@freckle/exhaustive-js

Provides a helper function for checking exhaustiveness. Exhaustiveness checking is a feature of a language where the type checker guarantees that all cases were covered.

Install

pnpm add @freckle/exhaustive

This package is ESM-only.

Usage

import {exhaustive} from '@freckle/exhaustive'

type Status = 'success' | 'failure'

function getStatusMessage(status: Status): string {
  switch (status) {
    case 'success':
      return 'The operation completed successfully.'
    case 'failure':
      return 'The operation failed.'
    default:
      return exhaustive(status)
  }
}

Usage in a reducer where returning the state itself in the default case is a common pattern:

import {exhaustiveReducer} from '@freckle/exhaustive'

type TodoState = {...}
type TodoAction = {type: 'todoAdded', ...} | {type: 'todoToggled', ...}

const defaultTodoState = {...}

function todoReducer(
  state: TodoState = defaultTodoState,
  action: TodoAction
): TodoState {
  switch (action.type) {
    case 'todoAdded':
      return {...}
    case 'todoToggled':
      return {...}
    default:
      return exhaustiveReducer(action.type, state)
  }
}

Development

• Package manager: pnpm (Node version pinned in .nvmrc)
• pnpm build — tsc via tsconfig.build.json; emits to dist/
• pnpm test — Vitest
• pnpm coverage — Vitest with coverage, gated at 70% (lines/branches/functions/statements)
• pnpm typecheck — tsc --noEmit, includes test files
• pnpm lint — ESLint
• pnpm format / pnpm format-check — Prettier
• pnpm knip — unused files/dependencies/exports
• CI runs all of the above on every PR, plus a check that dist/ is up to date

dist/ is committed. Run pnpm build before pushing.

Release

See RELEASE.md for more details.