This PR moves the internal logic associated with `req.ua` into an explicit method the user should to call to have the same behavior.
**before**
```typescript
// middleware.ts
import { NextRequest, NextResponse } from 'next/server'
export function middleware(request: NextRequest) {
const url = request.nextUrl
const viewport = request.ua.device.type === 'mobile' ? 'mobile' : 'desktop'
url.searchParams.set('viewport', viewport)
return NextResponse.rewrites(url)
}
```
**after**
```typescript
// middleware.ts
import { NextRequest, NextResponse, userAgent } from 'next/server'
export function middleware(request: NextRequest) {
const url = request.nextUrl
const { device } = userAgent(request)
const viewport = device.type === 'mobile' ? 'mobile' : 'desktop'
url.searchParams.set('viewport', viewport)
return NextResponse.rewrites(url)
}
```
This potentially will save the extra 17 kB related to the size of `ua-parser-js`
This allows TypeScript users to have type safety for middleware functions.
- Closes#30490
Co-authored-by: Lee Robinson <9113740+leerob@users.noreply.github.com>
Co-authored-by: JJ Kasper <22380829+ijjk@users.noreply.github.com>
This PR adds support for [Middleware as per RFC ](https://github.com/vercel/next.js/discussions/29750).
## Feature
- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`
## Documentation / Examples
- [ ] Make sure the linting passes
