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# @rushstack/eslint-patch
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@rushstack/eslint-patch enhances ESLint with better support for large scale monorepos through runtime patches that enable enhanced functionality. It operates as "monkey patches" that modify the ESLint engine in memory, maintaining full compatibility with existing ESLint versions and editor extensions.
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## Package Information
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- **Package Name**: @rushstack/eslint-patch
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- **Package Type**: npm
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- **Language**: TypeScript
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- **Installation**: `npm install --save-dev @rushstack/eslint-patch`
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## Core Imports
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The package does not have a default entry point and must be imported using specific feature paths. Attempting to import the main entry point will throw an error with usage instructions:
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```javascript
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// For modern module resolution patch
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require("@rushstack/eslint-patch/modern-module-resolution");
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// For custom config package names patch  
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require("@rushstack/eslint-patch/custom-config-package-names");
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// For bulk suppressions patch
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require("@rushstack/eslint-patch/eslint-bulk-suppressions");
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```
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## Basic Usage
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Add patches to the top of your `.eslintrc.js` file:
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```javascript
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// Load patches (order matters for some combinations)
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require("@rushstack/eslint-patch/modern-module-resolution");
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require("@rushstack/eslint-patch/custom-config-package-names");
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require("@rushstack/eslint-patch/eslint-bulk-suppressions");
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module.exports = {
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  extends: ['@your-company/eslint-config'],
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  parserOptions: { tsconfigRootDir: __dirname }
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};
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```
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The patches automatically detect and support ESLint versions 6.x, 7.x, 8.x, and 9.x.
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## Architecture
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@rushstack/eslint-patch is built around several key components:
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- **Runtime Patching System**: Core infrastructure that detects ESLint version and applies appropriate patches
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- **Module Resolution Override**: Patches ESLint's plugin and config loading to support monorepo scenarios
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- **Suppression Management**: File-based bulk suppression system for managing legacy lint violations
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- **Version Compatibility**: Automatic detection and handling of different ESLint major versions
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## Capabilities
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### Modern Module Resolution
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Allows ESLint config packages to provide their own plugin dependencies, eliminating the need to copy+paste devDependencies across projects in a monorepo.
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```javascript { .api }
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// Entry point that applies the patch
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require("@rushstack/eslint-patch/modern-module-resolution");
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```
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[Modern Module Resolution](./modern-module-resolution.md)
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### Custom Config Package Names
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Removes ESLint's requirement for 'eslint-config' to appear in shareable config package names, enabling rig packages to provide ESLint configurations.
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```javascript { .api }
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// Entry point that applies the patch  
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require("@rushstack/eslint-patch/custom-config-package-names");
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```
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[Custom Config Package Names](./custom-config-package-names.md)
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### Bulk Suppressions
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Enables machine-generated lint suppressions to be stored in a separate `.eslint-bulk-suppressions.json` file rather than cluttering source code with thousands of `// eslint-ignore-next-line` directives.
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```javascript { .api }
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// Entry point that applies the patch
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require("@rushstack/eslint-patch/eslint-bulk-suppressions");
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```
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[Bulk Suppressions](./bulk-suppressions.md)
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## Error Handling
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If patches cannot be applied due to unsupported ESLint versions or missing dependencies, the package will throw descriptive errors:
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- **Unsupported ESLint version**: Versions outside 6.x-9.x range
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- **Missing ESLint installation**: Cannot locate ESLint modules to patch
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- **Module resolution failures**: Cannot find required ESLint internal modules
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- **Default entry point access**: The main entry point throws an error by design to prevent accidental usage without specific feature imports
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## Supported ESLint Versions
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- ESLint 6.x
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- ESLint 7.x  
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- ESLint 8.x
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- ESLint 9.x (including flat config support)