ESLint issue after upgrading to Angular 20 (".eslintignore" no longer supported)

Question

After upgrading my Angular project to version 20, ESLint started throwing the following error when I run linting (using Nx):

[error] (node:20947) ESLintIgnoreWarning: The ".eslintignore" file is no longer supported. Switch to using the "ignores" property in "eslint.config.js".

[error] An unexpected error occurred: Error: Could not find config file. at t assertConfigurationExists (/*/config-loader.js:80:17)
at LegacyConfigLoader.loadConfigArrayForFile (/*/config-loader.js:414:3)

The project is an Nx monorepo with multiple Angular apps and libs. Here’s a simplified version of my setup:

At the root I have: eslint.client.js

// eslint.client.js

module.exports = {
    extends: ['.eslintrc.json'],
    ignorePatterns: ['!**/*'],
    overrides: [{
                parser: '@typescript-eslint/parser',
                parserOptions: {
                    ecmaVersion: 2019,
                    project: join(__dirname, './tsconfig.base.json'),
                    sourceType: 'module',
                },
                files: ['*.ts'],
                extends: ['plugin:@nx/typescript', 'plugin:@nx/angular', 'plugin:@angular-eslint/template/process-inline-templates', ],
                rules: { // custom rules... }, }, ], };

And in each app/lib I have something like:

// .eslintrc.json
{
  "extends": ["../../../eslint.client.js"],
  "ignorePatterns": ["!**/*"]
}

Any idea?

Alireza Ahmadi · Accepted Answer · 2025-11-14 08:36:23Z

1. Quick fix

Just add the following line in .vscode/settings.json

"eslint.useFlatConfig": false,

2. Main Solution

Since ESLint v9, .eslintrc.* and .eslintignore are no longer supported.
Nx 20 uses ESLint v9 → your current config is ignored → error appears.

Here is the fix

Remove all .eslintrc.json files
Create a single eslint.config.js at the workspace root
Add a lightweight eslint.config.js inside each app/lib

Example — Root eslint.config.js:

import { join } from 'path';
import nx from '@nx/eslint-plugin';

export default [
  {
    ignores: ['**/dist/**', '**/tmp/**'],
  },
  {
    files: ['**/*.ts'],
    languageOptions: {
      parser: '@typescript-eslint/parser',
      parserOptions: {
        project: join(process.cwd(), 'tsconfig.base.json'),
      },
    },
    plugins: {
      nx,
      '@typescript-eslint': require('@typescript-eslint/eslint-plugin'),
    },
    extends: [
      'plugin:@nx/typescript',
      'plugin:@nx/angular',
      'plugin:@angular-eslint/template/process-inline-templates',
    ],
    rules: {
      // custom rules…
    },
  },
];

Example — App/Lib eslint.config.js:

export default [
  {
    extends: ['../../eslint.config.js'],
  },
];

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