Show new replies early if the fetch-all-replies task takes long to finish (#36481)

app/javascript/mastodon/features/status/components/refresh_controller.tsx

@@ -38,7 +38,7 @@ const messages = defineMessages({
   },
   success: {
     id: 'status.context.loading_success',
-    defaultMessage: 'All replies loaded',
+    defaultMessage: 'New replies loaded',
   },
   error: {
     id: 'status.context.loading_error',
@@ -81,22 +81,38 @@ export const RefreshController: React.FC<{
   useEffect(() => {
     let timeoutId: ReturnType<typeof setTimeout>;
 
-    const scheduleRefresh = (refresh: AsyncRefreshHeader) => {
+    const scheduleRefresh = (
+      refresh: AsyncRefreshHeader,
+      iteration: number,
+    ) => {
       timeoutId = setTimeout(() => {
         void apiGetAsyncRefresh(refresh.id).then((result) => {
-          // If the refresh status is not finished,
-          // schedule another refresh and exit
-          if (result.async_refresh.status !== 'finished') {
-            scheduleRefresh(refresh);
+          // At three scheduled refreshes, we consider the job
+          // long-running and attempt to fetch any new replies so far
+          const isLongRunning = iteration === 3;
+
+          const { status, result_count } = result.async_refresh;
+
+          // If the refresh status is not finished and not long-running,
+          // we just schedule another refresh and exit
+          if (status === 'running' && !isLongRunning) {
+            scheduleRefresh(refresh, iteration + 1);
             return;
           }
 
-          // Refresh status is finished. The action below will clear `refreshHeader`
+          // If refresh status is finished, clear `refreshHeader`
+          // (we don't want to do this if it's just a long-running job)
+          if (status === 'finished') {
             dispatch(completeContextRefresh({ statusId }));
+          }
 
           // Exit if there's nothing to fetch
-          if (result.async_refresh.result_count === 0) {
+          if (result_count === 0) {
+            if (status === 'finished') {
               setLoadingState('idle');
+            } else {
+              scheduleRefresh(refresh, iteration + 1);
+            }
             return;
           }
 
@@ -106,10 +122,15 @@ export const RefreshController: React.FC<{
           // If so, they will populate `contexts.pendingReplies[statusId]`
           void dispatch(fetchContext({ statusId, prefetchOnly: true }))
             .then(() => {
-              // Reset loading state to `idle` – but if the fetch
-              // has resulted in new pending replies, the `hasPendingReplies`
+              // Reset loading state to `idle`. If the fetch has
+              // resulted in new pending replies, the `hasPendingReplies`
               // flag will switch the loading state to 'more-available'
+              if (status === 'finished') {
                 setLoadingState('idle');
+              } else {
+                // Keep background fetch going if `isLongRunning` is true
+                scheduleRefresh(refresh, iteration + 1);
+              }
             })
             .catch(() => {
               // Show an error if the fetch failed
@@ -121,7 +142,7 @@ export const RefreshController: React.FC<{
 
     // Initialise a refresh
     if (refreshHeader && !wasDismissed) {
-      scheduleRefresh(refreshHeader);
+      scheduleRefresh(refreshHeader, 1);
       setLoadingState('loading');
     }
 
@@ -135,7 +156,7 @@ export const RefreshController: React.FC<{
     if (loadingState === 'success') {
       const timeoutId = setTimeout(() => {
         setLoadingState('idle');
-      }, 3000);
+      }, 2500);
 
       return () => {
         clearTimeout(timeoutId);

app/javascript/mastodon/locales/en.json

@@ -876,7 +876,7 @@
   "status.contains_quote": "Contains quote",
   "status.context.loading": "Loading more replies",
   "status.context.loading_error": "Couldn't load new replies",
-  "status.context.loading_success": "All replies loaded",
+  "status.context.loading_success": "New replies loaded",
   "status.context.more_replies_found": "More replies found",
   "status.context.retry": "Retry",
   "status.context.show": "Show",

app/javascript/mastodon/reducers/contexts.ts

@@ -166,7 +166,10 @@ const updateContext = (state: Draft<State>, status: ApiStatusJSON): void => {
 export const contextsReducer = createReducer(initialState, (builder) => {
   builder
     .addCase(fetchContext.fulfilled, (state, action) => {
-      if (action.payload.prefetchOnly) {
+      const currentReplies = state.replies[action.meta.arg.statusId] ?? [];
+      const hasReplies = currentReplies.length > 0;
+      // Ignore prefetchOnly if there are no replies - then we can load them immediately
+      if (action.payload.prefetchOnly && hasReplies) {
         storePrefetchedReplies(
           state,
           action.meta.arg.statusId,
@@ -179,7 +182,7 @@ export const contextsReducer = createReducer(initialState, (builder) => {
           action.payload.context,
         );
 
-        if (action.payload.refresh) {
+        if (action.payload.refresh && !action.payload.prefetchOnly) {
           state.refreshing[action.meta.arg.statusId] = action.payload.refresh;
         }
       }