next/dist/esm/client/components/router-reducer/ppr-navigations.js

The React Framework

import { DEFAULT_SEGMENT_KEY } from '../../../shared/lib/segment';
import { matchSegment } from '../match-segments';
import { createRouterCacheKey } from './create-router-cache-key';
import { isNavigatingToNewRootLayout } from './is-navigating-to-new-root-layout';
const MPA_NAVIGATION_TASK = {
    route: null,
    node: null,
    dynamicRequestTree: null,
    children: null
};
// Creates a new Cache Node tree (i.e. copy-on-write) that represents the
// optimistic result of a navigation, using both the current Cache Node tree and
// data that was prefetched prior to navigation.
//
// At the moment we call this function, we haven't yet received the navigation
// response from the server. It could send back something completely different
// from the tree that was prefetched — due to rewrites, default routes, parallel
// routes, etc.
//
// But in most cases, it will return the same tree that we prefetched, just with
// the dynamic holes filled in. So we optimistically assume this will happen,
// and accept that the real result could be arbitrarily different.
//
// We'll reuse anything that was already in the previous tree, since that's what
// the server does.
//
// New segments (ones that don't appear in the old tree) are assigned an
// unresolved promise. The data for these promises will be fulfilled later, when
// the navigation response is received.
//
// The tree can be rendered immediately after it is created (that's why this is
// a synchronous function). Any new trees that do not have prefetch data will
// suspend during rendering, until the dynamic data streams in.
//
// Returns a Task object, which contains both the updated Cache Node and a path
// to the pending subtrees that need to be resolved by the navigation response.
//
// A return value of `null` means there were no changes, and the previous tree
// can be reused without initiating a server request.
export function startPPRNavigation(oldCacheNode, oldRouterState, newRouterState, prefetchData, prefetchHead, isPrefetchHeadPartial, isSamePageNavigation, scrollableSegmentsResult) {
    const segmentPath = [];
    return updateCacheNodeOnNavigation(oldCacheNode, oldRouterState, newRouterState, false, prefetchData, prefetchHead, isPrefetchHeadPartial, isSamePageNavigation, segmentPath, scrollableSegmentsResult);
}
function updateCacheNodeOnNavigation(oldCacheNode, oldRouterState, newRouterState, didFindRootLayout, prefetchData, prefetchHead, isPrefetchHeadPartial, isSamePageNavigation, segmentPath, scrollableSegmentsResult) {
    // Diff the old and new trees to reuse the shared layouts.
    const oldRouterStateChildren = oldRouterState[1];
    const newRouterStateChildren = newRouterState[1];
    const prefetchDataChildren = prefetchData !== null ? prefetchData[2] : null;
    if (!didFindRootLayout) {
        // We're currently traversing the part of the tree that was also part of
        // the previous route. If we discover a root layout, then we don't need to
        // trigger an MPA navigation. See beginRenderingNewRouteTree for context.
        const isRootLayout = newRouterState[4] === true;
        if (isRootLayout) {
            // Found a matching root layout.
            didFindRootLayout = true;
        }
    }
    const oldParallelRoutes = oldCacheNode.parallelRoutes;
    // Clone the current set of segment children, even if they aren't active in
    // the new tree.
    // TODO: We currently retain all the inactive segments indefinitely, until
    // there's an explicit refresh, or a parent layout is lazily refreshed. We
    // rely on this for popstate navigations, which update the Router State Tree
    // but do not eagerly perform a data fetch, because they expect the segment
    // data to already be in the Cache Node tree. For highly static sites that
    // are mostly read-only, this may happen only rarely, causing memory to
    // leak. We should figure out a better model for the lifetime of inactive
    // segments, so we can maintain instant back/forward navigations without
    // leaking memory indefinitely.
    const prefetchParallelRoutes = new Map(oldParallelRoutes);
    // As we diff the trees, we may sometimes modify (copy-on-write, not mutate)
    // the Route Tree that was returned by the server — for example, in the case
    // of default parallel routes, we preserve the currently active segment. To
    // avoid mutating the original tree, we clone the router state children along
    // the return path.
    let patchedRouterStateChildren = {};
    let taskChildren = null;
    // Most navigations require a request to fetch additional data from the
    // server, either because the data was not already prefetched, or because the
    // target route contains dynamic data that cannot be prefetched.
    //
    // However, if the target route is fully static, and it's already completely
    // loaded into the segment cache, then we can skip the server request.
    //
    // This starts off as `false`, and is set to `true` if any of the child
    // routes requires a dynamic request.
    let needsDynamicRequest = false;
    // As we traverse the children, we'll construct a FlightRouterState that can
    // be sent to the server to request the dynamic data. If it turns out that
    // nothing in the subtree is dynamic (i.e. needsDynamicRequest is false at the
    // end), then this will be discarded.
    // TODO: We can probably optimize the format of this data structure to only
    // include paths that are dynamic. Instead of reusing the
    // FlightRouterState type.
    let dynamicRequestTreeChildren = {};
    for(let parallelRouteKey in newRouterStateChildren){
        const newRouterStateChild = newRouterStateChildren[parallelRouteKey];
        const oldRouterStateChild = oldRouterStateChildren[parallelRouteKey];
        const oldSegmentMapChild = oldParallelRoutes.get(parallelRouteKey);
        const prefetchDataChild = prefetchDataChildren !== null ? prefetchDataChildren[parallelRouteKey] : null;
        const newSegmentChild = newRouterStateChild[0];
        const newSegmentPathChild = segmentPath.concat([
            parallelRouteKey,
            newSegmentChild
        ]);
        const newSegmentKeyChild = createRouterCacheKey(newSegmentChild);
        const oldSegmentChild = oldRouterStateChild !== undefined ? oldRouterStateChild[0] : undefined;
        const oldCacheNodeChild = oldSegmentMapChild !== undefined ? oldSegmentMapChild.get(newSegmentKeyChild) : undefined;
        let taskChild;
        if (newSegmentChild === DEFAULT_SEGMENT_KEY) {
            // This is another kind of leaf segment — a default route.
            //
            // Default routes have special behavior. When there's no matching segment
            // for a parallel route, Next.js preserves the currently active segment
            // during a client navigation — but not for initial render. The server
            // leaves it to the client to account for this. So we need to handle
            // it here.
            if (oldRouterStateChild !== undefined) {
                // Reuse the existing Router State for this segment. We spawn a "task"
                // just to keep track of the updated router state; unlike most, it's
                // already fulfilled and won't be affected by the dynamic response.
                taskChild = spawnReusedTask(oldRouterStateChild);
            } else {
                // There's no currently active segment. Switch to the "create" path.
                taskChild = beginRenderingNewRouteTree(oldRouterStateChild, newRouterStateChild, didFindRootLayout, prefetchDataChild !== undefined ? prefetchDataChild : null, prefetchHead, isPrefetchHeadPartial, newSegmentPathChild, scrollableSegmentsResult);
            }
        } else if (isSamePageNavigation && // Check if this is a page segment.
        // TODO: We're not consistent about how we do this check. Some places
        // check if the segment starts with PAGE_SEGMENT_KEY, but most seem to
        // check if there any any children, which is why I'm doing it here. We
        // should probably encode an empty children set as `null` though. Either
        // way, we should update all the checks to be consistent.
        Object.keys(newRouterStateChild[1]).length === 0) {
            // We special case navigations to the exact same URL as the current
            // location. It's a common UI pattern for apps to refresh when you click a
            // link to the current page. So when this happens, we refresh the dynamic
            // data in the page segments.
            //
            // Note that this does not apply if the any part of the hash or search
            // query has changed. This might feel a bit weird but it makes more sense
            // when you consider that the way to trigger this behavior is to click
            // the same link multiple times.
            //
            // TODO: We should probably refresh the *entire* route when this case
            // occurs, not just the page segments. Essentially treating it the same as
            // a refresh() triggered by an action, which is the more explicit way of
            // modeling the UI pattern described above.
            //
            // Also note that this only refreshes the dynamic data, not static/
            // cached data. If the page segment is fully static and prefetched, the
            // request is skipped. (This is also how refresh() works.)
            taskChild = beginRenderingNewRouteTree(oldRouterStateChild, newRouterStateChild, didFindRootLayout, prefetchDataChild !== undefined ? prefetchDataChild : null, prefetchHead, isPrefetchHeadPartial, newSegmentPathChild, scrollableSegmentsResult);
        } else if (oldRouterStateChild !== undefined && oldSegmentChild !== undefined && matchSegment(newSegmentChild, oldSegmentChild)) {
            if (oldCacheNodeChild !== undefined && oldRouterStateChild !== undefined) {
                // This segment exists in both the old and new trees. Recursively update
                // the children.
                taskChild = updateCacheNodeOnNavigation(oldCacheNodeChild, oldRouterStateChild, newRouterStateChild, didFindRootLayout, prefetchDataChild, prefetchHead, isPrefetchHeadPartial, isSamePageNavigation, newSegmentPathChild, scrollableSegmentsResult);
            } else {
                // There's no existing Cache Node for this segment. Switch to the
                // "create" path.
                taskChild = beginRenderingNewRouteTree(oldRouterStateChild, newRouterStateChild, didFindRootLayout, prefetchDataChild !== undefined ? prefetchDataChild : null, prefetchHead, isPrefetchHeadPartial, newSegmentPathChild, scrollableSegmentsResult);
            }
        } else {
            // This is a new tree. Switch to the "create" path.
            taskChild = beginRenderingNewRouteTree(oldRouterStateChild, newRouterStateChild, didFindRootLayout, prefetchDataChild !== undefined ? prefetchDataChild : null, prefetchHead, isPrefetchHeadPartial, newSegmentPathChild, scrollableSegmentsResult);
        }
        if (taskChild !== null) {
            // Recursively propagate up the child tasks.
            if (taskChild.route === null) {
                // One of the child tasks discovered a change to the root layout.
                // Immediately unwind from this recursive traversal.
                return MPA_NAVIGATION_TASK;
            }
            if (taskChildren === null) {
                taskChildren = new Map();
            }
            taskChildren.set(parallelRouteKey, taskChild);
            const newCacheNodeChild = taskChild.node;
            if (newCacheNodeChild !== null) {
                const newSegmentMapChild = new Map(oldSegmentMapChild);
                newSegmentMapChild.set(newSegmentKeyChild, newCacheNodeChild);
                prefetchParallelRoutes.set(parallelRouteKey, newSegmentMapChild);
            }
            // The child tree's route state may be different from the prefetched
            // route sent by the server. We need to clone it as we traverse back up
            // the tree.
            const taskChildRoute = taskChild.route;
            patchedRouterStateChildren[parallelRouteKey] = taskChildRoute;
            const dynamicRequestTreeChild = taskChild.dynamicRequestTree;
            if (dynamicRequestTreeChild !== null) {
                // Something in the child tree is dynamic.
                needsDynamicRequest = true;
                dynamicRequestTreeChildren[parallelRouteKey] = dynamicRequestTreeChild;
            } else {
                dynamicRequestTreeChildren[parallelRouteKey] = taskChildRoute;
            }
        } else {
            // The child didn't change. We can use the prefetched router state.
            patchedRouterStateChildren[parallelRouteKey] = newRouterStateChild;
            dynamicRequestTreeChildren[parallelRouteKey] = newRouterStateChild;
        }
    }
    if (taskChildren === null) {
        // No new tasks were spawned.
        return null;
    }
    const newCacheNode = {
        lazyData: null,
        rsc: oldCacheNode.rsc,
        // We intentionally aren't updating the prefetchRsc field, since this node
        // is already part of the current tree, because it would be weird for
        // prefetch data to be newer than the final data. It probably won't ever be
        // observable anyway, but it could happen if the segment is unmounted then
        // mounted again, because LayoutRouter will momentarily switch to rendering
        // prefetchRsc, via useDeferredValue.
        prefetchRsc: oldCacheNode.prefetchRsc,
        head: oldCacheNode.head,
        prefetchHead: oldCacheNode.prefetchHead,
        loading: oldCacheNode.loading,
        // Everything is cloned except for the children, which we computed above.
        parallelRoutes: prefetchParallelRoutes
    };
    return {
        // Return a cloned copy of the router state with updated children.
        route: patchRouterStateWithNewChildren(newRouterState, patchedRouterStateChildren),
        node: newCacheNode,
        dynamicRequestTree: needsDynamicRequest ? patchRouterStateWithNewChildren(newRouterState, dynamicRequestTreeChildren) : null,
        children: taskChildren
    };
}
function beginRenderingNewRouteTree(oldRouterState, newRouterState, didFindRootLayout, prefetchData, possiblyPartialPrefetchHead, isPrefetchHeadPartial, segmentPath, scrollableSegmentsResult) {
    if (!didFindRootLayout) {
        // The route tree changed before we reached a layout. (The highest-level
        // layout in a route tree is referred to as the "root" layout.) This could
        // mean that we're navigating between two different root layouts. When this
        // happens, we perform a full-page (MPA-style) navigation.
        //
        // However, the algorithm for deciding where to start rendering a route
        // (i.e. the one performed in order to reach this function) is stricter
        // than the one used to detect a change in the root layout. So just because
        // we're re-rendering a segment outside of the root layout does not mean we
        // should trigger a full-page navigation.
        //
        // Specifically, we handle dynamic parameters differently: two segments are
        // considered the same even if their parameter values are different.
        //
        // Refer to isNavigatingToNewRootLayout for details.
        //
        // Note that we only have to perform this extra traversal if we didn't
        // already discover a root layout in the part of the tree that is unchanged.
        // In the common case, this branch is skipped completely.
        if (oldRouterState === undefined || isNavigatingToNewRootLayout(oldRouterState, newRouterState)) {
            // The root layout changed. Perform a full-page navigation.
            return MPA_NAVIGATION_TASK;
        }
    }
    return createCacheNodeOnNavigation(newRouterState, prefetchData, possiblyPartialPrefetchHead, isPrefetchHeadPartial, segmentPath, scrollableSegmentsResult);
}
function createCacheNodeOnNavigation(routerState, prefetchData, possiblyPartialPrefetchHead, isPrefetchHeadPartial, segmentPath, scrollableSegmentsResult) {
    // Same traversal as updateCacheNodeNavigation, but we switch to this path
    // once we reach the part of the tree that was not in the previous route. We
    // don't need to diff against the old tree, we just need to create a new one.
    if (prefetchData === null) {
        // There's no prefetch for this segment. Everything from this point will be
        // requested from the server, even if there are static children below it.
        // Create a terminal task node that will later be fulfilled by
        // server response.
        return spawnPendingTask(routerState, null, possiblyPartialPrefetchHead, isPrefetchHeadPartial, segmentPath, scrollableSegmentsResult);
    }
    const routerStateChildren = routerState[1];
    const isPrefetchRscPartial = prefetchData[4];
    // The head is assigned to every leaf segment delivered by the server. Based
    // on corresponding logic in fill-lazy-items-till-leaf-with-head.ts
    const isLeafSegment = Object.keys(routerStateChildren).length === 0;
    // If prefetch data is available for a segment, and it's fully static (i.e.
    // does not contain any dynamic holes), we don't need to request it from
    // the server.
    if (// Check if the segment data is partial
    isPrefetchRscPartial || // Check if the head is partial (only relevant if this is a leaf segment)
    isPrefetchHeadPartial && isLeafSegment) {
        // We only have partial data from this segment. Like missing segments, we
        // must request the full data from the server.
        return spawnPendingTask(routerState, prefetchData, possiblyPartialPrefetchHead, isPrefetchHeadPartial, segmentPath, scrollableSegmentsResult);
    }
    // The prefetched segment is fully static, so we don't need to request a new
    // one from the server. Keep traversing down the tree until we reach something
    // that requires a dynamic request.
    const prefetchDataChildren = prefetchData[2];
    const taskChildren = new Map();
    const cacheNodeChildren = new Map();
    let dynamicRequestTreeChildren = {};
    let needsDynamicRequest = false;
    if (isLeafSegment) {
        // The segment path of every leaf segment (i.e. page) is collected into
        // a result array. This is used by the LayoutRouter to scroll to ensure that
        // new pages are visible after a navigation.
        // TODO: We should use a string to represent the segment path instead of
        // an array. We already use a string representation for the path when
        // accessing the Segment Cache, so we can use the same one.
        scrollableSegmentsResult.push(segmentPath);
    } else {
        for(let parallelRouteKey in routerStateChildren){
            const routerStateChild = routerStateChildren[parallelRouteKey];
            const prefetchDataChild = prefetchDataChildren !== null ? prefetchDataChildren[parallelRouteKey] : null;
            const segmentChild = routerStateChild[0];
            const segmentPathChild = segmentPath.concat([
                parallelRouteKey,
                segmentChild
            ]);
            const segmentKeyChild = createRouterCacheKey(segmentChild);
            const taskChild = createCacheNodeOnNavigation(routerStateChild, prefetchDataChild, possiblyPartialPrefetchHead, isPrefetchHeadPartial, segmentPathChild, scrollableSegmentsResult);
            taskChildren.set(parallelRouteKey, taskChild);
            const dynamicRequestTreeChild = taskChild.dynamicRequestTree;
            if (dynamicRequestTreeChild !== null) {
                // Something in the child tree is dynamic.
                needsDynamicRequest = true;
                dynamicRequestTreeChildren[parallelRouteKey] = dynamicRequestTreeChild;
            } else {
                dynamicRequestTreeChildren[parallelRouteKey] = routerStateChild;
            }
            const newCacheNodeChild = taskChild.node;
            if (newCacheNodeChild !== null) {
                const newSegmentMapChild = new Map();
                newSegmentMapChild.set(segmentKeyChild, newCacheNodeChild);
                cacheNodeChildren.set(parallelRouteKey, newSegmentMapChild);
            }
        }
    }
    const rsc = prefetchData[1];
    const loading = prefetchData[3];
    return {
        // Since we're inside a new route tree, unlike the
        // `updateCacheNodeOnNavigation` path, the router state on the children
        // tasks is always the same as the router state we pass in. So we don't need
        // to clone/modify it.
        route: routerState,
        node: {
            lazyData: null,
            // Since this is a fully static segment, we don't need to use the
            // `prefetchRsc` field.
            rsc,
            prefetchRsc: null,
            head: isLeafSegment ? possiblyPartialPrefetchHead : null,
            prefetchHead: null,
            loading,
            parallelRoutes: cacheNodeChildren
        },
        dynamicRequestTree: needsDynamicRequest ? patchRouterStateWithNewChildren(routerState, dynamicRequestTreeChildren) : null,
        children: taskChildren
    };
}
function patchRouterStateWithNewChildren(baseRouterState, newChildren) {
    const clone = [
        baseRouterState[0],
        newChildren
    ];
    // Based on equivalent logic in apply-router-state-patch-to-tree, but should
    // confirm whether we need to copy all of these fields. Not sure the server
    // ever sends, e.g. the refetch marker.
    if (2 in baseRouterState) {
        clone[2] = baseRouterState[2];
    }
    if (3 in baseRouterState) {
        clone[3] = baseRouterState[3];
    }
    if (4 in baseRouterState) {
        clone[4] = baseRouterState[4];
    }
    return clone;
}
function spawnPendingTask(routerState, prefetchData, prefetchHead, isPrefetchHeadPartial, segmentPath, scrollableSegmentsResult) {
    // Create a task that will later be fulfilled by data from the server.
    // Clone the prefetched route tree and the `refetch` marker to it. We'll send
    // this to the server so it knows where to start rendering.
    const dynamicRequestTree = patchRouterStateWithNewChildren(routerState, routerState[1]);
    dynamicRequestTree[3] = 'refetch';
    const newTask = {
        route: routerState,
        // Corresponds to the part of the route that will be rendered on the server.
        node: createPendingCacheNode(routerState, prefetchData, prefetchHead, isPrefetchHeadPartial, segmentPath, scrollableSegmentsResult),
        // Because this is non-null, and it gets propagated up through the parent
        // tasks, the root task will know that it needs to perform a server request.
        dynamicRequestTree,
        children: null
    };
    return newTask;
}
function spawnReusedTask(reusedRouterState) {
    // Create a task that reuses an existing segment, e.g. when reusing
    // the current active segment in place of a default route.
    return {
        route: reusedRouterState,
        node: null,
        dynamicRequestTree: null,
        children: null
    };
}
// Writes a dynamic server response into the tree created by
// updateCacheNodeOnNavigation. All pending promises that were spawned by the
// navigation will be resolved, either with dynamic data from the server, or
// `null` to indicate that the data is missing.
//
// A `null` value will trigger a lazy fetch during render, which will then patch
// up the tree using the same mechanism as the non-PPR implementation
// (serverPatchReducer).
//
// Usually, the server will respond with exactly the subset of data that we're
// waiting for — everything below the nearest shared layout. But technically,
// the server can return anything it wants.
//
// This does _not_ create a new tree; it modifies the existing one in place.
// Which means it must follow the Suspense rules of cache safety.
export function listenForDynamicRequest(task, responsePromise) {
    responsePromise.then((param)=>{
        let { flightData } = param;
        if (typeof flightData === 'string') {
            // Happens when navigating to page in `pages` from `app`. We shouldn't
            // get here because should have already handled this during
            // the prefetch.
            return;
        }
        for (const normalizedFlightData of flightData){
            const { segmentPath, tree: serverRouterState, seedData: dynamicData, head: dynamicHead } = normalizedFlightData;
            if (!dynamicData) {
                continue;
            }
            writeDynamicDataIntoPendingTask(task, segmentPath, serverRouterState, dynamicData, dynamicHead);
        }
        // Now that we've exhausted all the data we received from the server, if
        // there are any remaining pending tasks in the tree, abort them now.
        // If there's any missing data, it will trigger a lazy fetch.
        abortTask(task, null);
    }, (error)=>{
        // This will trigger an error during render
        abortTask(task, error);
    });
}
function writeDynamicDataIntoPendingTask(rootTask, segmentPath, serverRouterState, dynamicData, dynamicHead) {
    // The data sent by the server represents only a subtree of the app. We need
    // to find the part of the task tree that matches the server response, and
    // fulfill it using the dynamic data.
    //
    // segmentPath represents the parent path of subtree. It's a repeating pattern
    // of parallel route key and segment:
    //
    //   [string, Segment, string, Segment, string, Segment, ...]
    //
    // Iterate through the path and finish any tasks that match this payload.
    let task = rootTask;
    for(let i = 0; i < segmentPath.length; i += 2){
        const parallelRouteKey = segmentPath[i];
        const segment = segmentPath[i + 1];
        const taskChildren = task.children;
        if (taskChildren !== null) {
            const taskChild = taskChildren.get(parallelRouteKey);
            if (taskChild !== undefined) {
                const taskSegment = taskChild.route[0];
                if (matchSegment(segment, taskSegment)) {
                    // Found a match for this task. Keep traversing down the task tree.
                    task = taskChild;
                    continue;
                }
            }
        }
        // We didn't find a child task that matches the server data. Exit. We won't
        // abort the task, though, because a different FlightDataPath may be able to
        // fulfill it (see loop in listenForDynamicRequest). We only abort tasks
        // once we've run out of data.
        return;
    }
    finishTaskUsingDynamicDataPayload(task, serverRouterState, dynamicData, dynamicHead);
}
function finishTaskUsingDynamicDataPayload(task, serverRouterState, dynamicData, dynamicHead) {
    if (task.dynamicRequestTree === null) {
        // Everything in this subtree is already complete. Bail out.
        return;
    }
    // dynamicData may represent a larger subtree than the task. Before we can
    // finish the task, we need to line them up.
    const taskChildren = task.children;
    const taskNode = task.node;
    if (taskChildren === null) {
        // We've reached the leaf node of the pending task. The server data tree
        // lines up the pending Cache Node tree. We can now switch to the
        // normal algorithm.
        if (taskNode !== null) {
            finishPendingCacheNode(taskNode, task.route, serverRouterState, dynamicData, dynamicHead);
            // Set this to null to indicate that this task is now complete.
            task.dynamicRequestTree = null;
        }
        return;
    }
    // The server returned more data than we need to finish the task. Skip over
    // the extra segments until we reach the leaf task node.
    const serverChildren = serverRouterState[1];
    const dynamicDataChildren = dynamicData[2];
    for(const parallelRouteKey in serverRouterState){
        const serverRouterStateChild = serverChildren[parallelRouteKey];
        const dynamicDataChild = dynamicDataChildren[parallelRouteKey];
        const taskChild = taskChildren.get(parallelRouteKey);
        if (taskChild !== undefined) {
            const taskSegment = taskChild.route[0];
            if (matchSegment(serverRouterStateChild[0], taskSegment) && dynamicDataChild !== null && dynamicDataChild !== undefined) {
                // Found a match for this task. Keep traversing down the task tree.
                return finishTaskUsingDynamicDataPayload(taskChild, serverRouterStateChild, dynamicDataChild, dynamicHead);
            }
        }
    // We didn't find a child task that matches the server data. We won't abort
    // the task, though, because a different FlightDataPath may be able to
    // fulfill it (see loop in listenForDynamicRequest). We only abort tasks
    // once we've run out of data.
    }
}
function createPendingCacheNode(routerState, prefetchData, prefetchHead, isPrefetchHeadPartial, segmentPath, scrollableSegmentsResult) {
    const routerStateChildren = routerState[1];
    const prefetchDataChildren = prefetchData !== null ? prefetchData[2] : null;
    const parallelRoutes = new Map();
    for(let parallelRouteKey in routerStateChildren){
        const routerStateChild = routerStateChildren[parallelRouteKey];
        const prefetchDataChild = prefetchDataChildren !== null ? prefetchDataChildren[parallelRouteKey] : null;
        const segmentChild = routerStateChild[0];
        const segmentPathChild = segmentPath.concat([
            parallelRouteKey,
            segmentChild
        ]);
        const segmentKeyChild = createRouterCacheKey(segmentChild);
        const newCacheNodeChild = createPendingCacheNode(routerStateChild, prefetchDataChild === undefined ? null : prefetchDataChild, prefetchHead, isPrefetchHeadPartial, segmentPathChild, scrollableSegmentsResult);
        const newSegmentMapChild = new Map();
        newSegmentMapChild.set(segmentKeyChild, newCacheNodeChild);
        parallelRoutes.set(parallelRouteKey, newSegmentMapChild);
    }
    // The head is assigned to every leaf segment delivered by the server. Based
    // on corresponding logic in fill-lazy-items-till-leaf-with-head.ts
    const isLeafSegment = parallelRoutes.size === 0;
    if (isLeafSegment) {
        // The segment path of every leaf segment (i.e. page) is collected into
        // a result array. This is used by the LayoutRouter to scroll to ensure that
        // new pages are visible after a navigation.
        // TODO: We should use a string to represent the segment path instead of
        // an array. We already use a string representation for the path when
        // accessing the Segment Cache, so we can use the same one.
        scrollableSegmentsResult.push(segmentPath);
    }
    const maybePrefetchRsc = prefetchData !== null ? prefetchData[1] : null;
    const maybePrefetchLoading = prefetchData !== null ? prefetchData[3] : null;
    return {
        lazyData: null,
        parallelRoutes: parallelRoutes,
        prefetchRsc: maybePrefetchRsc !== undefined ? maybePrefetchRsc : null,
        prefetchHead: isLeafSegment ? prefetchHead : [
            null,
            null
        ],
        // TODO: Technically, a loading boundary could contain dynamic data. We must
        // have separate `loading` and `prefetchLoading` fields to handle this, like
        // we do for the segment data and head.
        loading: maybePrefetchLoading !== undefined ? maybePrefetchLoading : null,
        // Create a deferred promise. This will be fulfilled once the dynamic
        // response is received from the server.
        rsc: createDeferredRsc(),
        head: isLeafSegment ? createDeferredRsc() : null
    };
}
function finishPendingCacheNode(cacheNode, taskState, serverState, dynamicData, dynamicHead) {
    // Writes a dynamic response into an existing Cache Node tree. This does _not_
    // create a new tree, it updates the existing tree in-place. So it must follow
    // the Suspense rules of cache safety — it can resolve pending promises, but
    // it cannot overwrite existing data. It can add segments to the tree (because
    // a missing segment will cause the layout router to suspend).
    // but it cannot delete them.
    //
    // We must resolve every promise in the tree, or else it will suspend
    // indefinitely. If we did not receive data for a segment, we will resolve its
    // data promise to `null` to trigger a lazy fetch during render.
    const taskStateChildren = taskState[1];
    const serverStateChildren = serverState[1];
    const dataChildren = dynamicData[2];
    // The router state that we traverse the tree with (taskState) is the same one
    // that we used to construct the pending Cache Node tree. That way we're sure
    // to resolve all the pending promises.
    const parallelRoutes = cacheNode.parallelRoutes;
    for(let parallelRouteKey in taskStateChildren){
        const taskStateChild = taskStateChildren[parallelRouteKey];
        const serverStateChild = serverStateChildren[parallelRouteKey];
        const dataChild = dataChildren[parallelRouteKey];
        const segmentMapChild = parallelRoutes.get(parallelRouteKey);
        const taskSegmentChild = taskStateChild[0];
        const taskSegmentKeyChild = createRouterCacheKey(taskSegmentChild);
        const cacheNodeChild = segmentMapChild !== undefined ? segmentMapChild.get(taskSegmentKeyChild) : undefined;
        if (cacheNodeChild !== undefined) {
            if (serverStateChild !== undefined && matchSegment(taskSegmentChild, serverStateChild[0])) {
                if (dataChild !== undefined && dataChild !== null) {
                    // This is the happy path. Recursively update all the children.
                    finishPendingCacheNode(cacheNodeChild, taskStateChild, serverStateChild, dataChild, dynamicHead);
                } else {
                    // The server never returned data for this segment. Trigger a lazy
                    // fetch during render. This shouldn't happen because the Route Tree
                    // and the Seed Data tree sent by the server should always be the same
                    // shape when part of the same server response.
                    abortPendingCacheNode(taskStateChild, cacheNodeChild, null);
                }
            } else {
                // The server never returned data for this segment. Trigger a lazy
                // fetch during render.
                abortPendingCacheNode(taskStateChild, cacheNodeChild, null);
            }
        } else {
        // The server response matches what was expected to receive, but there's
        // no matching Cache Node in the task tree. This is a bug in the
        // implementation because we should have created a node for every
        // segment in the tree that's associated with this task.
        }
    }
    // Use the dynamic data from the server to fulfill the deferred RSC promise
    // on the Cache Node.
    const rsc = cacheNode.rsc;
    const dynamicSegmentData = dynamicData[1];
    if (rsc === null) {
        // This is a lazy cache node. We can overwrite it. This is only safe
        // because we know that the LayoutRouter suspends if `rsc` is `null`.
        cacheNode.rsc = dynamicSegmentData;
    } else if (isDeferredRsc(rsc)) {
        // This is a deferred RSC promise. We can fulfill it with the data we just
        // received from the server. If it was already resolved by a different
        // navigation, then this does nothing because we can't overwrite data.
        rsc.resolve(dynamicSegmentData);
    } else {
    // This is not a deferred RSC promise, nor is it empty, so it must have
    // been populated by a different navigation. We must not overwrite it.
    }
    // Check if this is a leaf segment. If so, it will have a `head` property with
    // a pending promise that needs to be resolved with the dynamic head from
    // the server.
    const head = cacheNode.head;
    if (isDeferredRsc(head)) {
        head.resolve(dynamicHead);
    }
}
export function abortTask(task, error) {
    const cacheNode = task.node;
    if (cacheNode === null) {
        // This indicates the task is already complete.
        return;
    }
    const taskChildren = task.children;
    if (taskChildren === null) {
        // Reached the leaf task node. This is the root of a pending cache
        // node tree.
        abortPendingCacheNode(task.route, cacheNode, error);
    } else {
        // This is an intermediate task node. Keep traversing until we reach a
        // task node with no children. That will be the root of the cache node tree
        // that needs to be resolved.
        for (const taskChild of taskChildren.values()){
            abortTask(taskChild, error);
        }
    }
    // Set this to null to indicate that this task is now complete.
    task.dynamicRequestTree = null;
}
function abortPendingCacheNode(routerState, cacheNode, error) {
    // For every pending segment in the tree, resolve its `rsc` promise to `null`
    // to trigger a lazy fetch during render.
    //
    // Or, if an error object is provided, it will error instead.
    const routerStateChildren = routerState[1];
    const parallelRoutes = cacheNode.parallelRoutes;
    for(let parallelRouteKey in routerStateChildren){
        const routerStateChild = routerStateChildren[parallelRouteKey];
        const segmentMapChild = parallelRoutes.get(parallelRouteKey);
        if (segmentMapChild === undefined) {
            continue;
        }
        const segmentChild = routerStateChild[0];
        const segmentKeyChild = createRouterCacheKey(segmentChild);
        const cacheNodeChild = segmentMapChild.get(segmentKeyChild);
        if (cacheNodeChild !== undefined) {
            abortPendingCacheNode(routerStateChild, cacheNodeChild, error);
        } else {
        // This shouldn't happen because we're traversing the same tree that was
        // used to construct the cache nodes in the first place.
        }
    }
    const rsc = cacheNode.rsc;
    if (isDeferredRsc(rsc)) {
        if (error === null) {
            // This will trigger a lazy fetch during render.
            rsc.resolve(null);
        } else {
            // This will trigger an error during rendering.
            rsc.reject(error);
        }
    }
    // Check if this is a leaf segment. If so, it will have a `head` property with
    // a pending promise that needs to be resolved. If an error was provided, we
    // will not resolve it with an error, since this is rendered at the root of
    // the app. We want the segment to error, not the entire app.
    const head = cacheNode.head;
    if (isDeferredRsc(head)) {
        head.resolve(null);
    }
}
export function updateCacheNodeOnPopstateRestoration(oldCacheNode, routerState) {
    // A popstate navigation reads data from the local cache. It does not issue
    // new network requests (unless the cache entries have been evicted). So, we
    // update the cache to drop the prefetch data for any segment whose dynamic
    // data was already received. This prevents an unnecessary flash back to PPR
    // state during a back/forward navigation.
    //
    // This function clones the entire cache node tree and sets the `prefetchRsc`
    // field to `null` to prevent it from being rendered. We can't mutate the node
    // in place because this is a concurrent data structure.
    const routerStateChildren = routerState[1];
    const oldParallelRoutes = oldCacheNode.parallelRoutes;
    const newParallelRoutes = new Map(oldParallelRoutes);
    for(let parallelRouteKey in routerStateChildren){
        const routerStateChild = routerStateChildren[parallelRouteKey];
        const segmentChild = routerStateChild[0];
        const segmentKeyChild = createRouterCacheKey(segmentChild);
        const oldSegmentMapChild = oldParallelRoutes.get(parallelRouteKey);
        if (oldSegmentMapChild !== undefined) {
            const oldCacheNodeChild = oldSegmentMapChild.get(segmentKeyChild);
            if (oldCacheNodeChild !== undefined) {
                const newCacheNodeChild = updateCacheNodeOnPopstateRestoration(oldCacheNodeChild, routerStateChild);
                const newSegmentMapChild = new Map(oldSegmentMapChild);
                newSegmentMapChild.set(segmentKeyChild, newCacheNodeChild);
                newParallelRoutes.set(parallelRouteKey, newSegmentMapChild);
            }
        }
    }
    // Only show prefetched data if the dynamic data is still pending.
    //
    // Tehnically, what we're actually checking is whether the dynamic network
    // response was received. But since it's a streaming response, this does not
    // mean that all the dynamic data has fully streamed in. It just means that
    // _some_ of the dynamic data was received. But as a heuristic, we assume that
    // the rest dynamic data will stream in quickly, so it's still better to skip
    // the prefetch state.
    const rsc = oldCacheNode.rsc;
    const shouldUsePrefetch = isDeferredRsc(rsc) && rsc.status === 'pending';
    return {
        lazyData: null,
        rsc,
        head: oldCacheNode.head,
        prefetchHead: shouldUsePrefetch ? oldCacheNode.prefetchHead : [
            null,
            null
        ],
        prefetchRsc: shouldUsePrefetch ? oldCacheNode.prefetchRsc : null,
        loading: oldCacheNode.loading,
        // These are the cloned children we computed above
        parallelRoutes: newParallelRoutes
    };
}
const DEFERRED = Symbol();
// This type exists to distinguish a DeferredRsc from a Flight promise. It's a
// compromise to avoid adding an extra field on every Cache Node, which would be
// awkward because the pre-PPR parts of codebase would need to account for it,
// too. We can remove it once type Cache Node type is more settled.
function isDeferredRsc(value) {
    return value && value.tag === DEFERRED;
}
function createDeferredRsc() {
    let resolve;
    let reject;
    const pendingRsc = new Promise((res, rej)=>{
        resolve = res;
        reject = rej;
    });
    pendingRsc.status = 'pending';
    pendingRsc.resolve = (value)=>{
        if (pendingRsc.status === 'pending') {
            const fulfilledRsc = pendingRsc;
            fulfilledRsc.status = 'fulfilled';
            fulfilledRsc.value = value;
            resolve(value);
        }
    };
    pendingRsc.reject = (error)=>{
        if (pendingRsc.status === 'pending') {
            const rejectedRsc = pendingRsc;
            rejectedRsc.status = 'rejected';
            rejectedRsc.reason = error;
            reject(error);
        }
    };
    pendingRsc.tag = DEFERRED;
    return pendingRsc;
}

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