feat: add flat config support

This change adds support for ESLint's new Flat config system.  It maintains backwards compatibility with eslintrc style configs as well.

To achieve this, we're now dynamically creating flat configs on a new `flatConfigs` export.  I was a bit on the fence about using this convention, or the other convention that's become prevalent in the community: adding the flat configs directly to the `configs` object, but with a 'flat/' prefix.  I like this better, since it's slightly more ergonomic when using it in practice.  e.g. `...importX.flatConfigs.recommended` vs `...importX.configs['flat/recommended']`, but i'm open to changing that.

Example Usage

```js
import importPlugin from 'eslint-plugin-import';
import js from '@eslint/js';
import tsParser from '@typescript-eslint/parser';

export default [
  js.configs.recommended,
  importPlugin.flatConfigs.recommended,
  importPlugin.flatConfigs.react,
  importPlugin.flatConfigs.typescript,
  {
    files: ['**/*.{js,mjs,cjs,jsx,mjsx,ts,tsx,mtsx}'],
    languageOptions: {
      parser: tsParser,
      ecmaVersion: 'latest',
      sourceType: 'module',
    },
    ignores: ['eslint.config.js'],
    rules: {
      'no-unused-vars': 'off',
      'import/no-dynamic-require': 'warn',
      'import/no-nodejs-modules': 'warn',
    },
  },
];
```

Closes #29

.changeset/great-dodos-dream.md

@@ -0,0 +1,5 @@
+---
+"eslint-plugin-import-x": minor
+---
+
+add support for flat configs

package.json

@@ -35,7 +35,7 @@
     "codesandbox:install": "yarn --ignore-engines",
     "lint": "run-p lint:*",
     "lint:docs": "yarn update:eslint-docs --check",
-    "lint:es": "ESLINT_USE_FLAT_CONFIG=false eslint . --cache",
+    "lint:es": "cross-env ESLINT_USE_FLAT_CONFIG=false eslint . --cache",
     "lint:tsc": "tsc -p tsconfig.base.json --noEmit",
     "prepare": "patch-package",
     "release": "changeset publish",

src/config/flat/electron.ts

@@ -0,0 +1,10 @@
+import type { PluginFlatConfig } from '../../types'
+
+/**
+ * Default settings for Electron applications.
+ */
+export default {
+  settings: {
+    'import-x/core-modules': ['electron'],
+  },
+} satisfies PluginFlatConfig

src/config/flat/errors.ts

@@ -0,0 +1,15 @@
+import type { PluginFlatConfig } from '../../types'
+
+/**
+ * unopinionated config. just the things that are necessarily runtime errors
+ * waiting to happen.
+ */
+export default {
+  rules: {
+    'import-x/no-unresolved': 2,
+    'import-x/named': 2,
+    'import-x/namespace': 2,
+    'import-x/default': 2,
+    'import-x/export': 2,
+  },
+} satisfies PluginFlatConfig

src/config/flat/react-native.ts

@@ -0,0 +1,15 @@
+import type { PluginFlatBaseConfig } from '../../types'
+
+/**
+ * adds platform extensions to Node resolver
+ */
+export default {
+  settings: {
+    'import-x/resolver': {
+      node: {
+        // Note: will not complain if only _one_ of these files exists.
+        extensions: ['.js', '.web.js', '.ios.js', '.android.js'],
+      },
+    },
+  },
+} satisfies PluginFlatBaseConfig

src/config/flat/react.ts

@@ -0,0 +1,21 @@
+import type { PluginFlatBaseConfig } from '../../types'
+
+/**
+ * Adds `.jsx` as an extension, and enables JSX parsing.
+ *
+ * Even if _you_ aren't using JSX (or .jsx) directly, if your dependencies
+ * define jsnext:main and have JSX internally, you may run into problems
+ * if you don't enable these settings at the top level.
+ */
+export default {
+  settings: {
+    'import-x/extensions': ['.js', '.jsx', '.mjs', '.cjs'],
+  },
+  languageOptions: {
+    parserOptions: {
+      ecmaFeatures: {
+        jsx: true,
+      },
+    },
+  },
+} satisfies PluginFlatBaseConfig

src/config/flat/recommended.ts

@@ -0,0 +1,27 @@
+import type { PluginFlatBaseConfig } from '../../types'
+
+/**
+ * The basics.
+ */
+export default {
+  rules: {
+    // analysis/correctness
+    'import-x/no-unresolved': 'error',
+    'import-x/named': 'error',
+    'import-x/namespace': 'error',
+    'import-x/default': 'error',
+    'import-x/export': 'error',
+
+    // red flags (thus, warnings)
+    'import-x/no-named-as-default': 'warn',
+    'import-x/no-named-as-default-member': 'warn',
+    'import-x/no-duplicates': 'warn',
+  },
+
+  // need all these for parsing dependencies (even if _your_ code doesn't need
+  // all of them)
+  languageOptions: {
+    ecmaVersion: 2018,
+    sourceType: 'module',
+  },
+} satisfies PluginFlatBaseConfig

src/config/flat/stage-0.ts

@@ -0,0 +1,12 @@
+import type { PluginFlatBaseConfig } from '../../types'
+
+/**
+ * Rules in progress.
+ *
+ * Do not expect these to adhere to semver across releases.
+ */
+export default {
+  rules: {
+    'import-x/no-deprecated': 1,
+  },
+} satisfies PluginFlatBaseConfig

src/config/flat/typescript.ts

@@ -0,0 +1,41 @@
+import type { PluginFlatBaseConfig } from '../../types'
+
+/**
+ * This config:
+ * 1) adds `.jsx`, `.ts`, `.cts`, `.mts`, and `.tsx` as an extension
+ * 2) enables JSX/TSX parsing
+ */
+
+// Omit `.d.ts` because 1) TypeScript compilation already confirms that
+// types are resolved, and 2) it would mask an unresolved
+// `.ts`/`.tsx`/`.js`/`.jsx` implementation.
+const typeScriptExtensions = ['.ts', '.tsx', '.cts', '.mts'] as const
+
+const allExtensions = [
+  ...typeScriptExtensions,
+  '.js',
+  '.jsx',
+  '.cjs',
+  '.mjs',
+] as const
+
+export default {
+  settings: {
+    'import-x/extensions': allExtensions,
+    'import-x/external-module-folders': ['node_modules', 'node_modules/@types'],
+    'import-x/parsers': {
+      '@typescript-eslint/parser': [...typeScriptExtensions],
+    },
+    'import-x/resolver': {
+      node: {
+        extensions: allExtensions,
+      },
+    },
+  },
+  rules: {
+    // analysis/correctness
+
+    // TypeScript compilation already ensures that named imports exist in the referenced module
+    'import-x/named': 'off',
+  },
+} satisfies PluginFlatBaseConfig

src/config/flat/warnings.ts

@@ -0,0 +1,12 @@
+import type { PluginFlatBaseConfig } from '../../types'
+
+/**
+ * more opinionated config.
+ */
+export default {
+  rules: {
+    'import-x/no-named-as-default': 1,
+    'import-x/no-named-as-default-member': 1,
+    'import-x/no-duplicates': 1,
+  },
+} satisfies PluginFlatBaseConfig

src/config/typescript.ts

@@ -9,16 +9,22 @@ import type { PluginConfig } from '../types'
 // Omit `.d.ts` because 1) TypeScript compilation already confirms that
 // types are resolved, and 2) it would mask an unresolved
 // `.ts`/`.tsx`/`.js`/`.jsx` implementation.
-const typeScriptExtensions = ['.ts', '.tsx'] as const
+const typeScriptExtensions = ['.ts', '.tsx', '.cts', '.mts'] as const
 
-const allExtensions = [...typeScriptExtensions, '.js', '.jsx'] as const
+const allExtensions = [
+  ...typeScriptExtensions,
+  '.js',
+  '.jsx',
+  '.cjs',
+  '.mjs',
+] as const
 
 export = {
   settings: {
     'import-x/extensions': allExtensions,
     'import-x/external-module-folders': ['node_modules', 'node_modules/@types'],
     'import-x/parsers': {
-      '@typescript-eslint/parser': [...typeScriptExtensions, '.cts', '.mts'],
+      '@typescript-eslint/parser': [...typeScriptExtensions],
     },
     'import-x/resolver': {
       node: {

src/index.ts

@@ -1,14 +1,25 @@
 import type { TSESLint } from '@typescript-eslint/utils'
 
-// rules
+import { name, version } from '../package.json'
+
 import electron from './config/electron'
 import errors from './config/errors'
+import electronFlat from './config/flat/electron'
+import errorsFlat from './config/flat/errors'
+import reactFlat from './config/flat/react'
+import reactNativeFlat from './config/flat/react-native'
+import recommendedFlat from './config/flat/recommended'
+import stage0Flat from './config/flat/stage-0'
+import typescriptFlat from './config/flat/typescript'
+import warningsFlat from './config/flat/warnings'
 import react from './config/react'
 import reactNative from './config/react-native'
 import recommended from './config/recommended'
 import stage0 from './config/stage-0'
 import typescript from './config/typescript'
 import warnings from './config/warnings'
+
+// rules
 import consistentTypeSpecifierStyle from './rules/consistent-type-specifier-style'
 import default_ from './rules/default'
 import dynamicImportChunkname from './rules/dynamic-import-chunkname'
@@ -55,23 +66,11 @@ import order from './rules/order'
 import preferDefaultExport from './rules/prefer-default-export'
 import unambiguous from './rules/unambiguous'
 // configs
-import type { PluginConfig } from './types'
-
-const configs = {
-  recommended,
-
-  errors,
-  warnings,
-
-  // shhhh... work in progress "secret" rules
-  'stage-0': stage0,
-
-  // useful stuff for folks using various environments
-  react,
-  'react-native': reactNative,
-  electron,
-  typescript,
-} satisfies Record<string, PluginConfig>
+import type {
+  PluginConfig,
+  PluginFlatBaseConfig,
+  PluginFlatConfig,
+} from './types'
 
 const rules = {
   'no-unresolved': noUnresolved,
@@ -129,7 +128,56 @@ const rules = {
   'imports-first': importsFirst,
 } satisfies Record<string, TSESLint.RuleModule<string, readonly unknown[]>>
 
+const configs = {
+  recommended,
+
+  errors,
+  warnings,
+
+  // shhhh... work in progress "secret" rules
+  'stage-0': stage0,
+
+  // useful stuff for folks using various environments
+  react,
+  'react-native': reactNative,
+  electron,
+  typescript,
+} satisfies Record<string, PluginConfig>
+
+// Base Plugin Object
+const plugin = {
+  meta: { name, version },
+  rules,
+}
+
+// Create flat configs (Only ones that declare plugins and parser options need to be different from the legacy config)
+const createFlatConfig = (
+  baseConfig: PluginFlatBaseConfig,
+  configName: string,
+): PluginFlatConfig => ({
+  ...baseConfig,
+  name: `import-x/${configName}`,
+  plugins: { 'import-x': plugin },
+})
+
+const flatConfigs = {
+  recommended: createFlatConfig(recommendedFlat, 'recommended'),
+
+  errors: createFlatConfig(errorsFlat, 'errors'),
+  warnings: createFlatConfig(warningsFlat, 'warnings'),
+
+  // shhhh... work in progress "secret" rules
+  'stage-0': createFlatConfig(stage0Flat, 'stage-0'),
+
+  // useful stuff for folks using various environments
+  react: reactFlat,
+  'react-native': reactNativeFlat,
+  electron: electronFlat,
+  typescript: typescriptFlat,
+} satisfies Record<string, PluginFlatConfig>
+
 export = {
   configs,
+  flatConfigs,
   rules,
 }

src/types.ts

@@ -70,6 +70,15 @@ export type PluginConfig = {
   rules?: Record<`${PluginName}/${string}`, TSESLint.Linter.RuleEntry>
 } & TSESLint.Linter.ConfigType
 
+export type PluginFlatBaseConfig = {
+  settings?: PluginSettings
+  rules?: Record<`${PluginName}/${string}`, TSESLint.FlatConfig.RuleEntry>
+} & TSESLint.FlatConfig.Config
+
+export type PluginFlatConfig = PluginFlatBaseConfig & {
+  name?: `${PluginName}/${string}`
+}
+
 export type RuleContext<
   TMessageIds extends string = string,
   TOptions extends readonly unknown[] = readonly unknown[],

src/utils/ignore.ts

@@ -28,7 +28,7 @@ function validExtensions(context: ChildContext | RuleContext) {
 export function getFileExtensions(settings: PluginSettings) {
   // start with explicit JS-parsed extensions
   const exts = new Set<FileExtension>(
-    settings['import-x/extensions'] || ['.js'],
+    settings['import-x/extensions'] || ['.js', '.mjs', '.cjs'],
   )
 
   // all alternate parser extensions are also valid