feat(linter): support yaml for flat config conversion (#20022)

packages/eslint/package.json

@@ -30,7 +30,8 @@
   "executors": "./executors.json",
   "generators": "./generators.json",
   "peerDependencies": {
-    "eslint": "^8.0.0"
+    "eslint": "^8.0.0",
+    "js-yaml": "4.1.0"
   },
   "dependencies": {
     "tslib": "^2.3.0",
@@ -41,6 +42,9 @@
   "peerDependenciesMeta": {
     "eslint": {
       "optional": true
+    },
+    "js-yaml": {
+      "optional": true
     }
   },
   "publishConfig": {

packages/eslint/src/generators/convert-to-flat-config/__snapshots__/generator.spec.ts.snap

@@ -5,10 +5,12 @@ exports[`convert-to-flat-config generator should add env configuration 1`] = `
 const nxEslintPlugin = require('@nx/eslint-plugin');
 const globals = require('globals');
 const js = require('@eslint/js');
+
 const compat = new FlatCompat({
   baseDirectory: __dirname,
   recommendedConfig: js.configs.recommended,
 });
+
 module.exports = [
   { plugins: { '@nx': nxEslintPlugin } },
   { languageOptions: { globals: { ...globals.browser, ...globals.node } } },
@@ -49,10 +51,12 @@ exports[`convert-to-flat-config generator should add global and env configuratio
 const nxEslintPlugin = require('@nx/eslint-plugin');
 const globals = require('globals');
 const js = require('@eslint/js');
+
 const compat = new FlatCompat({
   baseDirectory: __dirname,
   recommendedConfig: js.configs.recommended,
 });
+
 module.exports = [
   { plugins: { '@nx': nxEslintPlugin } },
   {
@@ -96,10 +100,12 @@ exports[`convert-to-flat-config generator should add global configuration 1`] =
 "const { FlatCompat } = require('@eslint/eslintrc');
 const nxEslintPlugin = require('@nx/eslint-plugin');
 const js = require('@eslint/js');
+
 const compat = new FlatCompat({
   baseDirectory: __dirname,
   recommendedConfig: js.configs.recommended,
 });
+
 module.exports = [
   { plugins: { '@nx': nxEslintPlugin } },
   { languageOptions: { globals: { myCustomGlobal: 'readonly' } } },
@@ -139,10 +145,12 @@ exports[`convert-to-flat-config generator should add global eslintignores 1`] =
 "const { FlatCompat } = require('@eslint/eslintrc');
 const nxEslintPlugin = require('@nx/eslint-plugin');
 const js = require('@eslint/js');
+
 const compat = new FlatCompat({
   baseDirectory: __dirname,
   recommendedConfig: js.configs.recommended,
 });
+
 module.exports = [
   { plugins: { '@nx': nxEslintPlugin } },
   {
@@ -183,10 +191,12 @@ exports[`convert-to-flat-config generator should add parser 1`] = `
 const nxEslintPlugin = require('@nx/eslint-plugin');
 const typescriptEslintParser = require('@typescript-eslint/parser');
 const js = require('@eslint/js');
+
 const compat = new FlatCompat({
   baseDirectory: __dirname,
   recommendedConfig: js.configs.recommended,
 });
+
 module.exports = [
   { plugins: { '@nx': nxEslintPlugin } },
   { languageOptions: { parser: typescriptEslintParser } },
@@ -229,10 +239,12 @@ const eslintPluginSingleName = require('eslint-plugin-single-name');
 const scopeEslintPluginWithName = require('@scope/eslint-plugin-with-name');
 const justScopeEslintPlugin = require('@just-scope/eslint-plugin');
 const js = require('@eslint/js');
+
 const compat = new FlatCompat({
   baseDirectory: __dirname,
   recommendedConfig: js.configs.recommended,
 });
+
 module.exports = [
   {
     plugins: {
@@ -278,10 +290,12 @@ exports[`convert-to-flat-config generator should add settings 1`] = `
 "const { FlatCompat } = require('@eslint/eslintrc');
 const nxEslintPlugin = require('@nx/eslint-plugin');
 const js = require('@eslint/js');
+
 const compat = new FlatCompat({
   baseDirectory: __dirname,
   recommendedConfig: js.configs.recommended,
 });
+
 module.exports = [
   { plugins: { '@nx': nxEslintPlugin } },
   { settings: { sharedData: 'Hello' } },
@@ -317,41 +331,16 @@ module.exports = [
 "
 `;
 
-exports[`convert-to-flat-config generator should handle custom eslintignores 1`] = `
+exports[`convert-to-flat-config generator should convert json successfully 1`] = `
-"const baseConfig = require('../../eslint.config.js');
-module.exports = [
-  ...baseConfig,
-  {
-    files: [
-      'libs/test-lib/**/*.ts',
-      'libs/test-lib/**/*.tsx',
-      'libs/test-lib/**/*.js',
-      'libs/test-lib/**/*.jsx',
-    ],
-    rules: {},
-  },
-  {
-    files: ['libs/test-lib/**/*.ts', 'libs/test-lib/**/*.tsx'],
-    rules: {},
-  },
-  {
-    files: ['libs/test-lib/**/*.js', 'libs/test-lib/**/*.jsx'],
-    rules: {},
-  },
-  { ignores: ['libs/test-lib/ignore/me'] },
-  { ignores: ['libs/test-lib/ignore/me/as/well'] },
-];
-"
-`;
-
-exports[`convert-to-flat-config generator should run successfully 1`] = `
 "const { FlatCompat } = require('@eslint/eslintrc');
 const nxEslintPlugin = require('@nx/eslint-plugin');
 const js = require('@eslint/js');
+
 const compat = new FlatCompat({
   baseDirectory: __dirname,
   recommendedConfig: js.configs.recommended,
 });
+
 module.exports = [
   { plugins: { '@nx': nxEslintPlugin } },
   {
@@ -386,8 +375,9 @@ module.exports = [
 "
 `;
 
-exports[`convert-to-flat-config generator should run successfully 2`] = `
+exports[`convert-to-flat-config generator should convert json successfully 2`] = `
 "const baseConfig = require('../../eslint.config.js');
+
 module.exports = [
   ...baseConfig,
   {
@@ -410,3 +400,171 @@ module.exports = [
 ];
 "
 `;
+
+exports[`convert-to-flat-config generator should convert yaml successfully 1`] = `
+"const { FlatCompat } = require('@eslint/eslintrc');
+const nxEslintPlugin = require('@nx/eslint-plugin');
+const js = require('@eslint/js');
+
+const compat = new FlatCompat({
+  baseDirectory: __dirname,
+  recommendedConfig: js.configs.recommended,
+});
+
+module.exports = [
+  { plugins: { '@nx': nxEslintPlugin } },
+  {
+    files: ['**/*.ts', '**/*.tsx', '**/*.js', '**/*.jsx'],
+    rules: {
+      '@nx/enforce-module-boundaries': [
+        'error',
+        {
+          enforceBuildableLibDependency: true,
+          allow: [],
+          depConstraints: [
+            {
+              sourceTag: '*',
+              onlyDependOnLibsWithTags: ['*'],
+            },
+          ],
+        },
+      ],
+    },
+  },
+  ...compat.config({ extends: ['plugin:@nx/typescript'] }).map((config) => ({
+    ...config,
+    files: ['**/*.ts', '**/*.tsx'],
+    rules: {},
+  })),
+  ...compat.config({ extends: ['plugin:@nx/javascript'] }).map((config) => ({
+    ...config,
+    files: ['**/*.js', '**/*.jsx'],
+    rules: {},
+  })),
+];
+"
+`;
+
+exports[`convert-to-flat-config generator should convert yaml successfully 2`] = `
+"const baseConfig = require('../../eslint.config.js');
+
+module.exports = [
+  ...baseConfig,
+  {
+    files: [
+      'libs/test-lib/**/*.ts',
+      'libs/test-lib/**/*.tsx',
+      'libs/test-lib/**/*.js',
+      'libs/test-lib/**/*.jsx',
+    ],
+    rules: {},
+  },
+  {
+    files: ['libs/test-lib/**/*.ts', 'libs/test-lib/**/*.tsx'],
+    rules: {},
+  },
+  {
+    files: ['libs/test-lib/**/*.js', 'libs/test-lib/**/*.jsx'],
+    rules: {},
+  },
+];
+"
+`;
+
+exports[`convert-to-flat-config generator should convert yml successfully 1`] = `
+"const { FlatCompat } = require('@eslint/eslintrc');
+const nxEslintPlugin = require('@nx/eslint-plugin');
+const js = require('@eslint/js');
+
+const compat = new FlatCompat({
+  baseDirectory: __dirname,
+  recommendedConfig: js.configs.recommended,
+});
+
+module.exports = [
+  { plugins: { '@nx': nxEslintPlugin } },
+  {
+    files: ['**/*.ts', '**/*.tsx', '**/*.js', '**/*.jsx'],
+    rules: {
+      '@nx/enforce-module-boundaries': [
+        'error',
+        {
+          enforceBuildableLibDependency: true,
+          allow: [],
+          depConstraints: [
+            {
+              sourceTag: '*',
+              onlyDependOnLibsWithTags: ['*'],
+            },
+          ],
+        },
+      ],
+    },
+  },
+  ...compat.config({ extends: ['plugin:@nx/typescript'] }).map((config) => ({
+    ...config,
+    files: ['**/*.ts', '**/*.tsx'],
+    rules: {},
+  })),
+  ...compat.config({ extends: ['plugin:@nx/javascript'] }).map((config) => ({
+    ...config,
+    files: ['**/*.js', '**/*.jsx'],
+    rules: {},
+  })),
+];
+"
+`;
+
+exports[`convert-to-flat-config generator should convert yml successfully 2`] = `
+"const baseConfig = require('../../eslint.config.js');
+
+module.exports = [
+  ...baseConfig,
+  {
+    files: [
+      'libs/test-lib/**/*.ts',
+      'libs/test-lib/**/*.tsx',
+      'libs/test-lib/**/*.js',
+      'libs/test-lib/**/*.jsx',
+    ],
+    rules: {},
+  },
+  {
+    files: ['libs/test-lib/**/*.ts', 'libs/test-lib/**/*.tsx'],
+    rules: {},
+  },
+  {
+    files: ['libs/test-lib/**/*.js', 'libs/test-lib/**/*.jsx'],
+    rules: {},
+  },
+];
+"
+`;
+
+exports[`convert-to-flat-config generator should handle custom eslintignores 1`] = `
+"const baseConfig = require('../../eslint.config.js');
+
+module.exports = [
+  ...baseConfig,
+  {
+    files: [
+      'libs/test-lib/**/*.ts',
+      'libs/test-lib/**/*.tsx',
+      'libs/test-lib/**/*.js',
+      'libs/test-lib/**/*.jsx',
+    ],
+    rules: {},
+  },
+  {
+    files: ['libs/test-lib/**/*.ts', 'libs/test-lib/**/*.tsx'],
+    rules: {},
+  },
+  {
+    files: ['libs/test-lib/**/*.js', 'libs/test-lib/**/*.jsx'],
+    rules: {},
+  },
+  { ignores: ['libs/test-lib/ignore/me'] },
+  { ignores: ['libs/test-lib/ignore/me/as/well'] },
+];
+"
+`;

packages/eslint/src/generators/convert-to-flat-config/converters/json-converter.spec.ts

@@ -1,4 +1,4 @@
-import { Tree } from '@nx/devkit';
+import { Tree, readJson } from '@nx/devkit';
 import { createTreeWithEmptyWorkspace } from '@nx/devkit/testing';
 import { convertEslintJsonToFlatConfig } from './json-converter';
 
@@ -58,22 +58,23 @@ describe('convertEslintJsonToFlatConfig', () => {
 
     tree.write('.eslintignore', 'node_modules\nsomething/else');
 
-    convertEslintJsonToFlatConfig(
+    const { content } = convertEslintJsonToFlatConfig(
       tree,
       '',
-      '.eslintrc.json',
+      readJson(tree, '.eslintrc.json'),
-      'eslint.config.js',
       ['.eslintignore']
     );
 
-    expect(tree.read('eslint.config.js', 'utf-8')).toMatchInlineSnapshot(`
+    expect(content).toMatchInlineSnapshot(`
       "const { FlatCompat } = require("@eslint/eslintrc");
       const nxEslintPlugin = require("@nx/eslint-plugin");
       const js = require("@eslint/js");
+
       const compat = new FlatCompat({
           baseDirectory: __dirname,
           recommendedConfig: js.configs.recommended,
       });
+
       module.exports = [
           { plugins: { "@nx": nxEslintPlugin } },
           {
@@ -118,8 +119,6 @@ describe('convertEslintJsonToFlatConfig', () => {
       ];
       "
     `);
-
-    expect(tree.exists('.eslintrc.json')).toBeFalsy();
   });
 
   it('should convert project configs', async () => {
@@ -170,23 +169,24 @@ describe('convertEslintJsonToFlatConfig', () => {
 
     tree.write('mylib/.eslintignore', 'node_modules\nsomething/else');
 
-    convertEslintJsonToFlatConfig(
+    const { content } = convertEslintJsonToFlatConfig(
       tree,
       'mylib',
-      '.eslintrc.json',
+      readJson(tree, 'mylib/.eslintrc.json'),
-      'eslint.config.js',
       ['mylib/.eslintignore']
     );
 
-    expect(tree.read('mylib/eslint.config.js', 'utf-8')).toMatchInlineSnapshot(`
+    expect(content).toMatchInlineSnapshot(`
       "const { FlatCompat } = require("@eslint/eslintrc");
       const baseConfig = require("../../eslint.config.js");
       const globals = require("globals");
       const js = require("@eslint/js");
+
       const compat = new FlatCompat({
           baseDirectory: __dirname,
           recommendedConfig: js.configs.recommended,
       });
+
       module.exports = [
           ...baseConfig,
           ...compat.extends("plugin:@nx/react-typescript", "next", "next/core-web-vitals"),
@@ -228,7 +228,5 @@ describe('convertEslintJsonToFlatConfig', () => {
       ];
       "
     `);
-
-    expect(tree.exists('mylib/.eslintrc.json')).toBeFalsy();
   });
 });

packages/eslint/src/generators/convert-to-flat-config/converters/json-converter.ts

@@ -1,13 +1,6 @@
-import {
+import { Tree, names } from '@nx/devkit';
-  Tree,
-  addDependenciesToPackageJson,
-  names,
-  readJson,
-} from '@nx/devkit';
-import { join } from 'path';
 import { ESLint } from 'eslint';
 import * as ts from 'typescript';
-import { eslintVersion, eslintrcVersion } from '../../../utils/versions';
 import {
   createNodeList,
   generateAst,
@@ -26,21 +19,20 @@ import { getPluginImport } from '../../utils/eslint-file';
 export function convertEslintJsonToFlatConfig(
   tree: Tree,
   root: string,
-  sourceFile: string,
+  config: ESLint.ConfigData,
-  destinationFile: string,
   ignorePaths: string[]
-) {
+): { content: string; addESLintRC: boolean; addESLintJS: boolean } {
   const importsMap = new Map<string, string>();
   const exportElements: ts.Expression[] = [];
   let isFlatCompatNeeded = false;
+  let isESLintJSNeeded = false;
   let combinedConfig: ts.PropertyAssignment[] = [];
   let languageOptions: ts.PropertyAssignment[] = [];
 
-  // read original config
-  const config: ESLint.ConfigData = readJson(tree, `${root}/${sourceFile}`);
-
   if (config.extends) {
-    isFlatCompatNeeded = addExtends(importsMap, exportElements, config, tree);
+    const extendsResult = addExtends(importsMap, exportElements, config);
+    isFlatCompatNeeded = extendsResult.isFlatCompatNeeded;
+    isESLintJSNeeded = extendsResult.isESLintJSNeeded;
   }
 
   if (config.plugins) {
@@ -188,36 +180,28 @@ export function convertEslintJsonToFlatConfig(
     }
   }
 
-  tree.delete(join(root, sourceFile));
-
   // create the node list and print it to new file
   const nodeList = createNodeList(
     importsMap,
     exportElements,
     isFlatCompatNeeded
   );
-  const content = stringifyNodeList(nodeList, root, destinationFile);
-  tree.write(join(root, destinationFile), content);
 
-  if (isFlatCompatNeeded) {
+  return {
-    addDependenciesToPackageJson(
+    content: stringifyNodeList(nodeList, root),
-      tree,
+    addESLintRC: isFlatCompatNeeded,
-      {},
+    addESLintJS: isESLintJSNeeded,
-      {
+  };
-        '@eslint/eslintrc': eslintrcVersion,
-      }
-    );
-  }
 }
 
 // add parsed extends to export blocks and add import statements
 function addExtends(
   importsMap: Map<string, string | string[]>,
   configBlocks: ts.Expression[],
-  config: ESLint.ConfigData,
+  config: ESLint.ConfigData
-  tree: Tree
+): { isFlatCompatNeeded: boolean; isESLintJSNeeded: boolean } {
-): boolean {
   let isFlatCompatNeeded = false;
+  let isESLintJSNeeded = false;
   const extendsConfig = Array.isArray(config.extends)
     ? config.extends
     : [config.extends];
@@ -253,13 +237,7 @@ function addExtends(
     });
 
     if (eslintPluginExtends.length) {
-      addDependenciesToPackageJson(
+      isESLintJSNeeded = true;
-        tree,
-        {},
-        {
-          '@eslint/js': eslintVersion,
-        }
-      );
 
       importsMap.set('@eslint/js', 'js');
       eslintPluginExtends.forEach((plugin) => {
@@ -277,18 +255,12 @@ function addExtends(
   }
   if (eslintrcConfigs.length) {
     isFlatCompatNeeded = true;
-    addDependenciesToPackageJson(
+    isESLintJSNeeded = true;
-      tree,
-      {},
-      {
-        '@eslint/js': eslintVersion,
-      }
-    );
 
     configBlocks.push(generatePluginExtendsElement(eslintrcConfigs));
   }
 
-  return isFlatCompatNeeded;
+  return { isFlatCompatNeeded, isESLintJSNeeded };
 }
 
 function addPlugins(

packages/eslint/src/generators/convert-to-flat-config/generator.spec.ts

@@ -12,7 +12,7 @@ import { ConvertToFlatConfigGeneratorSchema } from './schema';
 import { lintProjectGenerator } from '../lint-project/lint-project';
 import { Linter } from '../utils/linter';
 import { eslintrcVersion } from '../../utils/versions';
-import { read } from 'fs';
+import { dump } from 'js-yaml';
 
 describe('convert-to-flat-config generator', () => {
   let tree: Tree;
@@ -42,7 +42,7 @@ describe('convert-to-flat-config generator', () => {
     });
   });
 
-  it('should run successfully', async () => {
+  it('should convert json successfully', async () => {
     await lintProjectGenerator(tree, {
       skipFormat: false,
       linter: Linter.EsLint,
@@ -68,6 +68,66 @@ describe('convert-to-flat-config generator', () => {
     );
   });
 
+  it('should convert yaml successfully', async () => {
+    await lintProjectGenerator(tree, {
+      skipFormat: false,
+      linter: Linter.EsLint,
+      eslintFilePatterns: ['**/*.ts'],
+      project: 'test-lib',
+      setParserOptionsProject: false,
+    });
+    const yamlContent = dump(readJson(tree, 'libs/test-lib/.eslintrc.json'));
+    tree.delete('libs/test-lib/.eslintrc.json');
+    tree.write('libs/test-lib/.eslintrc.yaml', yamlContent);
+
+    await convertToFlatConfigGenerator(tree, options);
+
+    expect(tree.exists('eslint.config.js')).toBeTruthy();
+    expect(tree.read('eslint.config.js', 'utf-8')).toMatchSnapshot();
+    expect(tree.exists('libs/test-lib/eslint.config.js')).toBeTruthy();
+    expect(
+      tree.read('libs/test-lib/eslint.config.js', 'utf-8')
+    ).toMatchSnapshot();
+    // check nx.json changes
+    const nxJson = readJson(tree, 'nx.json');
+    expect(nxJson.targetDefaults.lint.inputs).toContain(
+      '{workspaceRoot}/eslint.config.js'
+    );
+    expect(nxJson.namedInputs.production).toContain(
+      '!{projectRoot}/eslint.config.js'
+    );
+  });
+
+  it('should convert yml successfully', async () => {
+    await lintProjectGenerator(tree, {
+      skipFormat: false,
+      linter: Linter.EsLint,
+      eslintFilePatterns: ['**/*.ts'],
+      project: 'test-lib',
+      setParserOptionsProject: false,
+    });
+    const yamlContent = dump(readJson(tree, 'libs/test-lib/.eslintrc.json'));
+    tree.delete('libs/test-lib/.eslintrc.json');
+    tree.write('libs/test-lib/.eslintrc.yml', yamlContent);
+
+    await convertToFlatConfigGenerator(tree, options);
+
+    expect(tree.exists('eslint.config.js')).toBeTruthy();
+    expect(tree.read('eslint.config.js', 'utf-8')).toMatchSnapshot();
+    expect(tree.exists('libs/test-lib/eslint.config.js')).toBeTruthy();
+    expect(
+      tree.read('libs/test-lib/eslint.config.js', 'utf-8')
+    ).toMatchSnapshot();
+    // check nx.json changes
+    const nxJson = readJson(tree, 'nx.json');
+    expect(nxJson.targetDefaults.lint.inputs).toContain(
+      '{workspaceRoot}/eslint.config.js'
+    );
+    expect(nxJson.namedInputs.production).toContain(
+      '!{projectRoot}/eslint.config.js'
+    );
+  });
+
   it('should add plugin extends', async () => {
     await lintProjectGenerator(tree, {
       skipFormat: false,
@@ -86,10 +146,12 @@ describe('convert-to-flat-config generator', () => {
       "const { FlatCompat } = require('@eslint/eslintrc');
       const nxEslintPlugin = require('@nx/eslint-plugin');
       const js = require('@eslint/js');
+
       const compat = new FlatCompat({
         baseDirectory: __dirname,
         recommendedConfig: js.configs.recommended,
       });
+
       module.exports = [
         ...compat.extends('plugin:storybook/recommended'),
         { plugins: { '@nx': nxEslintPlugin } },
@@ -127,6 +189,7 @@ describe('convert-to-flat-config generator', () => {
     expect(tree.read('libs/test-lib/eslint.config.js', 'utf-8'))
       .toMatchInlineSnapshot(`
       "const baseConfig = require('../../eslint.config.js');
+
       module.exports = [
         ...baseConfig,
         {
@@ -337,10 +400,12 @@ describe('convert-to-flat-config generator', () => {
       "const { FlatCompat } = require('@eslint/eslintrc');
       const nxEslintPlugin = require('@nx/eslint-plugin');
       const js = require('@eslint/js');
+
       const compat = new FlatCompat({
         baseDirectory: __dirname,
         recommendedConfig: js.configs.recommended,
       });
+
       module.exports = [
         { plugins: { '@nx': nxEslintPlugin } },
         {

packages/eslint/src/generators/convert-to-flat-config/generator.ts

@@ -1,8 +1,10 @@
 import {
+  addDependenciesToPackageJson,
   formatFiles,
   getProjects,
   NxJsonConfiguration,
   ProjectConfiguration,
+  readJson,
   readNxJson,
   Tree,
   updateJson,
@@ -10,7 +12,11 @@ import {
 } from '@nx/devkit';
 import { ConvertToFlatConfigGeneratorSchema } from './schema';
 import { findEslintFile } from '../utils/eslint-file';
+import { join } from 'path';
+import { eslintrcVersion, eslintVersion } from '../../utils/versions';
+import { ESLint } from 'eslint';
 import { convertEslintJsonToFlatConfig } from './converters/json-converter';
+import { load } from 'js-yaml';
 
 export async function convertToFlatConfigGenerator(
   tree: Tree,
@@ -20,9 +26,9 @@ export async function convertToFlatConfigGenerator(
   if (!eslintFile) {
     throw new Error('Could not find root eslint file');
   }
-  if (!eslintFile.endsWith('.json')) {
+  if (eslintFile.endsWith('.js')) {
     throw new Error(
-      'Only json eslint config files are supported for conversion'
+      'Only json and yaml eslint config files are supported for conversion'
     );
   }
 
@@ -60,15 +66,15 @@ export async function convertToFlatConfigGenerator(
 export default convertToFlatConfigGenerator;
 
 function convertRootToFlatConfig(tree: Tree, eslintFile: string) {
-  if (eslintFile.endsWith('.base.json')) {
+  if (/\.base\.(js|json|yml|yaml)$/.test(eslintFile)) {
-    convertConfigToFlatConfig(
+    convertConfigToFlatConfig(tree, '', eslintFile, 'eslint.base.config.js');
-      tree,
-      '',
-      '.eslintrc.base.json',
-      'eslint.base.config.js'
-    );
   }
-  convertConfigToFlatConfig(tree, '', '.eslintrc.json', 'eslint.config.js');
+  convertConfigToFlatConfig(
+    tree,
+    '',
+    eslintFile.replace('.base.', '.'),
+    'eslint.config.js'
+  );
 }
 
 function convertProjectToFlatConfig(
@@ -78,7 +84,8 @@ function convertProjectToFlatConfig(
   nxJson: NxJsonConfiguration,
   eslintIgnoreFiles: Set<string>
 ) {
-  if (tree.exists(`${projectConfig.root}/.eslintrc.json`)) {
+  const eslintFile = findEslintFile(tree, projectConfig.root);
+  if (eslintFile && !eslintFile.endsWith('.js')) {
     if (projectConfig.targets) {
       const eslintTargets = Object.keys(projectConfig.targets || {}).filter(
         (t) => projectConfig.targets[t].executor === '@nx/eslint:lint'
@@ -105,7 +112,7 @@ function convertProjectToFlatConfig(
         convertConfigToFlatConfig(
           tree,
           projectConfig.root,
-          '.eslintrc.json',
+          eslintFile,
           'eslint.config.js',
           ignorePath
         );
@@ -153,5 +160,67 @@ function convertConfigToFlatConfig(
   const ignorePaths = ignorePath
     ? [ignorePath, `${root}/.eslintignore`]
     : [`${root}/.eslintignore`];
-  convertEslintJsonToFlatConfig(tree, root, source, target, ignorePaths);
+
+  if (source.endsWith('.json')) {
+    const config: ESLint.ConfigData = readJson(tree, `${root}/${source}`);
+    const conversionResult = convertEslintJsonToFlatConfig(
+      tree,
+      root,
+      config,
+      ignorePaths
+    );
+    return processConvertedConfig(tree, root, source, target, conversionResult);
+  }
+  if (source.endsWith('.yaml') || source.endsWith('.yml')) {
+    const originalContent = tree.read(`${root}/${source}`, 'utf-8');
+    const config = load(originalContent, {
+      json: true,
+      filename: source,
+    }) as ESLint.ConfigData;
+    const conversionResult = convertEslintJsonToFlatConfig(
+      tree,
+      root,
+      config,
+      ignorePaths
+    );
+    return processConvertedConfig(tree, root, source, target, conversionResult);
+  }
+}
+
+function processConvertedConfig(
+  tree: Tree,
+  root: string,
+  source: string,
+  target: string,
+  {
+    content,
+    addESLintRC,
+    addESLintJS,
+  }: { content: string; addESLintRC: boolean; addESLintJS: boolean }
+) {
+  // remove original config file
+  tree.delete(join(root, source));
+
+  // save new
+  tree.write(join(root, target), content);
+
+  // add missing packages
+  if (addESLintRC) {
+    addDependenciesToPackageJson(
+      tree,
+      {},
+      {
+        '@eslint/eslintrc': eslintrcVersion,
+      }
+    );
+  }
+  if (addESLintJS) {
+    addDependenciesToPackageJson(
+      tree,
+      {},
+      {
+        '@eslint/js': eslintVersion,
+      }
+    );
+  }
 }

packages/eslint/src/generators/init/global-eslint-config.ts

@@ -7,7 +7,6 @@ import {
   generateFlatOverride,
   stringifyNodeList,
 } from '../utils/flat-config/ast-utils';
-import { addPluginsToLintConfig } from '../utils/eslint-file';
 
 /**
  * This configuration is intended to apply to all TypeScript source files.
@@ -97,7 +96,7 @@ export const getGlobalFlatEslintConfiguration = (
   rootProject?: boolean
 ): string => {
   const nodeList = createNodeList(new Map(), [], true);
-  let content = stringifyNodeList(nodeList, '', 'eslint.config.js');
+  let content = stringifyNodeList(nodeList, '');
   content = addImportToFlatConfig(content, 'nxPlugin', '@nx/eslint-plugin');
   content = addPluginsToExportsBlock(content, [
     { name: '@nx', varName: 'nxPlugin', imp: '@nx/eslint-plugin' },

packages/eslint/src/generators/lint-project/lint-project.ts

@@ -209,11 +209,7 @@ function createEsLintConfiguration(
       nodes.push(generateFlatOverride(override, projectConfig.root));
     });
     const nodeList = createNodeList(importMap, nodes, isCompatNeeded);
-    const content = stringifyNodeList(
+    const content = stringifyNodeList(nodeList, projectConfig.root);
-      nodeList,
-      projectConfig.root,
-      'eslint.config.js'
-    );
     tree.write(join(projectConfig.root, 'eslint.config.js'), content);
   } else {
     writeJson(tree, join(projectConfig.root, `.eslintrc.json`), {

packages/eslint/src/generators/utils/flat-config/ast-utils.ts

@@ -695,18 +695,27 @@ export function stringifyNodeList(
     | ts.ExpressionStatement
     | ts.SourceFile
   >,
-  root: string,
+  root: string
-  fileName: string
 ): string {
   const printer = ts.createPrinter({ newLine: ts.NewLineKind.LineFeed });
   const resultFile = ts.createSourceFile(
-    joinPathFragments(root, fileName),
+    joinPathFragments(root, ''),
     '',
     ts.ScriptTarget.Latest,
     true,
     ts.ScriptKind.JS
   );
-  return printer.printList(ts.ListFormat.MultiLine, nodes, resultFile);
+  return (
+    printer
+      .printList(ts.ListFormat.MultiLine, nodes, resultFile)
+      // add new line before compat initialization
+      .replace(
+        /const compat = new FlatCompat/,
+        '\nconst compat = new FlatCompat'
+      )
+      // add new line before module.exports = ...
+      .replace(/module\.exports/, '\nmodule.exports')
+  );
 }
 
 /**

packages/next/src/generators/application/lib/add-linting.spec.ts

@@ -124,6 +124,7 @@ describe('updateEslint', () => {
       "const FlatCompat = require("@eslint/eslintrc");
       const js = require("@eslint/js");
       const baseConfig = require("../eslint.config.js");
+
       const compat = new FlatCompat({
             baseDirectory: __dirname,
             recommendedConfig: js.configs.recommended,