@clearlint/eslint-migrate

Analyze and migrate ESLint v9 configs to v10. Understand your migration cost before you commit.

The Problem

ESLint v10 removes eslintrc format entirely. If your project uses .eslintrc, .eslintrc.json, or package.json eslintConfig, you need to:

1. Convert to flat config (eslint.config.js)
2. Handle removed rules
3. Adjust rule options that changed

This tool analyzes your current config and generates a v10-compatible flat config.

Usage

npx @clearlint/eslint-migrate analyze [dir]
npx @clearlint/eslint-migrate generate [dir]
npx @clearlint/eslint-migrate report [dir]

analyze — Understand your migration cost

npx @clearlint/eslint-migrate analyze ./my-project

Output:

🔍 Analyzing ESLint config in: ./my-project

  Config type: eslintrc
  Config file: .eslintrc.json

  Rules analyzed: 42
  Compatible:     38
  Removed:        3
  Needs review:   1
  Unknown:        0

  Details:
    ✅ no-eval: compatible
    ❌ callback-return: removed in v10
    ⚠️  custom-rule: needs review

generate — Create a v10 flat config

npx @clearlint/eslint-migrate generate ./my-project

Creates eslint.config.js with:

• All compatible rules preserved
• Removed rules removed (commented out with migration notes)
• Unknown rules flagged for manual review

report — Full migration report

npx @clearlint/eslint-migrate report ./my-project

Generates eslint-migration-report.json with:

• Rule-by-rule compatibility analysis
• Effort estimate (low / medium / high)
• Step-by-step recommendations

Install

npm install --save-dev @clearlint/eslint-migrate

How it works

1. Discover — Finds your ESLint config (eslintrc, flat, or package.json)
2. Analyze — Checks each rule against the v10 rule set
3. Generate — Creates a flat config with migration notes
4. Report — Produces a structured JSON report

Migration Phases

| Phase | Description | Command | |-------|-------------|---------| | 1 | Config discovery | eslint-migrate analyze | | 2 | Rule compatibility | (included in analyze) | | 3 | Config generation | eslint-migrate generate | | 4 | Report + effort estimate | eslint-migrate report |

Caveats

• The generated config is a starting point, not a drop-in replacement
• Custom plugin rules and shareable configs are not analyzed
• Always run npx eslint . after migration to verify
• ESLint v10 removes approximately 15 core rules — the tool flags these

Disclaimer: This tool assists with ESLint v10 migration planning. Always verify the generated config against your project's requirements. Rule behavior may differ between v9 and v10 even for compatible rules.