eslint.config.mjs

// Copyright (c) 2026 The Brave Authors. All rights reserved.
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.

import { defineConfig, globalIgnores } from 'eslint/config'

import jest from 'eslint-plugin-jest'
import importPlugin from 'eslint-plugin-import'
import licenses from 'eslint-plugin-licenses'
import noUnsanitized from 'eslint-plugin-no-unsanitized'
import reactHooks from 'eslint-plugin-react-hooks'
import love from 'eslint-config-love'
import prettier from 'eslint-config-prettier/flat'
import tslint from 'typescript-eslint'
import eslintJs from '@eslint/js'
import globals from 'globals'

// Config layout: each plugin or override is a separate array entry.
// Guidelines:
//   - One section per plugin; do not combine rules from different plugins
//     in one section.
//   - Each section should have a comment stating its purpose and which files
//     it targets.
// Verify changes with: npm run eslint (about 1 min).
export default defineConfig([
  // Setup project-wide language options.
  {
    languageOptions: {
      globals: {
        ...globals.browser,
        ...globals.jest,
        ...globals.node,
        chrome: 'readonly',
      },
    },
  },

  // Turn off rules that conflict with Prettier formatting (all files).
  prettier,

  // ESLint core recommended rules for JavaScript (.js files + related).
  eslintJs.configs.recommended,

  // Prevents unsafe DOM injection, e.g. innerHTML (all files).
  noUnsanitized.configs.recommended,

  // React Hooks rules and related React best practices (.tsx and .jsx files).
  reactHooks.configs.flat.recommended,

  // Jest test lint rules. (.ts and .js test files).
  jest.configs['flat/recommended'],

  // TypeScript syntax and basic correctness; does not use type information (.ts, .tsx, .mts files).
  tslint.configs.recommended,

  // Stricter TypeScript rules using the type checker
  {
    ...love,
    files: ['**/*.{ts,tsx,mts}'],
    languageOptions: {
      ...love.languageOptions,
      parserOptions: {
        project: './tsconfig-lint.json',
      },
    },
  },

  // Enforce license header in file (all files). Overlaps with PRESUBMIT.
  {
    plugins: {
      licenses,
    },
    rules: {
      'licenses/header': [
        2,
        {
          tryUseCreatedYear: true,
          comment: {
            allow: 'both',
            prefer: 'line',
          },
          header: [
            'Copyright (c) {YEAR} The Brave Authors. All rights reserved.',
            'This Source Code Form is subject to the terms of the Mozilla Public',
            'License, v. 2.0. If a copy of the MPL was not distributed with this file,',
            'You can obtain one at https://mozilla.org/MPL/2.0/.',
          ],
          altHeaders: [
            [
              'Copyright (c) {YEAR} The Brave Authors. All rights reserved.',
              '* This Source Code Form is subject to the terms of the Mozilla Public',
              '* License, v. 2.0. If a copy of the MPL was not distributed with this file,',
              '* You can obtain one at https://mozilla.org/MPL/2.0/.',
            ],
            [
              'This Source Code Form is subject to the terms of the Mozilla Public',
              '* License, v. 2.0. If a copy of the MPL was not distributed with this file,',
              '* You can obtain one at https://mozilla.org/MPL/2.0/.',
            ],
            [
              'Copyright (c) {YEAR} The Brave Authors. All rights reserved.',
              'This Source Code Form is subject to the terms of the Mozilla Public',
              'License, v. 2.0. If a copy of the MPL was not distributed with this file,',
              'you can obtain one at https://mozilla.org/MPL/2.0/.',
            ],
          ],
        },
      ],
    },
  },

  globalIgnores([
    '.storybook/*',
    'browser/*',
    'ui/webui/resources/*',
    '**/*.d.ts',
    'tools/chromium_src/lit_mangler/*.ts',

    // External or vendored code; not maintained in this repo
    'vendor/',
    'third_party/',
    'tools/crates/vendor/',

    // Not purely JavaScript, contains `<template>` expressions.
    'ios/brave-ios/Sources/Brave/Frontend/UserContent/UserScripts/',
    'ios/brave-ios/Sources/Brave/Assets/**/*.js',

    // Generated by scripts, skip linting
    'ios/brave-ios/Sources/AIChat/Components/Markdown/CodeHighlight/Scripts/highlight.min.js',
    'components/brave_wallet/resources/solana_web3_script.js',
    'test/data/ephemeral-storage/static/js/libs/js.cookie.min.js',
  ]),

  {
    // Project-wide disabled rules (all files).
    rules: {
      'array-callback-return': 'off',
      'arrow-body-style': 'off',
      'complexity': 'off',
      'curly': 'off',
      'eqeqeq': 'off',
      'guard-for-in': 'off',
      'logical-assignment-operators': 'off',
      'max-lines': 'off',
      'max-nested-callbacks': 'off',
      'new-cap': 'off',
      'no-alert': 'off',
      'no-async-promise-executor': 'off',
      'no-await-in-loop': 'off',
      'no-case-declarations': 'off',
      'no-console': 'off',
      'no-fallthrough': 'off',
      'no-implicit-globals': 'off',
      'no-lonely-if': 'off',
      'no-multi-assign': 'off',
      'no-named-default': 'off',
      'no-negated-condition': 'off',
      'no-new-func': 'off',
      'no-new-wrappers': 'off',
      'no-param-reassign': 'off',
      'no-plusplus': 'off',
      'no-promise-executor-return': 'off',
      'no-prototype-builtins': 'off',
      'no-return-assign': 'off',
      'no-template-curly-in-string': 'off',
      'no-useless-assignment': 'off',
      'no-useless-concat': 'off',
      'no-useless-escape': 'off',
      'operator-assignment': 'off',
      'prefer-arrow-callback': 'off',
      'prefer-const': 'off',
      'prefer-exponentiation-operator': 'off',
      'prefer-named-capture-group': 'off',
      'prefer-object-spread': 'off',
      'prefer-regex-literals': 'off',
      'prefer-spread': 'off',
      'prefer-template': 'off',
      'preserve-caught-error': 'off',
      'promise/avoid-new': 'off',
      'radix': 'off',
      'require-atomic-updates': 'off',
      'require-unicode-regexp': 'off',
      'strict': 'off',

      '@typescript-eslint/array-type': 'off',
      '@typescript-eslint/await-thenable': 'off',
      '@typescript-eslint/ban-ts-comment': 'off',
      '@typescript-eslint/class-literal-property-style': 'off',
      '@typescript-eslint/class-methods-use-this': 'off',
      '@typescript-eslint/consistent-generic-constructors': 'off',
      '@typescript-eslint/consistent-indexed-object-style': 'off',
      '@typescript-eslint/consistent-type-assertions': 'off',
      '@typescript-eslint/consistent-type-definitions': 'off',
      '@typescript-eslint/consistent-type-exports': 'off',
      '@typescript-eslint/consistent-type-imports': 'off',
      '@typescript-eslint/dot-notation': 'off',
      '@typescript-eslint/explicit-function-return-type': 'off',
      '@typescript-eslint/init-declarations': 'off',
      '@typescript-eslint/max-params': 'off',
      '@typescript-eslint/method-signature-style': 'off',
      '@typescript-eslint/no-base-to-string': 'off',
      '@typescript-eslint/no-confusing-void-expression': 'off',
      '@typescript-eslint/no-deprecated': 'off',
      '@typescript-eslint/no-duplicate-type-constituents': 'off',
      '@typescript-eslint/no-dynamic-delete': 'off',
      '@typescript-eslint/no-empty-function': 'off',
      '@typescript-eslint/no-empty-object-type': 'off',
      '@typescript-eslint/no-explicit-any': 'off',
      '@typescript-eslint/no-floating-promises': 'off',
      '@typescript-eslint/no-implied-eval': 'off',
      '@typescript-eslint/no-import-type-side-effects': 'off',
      '@typescript-eslint/no-inferrable-types': 'off',
      '@typescript-eslint/no-invalid-void-type': 'off',
      '@typescript-eslint/no-magic-numbers': 'off',
      '@typescript-eslint/no-misused-promises': 'off',
      '@typescript-eslint/no-misused-spread': 'off',
      '@typescript-eslint/no-namespace': 'off',
      '@typescript-eslint/no-non-null-assertion': 'off',
      '@typescript-eslint/no-redundant-type-constituents': 'off',
      '@typescript-eslint/no-unnecessary-boolean-literal-compare': 'off',
      '@typescript-eslint/no-unnecessary-condition': 'off',
      '@typescript-eslint/no-unnecessary-template-expression': 'off',
      '@typescript-eslint/no-unnecessary-type-arguments': 'off',
      '@typescript-eslint/no-unnecessary-type-assertion': 'off',
      '@typescript-eslint/no-unnecessary-type-conversion': 'off',
      '@typescript-eslint/no-unnecessary-type-parameters': 'off',
      '@typescript-eslint/no-unsafe-argument': 'off',
      '@typescript-eslint/no-unsafe-assignment': 'off',
      '@typescript-eslint/no-unsafe-call': 'off',
      '@typescript-eslint/no-unsafe-declaration-merging': 'off',
      '@typescript-eslint/no-unsafe-enum-comparison': 'off',
      '@typescript-eslint/no-unsafe-function-type': 'off',
      '@typescript-eslint/no-unsafe-member-access': 'off',
      '@typescript-eslint/no-unsafe-return': 'off',
      '@typescript-eslint/no-unsafe-type-assertion': 'off',
      '@typescript-eslint/no-unused-expressions': 'off',
      '@typescript-eslint/no-unused-vars': 'off',
      '@typescript-eslint/no-useless-constructor': 'off',
      '@typescript-eslint/no-useless-default-assignment': 'off',
      '@typescript-eslint/no-wrapper-object-types': 'off',
      '@typescript-eslint/non-nullable-type-assertion-style': 'off',
      '@typescript-eslint/prefer-destructuring': 'off',
      '@typescript-eslint/prefer-find': 'off',
      '@typescript-eslint/prefer-for-of': 'off',
      '@typescript-eslint/prefer-literal-enum-member': 'off',
      '@typescript-eslint/prefer-nullish-coalescing': 'off',
      '@typescript-eslint/prefer-optional-chain': 'off',
      '@typescript-eslint/prefer-promise-reject-errors': 'off',
      '@typescript-eslint/prefer-readonly': 'off',
      '@typescript-eslint/prefer-regexp-exec': 'off',
      '@typescript-eslint/prefer-string-starts-ends-with': 'off',
      '@typescript-eslint/promise-function-async': 'off',
      '@typescript-eslint/require-array-sort-compare': 'off',
      '@typescript-eslint/require-await': 'off',
      '@typescript-eslint/restrict-plus-operands': 'off',
      '@typescript-eslint/restrict-template-expressions': 'off',
      '@typescript-eslint/return-await': 'off',
      '@typescript-eslint/strict-boolean-expressions': 'off',
      '@typescript-eslint/strict-void-return': 'off',
      '@typescript-eslint/switch-exhaustiveness-check': 'off',
      '@typescript-eslint/unbound-method': 'off',
      '@typescript-eslint/use-unknown-in-catch-callback-variable': 'off',

      '@eslint-community/eslint-comments/disable-enable-pair': 'off',
      '@eslint-community/eslint-comments/no-duplicate-disable': 'off',
      '@eslint-community/eslint-comments/require-description': 'off',

      'import/enforce-node-protocol-usage': 'off',
      'import/no-absolute-path': 'off',

      'react-hooks/immutability': 'off',
      'react-hooks/preserve-manual-memoization': 'off',
      'react-hooks/purity': 'off',
      'react-hooks/refs': 'off',
      'react-hooks/rules-of-hooks': 'off',
      'react-hooks/set-state-in-effect': 'off',
      'react-hooks/static-components': 'off',
      'react-hooks/use-memo': 'off',
    },
  },
  {
    // Brave JavaScript files uses require() to load modules.
    files: ['**/*.{js,jsx,mjs,cjs}'],
    rules: {
      '@typescript-eslint/no-require-imports': 'off',
    },
  },
  {
    files: ['build/commands/**/*.{js,cjs,mjs,ts,cts,mts}'],
    plugins: {
      import: importPlugin,
    },
    rules: {
      ...importPlugin.flatConfigs.recommended.rules,

      'import/enforce-node-protocol-usage': ['error', 'always'],

      // Enforce import resolution for build/commands scripts. When running
      // TypeScript natively via Node.js (no transpilation), imports must use
      // the real file extension. For example, if a file is named config.ts,
      // importing it as './config.js' is an error.
      'import/no-unresolved': 'error',
    },
  },
  {
    // Test data files; skips some non-important rules.
    files: ['test/data/**/*.js'],
    rules: {
      'licenses/header': 'off',
      'no-undef': 'off',
    },
  },

  {
    // Specific rules for NodeJS targets (except build/commands)
    files: ['**/*.test.{js,ts}', '**/*.{cts,cjs}'],
    ignores: ['build/commands/**/*'],
    plugins: {
      import: importPlugin,
    },
    rules: {
      ...importPlugin.flatConfigs.recommended.rules,
      'import/no-unresolved': 'off',
      'import/enforce-node-protocol-usage': ['error', 'always'],
    },
  },
])