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# Modern Module Resolution
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Modern Module Resolution patch solves the longstanding issue where ESLint requires plugins to be installed as peer dependencies in every project that uses a shareable config, even when the config package itself provides those plugins.
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## Capabilities
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### Module Resolution Patch
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Applies runtime patches to ESLint's ConfigArrayFactory to resolve plugins relative to the config file instead of the project root.
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```javascript { .api }
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/**
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 * Applies the modern module resolution patch to ESLint
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 * Must be required before ESLint processes any configuration
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 */
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require("@rushstack/eslint-patch/modern-module-resolution");
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```
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**Usage Example:**
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```javascript
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// .eslintrc.js
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require("@rushstack/eslint-patch/modern-module-resolution");
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module.exports = {
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  extends: ['@your-company/eslint-config'], // This config can now provide its own plugins
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  parserOptions: { tsconfigRootDir: __dirname }
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};
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```
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### ESLint Version Support
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The patch automatically detects and handles different ESLint versions:
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- **ESLint 6.x**: Patches `_loadPlugin` method with importerPath parameter
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- **ESLint 7.x/8.x**: Patches `_loadPlugin` method with context object
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- **ESLint 9.x**: Supports both legacy and flat config modes
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### Plugin Resolution Behavior
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When ESLint attempts to load a plugin:
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1. **Primary Resolution**: Tries to resolve plugin relative to the config file location
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2. **Fallback Resolution**: If primary fails with MODULE_NOT_FOUND or invalid path, falls back to original ESLint behavior
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3. **Error Propagation**: Non-resolution errors are re-thrown unchanged
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```javascript { .api }
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// Internal patch behavior (not directly callable)
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interface ModuleResolver {
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  resolve(moduleName: string, relativeToPath: string): string;
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}
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```
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### Config Package Structure
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With this patch, config packages can be structured as follows:
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```json
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{
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  "name": "@your-company/eslint-config",
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  "dependencies": {
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    "@typescript-eslint/eslint-plugin": "^5.0.0",
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    "eslint-plugin-react": "^7.0.0"
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  },
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  "peerDependencies": {
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    "eslint": "^8.0.0"
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  }
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}
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```
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Consumer projects only need:
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```json
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{
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  "devDependencies": {
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    "@rushstack/eslint-patch": "^1.12.0",
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    "@your-company/eslint-config": "^1.0.0",
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    "eslint": "^8.0.0"
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  }
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}
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```
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### Compatibility Notes
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- **ESLint Flat Config**: ESLint 8.21.0+ includes native flat config mode (`ESLINT_USE_FLAT_CONFIG`) that may reduce need for this patch
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- **Editor Extensions**: Works with VS Code ESLint extension, WebStorm, and other editor integrations
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- **Monorepo Support**: Particularly useful in Rush Stack monorepos and similar setups
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### Error Handling
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The patch handles several error scenarios:
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- **MODULE_NOT_FOUND**: Falls back to original resolution
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- **ERR_INVALID_ARG_VALUE**: Falls back to original resolution (invalid importer path)
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- **Other errors**: Re-thrown unchanged to preserve original ESLint error handling