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Janka Uryga
3cdb56c251
Implements `unstable_prefetch()`, which is intended for use in
`partialPrefetching`. `await unstable_prefetch()` excludes content from
the app shell -- it will only be available when using `prefetch={true}`
(speculative prefetch) or during navigations.
As a rule of thumb, `unstable_prefetch()` resolves whenever static
`params` would:
- in a static prerender
- but NOT the app shell extracted from it, which is param-less
- in a runtime prefetch (`prefetch={true}`)
- but NOT a runtime app shell, which is param-less
Note that `prefetch()` is URL data, so using it in an App Shell without
Suspense will trigger an instant insight.
### Implementation notes
`prefetch()` is treated like URL data, so it resolves in the
`PrefetchStatic/PrefetchRuntime` stages added in #96908. The
implementation is basically analogous to `unstable_navigation()` except
using different stages. i've considered abstracting them into one
implementation, but decided against that for now, we can deduplicate
later.
Error messages about URL data have not been updated to mention it yet --
we will do that as a follow up, along with docs.
`await prefetch()` does not count as a runtime data access, meaning that
it won't affect the static prefetch hint for a route. however `await
prefetch(); await cookies()` does deopt the route, because using a
speculative runtime prefetch would reveal more content. Note that this
may cause us to unnecessarily deopt a shell to runtime even if only the
speculative part of the content would be improved by a runtime request;
this is not a new issue, but it's something we should optimize.