eslint-baseline

0.4.0 verified Sat Apr 25 auth: no javascript

eslint-baseline (v0.4.0) is a tool to run ESLint with a baseline file, allowing legacy projects to adopt linting by ignoring existing errors. It creates a `.eslint-baseline.json` file storing known violations, and subsequent runs only report new errors. Key differentiators: hash-based error identification (improved location-based detection), simple CLI workflow, and explicit baseline update command. Released November 2024 with minor features; peer dependency on ESLint 8.x. In early development with unstable APIs.

Common errors

error Error: Cannot find module 'eslint' ↓

cause eslint is not installed or not in node_modules.

fix

Run npm install --save-dev eslint (eslint is a peer dependency).

error Error: Failed to load plugin 'xxx' declared in '.eslintrc' ↓

cause A required ESLint plugin is missing.

fix

Install the missing plugin, e.g., npm install --save-dev eslint-plugin-react.

error Error: ESLint configuration is invalid: Unexpected top-level property "xxx" ↓

cause Invalid ESLint config file (e.g., .eslintrc.json).

fix

Check ESLint documentation for valid config properties; fix the config.

error Error: ENOENT: no such file or directory, open '.eslint-baseline.json' ↓

cause Baseline file not found; likely first run without --init or --update-baseline.

fix

Run npx eslint-baseline --init or npx eslint-baseline --update-baseline.

Warnings

breaking v0.3.0 introduced hash-based error identification; location-based baseline files from older versions are incompatible. ↓

fix Run eslint-baseline --update-baseline to regenerate baseline file.

deprecated Location-based error identification deprecated in favor of hash-based approach since v0.3.2. ↓

fix Update to latest version and regenerate baseline.

gotcha Editing files with existing errors may shift error locations, causing them to appear as new errors until baseline is updated. ↓

fix Run eslint-baseline --update-baseline after editing files to refresh baseline.

gotcha Programmatic API is not stable; breaking changes may occur without major version bump. ↓

fix Pin exact version and test updates.

Install

npm install eslint-baseline

yarn add eslint-baseline

pnpm add eslint-baseline

Imports

cli
```
npx eslint-baseline
```
eslint-baseline is a CLI tool, not a library. Use via npx or as a script in package.json.

default

wrong

const eslintBaseline = require('eslint-baseline')

correct

import eslintBaseline from 'eslint-baseline'

ESM-only since v0.1.0; no CommonJS support.

ESLintBaseline
```
import { ESLintBaseline } from 'eslint-baseline'
```
Named export for programmatic use; not commonly used.

Quickstart

Demonstrates installing eslint-baseline, initializing a baseline, configuring package.json scripts, and running lint with baseline update.

npm install --save-dev eslint eslint-baseline
npx eslint-baseline --init
echo "Add lint scripts to package.json:"
echo '"scripts": { "lint": "eslint-baseline .", "lint:update-baseline": "eslint-baseline --update-baseline ." }'
npm run lint
# Creates .eslint-baseline.json; subsequent runs only show new errors
npm run lint:update-baseline
# Updates baseline to include new errors