store: Add field for tracking loading status.

When an error occurs to a getEvents call, there isn't a visual
indicator for the retry attempts. This prepares the data model for
the feature.

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

Author: PIG208

lib/model/store.dart

@@ -297,6 +297,15 @@ class PerAccountStore extends ChangeNotifier with ChannelStore, MessageStore {
   final GlobalStore _globalStore;
   final ApiConnection connection; // TODO(#135): update zulipFeatureLevel with events
 
+  bool get isLoading => _isLoading;
+  bool _isLoading = false;
+  @visibleForTesting
+  set isLoading(bool value) {
+    if (_isLoading == value) return;
+    _isLoading = value;
+    notifyListeners();
+  }
+
   ////////////////////////////////
   // Data attached to the realm or the server.
 
@@ -770,6 +779,7 @@ class UpdateMachine {
         result = await getEvents(store.connection,
           queueId: queueId, lastEventId: lastEventId);
       } catch (e) {
+        store.isLoading = true;
         switch (e) {
           case ZulipApiException(code: 'BAD_EVENT_QUEUE_ID'):
             assert(debugLog('Lost event queue for $store.  Replacing…'));
@@ -797,6 +807,7 @@ class UpdateMachine {
         }
       }
 
+      store.isLoading = false;
       final events = result.events;
       for (final event in events) {
         await store.handleEvent(event);

test/model/store_checks.dart

@@ -28,6 +28,7 @@ extension GlobalStoreChecks on Subject<GlobalStore> {
 
 extension PerAccountStoreChecks on Subject<PerAccountStore> {
   Subject<ApiConnection> get connection => has((x) => x.connection, 'connection');
+  Subject<bool> get isLoading => has((x) => x.isLoading, 'isLoading');
   Subject<Uri> get realmUrl => has((x) => x.realmUrl, 'realmUrl');
   Subject<String> get zulipVersion => has((x) => x.zulipVersion, 'zulipVersion');
   Subject<int> get maxFileUploadSizeMib => has((x) => x.maxFileUploadSizeMib, 'maxFileUploadSizeMib');

test/model/store_test.dart

@@ -406,10 +406,12 @@ void main() {
       updateMachine.debugAdvanceLoop();
       async.flushMicrotasks();
       await Future<void>.delayed(Duration.zero);
+      check(store).isLoading.isTrue();
 
       // The global store has a new store.
       check(globalStore.perAccountSync(store.accountId)).not((it) => it.identicalTo(store));
       updateFromGlobalStore();
+      check(store).isLoading.isFalse();
 
       // The new UpdateMachine updates the new store.
       updateMachine.debugPauseLoop();
@@ -435,8 +437,9 @@ void main() {
         // Make the request, inducing an error in it.
         prepareError();
         updateMachine.debugAdvanceLoop();
-        async.flushMicrotasks();
+        async.elapse(Duration.zero);
         checkLastRequest(lastEventId: 1);
+        check(store).isLoading.isTrue();
 
         // Polling doesn't resume immediately; there's a timer.
         check(async.pendingTimers).length.equals(1);
@@ -452,6 +455,7 @@ void main() {
         async.flushTimers();
         checkLastRequest(lastEventId: 1);
         check(updateMachine.lastEventId).equals(2);
+        check(store).isLoading.isFalse();
       });
     }