RALF

Reliable Advanced Linting Framework

Fast, project-aware JS/TS linter with 61 built-in rules. ESLint/Biome compatible. Zero config required.

Written in Go. Regex engine powered by Rust's regex crate via rure-go. AST parsing via tree-sitter. Supports JavaScript, TypeScript, JSX, and TSX.

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Table of Contents

• Why RALF
• Installation
• Quick Start
• Example Output
• Rules
• Configuration
• Output Formats
• Roadmap
• Documentation
• License

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Why RALF

	ESLint	Biome	RALF
Language	JS	Rust	Go
Speed	Slow	Fast	Fast (Go + Rust regex via CGo)
Custom rules	JS visitors (slow)	None yet	Declarative (native speed)
Config migration	N/A	N/A	--from-eslint, --from-biome
Output formats	Stylish, JSON	JSON	Stylish, JSON, SARIF, GitHub Actions, compact
Auto-fix	Yes	Yes	Yes (--fix / --fix-dry-run)

Installation

npm (recommended):

npm install -D @ralfjs/cli   # per-project dev dependency
npm install -g @ralfjs/cli   # global install
npx @ralfjs/cli lint         # one-off without install

Binary download (macOS, Linux):

Download the latest binary from GitHub Releases for your platform, extract, and add to your PATH.

From source (requires Go, CGo, and Rust toolchain):

git clone https://github.com/ralfjs/ralf.git && cd ralf
./scripts/build-librure.sh  # builds Rust regex library
make build                   # builds ralf binary

Quick Start

# Lint your project (zero config — all 61 rules enabled)
ralf lint

# Generate a config file to customize rules
ralf init

# Migrate from ESLint
ralf init --from-eslint

# Migrate from Biome
ralf init --from-biome

# Auto-fix
ralf lint --fix

# Preview fixes without writing
ralf lint --fix-dry-run

# SARIF output for GitHub Code Scanning
ralf lint --format sarif > results.sarif

Suppress rules inline (in your JS/TS files):

// lint-disable-next-line no-console
console.log("debug");

// lint-disable no-console, no-var  (block start)
// lint-enable no-console, no-var   (block end)

// lint-disable-file no-console     (entire file)

Example Output

src/index.ts
  3:1  error  Use `let` or `const` instead of `var`  no-var
  7:5  error  Expected '===' and instead saw '=='.    eqeqeq
  12:3 warn   Unexpected console statement            no-console

src/utils.ts
  21:10 error  Duplicate key 'id'.                    no-dupe-keys

✖ 4 problems (3 errors, 1 warning)

Rules

61 built-in rules covering ESLint recommended and Biome stable equivalents:

Error prevention: no-dupe-keys, no-dupe-args, no-dupe-class-members, no-duplicate-case, no-self-assign, no-self-compare, valid-typeof, use-isnan, for-direction, getter-return, no-setter-return, no-unsafe-finally, no-unsafe-negation, no-unsafe-optional-chaining, no-constant-condition, no-loss-of-precision, no-fallthrough, no-inner-declarations, no-constructor-return, no-empty-character-class, no-sparse-arrays, no-cond-assign, no-compare-neg-zero

Best practices: eqeqeq, no-var, no-eval, no-implied-eval, no-new-func, no-caller, no-void, no-with, no-labels, no-extend-native, no-proto, no-iterator, no-new-wrappers, no-return-await, no-case-declarations, no-delete-var, no-octal, no-octal-escape, no-nonoctal-decimal-escape, no-multi-str, no-script-url, no-inner-html

Code quality: no-empty, no-empty-pattern, no-empty-static-block, no-useless-catch, no-extra-boolean-cast, no-shadow-restricted-names, no-prototype-builtins, require-yield, no-async-promise-executor, no-new-native-nonconstructor, no-obj-calls, no-regex-spaces, no-control-regex

Style: no-console, no-debugger, no-alert

Full rule gap analysis vs ESLint/Biome: #24

Configuration

Zero config works out of the box — all 61 rules enabled with sensible defaults.

To customize, run ralf init and edit the generated config:

{
  "rules": {
    "no-var": { "severity": "error" },
    "no-console": { "severity": "warn" },
    "eqeqeq": { "severity": "off" }
  },
  "ignores": ["dist/**", "*.test.js"],
  "overrides": [
    {
      "files": ["**/*.test.*"],
      "rules": { "no-console": { "severity": "off" } }
    }
  ]
}

Supports .ralfrc.json, .ralfrc.yaml, .ralfrc.yml, .ralfrc.toml, and .ralfrc.js.

See the Configuration Guide for full syntax: rule types (regex, AST pattern, structural query, builtin), auto-fix, where predicates, naming conventions, import ordering, extends, inline suppression, and migration from ESLint/Biome.

Output Formats

Format	Flag	Use Case
Stylish	--format stylish (default)	Human-readable, grouped by file
JSON	--format json	Machine-readable
SARIF	--format sarif	GitHub Code Scanning
GitHub	--format github	GitHub Actions annotations
Compact	--format compact	Grep-friendly, one line per diagnostic

Roadmap

Milestone	Key Deliverable
v0.1 (current)	Linter MVP — 61 rules, CLI, config, SARIF, migration
v0.2	Project-aware — SQLite cache, module graph, LSP, VS Code
v0.3	Formatter — dprint WASM, import sorting
v0.4	WASM plugins — Go/Rust/AS SDKs
v1.0	Type-aware rules via typescript-go, scope analysis, CFG

Documentation

• Configuration Guide — full config syntax reference
• Architecture & Design — technical spec, benchmarks, implementation plan
• Branching & Releases — Git Flow, versioning
• Development Status — detailed feature matrix
• Contributing — dev setup, code style, testing

License

MIT