Avoid calling shouldRevalidate on interrupted initial load fetchers

Author: brophdawg11

.changeset/skip-fetcher-revalidate.md

@@ -0,0 +1,5 @@
+---
+"@remix-run/router": patch
+---
+
+Avoid calling `shouldRevalidate` for fetchers that have not yet completed a data load

packages/router/__tests__/router-test.ts

@@ -10845,6 +10845,62 @@ describe("a router", () => {
         });
         expect(t.router.state.fetchers.get(actionKey)).toBeUndefined();
       });
+
+      it("does not call shouldRevalidate if fetcher has no data (called 2x rapidly)", async () => {
+        // This is specifically for a Remix use case where the initial fetcher.load
+        // call hasn't completed (and hasn't even loaded the route module yet), so
+        // there isn't even a shouldRevalidate implementation to access yet.  If
+        // there's no data it should just interrupt the existing load and load again,
+        // it's not a "revalidation"
+        let spy = jest.fn(() => true);
+        let t = setup({
+          routes: [
+            {
+              id: "root",
+              path: "/",
+              children: [
+                {
+                  index: true,
+                },
+                {
+                  path: "page",
+                },
+              ],
+            },
+            {
+              id: "fetch",
+              path: "/fetch",
+              loader: true,
+              shouldRevalidate: spy,
+            },
+          ],
+        });
+
+        let key = "key";
+        let A = await t.fetch("/fetch", key, "root");
+        expect(t.router.state.fetchers.get(key)?.state).toBe("loading");
+        expect(A.loaders.fetch.signal.aborted).toBe(false);
+
+        // This should trigger an automatic revalidation of the fetcher since it
+        // hasn't loaded yet
+        let B = await t.navigate("/page", undefined, ["fetch"]);
+        expect(t.router.state.fetchers.get(key)?.state).toBe("loading");
+        expect(A.loaders.fetch.signal.aborted).toBe(true);
+        expect(B.loaders.fetch.signal.aborted).toBe(false);
+
+        // No-op since the original call was aborted
+        await A.loaders.fetch.resolve("A");
+        expect(t.router.state.fetchers.get(key)?.state).toBe("loading");
+
+        // Complete the navigation
+        await B.loaders.fetch.resolve("B");
+        expect(t.router.state.navigation.state).toBe("idle");
+        expect(t.router.state.fetchers.get(key)).toMatchObject({
+          state: "idle",
+          data: "B",
+        });
+        expect(spy).not.toHaveBeenCalled();
+      });
     });
 
     describe("fetcher ?index params", () => {

packages/router/router.ts

@@ -1481,6 +1481,7 @@ export function createRouter(init: RouterInit): Router {
       cancelledDeferredRoutes,
       cancelledFetcherLoads,
       fetchLoadMatches,
+      fetchRedirectIds,
       routesToUse,
       basename,
       pendingActionData,
@@ -1539,6 +1540,9 @@ export function createRouter(init: RouterInit): Router {
 
     pendingNavigationLoadId = ++incrementingLoadId;
     revalidatingFetchers.forEach((rf) => {
+      if (fetchControllers.has(rf.key)) {
+        abortFetcher(rf.key);
+      }
       if (rf.controller) {
         // Fetchers use an independent AbortController so that aborting a fetcher
         // (via deleteFetcher) does not abort the triggering navigation that
@@ -1806,6 +1810,7 @@ export function createRouter(init: RouterInit): Router {
       cancelledDeferredRoutes,
       cancelledFetcherLoads,
       fetchLoadMatches,
+      fetchRedirectIds,
       routesToUse,
       basename,
       { [match.route.id]: actionResult.data },
@@ -1825,6 +1830,9 @@ export function createRouter(init: RouterInit): Router {
           existingFetcher ? existingFetcher.data : undefined
         );
         state.fetchers.set(staleKey, revalidatingFetcher);
+        if (fetchControllers.has(staleKey)) {
+          abortFetcher(staleKey);
+        }
         if (rf.controller) {
           fetchControllers.set(staleKey, rf.controller);
         }
@@ -3276,6 +3284,7 @@ function getMatchesToLoad(
   cancelledDeferredRoutes: string[],
   cancelledFetcherLoads: string[],
   fetchLoadMatches: Map<string, FetchLoadMatch>,
+  fetchRedirectIds: Set<string>,
   routesToUse: AgnosticDataRouteObject[],
   basename: string | undefined,
   pendingActionData?: RouteData,
@@ -3361,34 +3370,38 @@ function getMatchesToLoad(
       return;
     }
 
+    // Revalidating fetchers are decoupled from the route matches since they
+    // load from a static href.  They only set `defaultShouldRevalidate` on
+    // explicit revalidation due to submission, useRevalidator, or X-Remix-Revalidate
+    //
+    // They automatically revalidate without even calling shouldRevalidate if:
+    // - They were cancelled
+    // - They're in the middle of their first load and therefore this is still
+    //   an initial load and not a revalidation
+    //
+    // If neither of those is true, then they _always_ check shouldRevalidate
+    let fetcher = state.fetchers.get(key);
+    let isPerformingInitialLoad =
+      fetcher &&
+      fetcher.state !== "idle" &&
+      fetcher.data === undefined &&
+      // If a fetcher.load redirected then it'll be "loading" without any data
+      // so ensure we're not processing the redirect from this fetcher
+      !fetchRedirectIds.has(key);
     let fetcherMatch = getTargetMatch(fetcherMatches, f.path);
-
-    if (cancelledFetcherLoads.includes(key)) {
-      revalidatingFetchers.push({
-        key,
-        routeId: f.routeId,
-        path: f.path,
-        matches: fetcherMatches,
-        match: fetcherMatch,
-        controller: new AbortController(),
+    let shouldRevalidate =
+      cancelledFetcherLoads.includes(key) ||
+      isPerformingInitialLoad ||
+      shouldRevalidateLoader(fetcherMatch, {
+        currentUrl,
+        currentParams: state.matches[state.matches.length - 1].params,
+        nextUrl,
+        nextParams: matches[matches.length - 1].params,
+        ...submission,
+        actionResult,
+        defaultShouldRevalidate: isRevalidationRequired,
       });
-      return;
-    }
 
-    // Revalidating fetchers are decoupled from the route matches since they
-    // hit a static href, so they _always_ check shouldRevalidate and the
-    // default is strictly if a revalidation is explicitly required (action
-    // submissions, useRevalidator, X-Remix-Revalidate).
-    let shouldRevalidate = shouldRevalidateLoader(fetcherMatch, {
-      currentUrl,
-      currentParams: state.matches[state.matches.length - 1].params,
-      nextUrl,
-      nextParams: matches[matches.length - 1].params,
-      ...submission,
-      actionResult,
-      // Forced revalidation due to submission, useRevalidator, or X-Remix-Revalidate
-      defaultShouldRevalidate: isRevalidationRequired,
-    });
     if (shouldRevalidate) {
       revalidatingFetchers.push({
         key,