Utility Functions Analysis

Overview

The utilities module provides common helper functions used throughout the use-mcp library. Currently, it contains a single assertion utility function.

File Structure

src/utils/assert.ts - Assertion Utility

Function Overview (Lines 1-11)

The assert function provides runtime assertion checking with TypeScript type narrowing support.

Function Signature (Line 7)

export function assert(condition: unknown, message: string): asserts condition

Parameters:

  • condition: The condition to check (accepts any type for flexibility)
  • message: Error message to throw if condition is false

Return Type:

  • Uses TypeScript's asserts condition syntax for type narrowing
  • Tells TypeScript that if the function returns normally, the condition is truthy

Implementation (Lines 8-10)

if (!condition) {
  throw new Error(message)
}

Logic:

  • Line 8: Checks if condition is falsy
  • Line 9: Throws Error with provided message if condition fails

Usage Patterns

This utility is used throughout the codebase for:

  1. Null/Undefined Checks:

    assert(authProviderRef.current, 'Auth Provider must be initialized')
// TypeScript now knows authProviderRef.current is not null

  2. Existence Validation:

    assert(clientRef.current, 'Client must be initialized')
// TypeScript narrows the type to exclude null/undefined

  3. Runtime Invariants:

    assert(state === 'ready', 'Client must be ready for operation')
// Ensures runtime state matches expected condition

TypeScript Integration

The function leverages TypeScript's assertion signatures:

  • Type Narrowing: After assert() call, TypeScript knows the condition is true
  • Compile-time Safety: Helps catch potential null/undefined access at compile time
  • Runtime Safety: Provides clear error messages when assumptions are violated

Error Handling

  • Immediate Failure: Throws Error immediately on false condition
  • Clear Messages: Requires descriptive error message for debugging
  • Stack Traces: Standard Error object provides call stack information

Design Philosophy

1. Defensive Programming

  • Validates assumptions throughout the codebase
  • Fails fast with clear error messages
  • Prevents silent failures or undefined behavior

2. TypeScript Integration

  • Leverages TypeScript's type system for compile-time safety
  • Provides runtime validation for dynamic conditions
  • Bridges gap between static typing and runtime reality

3. Developer Experience

  • Clear, descriptive error messages
  • Consistent assertion pattern across codebase
  • Helps identify bugs during development

4. Minimal Overhead

  • Simple implementation with minimal performance impact
  • No dependencies on external libraries
  • Straightforward debugging with standard Error objects

Usage Throughout Codebase

The assert function is used extensively in the React hook implementation (useMcp.ts):

  1. Provider Validation (Line 202, 384, 533, 602):

    assert(authProviderRef.current, 'Auth Provider must be initialized')

  2. Client Validation (Line 203):

    assert(clientRef.current, 'Client must be initialized')

These assertions ensure that critical components are properly initialized before use, providing both runtime safety and TypeScript type narrowing.

Potential Extensions

While the current implementation is minimal, the utility module could be extended with:

  1. Development-only Assertions: Assertions that are removed in production builds
  2. Type Guards: More specific type checking utilities
  3. Validation Helpers: Functions for validating specific data structures
  4. Debug Utilities: Enhanced logging and debugging tools

However, the current minimal approach aligns with the library's philosophy of keeping dependencies light and providing essential functionality without bloat.