attw Plugin

attw ("Are the Types Wrong") tests whether the TypeScript types shipped in an npm package actually resolve under every module-resolution strategy (node10, node16 CJS/ESM, bundler). Catches masquerading files, missing .d.ts, wrong types conditions — before users report them.

Commands

Checking

• attw check pack — Pack the local package and check its types
• attw check npm <pkg> — Check a published npm package
• attw check tarball <file.tgz> — Check a .tgz tarball
• attw _ _ — Passthrough to attw CLI

Usage Examples

• "Check if my package's types resolve correctly"
• "Does lodash's types work under node16 ESM?"
• "Verify the built tarball has correct types"
• "Add an attw check to my publish workflow"

Installation

npm install -g @arethetypeswrong/cli
# or: npx @arethetypeswrong/cli

Examples

# Standard pre-publish check
attw --pack .

# Inspect a published package
attw --from-npm react@19

# Machine-readable output
attw --pack . --format json

# Only check specific entrypoints
attw --pack . --entrypoints ./index.d.ts

Key Features

• Tests every resolution mode: node10, node16 CJS, node16 ESM, bundler
• Detects "masquerading" files (ESM syntax in .js under type:commonjs, etc.)
• --format table|json|flipped output
• Pairs with publint for complete pre-publish verification