store: Expect AccountNotFoundException when reloading store

This can happen when `removeAccount` was called
during `doLoadPerAccount`, possibly due to the user logging out
from choose-account page while the store is getting reloaded.

However, it is currently not reachable live because of a bug in
`UpdateMachine.load`.  See #1354.

Modulo the bug, `UpdateMachine` can safely ignore this error
acknowledging that the reload has failed, given that the user
can continue using the app by navigating from choose-account page.

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

lib/model/store.dart

@@ -1220,8 +1220,14 @@ class UpdateMachine {
       if (_disposed) return;
     }
 
-    await store._globalStore._reloadPerAccount(store.accountId);
-    assert(_disposed);
+    try {
+      await store._globalStore._reloadPerAccount(store.accountId);
+    } on AccountNotFoundException {
+      assert(debugLog('… Event queue not replaced; account was logged out.'));
+      return;
+    } finally {
+      assert(_disposed);
+    }
     assert(debugLog('… Event queue replaced.'));
   }
 

test/example_data.dart

@@ -879,6 +879,7 @@ ChannelUpdateEvent channelUpdateEvent(
 TestGlobalStore globalStore({List<Account> accounts = const []}) {
   return TestGlobalStore(accounts: accounts);
 }
+const _globalStore = globalStore;
 
 InitialSnapshot initialSnapshot({
   String? queueId,
@@ -949,10 +950,14 @@ InitialSnapshot initialSnapshot({
 }
 const _initialSnapshot = initialSnapshot;
 
-PerAccountStore store({Account? account, InitialSnapshot? initialSnapshot}) {
+PerAccountStore store({
+  GlobalStore? globalStore,
+  Account? account,
+  InitialSnapshot? initialSnapshot,
+}) {
   final effectiveAccount = account ?? selfAccount;
   return PerAccountStore.fromInitialSnapshot(
-    globalStore: globalStore(accounts: [effectiveAccount]),
+    globalStore: globalStore ?? _globalStore(accounts: [effectiveAccount]),
     accountId: effectiveAccount.id,
     initialSnapshot: initialSnapshot ?? _initialSnapshot(),
   );

test/model/store_test.dart

@@ -13,6 +13,7 @@ import 'package:zulip/api/route/events.dart';
 import 'package:zulip/api/route/messages.dart';
 import 'package:zulip/api/route/realm.dart';
 import 'package:zulip/log.dart';
+import 'package:zulip/model/actions.dart';
 import 'package:zulip/model/store.dart';
 import 'package:zulip/notifications/receive.dart';
 
@@ -969,6 +970,65 @@ void main() {
     });
   });
 
+  group('UpdateMachine.poll reload failure', () {
+    late LoadingTestGlobalStore globalStore;
+
+    List<Completer<PerAccountStore>> completers() =>
+      globalStore.completers[eg.selfAccount.id]!;
+
+    Future<void> prepareReload(FakeAsync async) async {
+      globalStore = LoadingTestGlobalStore(accounts: [eg.selfAccount]);
+      final future = globalStore.perAccount(eg.selfAccount.id);
+      final store = eg.store(globalStore: globalStore, account: eg.selfAccount);
+      completers().single.complete(store);
+      await future;
+      completers().clear();
+      final updateMachine = globalStore.updateMachines[eg.selfAccount.id] =
+        UpdateMachine.fromInitialSnapshot(
+          store: store, initialSnapshot: eg.initialSnapshot());
+      updateMachine.debugPauseLoop();
+      updateMachine.poll();
+
+      (store.connection as FakeApiConnection).prepare(
+        apiException: eg.apiExceptionBadEventQueueId());
+      updateMachine.debugAdvanceLoop();
+      async.elapse(Duration.zero);
+      check(store).isLoading.isTrue();
+    }
+
+    void checkReloadFailure({
+      required Future<void> Function() completeLoading,
+    }) {
+      awaitFakeAsync((async) async {
+        await prepareReload(async);
+        check(completers()).single.isCompleted.isFalse();
+
+        await completeLoading();
+        check(completers()).single.isCompleted.isTrue();
+        check(globalStore.takeDoRemoveAccountCalls()).single.equals(eg.selfAccount.id);
+
+        async.elapse(TestGlobalStore.removeAccountDuration);
+        check(globalStore.perAccountSync(eg.selfAccount.id)).isNull();
+
+        async.flushTimers();
+        // Reload never succeeds and there are no unhandled errors.
+        check(globalStore.perAccountSync(eg.selfAccount.id)).isNull();
+      });
+    }
+
+    Future<void> logOutAndCompleteWithNewStore() async {
+      // [PerAccountStore.fromInitialSnapshot] requires the account
+      // to be in the global store when called; do so before logging out.
+      final newStore = eg.store(globalStore: globalStore, account: eg.selfAccount);
+      await logOutAccount(globalStore, eg.selfAccount.id);
+      completers().single.complete(newStore);
+    }
+
+    test('user logged out before new store is loaded', () => awaitFakeAsync((async) async {
+      checkReloadFailure(completeLoading: logOutAndCompleteWithNewStore);
+    }));
+  });
+
   group('UpdateMachine.registerNotificationToken', () {
     late UpdateMachine updateMachine;
     late FakeApiConnection connection;

test/stdlib_checks.dart

@@ -5,6 +5,7 @@
 /// part of the Dart standard library.
 library;
 
+import 'dart:async';
 import 'dart:convert';
 
 import 'package:checks/checks.dart';
@@ -74,6 +75,10 @@ Object? deepToJson(Object? object) {
   return (result, true);
 }
 
+extension CompleterChecks<T> on Subject<Completer<T>> {
+  Subject<bool> get isCompleted => has((x) => x.isCompleted, 'isCompleted');
+}
+
 extension JsonChecks on Subject<Object?> {
   /// Expects that the value is deeply equal to [expected],
   /// after calling [deepToJson] on both.