next/dist/esm/client/components/router-reducer/create-initial-router-state.js

The React Framework

import { createHrefFromUrl } from './create-href-from-url';
import { extractPathFromFlightRouterState } from './compute-changed-path';
import { getFlightDataPartsFromPath } from '../../flight-data-helpers';
import { createInitialCacheNodeForHydration } from './ppr-navigations';
import { convertRootFlightRouterStateToRouteTree, resolveStaleAt, processRuntimePrefetchStream, writeDynamicRenderResponseIntoCache, writePrerenderResponseIntoCache } from '../segment-cache/cache';
import { FetchStrategy } from '../segment-cache/types';
import { UnknownDynamicStaleTime, computeDynamicStaleAt } from '../segment-cache/bfcache';
import { decodeStageUntilBoundary } from './fetch-server-response';
import { discoverKnownRoute } from '../segment-cache/optimistic-routes';
export function createInitialRouterState({ navigatedAt, initialRSCPayload, initialFlightStreamForCache, location }) {
    const { c: initialCanonicalUrlParts, f: initialFlightData, q: initialRenderedSearch, i: initialCouldBeIntercepted, S: initialSupportsPerSegmentPrefetching, s: initialStaleTime, l: initialStaticStageByteLength, h: initialHeadVaryParams, r: initialRootVaryParams, p: initialRuntimePrefetchStream, d: initialDynamicStaleTimeSeconds } = initialRSCPayload;
    // When initialized on the server, the canonical URL is provided as an array of parts.
    // This is to ensure that when the RSC payload streamed to the client, crawlers don't interpret it
    // as a URL that should be crawled.
    const initialCanonicalUrl = initialCanonicalUrlParts.join('/');
    const normalizedFlightData = getFlightDataPartsFromPath(initialFlightData[0]);
    const { tree: initialTree, seedData: initialSeedData, head: initialHead } = normalizedFlightData;
    // For the SSR render, seed data should always be available (we only send back a `null` response
    // in the case of a `loading` segment, pre-PPR.)
    const canonicalUrl = // location.href is read as the initial value for canonicalUrl in the browser
    // This is safe to do as canonicalUrl can't be rendered, it's only used to control the history updates in the useEffect further down in this file.
    location ? createHrefFromUrl(location) : initialCanonicalUrl;
    // Convert the initial FlightRouterState into the RouteTree type.
    // NOTE: The metadataVaryPath isn't used for anything currently because the
    // head is embedded into the CacheNode tree, but eventually we'll lift it out
    // and store it on the top-level state object.
    //
    // For statically-generated-at-build-time HTML pages, the FlightRouterState
    // baked into the initial RSC payload won't have the correct segment inlining
    // hints because those are computed after the pre-render. The server marks
    // these trees with InliningHintsStale, which causes the route cache entry
    // to be immediately expired. The next prefetch will re-fetch the tree with
    // correct hints from the /_tree response.
    const acc = {
        metadataVaryPath: null
    };
    const initialRouteTree = convertRootFlightRouterStateToRouteTree(initialTree, initialRenderedSearch, acc);
    const metadataVaryPath = acc.metadataVaryPath;
    const initialTask = createInitialCacheNodeForHydration(navigatedAt, initialRouteTree, initialSeedData, initialHead, computeDynamicStaleAt(navigatedAt, initialDynamicStaleTimeSeconds ?? UnknownDynamicStaleTime));
    // The following only applies in the browser (location !== null) since neither
    // route learning nor segment cache state persists from SSR to client.
    if (location !== null && metadataVaryPath !== null) {
        // Learn the route pattern so we can predict it for future navigations.
        discoverKnownRoute(Date.now(), location.pathname, location.search, null, null, initialRouteTree, metadataVaryPath, initialCouldBeIntercepted, canonicalUrl, initialSupportsPerSegmentPrefetching, false // hasDynamicRewrite
        );
        // TODO: Implement Shell extraction as part of Cached Navigations.
        // Intentionally holding off on doing this until we decide how the Cached
        // Navigations behavior should work in combination with App Shells.
        // Write the initial seed data into the segment cache so subsequent
        // navigations to the initial page can serve cached segments instantly.
        if (initialSeedData !== null && initialStaleTime !== undefined) {
            if (initialStaticStageByteLength !== undefined && initialFlightStreamForCache != null) {
                // Partially static page — truncate the cloned Flight stream at the
                // static stage byte boundary, decode, and cache the static subset.
                // Promise.resolve wraps the Flight-deserialized thenable into a
                // native Promise so we can chain `.then` on it safely.
                Promise.resolve(initialStaticStageByteLength).then(async (byteLength)=>{
                    const staticStageResponse = await decodeStageUntilBoundary(initialFlightStreamForCache, byteLength, undefined);
                    const now = Date.now();
                    const staleAt = await resolveStaleAt(now, staticStageResponse.s);
                    writePrerenderResponseIntoCache(now, FetchStrategy.PPR, staticStageResponse.f, undefined, staticStageResponse.h, staticStageResponse.r ?? null, staleAt, initialTree, initialRenderedSearch, true // isResponsePartial
                    );
                }).catch(()=>{
                // The static stage processing failed. Not fatal — the page
                // rendered normally, we just won't write into the cache.
                });
            } else {
                // Fully static page — cache the entire decoded seed data as-is. We're
                // not using the initial response here (which would allow us to combine
                // the two branches) to avoid unnecessary decoding of the Flight data,
                // since we can just take the seed data that we already decoded during
                // hydration and write it into the cache directly.
                const now = Date.now();
                resolveStaleAt(now, initialStaleTime).then((staleAt)=>{
                    writePrerenderResponseIntoCache(now, FetchStrategy.PPR, initialFlightData, undefined, initialHeadVaryParams, initialRootVaryParams ?? null, staleAt, initialTree, initialRenderedSearch, false // isResponsePartial
                    );
                }).catch(()=>{
                // The static stage processing failed. Not fatal — the page
                // rendered normally, we just won't write into the cache.
                });
                // Cancel the stream clone — fully static path doesn't need it.
                initialFlightStreamForCache?.cancel();
            }
        } else {
            // No caching — cancel the unused stream clone.
            initialFlightStreamForCache?.cancel();
        }
        // If the initial RSC payload includes an embedded runtime prefetch stream,
        // decode it and write the runtime data into the segment cache. This allows
        // subsequent navigations to serve runtime-prefetchable content from cache
        // without a separate prefetch request.
        if (initialRuntimePrefetchStream != null) {
            processRuntimePrefetchStream(Date.now(), initialRuntimePrefetchStream, initialTree, initialRenderedSearch).then((processed)=>{
                if (processed !== null) {
                    writeDynamicRenderResponseIntoCache(Date.now(), FetchStrategy.PPRRuntime, processed.flightDatas, processed.buildId, processed.isResponsePartial, processed.headVaryParams, processed.rootVaryParamsIterable, processed.staleAt, processed.navigationSeed, null);
                }
            }).catch(()=>{
            // Runtime prefetch cache write failed. Not fatal — the page rendered
            // normally, we just won't cache runtime data.
            });
        }
    }
    // NOTE: We intentionally don't check if any data needs to be fetched from the
    // server. We assume the initial hydration payload is sufficient to render
    // the page.
    //
    // The completeness of the initial data is an important property that we rely
    // on as a last-ditch mechanism for recovering the app; we must always be able
    // to reload a fresh HTML document to get to a consistent state.
    //
    // In the future, there may be cases where the server intentionally sends
    // partial data and expects the client to fill in the rest, in which case this
    // logic may change. (There already is a similar case where the server sends
    // _no_ hydration data in the HTML document at all, and the client fetches it
    // separately, but that's different because we still end up hydrating with a
    // complete tree.)
    const initialState = {
        tree: initialTask.route,
        cache: initialTask.node,
        pushRef: {
            pendingPush: false,
            mpaNavigation: false,
            // First render needs to preserve the previous window.history.state
            // to avoid it being overwritten on navigation back/forward with MPA Navigation.
            preserveCustomHistoryState: true
        },
        focusAndScrollRef: {
            scrollRef: null,
            forceScroll: false,
            onlyHashChange: false,
            hashFragment: null
        },
        canonicalUrl,
        renderedSearch: initialRenderedSearch,
        // the || operator is intentional, the pathname can be an empty string
        nextUrl: (extractPathFromFlightRouterState(initialTree) || location?.pathname) ?? null,
        previousNextUrl: null,
        debugInfo: null
    };
    return initialState;
}

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