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Janka UrygaandGitHub
46681d90f0
This PR makes Sync IO behavior more restrictive when `partialPrefetching` is on (either globally or for a page). - Previously, we allowed `await cookies(); Date.now()` in in segments that won't ever be runtime prefetched. This was achieved by separating segments into "early" and "late" stages and only erroring in the "early" ones. - After this PR, it will always be an error to do sync IO anywhere other than after `io()`/`connection()`/uncached IO (i.e. outside the Dynamic stage). We're doing this mainly because with `partialPrefetching`, `cookies()` resolves in App Shells, and sync IO causes a severe deopt in any prerender. `allow-runtime` also opts a route into `partialPrefetching`, which means that even the segments above the runtime prefetch boundary will need an App Shell and can't tolerate Sync IO. This PR removes all early/late stage separation, because we no longer need to vary the Sync IO behavior on the segment. Instead, we now pick whether a stageController should use - `SyncIOMode.AllowedInRuntimeOrDynamic` (legacy) - `SyncIOMode.AllowedInDynamic` (`partialPrefetching`) - `SyncIOMode.Untracked` if it needs to opt out I've removed the existing tests that asserted that sync IO is allowed in segments above the `allow-runtime` boundary. Instead, we check that sync io either errors (if partialPrefetching is on) or is allowed (if partialPrefetching is off) Closes NAR-855
51 lines
1.7 KiB
TypeScript
51 lines
1.7 KiB
TypeScript
import { Instant } from 'next'
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import { cookies } from 'next/headers'
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import { Fragment, Suspense } from 'react'
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export const instant: Instant = {
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level: 'experimental-error',
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unstable_samples: [{ cookies: [{ name: 'testCookie', value: 'testValue' }] }],
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}
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// cookies() is passed as a promise input to a public "use cache" function.
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// The cache doesn't read the cookies in its body — they're only part of the cache key.
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// After the cache resolves, Date.now() is sync IO that should error.
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//
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// This test validates that the cache input encoding resolves in the
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// Runtime stage. Date.now() should either error or be allowed
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// depending on if partialPrefetching is enabled or not.
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async function cachedFn(cookiePromise: Promise<string>) {
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'use cache'
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// Intentionally not reading the cookie promise in the body.
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// It's only used as part of the cache key via input encoding.
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return 'cached result'
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}
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export default async function Page() {
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return (
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<main>
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<p>
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Page with sync IO after cache with cookie input:{' '}
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<SuspenseIfNotPartialPrefetching>
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<SyncIOAfterCache />
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</SuspenseIfNotPartialPrefetching>
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</p>
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</main>
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)
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}
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// Before partialPrefetching, cookies() is not allowed in shells,
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// so it would fail instant validation unless wrapped in suspense.
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// We're not interested in checking if cookies blocks,
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// only in wheter the Sync IO after triggers an error.
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const SuspenseIfNotPartialPrefetching = process.env.__NEXT_PARTIAL_PREFETCHING
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? Fragment
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: Suspense
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async function SyncIOAfterCache() {
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const cookiePromise = cookies().then((c) => c.get('testCookie')?.value ?? '')
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await cachedFn(cookiePromise)
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return Date.now()
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}
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