fa19c4410f
After speaking with @timneutkens, this PR provides a smoother experience to users trying to migrate over to app without affecting users in pages.
This PR adds a new export available from `next/compat/router` that exposes a `useRouter()` hook that can be used in both `app/` and `pages/`. It differs from `next/router` in that it does not throw an error when the pages router is not mounted, and instead has a return type of `NextRouter | null`. This allows developers to convert components to support running in both `app/` and `pages/` as they are transitioning over to `app/`.
A component that before looked like this:
```tsx
import { useRouter } from 'next/router';
const MyComponent = () => {
const { isReady, query } = useRouter();
// ...
};
```
Will error when converted over to `next/compat/router`, as `null` cannot be destructured. Instead, developers will be able to take advantage of new hooks:
```tsx
import { useEffect } from 'react';
import { useRouter } from 'next/compat/router';
import { useSearchParams } from 'next/navigation';
const MyComponent = () => {
const router = useRouter() // may be null or a NextRouter instance
const searchParams = useSearchParams()
useEffect(() => {
if (router && !router.isReady) {
return
}
// In `app/`, searchParams will be ready immediately with the values, in
// `pages/` it will be available after the router is ready.
const search = searchParams.get('search')
// ...
}, [router, searchParams])
// ...
}
```
This component will now work in both `pages/` and `app/`. When the component is no longer used in `pages/`, you can remove the references to the compat router:
```tsx
import { useSearchParams } from 'next/navigation';
const MyComponent = () => {
const searchParams = useSearchParams()
// As this component is only used in `app/`, the compat router can be removed.
const search = searchParams.get('search')
// ...
}
```
Note that as of Next.js 13, calling `useRouter` from `next/router` will throw an error when not mounted. This now includes an error page that can be used to assist developers.
We hope to introduce a codemod that can convert instances of your `useRouter` from `next/router` to `next/compat/router` in the future.
Co-authored-by: JJ Kasper <22380829+ijjk@users.noreply.github.com>
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NextRouter was not mounted
Why This Error Occurred
A component used useRouter outside a Next.js application, or was rendered outside a Next.js application. This can happen when doing unit testing on components that use the useRouter hook as they are not configured with Next.js' contexts.
Possible Ways to Fix It
If used in a test, mock out the router by mocking the next/router's useRouter() hook.