ts-register-router: Register Router Type for Global Inference

Priority: CRITICAL

Explanation

Register your router instance with TypeScript's module declaration to enable type inference across your entire application. Without registration, hooks like useNavigate, useParams, and useSearch won't know your route structure.

Bad Example

// router.tsx - Missing type registration
import { createRouter, createRootRoute } from '@tanstack/react-router'
import { routeTree } from './routeTree.gen'

export const router = createRouter({ routeTree })

// components/Navigation.tsx
import { useNavigate } from '@tanstack/react-router'

function Navigation() {
  const navigate = useNavigate()

  // TypeScript doesn't know valid routes - no autocomplete or type checking
  navigate({ to: '/posts/$postId' })  // No error even if route doesn't exist
}

Good Example

// router.tsx
import { createRouter } from '@tanstack/react-router'
import { routeTree } from './routeTree.gen'

export const router = createRouter({ routeTree })

// Register the router instance for type inference
declare module '@tanstack/react-router' {
  interface Register {
    router: typeof router
  }
}

// components/Navigation.tsx
import { useNavigate } from '@tanstack/react-router'

function Navigation() {
  const navigate = useNavigate()

  // Full type safety - TypeScript knows all valid routes
  navigate({ to: '/posts/$postId', params: { postId: '123' } })

  // Type error if route doesn't exist
  navigate({ to: '/invalid-route' })  // Error: Type '"/invalid-route"' is not assignable...

  // Autocomplete for params
  navigate({
    to: '/users/$userId/posts/$postId',
    params: { userId: '1', postId: '2' },  // Both required
  })
}

Benefits of Registration

// After registration, all these get full type inference:

// 1. Navigation
const navigate = useNavigate()
navigate({ to: '/posts/$postId', params: { postId: '123' } })

// 2. Link component
<Link to="/posts/$postId" params={{ postId: '123' }}>View Post</Link>

// 3. useParams hook
const { postId } = useParams({ from: '/posts/$postId' })  // postId: string

// 4. useSearch hook
const search = useSearch({ from: '/posts' })  // Knows search param types

// 5. useLoaderData hook
const data = useLoaderData({ from: '/posts/$postId' })  // Knows loader return type

File-Based Routing Setup

// With file-based routing, routeTree is auto-generated
// router.tsx
import { createRouter } from '@tanstack/react-router'
import { routeTree } from './routeTree.gen'  // Generated file

export const router = createRouter({
  routeTree,
  defaultPreload: 'intent',
})

declare module '@tanstack/react-router' {
  interface Register {
    router: typeof router
  }
}

Context

Must be done once, typically in your router configuration file
Enables IDE autocomplete for routes, params, and search params
Catches invalid routes at compile time
Works with both file-based and code-based routing
Required for full TypeScript benefits of TanStack Router

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