next/dist/esm/client/components/router-reducer/refetch-inactive-parallel-segments.js

The React Framework

import { applyFlightData } from './apply-flight-data';
import { fetchServerResponse } from './fetch-server-response';
import { PAGE_SEGMENT_KEY } from '../../../shared/lib/segment';
/**
 * Refreshes inactive segments that are still in the current FlightRouterState.
 * A segment is considered "inactive" when the server response indicates it didn't match to a page component.
 * This happens during a soft-navigation, where the server will want to patch in the segment
 * with the "default" component, but we explicitly ignore the server in this case
 * and keep the existing state for that segment. New data for inactive segments are inherently
 * not part of the server response when we patch the tree, because they were associated with a response
 * from an earlier navigation/request. For each segment, once it becomes "active", we encode the URL that provided
 * the data for it. This function traverses parallel routes looking for these markers so that it can re-fetch
 * and patch the new data into the tree.
 */ export async function refreshInactiveParallelSegments(options) {
    const fetchedSegments = new Set();
    await refreshInactiveParallelSegmentsImpl({
        ...options,
        rootTree: options.updatedTree,
        fetchedSegments
    });
}
async function refreshInactiveParallelSegmentsImpl(param) {
    let { state, updatedTree, updatedCache, includeNextUrl, fetchedSegments, rootTree = updatedTree, canonicalUrl } = param;
    const [, parallelRoutes, refetchPath, refetchMarker] = updatedTree;
    const fetchPromises = [];
    if (refetchPath && refetchPath !== canonicalUrl && refetchMarker === 'refresh' && // it's possible for the tree to contain multiple segments that contain data at the same URL
    // we keep track of them so we can dedupe the requests
    !fetchedSegments.has(refetchPath)) {
        fetchedSegments.add(refetchPath) // Mark this URL as fetched
        ;
        // Eagerly kick off the fetch for the refetch path & the parallel routes. This should be fine to do as they each operate
        // independently on their own cache nodes, and `applyFlightData` will copy anything it doesn't care about from the existing cache.
        const fetchPromise = fetchServerResponse(new URL(refetchPath, location.origin), {
            // refetch from the root of the updated tree, otherwise it will be scoped to the current segment
            // and might not contain the data we need to patch in interception route data (such as dynamic params from a previous segment)
            flightRouterState: [
                rootTree[0],
                rootTree[1],
                rootTree[2],
                'refetch'
            ],
            nextUrl: includeNextUrl ? state.nextUrl : null
        }).then((param)=>{
            let { flightData } = param;
            if (typeof flightData !== 'string') {
                for (const flightDataPath of flightData){
                    // we only pass the new cache as this function is called after clearing the router cache
                    // and filling in the new page data from the server. Meaning the existing cache is actually the cache that's
                    // just been created & has been written to, but hasn't been "committed" yet.
                    applyFlightData(updatedCache, updatedCache, flightDataPath);
                }
            } else {
            // When flightData is a string, it suggests that the server response should have triggered an MPA navigation
            // I'm not 100% sure of this decision, but it seems unlikely that we'd want to introduce a redirect side effect
            // when refreshing on-screen data, so handling this has been ommitted.
            }
        });
        fetchPromises.push(fetchPromise);
    }
    for(const key in parallelRoutes){
        const parallelFetchPromise = refreshInactiveParallelSegmentsImpl({
            state,
            updatedTree: parallelRoutes[key],
            updatedCache,
            includeNextUrl,
            fetchedSegments,
            rootTree,
            canonicalUrl
        });
        fetchPromises.push(parallelFetchPromise);
    }
    await Promise.all(fetchPromises);
}
/**
 * Walks the current parallel segments to determine if they are "active".
 * An active parallel route will have a `__PAGE__` segment in the FlightRouterState.
 * As opposed to a `__DEFAULT__` segment, which means there was no match for that parallel route.
 * We add a special marker here so that we know how to refresh its data when the router is revalidated.
 */ export function addRefreshMarkerToActiveParallelSegments(tree, path) {
    const [segment, parallelRoutes, , refetchMarker] = tree;
    // a page segment might also contain concatenated search params, so we do a partial match on the key
    if (segment.includes(PAGE_SEGMENT_KEY) && refetchMarker !== 'refresh') {
        tree[2] = path;
        tree[3] = 'refresh';
    }
    for(const key in parallelRoutes){
        addRefreshMarkerToActiveParallelSegments(parallelRoutes[key], path);
    }
}

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