When you're trying to migrate an application from `pages/` to `app/`,
you'll need to access data like search parameters and the pathname in a
way that lets you migrate safely.
This adds support for dynamic typing of some of those exported functions
from `next/navigation`, namely `useSearchParams` and `usePathname`.
Currently, `searchParams` can’t be known when prerendering if the page
doesn’t use [Server-side
Rendering](https://nextjs.org/docs/basic-features/data-fetching/get-server-side-props)
in the `pages/` directory. `pathname` can’t be known during prerendering
if the page is a fallback page or has been automatically statically
optimized when accessed from `pages/`.
To make migraitons easier, this adds a new feature to `next dev` that
will automatically add the correct types for `next/navigation`. It does
this by checking if you have both a `app/` and `pages/` directory. If it
detects you have a `app/` directory, it will also enable the suggested
Typescript feature,
[`structNullChecks`](https://www.typescriptlang.org/tsconfig#strictNullChecks)
which will warn developers when trying to access a value that may be
`null`.
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Co-authored-by: JJ Kasper <jj@jjsweb.site>
