Assess, plan, evolve.

Migrate ESLint projects from v9 to v10 — runs all four v9-to-v10 codemods in a single pass

• Bundle
• transformation
• migration
• +4

Migrate ESLint configuration from v8 to v9 flat config format

• transformation
• migration
• +3

Remove legacy env vars and CLI flags for ESLint v10

• transformation
• migration
• +3

Migrate removed Linter/ESLint constructor options and stricter rule config schema for ESLint v10

• transformation
• migration
• +3

Fix RuleTester test case structure for ESLint v10

• transformation
• migration
• +3

Migrate custom ESLint rules from v9 to v10 format

• transformation
• migration
• +3

Migrate custom ESLint rules from v8 to v9 format

• transformation
• migration
• +3

This codemod replaces configuration files for ESLint with corresponding biome.json for all the found rules. It also replaces Prettier configuration. ## Note: This codemod accepts manual user input, which is required to migrate away from eslint. In order to run it properly, run the following command: ```bash npx eslint --print-config <path-to-a-file-that-eslint-checks> | codemod eslint/biome/migrate-rules ``` It's important that you pass these rules to the codemod, because our codemods are limited in access for security purposes and have no access to most node features that could maliciously affect your system. This codemod requires internet connection. ## Example ### `package.json` ### Before ```json { "name": "package-name", "dependencies": { "prettier": "^3.1.0", "prettier-plugin-tailwindcss": "^0.5.4", "@tanstack/eslint-plugin-query": "^4.29.25", "@someorg/prettier-config": "^1.1.1" }, "devDependencies": { "eslint-plugin-airbnb": "^10.2.0", "eslint": "^10.2.0", "eslint-plugin-prettier": "^10.2.0", "eslint-config-prettier": "^10.2.0" }, "main": "./dist/index.cjs", "scripts": { "start": "pnpm run build:cjs && node ./dist/index.cjs", "lint:eslint": "eslint . --fix", "lint:prettier": "prettier --write ." }, "eslintIgnore": ["ignore-key"], "files": [ "prettier-test-no-replace", "README.md", ".codemodrc.json", "./dist/index.cjs" ], "lint-staged": { "*.js": "eslint --fix", "*.ts": "eslint --fix" }, "type": "module" } ``` ### After ```json { "name": "package-name", "dependencies": {}, "devDependencies": { "@biomejs/biome": "1.5.3" }, "main": "./dist/index.cjs", "scripts": { "start": "pnpm run build:cjs && node ./dist/index.cjs", "lint:eslint": "pnpm dlx @biomejs/biome lint . --apply", "lint:prettier": "pnpm dlx @biomejs/biome format --write .", "NOTE": "You can apply both linter, formatter and import ordering by using https://biomejs.dev/reference/cli/#biome-check", "NOTE2": "There is an ongoing work to release prettier-tailwind-plugin alternative: https://biomejs.dev/linter/rules/use-sorted-classes/, https://github.com/biomejs/biome/issues/1274" }, "files": [ "prettier-test-no-replace", "README.md", ".codemodrc.json", "./dist/index.cjs" ], "lint-staged": { "*.js": "pnpm dlx @biomejs/biome lint --apply", "*.ts": "pnpm dlx @biomejs/biome lint --apply" }, "type": "module" } ``` ### `.eslintrc.json` ### Before ```json { "rules": [...] } ``` ### After `Removed and replaced with corresponding rules in biome.json` ### `.prettierrc` ### Before ```json { "printWidth": 80 } ``` ### After `Removed and replaced with corresponding values in biome.json` ### `biome.json` ```json { "linter": { "ignore": [ "ignore-key", "dist", "build", "pnpm-lock.yaml", "node_modules" ], "rules": { "suspicious": { "noDoubleEquals": "warn", "noAssignInExpressions": "warn" }, "correctness": { "noUnusedVariables": "off" } } }, "formatter": { "ignore": [], "indentStyle": "tab" } } ```

• migration
• eslint

Change import from eslint-webpack-plugin to eslint-rspack-plugin. ### Before ```ts //change the import package from eslint-webpack-plugin to eslint-rspack-plugin const ESLintPlugin = require('eslint-webpack-plugin'); module.exports = { // ... plugins: [new ESLintPlugin(options)], // ... }; ``` ### After ```ts const ESLintPlugin = require('eslint-rspack-plugin'); module.exports = { // ... plugins: [new ESLintPlugin(options)], // ... }; ```

• webpack
• version 5
• +4

Rewrite eligible JavaScript-family else blocks whose only statement is an if into else-if chains, matching ESLint no-lonely-if without changing behavior.

• javascript
• typescript
• +4

Transform bracket notation with static string literal keys (e.g., `obj['prop']`) into equivalent dot notation (`obj.prop`) across JavaScript/TypeScript codebases when semantics are preserved, aligning with ESLint `dot-notation` best practices and improving readability and maintainability.

• eslint
• dot-notation
• +3

Normalize the top static ESM import block to eslint-plugin-import import/order grouping, blank-line, and alphabetical ordering conventions.

• imports
• eslint
• +3