@rightcapital/assertion-helpers

Type-safe assertion utilities for defensive programming in TypeScript applications.

Installation

npm install @rightcapital/assertion-helpers
# or
pnpm add @rightcapital/assertion-helpers
# or
yarn add @rightcapital/assertion-helpers

Usage

import { AssertionHelpers } from '@rightcapital/assertion-helpers';

// Basic assertion
AssertionHelpers.assert(user.age >= 18, 'User must be at least 18 years old');

// Non-nullable assertion with type narrowing
AssertionHelpers.assertNonNullable(user, 'User cannot be null');
// user is now typed as NonNullable<T>

// Ensure with type guard
const admin = AssertionHelpers.ensure(
  currentUser,
  isAdminUser,
  'Admin required',
);
// admin is now typed as AdminUser

Agent Skills

This package ships with an Agent Skill that teaches AI coding agents (Claude Code, Cursor, etc.) how to use the assertion-helpers API correctly, following the npm-based Agent Skills Convention.

Automatic discovery (recommended)

If your project uses skills-npm, the skill is discovered automatically from node_modules:

npx skills-npm

Manual installation

You can also install the skill directly using the skills CLI:

npx skills add https://github.com/RightCapitalHQ/frontend-libraries/tree/main/packages/assertion-helpers/skills

API Reference

See the generated documentation for detailed API reference.