { lintWorkspaceRuleGenerator } from './workspace-rule';
 
@@ -152,6 +152,49 @@ describe('@nx/eslint:workspace-rule', () => {
     `);
   });
 
+  describe('ESLint v9 + eslintrc workspaces', () => {
+    let originalEnv: string | undefined;
+
+    beforeEach(() => {
+      originalEnv = process.env.ESLINT_USE_FLAT_CONFIG;
+      process.env.ESLINT_USE_FLAT_CONFIG = 'false';
+      updateJson(tree, 'package.json', (json) => {
+        json.devDependencies = {
+          ...json.devDependencies,
+          eslint: '^9.8.0',
+        };
+        return json;
+      });
+    });
+
+    afterEach(() => {
+      if (originalEnv === undefined) {
+        delete process.env.ESLINT_USE_FLAT_CONFIG;
+      } else {
+        process.env.ESLINT_USE_FLAT_CONFIG = originalEnv;
+      }
+    });
+
+    it('should generate the flat-style rule-test template and install @typescript-eslint/rule-tester', async () => {
+      await lintWorkspaceRuleGenerator(tree, {
+        name: 'my-rule',
+        directory: 'rules',
+      });
+
+      const spec = tree.read(
+        'tools/eslint-rules/rules/my-rule.spec.ts',
+        'utf-8'
+      );
+      expect(spec).toContain("from '@typescript-eslint/rule-tester'");
+      expect(spec).not.toContain("from '@typescript-eslint/utils'");
+
+      const packageJson = readJson(tree, 'package.json');
+      expect(
+        packageJson.devDependencies['@typescript-eslint/rule-tester']
+      ).toBeDefined();
+    });
+  });
+
   describe('--dir', () => {
     it('should support creating the rule in a nested directory', async () => {
       await lintWorkspaceRuleGenerator(tree, {

@@ -13,6 +13,7 @@ import {
   Tree,
 } from '@nx/devkit';
 import { join } from 'path';
+import { coerce, major } from 'semver';
 import * as ts from 'typescript';
 import { workspaceLintPluginDir } from '../../utils/workspace-lint-rules';
 import { lintWorkspaceRulesProjectGenerator } from '../workspace-rules-project/workspace-rules-project';
@@ -34,6 +35,15 @@ export async function lintWorkspaceRuleGenerator(
   const tasks: GeneratorCallback[] = [];
 
   const flatConfig = useFlatConfig(tree);
+  // ESLint v9 dropped the eslintrc-style `RuleTester` API. typescript-eslint's
+  // recommended replacement for any v9 workspace (flat or eslintrc) is the
+  // separate `@typescript-eslint/rule-tester` package, which has a flat-style
+  // API that works with ESLint v8.57+ and v9 alike. We resolve the effective
+  // major from `versions(tree)` to cover both declared workspaces and fresh
+  // installs that will be bumped to v9.
+  const { eslintVersion, typescriptESLintVersion } = versions(tree);
+  const effectiveEslintMajor = major(coerce(eslintVersion));
+  const useFlatRuleTester = flatConfig || effectiveEslintMajor >= 9;
 
   const nxJson = readNxJson(tree);
   // Ensure that the workspace rules project has been created
@@ -46,8 +56,7 @@ export async function lintWorkspaceRuleGenerator(
     })
   );
 
-  if (flatConfig) {
-    const { typescriptESLintVersion } = versions(tree);
+  if (useFlatRuleTester) {
     tasks.push(
       addDependenciesToPackageJson(
         tree,
@@ -68,7 +77,7 @@ export async function lintWorkspaceRuleGenerator(
   generateFiles(tree, join(__dirname, 'files'), ruleDir, {
     tmpl: '',
     name: options.name,
-    flatConfig,
+    useFlatRuleTester,
   });
 
   const nameCamelCase = camelize(options.name);

@@ -70,7 +70,8 @@ exports[`@nx/eslint:workspace-rules-project should generate the required files 4
   "extends": "./tsconfig.json",
   "compilerOptions": {
     "outDir": "../../dist/out-tsc",
-    "types": ["jest", "node"]
+    "types": ["jest", "node"],
+    "isolatedModules": true
   },
   "include": [
     "jest.config.ts",

@@ -99,6 +99,13 @@ export async function lintWorkspaceRulesProjectGenerator(
     (json) => {
       delete json.compilerOptions?.module;
       delete json.compilerOptions?.moduleResolution;
+      // Inherits `module: node16` from the project's base `tsconfig.json`,
+      // which requires `isolatedModules: true` to reliably honor packages'
+      // `exports` maps (e.g. `@typescript-eslint/rule-tester`).
+      json.compilerOptions = {
+        ...json.compilerOptions,
+        isolatedModules: true,
+      };
 
       if (json.include) {
         json.include = json.include.map((v) => {

@@ -1,7 +1,14 @@
 import { type Tree } from '@nx/devkit';
 import { assertSupportedPackageVersion } from '@nx/devkit/internal';
-import { minSupportedEslintVersion } from './versions';
+import { warnEslintV8Deprecation } from './deprecation';
+import {
+  getInstalledEslintMajorVersion,
+  minSupportedEslintVersion,
+} from './versions';
 
 export function assertSupportedEslintVersion(tree: Tree): void {
   assertSupportedPackageVersion(tree, 'eslint', minSupportedEslintVersion);
+  if (getInstalledEslintMajorVersion(tree) === 8) {
+    warnEslintV8Deprecation();
+  }
 }
@@ -14,3 +14,15 @@ export function warnEslintExecutorGenerating(): void {
     'Generating a target that uses the deprecated `@nx/eslint:lint` executor. The executor will be removed in Nx v24. Run `nx g @nx/eslint:convert-to-inferred` next to migrate this target to the `@nx/eslint/plugin` inferred plugin and prevent future generators from emitting executor targets. See https://nx.dev/docs/guides/tasks--caching/convert-to-inferred for details.'
   );
 }
+
+// TODO(v24): Remove ESLint v8 support. Concrete removals:
+//   - Raise `minSupportedEslintVersion` to '9.0.0' in versions.ts.
+//   - Delete `versionMap[8]` and the `CompatVersions` type alias.
+//   - Delete this constant + `warnEslintV8Deprecation` and their call sites.
+//   - Drop the v8 branch in the workspace-rule generator/template.
+export const ESLINT_V8_DEPRECATION_MESSAGE =
+  'Support for ESLint v8 is deprecated and will be removed in Nx v24. Please upgrade to ESLint v9.';
+
+export function warnEslintV8Deprecation(): void {
+  logger.warn(ESLINT_V8_DEPRECATION_MESSAGE);
+}
@@ -0,0 +1,31 @@
+import { createTreeWithEmptyWorkspace } from '@nx/devkit/testing';
+import { versions } from './versions';
+
+describe('versions(tree)', () => {
+  let originalEnv: string | undefined;
+
+  beforeEach(() => {
+    originalEnv = process.env.ESLINT_USE_FLAT_CONFIG;
+  });
+
+  afterEach(() => {
+    if (originalEnv === undefined) {
+      delete process.env.ESLINT_USE_FLAT_CONFIG;
+    } else {
+      process.env.ESLINT_USE_FLAT_CONFIG = originalEnv;
+    }
+  });
+
+  it('should return the latest ESLint stack for fresh installs regardless of the flat-config preference', () => {
+    const tree = createTreeWithEmptyWorkspace();
+
+    process.env.ESLINT_USE_FLAT_CONFIG = 'false';
+    const eslintrcResult = versions(tree);
+
+    process.env.ESLINT_USE_FLAT_CONFIG = 'true';
+    const flatResult = versions(tree);
+
+    expect(eslintrcResult).toEqual(flatResult);
+    expect(eslintrcResult.eslintVersion).toMatch(/^\^9\./);
+  });
+});
@@ -5,7 +5,6 @@ import {
 } from '@nx/devkit/internal';
 import { join } from 'path';
 import { major } from 'semver';
-import { useFlatConfig } from './flat-config';
 
 export const nxVersion = require(join('@nx/eslint', 'package.json')).version;
 
@@ -43,11 +42,11 @@ export function versions(tree: Tree): EslintVersions {
     const eslintMajorVersion = major(installedEslintVersion);
     return versionMap[eslintMajorVersion as CompatVersions] ?? latestVersions;
   }
-  // No ESLint declared yet — fresh installs honor the user's flat-config
-  // preference. Without flat config, install ESLint v8 (eslintrc lane); with
-  // flat config, install ESLint v9. Both lanes ship typescript-eslint v8 to
-  // match the `@nx/eslint-plugin` `@typescript-eslint/parser` peer.
-  return useFlatConfig(tree) ? latestVersions : versionMap[8];
+  // No ESLint declared yet — fresh installs always go to the latest supported
+  // ESLint stack (v9 + typescript-eslint v8). The eslintrc config shape is
+  // still respected at the config-file level when `useFlatConfig(tree)` is
+  // false; only the installed package versions move forward.
+  return latestVersions;
 }
 
 export function getInstalledEslintVersion(tree?: Tree): string | null {