[eslint-config-expo] eslint config for expo projects

packages/eslint-config-expo/.eslintrc.js

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+module.exports = {
+  root: true,
+  extends: ['./default.js', 'prettier'],
+  plugins: ['prettier'],
+  env: {
+    node: true,
+  },
+  rules: {
+    'prettier/prettier': 'warn',
+  },
+};

packages/eslint-config-expo/CHANGELOG.md

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+# Changelog
+
+## Unpublished
+
+### 🛠 Breaking changes
+Create a minimal ESLint config for Expo projects.
+
+### 🎉 New features
+
+### 🐛 Bug fixes
+
+### 💡 Others

packages/eslint-config-expo/LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2016-present Expo
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

packages/eslint-config-expo/README.md

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+# eslint-config-expo
+
+Base ESLint config for Expo projects. This is a minimal config that supports JSX and TypeScript, platform-specific global variables, and file extensions like `.android.js`, `.ios.js` and `.web.js`. You are intended to compose this base config with the linter rules of your choice in your own ESLint configuration.
+
+## Installation
+
+```sh
+yarn add --dev eslint-config-expo
+```
+
+You will also need to install `eslint`:
+
+```sh
+yarn add --dev eslint
+```
+
+## Usage
+
+Import this config into your own ESLint [configuration](https://eslint.org/docs/latest/use/configure/configuration-files) using the `extends` option. ESLint checks both `package.json` and `.eslintrc.*` files for its configuration:
+
+### package.json
+```js
+{
+  "eslintConfig": {
+    "extends": ["expo", "eslint:recommended"]
+  }
+}
+```
+
+### .eslintrc.js
+```js
+module.exports = {
+  extends: ["expo", "eslint:recommended"],
+};
+```

packages/eslint-config-expo/default.js

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+const {
+  jsExtensions,
+  tsExtensions,
+  platformSubextensions,
+  computeExpoExtensions,
+} = require('./utils/extensions');
+
+const allExtensions = computeExpoExtensions(
+  [...jsExtensions, ...tsExtensions],
+  platformSubextensions
+);
+
+module.exports = {
+  extends: ['./utils/core.js', './utils/typescript.js', './utils/react.js', './utils/expo.js'],
+  globals: {
+    __DEV__: 'readonly',
+    ErrorUtils: false,
+    FormData: false,
+    XMLHttpRequest: false,
+    alert: false,
+    cancelAnimationFrame: false,
+    cancelIdleCallback: false,
+    clearImmediate: false,
+    fetch: false,
+    navigator: false,
+    process: false,
+    requestAnimationFrame: false,
+    requestIdleCallback: false,
+    setImmediate: false,
+    window: false,
+    'shared-node-browser': true,
+  },
+  settings: {
+    'import/extensions': allExtensions,
+    'import/resolver': {
+      node: { extensions: allExtensions },
+    },
+  },
+  overrides: [
+    {
+      files: ['*.web.*'],
+      env: { browser: true },
+    },
+  ],
+};

packages/eslint-config-expo/package.json

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+{
+  "name": "eslint-config-expo",
+  "version": "7.0.0",
+  "description": "ESLint config for Expo apps",
+  "main": "default.js",
+  "scripts": {
+    "lint": "eslint ."
+  },
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/expo/expo.git",
+    "directory": "packages/eslint-config-expo"
+  },
+  "keywords": [
+    "eslint-config",
+    "expo",
+    "react-native"
+  ],
+  "files": [
+    "README.md",
+    "default.js",
+    "utils"
+  ],
+  "author": "Expo",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/expo/expo/issues"
+  },
+  "homepage": "https://github.com/expo/expo/tree/main/packages/eslint-config-expo",
+  "dependencies": {
+    "@typescript-eslint/eslint-plugin": "^7.4.0",
+    "@typescript-eslint/parser": "^7.4.0",
+    "eslint-plugin-expo": "^0.0.1",
+    "eslint-plugin-import": "^2.29.1",
+    "eslint-plugin-react": "^7.34.0",
+    "eslint-plugin-react-hooks": "^4.6.0"
+  },
+  "devDependencies": {
+    "eslint": "^8.57.0",
+    "prettier": "^3.2.5",
+    "eslint-plugin-prettier": "^5.1.3"
+  },
+  "peerDependencies": {
+    "eslint": ">=8.10"
+  }
+}

packages/eslint-config-expo/utils/core.js

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+const { jsExtensions } = require('./extensions');
+
+module.exports = {
+  parserOptions: {
+    sourceType: 'module',
+    ecmaVersion: 2022,
+    ecmaFeatures: { impliedStrict: true, jsx: true },
+  },
+  env: { es2022: true },
+  globals: {
+    console: 'readonly',
+    exports: false,
+    global: false,
+    module: false,
+    require: false,
+  },
+  extends: ['plugin:import/errors'],
+  plugins: ['import', 'expo'],
+  rules: {
+    eqeqeq: ['warn', 'smart'],
+    'no-dupe-args': 'error',
+    'no-dupe-class-members': 'error',
+    'no-dupe-keys': 'error',
+    'no-duplicate-case': 'error',
+    'no-empty-character-class': 'warn',
+    'no-empty-pattern': 'warn',
+    'no-extend-native': 'warn',
+    'no-extra-bind': 'warn',
+    'no-redeclare': 'warn',
+    'no-undef': 'error',
+    'no-unreachable': 'warn',
+    'no-unsafe-negation': 'warn',
+    'no-unused-expressions': ['warn', { allowShortCircuit: true, enforceForJSX: true }],
+    'no-unused-labels': 'warn',
+    'no-unused-vars': [
+      'warn',
+      {
+        vars: 'all',
+        args: 'none',
+        ignoreRestSiblings: true,
+        caughtErrors: 'all',
+        caughtErrorsIgnorePattern: '^_',
+      },
+    ],
+    'no-with': 'warn',
+    'unicode-bom': ['warn', 'never'],
+    'use-isnan': 'error',
+    'valid-typeof': 'error',
+    'import/first': 'warn', //keep
+    'import/default': 'off',
+  },
+  settings: {
+    'import/extensions': jsExtensions,
+    'import/ignore': [
+      // react-native's main module is Flow, not JavaScript, and raises parse errors. Additionally,
+      // several other react-native-related packages still publish Flow code as their main source.
+      'node_modules[\\\\/]+@?react-native',
+    ],
+    'import/resolver': {
+      node: { extensions: jsExtensions },
+    },
+  },
+  overrides: [
+    {
+      files: ['*.d.ts'],
+      rules: {
+        'import/order': 'off',
+      },
+    },
+  ],
+};

packages/eslint-config-expo/utils/expo.js

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+module.exports = {
+  plugins: ['expo'],
+  rules: {
+    'expo/no-env-var-destructuring': ['error'],
+    'expo/no-dynamic-env-var': ['error'],
+  },
+};

packages/eslint-config-expo/utils/extensions.js

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+const jsExtensions = ['.js', '.jsx'];
+const tsExtensions = ['.ts', '.tsx', '.d.ts'];
+
+const platformSubextensions = ['.android', '.ios', '.web', '.native'];
+
+function computeExpoExtensions(baseExtensions, platformSubextensions) {
+  const expoExtensions = [];
+  for (const platform of [...platformSubextensions, '']) {
+    for (const base of baseExtensions) {
+      expoExtensions.push(`${platform}${base}`);
+    }
+  }
+  return expoExtensions;
+}
+
+module.exports = {
+  jsExtensions,
+  tsExtensions,
+  platformSubextensions,
+  computeExpoExtensions,
+};

packages/eslint-config-expo/utils/react.js

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+module.exports = {
+  parserOptions: { ecmaFeatures: { jsx: true } },
+  extends: ['plugin:react/recommended', 'plugin:react-hooks/recommended'],
+  rules: {
+    'react/jsx-no-duplicate-props': 'error',
+    'react/jsx-no-undef': 'error',
+    'react/jsx-uses-react': 'warn',
+    'react/jsx-uses-vars': 'warn',
+    'react/no-direct-mutation-state': 'warn',
+    'react/no-this-in-sfc': 'warn',
+    'react/no-unknown-property': 'warn',
+    'react/require-render-return': 'warn',
+    'react/react-in-jsx-scope': 'off',
+  },
+  settings: {
+    react: { version: 'detect' },
+  },
+};

packages/eslint-config-expo/utils/typescript.js

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+const { jsExtensions, tsExtensions } = require('./extensions');
+
+const allExtensions = [...jsExtensions, ...tsExtensions];
+
+module.exports = {
+  overrides: [
+    {
+      files: ['*.js', '*.jsx'],
+      settings: {
+        'import/parsers': {
+          '@typescript-eslint/parser': tsExtensions,
+        },
+      },
+    },
+    {
+      files: ['*.ts', '*.tsx', '*.d.ts'],
+      extends: ['plugin:import/typescript'],
+      parser: '@typescript-eslint/parser',
+      parserOptions: {
+        // eslint-plugin-react@7.32.2 accesses superTypeParameters, which is deprecated by
+        // typescript-estree and prints a warning by default
+        suppressDeprecatedPropertyWarnings: true,
+      },
+      plugins: ['@typescript-eslint'],
+      rules: {
+        '@typescript-eslint/array-type': ['warn', { default: 'array' }],
+        '@typescript-eslint/ban-types': [
+          'error',
+          {
+            types: {
+              Number: {
+                message: 'Use `number` instead.',
+                fixWith: 'number',
+              },
+              Boolean: {
+                message: 'Use `boolean` instead.',
+                fixWith: 'boolean',
+              },
+              Symbol: {
+                message: 'Use `symbol` instead.',
+                fixWith: 'symbol',
+              },
+              Object: {
+                message: 'Use `object` instead.',
+                fixWith: 'object',
+              },
+              String: {
+                message: 'Use `string` instead.',
+                fixWith: 'string',
+              },
+            },
+            extendDefaults: false,
+          },
+        ],
+        '@typescript-eslint/consistent-type-assertions': [
+          'warn',
+          { assertionStyle: 'as', objectLiteralTypeAssertions: 'allow' },
+        ],
+        '@typescript-eslint/no-extra-non-null-assertion': 'warn',
+
+        // Overrides
+        'no-dupe-class-members': 'off',
+        '@typescript-eslint/no-dupe-class-members': 'error',
+
+        'no-redeclare': 'off',
+        '@typescript-eslint/no-redeclare': 'warn',
+
+        'no-unused-vars': 'off',
+        '@typescript-eslint/no-unused-vars': [
+          'warn',
+          { vars: 'all', args: 'none', ignoreRestSiblings: true, caughtErrors: 'all' },
+        ],
+
+        'no-useless-constructor': 'off',
+        '@typescript-eslint/no-useless-constructor': 'warn',
+
+        // The typescript-eslint FAQ recommends turning off "no-undef" in favor of letting tsc check for
+        // undefined variables, including types
+        'no-undef': 'off',
+      },
+      settings: {
+        'import/extensions': allExtensions,
+        'import/parsers': {
+          '@typescript-eslint/parser': tsExtensions,
+        },
+        'import/resolver': {
+          node: { extensions: allExtensions },
+        },
+      },
+    },
+  ],
+};