store: Add "blocking future" option on GlobalStoreWidget

Author: gnprice

lib/widgets/store.dart

@@ -18,10 +18,18 @@ import 'page.dart';
 class GlobalStoreWidget extends StatefulWidget {
   const GlobalStoreWidget({
     super.key,
+    this.blockingFuture,
     this.placeholder = const LoadingPlaceholder(),
     required this.child,
   });
 
+  /// An additional future to await before showing the child.
+  ///
+  /// If [blockingFuture] is non-null, then this widget will build [child]
+  /// only after the future completes.  This widget's behavior is not affected
+  /// by whether the future's completion is with a value or with an error.
+  final Future<void>? blockingFuture;
+
   final Widget placeholder;
   final Widget child;
 
@@ -87,6 +95,9 @@ class _GlobalStoreWidgetState extends State<GlobalStoreWidget> {
     super.initState();
     (() async {
       final store = await ZulipBinding.instance.getGlobalStoreUniquely();
+      if (widget.blockingFuture != null) {
+        await widget.blockingFuture!.catchError((_) {});
+      }
       setState(() {
         this.store = store;
       });

test/widgets/store_test.dart

@@ -70,12 +70,12 @@ void main() {
             return const SizedBox.shrink();
           })));
     // First, shows a loading page instead of child.
-    check(tester.any(find.byType(CircularProgressIndicator))).isTrue();
+    check(find.byType(CircularProgressIndicator)).findsOne();
     check(globalStore).isNull();
 
     await tester.pump();
     // Then after loading, mounts child instead, with provided store.
-    check(tester.any(find.byType(CircularProgressIndicator))).isFalse();
+    check(find.byType(CircularProgressIndicator)).findsNothing();
     check(globalStore).identicalTo(testBinding.globalStore);
 
     await testBinding.globalStore.add(eg.selfAccount, eg.initialSnapshot());
@@ -84,6 +84,56 @@ void main() {
       .equals((accountId: eg.selfAccount.id, account: eg.selfAccount));
   });
 
+  testWidgets('GlobalStoreWidget awaits blockingFuture', (tester) async {
+    addTearDown(testBinding.reset);
+
+    final completer = Completer<void>();
+    await tester.pumpWidget(Directionality(textDirection: TextDirection.ltr,
+      child: GlobalStoreWidget(
+        blockingFuture: completer.future,
+        child: Text('done'))));
+
+    await tester.pump();
+    await tester.pump();
+    await tester.pump();
+    // Even after the store must have loaded,
+    // still shows loading page while blockingFuture is pending.
+    check(find.byType(CircularProgressIndicator)).findsOne();
+    check(find.text('done')).findsNothing();
+
+    // Once blockingFuture completes…
+    completer.complete();
+    await tester.pump();
+    // … mounts child instead of the loading page.
+    check(find.byType(CircularProgressIndicator)).findsNothing();
+    check(find.text('done')).findsOne();
+  });
+
+  testWidgets('GlobalStoreWidget handles failed blockingFuture like success', (tester) async {
+    addTearDown(testBinding.reset);
+
+    final completer = Completer<void>();
+    await tester.pumpWidget(Directionality(textDirection: TextDirection.ltr,
+      child: GlobalStoreWidget(
+        blockingFuture: completer.future,
+        child: Text('done'))));
+
+    await tester.pump();
+    await tester.pump();
+    await tester.pump();
+    // Even after the store must have loaded,
+    // still shows loading page while blockingFuture is pending.
+    check(find.byType(CircularProgressIndicator)).findsOne();
+    check(find.text('done')).findsNothing();
+
+    // Once blockingFuture completes, even with an error…
+    completer.completeError(Exception('oops'));
+    await tester.pump();
+    // … mounts child instead of the loading page.
+    check(find.byType(CircularProgressIndicator)).findsNothing();
+    check(find.text('done')).findsOne();
+  });
+
   testWidgets('GlobalStoreWidget.of updates dependents', (tester) async {
     addTearDown(testBinding.reset);