dialog [nfc]: Wrap showErrorDialog's return value

As a result, showErrorDialog no longer returns a Future that can be
mistakenly awaited.  The wrapped return value offers clarity on how the
Future is supposed to be used.

There is no user visible change because existing callers (other than
lightbox's) that wait for its return value are all asynchronous
handlers for UI elements like buttons, and waits unnecessarily.

See also discussion
  zulip#937 (comment).

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

Author: PIG208

lib/widgets/app.dart

@@ -313,75 +313,74 @@ class HomePage extends StatelessWidget {
     return Scaffold(
       appBar: ZulipAppBar(title: const Text("Home")),
       body: Center(
-        child:  ElevatedButtonTheme(
+        child: SingleChildScrollView(
+        child: ElevatedButtonTheme(
         data: ElevatedButtonThemeData(style: ButtonStyle(
           backgroundColor: WidgetStatePropertyAll(colorScheme.secondaryContainer),
           foregroundColor: WidgetStatePropertyAll(colorScheme.onSecondaryContainer))),
-        child: SingleChildScrollView(
-          child: Center(
-            child: Column(mainAxisAlignment: MainAxisAlignment.center, children: [
-              DefaultTextStyle.merge(
-                textAlign: TextAlign.center,
-                style: const TextStyle(fontSize: 18),
-                child: Column(children: [
-                  const Text('🚧 Under construction 🚧'),
-                  const SizedBox(height: 12),
-                  Text.rich(TextSpan(
-                    text: 'Connected to: ',
-                    children: [bold(store.realmUrl.toString())])),
-                  Text.rich(TextSpan(
-                    text: 'Zulip server version: ',
-                    children: [bold(store.zulipVersion)])),
-                  Text(zulipLocalizations.subscribedToNChannels(store.subscriptions.length)),
-                ])),
-              const SizedBox(height: 16),
-              ElevatedButton(
-                onPressed: () => Navigator.push(context,
-                  MessageListPage.buildRoute(context: context,
-                    narrow: const CombinedFeedNarrow())),
-                child: Text(zulipLocalizations.combinedFeedPageTitle)),
-              const SizedBox(height: 16),
-              ElevatedButton(
-                onPressed: () => Navigator.push(context,
-                  MessageListPage.buildRoute(context: context,
-                    narrow: const MentionsNarrow())),
-                child: Text(zulipLocalizations.mentionsPageTitle)),
-              const SizedBox(height: 16),
-              ElevatedButton(
-                onPressed: () => Navigator.push(context,
-                  MessageListPage.buildRoute(context: context,
-                    narrow: const MentionsNarrow())),
-                child: Text(zulipLocalizations.mentionsPageTitle)),
+        child: Center(
+          child: Column(mainAxisAlignment: MainAxisAlignment.center, children: [
+            DefaultTextStyle.merge(
+              textAlign: TextAlign.center,
+              style: const TextStyle(fontSize: 18),
+              child: Column(children: [
+                const Text('🚧 Under construction 🚧'),
+                const SizedBox(height: 12),
+                Text.rich(TextSpan(
+                  text: 'Connected to: ',
+                  children: [bold(store.realmUrl.toString())])),
+                Text.rich(TextSpan(
+                  text: 'Zulip server version: ',
+                  children: [bold(store.zulipVersion)])),
+                Text(zulipLocalizations.subscribedToNChannels(store.subscriptions.length)),
+              ])),
+            const SizedBox(height: 16),
+            ElevatedButton(
+              onPressed: () => Navigator.push(context,
+                MessageListPage.buildRoute(context: context,
+                  narrow: const CombinedFeedNarrow())),
+              child: Text(zulipLocalizations.combinedFeedPageTitle)),
+            const SizedBox(height: 16),
+            ElevatedButton(
+              onPressed: () => Navigator.push(context,
+                MessageListPage.buildRoute(context: context,
+                  narrow: const MentionsNarrow())),
+              child: Text(zulipLocalizations.mentionsPageTitle)),
+            const SizedBox(height: 16),
+            ElevatedButton(
+              onPressed: () => Navigator.push(context,
+                MessageListPage.buildRoute(context: context,
+                  narrow: const MentionsNarrow())),
+              child: Text(zulipLocalizations.mentionsPageTitle)),
+            const SizedBox(height: 16),
+            ElevatedButton(
+              onPressed: () => Navigator.push(context,
+                MessageListPage.buildRoute(context: context,
+                  narrow: const StarredMessagesNarrow())),
+              child: Text(zulipLocalizations.starredMessagesPageTitle)),
+            const SizedBox(height: 16),
+            ElevatedButton(
+              onPressed: () => Navigator.push(context,
+                InboxPage.buildRoute(context: context)),
+              child: const Text("Inbox")), // TODO(i18n)
+            const SizedBox(height: 16),
+            ElevatedButton(
+              onPressed: () => Navigator.push(context,
+                SubscriptionListPage.buildRoute(context: context)),
+              child: const Text("Subscribed channels")),
+            const SizedBox(height: 16),
+            ElevatedButton(
+              onPressed: () => Navigator.push(context,
+                RecentDmConversationsPage.buildRoute(context: context)),
+              child: Text(zulipLocalizations.recentDmConversationsPageTitle)),
+            if (testStreamId != null) ...[
               const SizedBox(height: 16),
               ElevatedButton(
                 onPressed: () => Navigator.push(context,
                   MessageListPage.buildRoute(context: context,
-                    narrow: const StarredMessagesNarrow())),
-                child: Text(zulipLocalizations.starredMessagesPageTitle)),
-              const SizedBox(height: 16),
-              ElevatedButton(
-                onPressed: () => Navigator.push(context,
-                  InboxPage.buildRoute(context: context)),
-                child: const Text("Inbox")), // TODO(i18n)
-              const SizedBox(height: 16),
-              ElevatedButton(
-                onPressed: () => Navigator.push(context,
-                  SubscriptionListPage.buildRoute(context: context)),
-                child: const Text("Subscribed channels")),
-              const SizedBox(height: 16),
-              ElevatedButton(
-                onPressed: () => Navigator.push(context,
-                  RecentDmConversationsPage.buildRoute(context: context)),
-                child: Text(zulipLocalizations.recentDmConversationsPageTitle)),
-              if (testStreamId != null) ...[
-                const SizedBox(height: 16),
-                ElevatedButton(
-                  onPressed: () => Navigator.push(context,
-                    MessageListPage.buildRoute(context: context,
-                      narrow: ChannelNarrow(testStreamId!))),
-                  child: const Text("#test here")), // scaffolding hack, see above
-              ],
-            ])),
-        ))));
+                    narrow: ChannelNarrow(testStreamId!))),
+                child: const Text("#test here")), // scaffolding hack, see above
+            ],
+          ]))))));
   }
 }

lib/widgets/dialog.dart

@@ -15,43 +15,44 @@ Widget _dialogActionText(String text) {
   );
 }
 
-/// Tracks the status of a dialog, in being still open or already closed.
+/// A wrapper providing access to the status of an [AlertDialog].
 ///
 /// See also:
 ///  * [showDialog], whose return value this class is intended to wrap.
-class DialogStatus {
-  const DialogStatus(this.closed);
+class DialogStatusController {
+  const DialogStatusController(this._closed);
 
   /// Resolves when the dialog is closed.
-  final Future<void> closed;
+  Future<void> get closed => _closed;
+  final Future<void> _closed;
 }
 
 /// Displays an [AlertDialog] with a dismiss button.
 ///
-/// The [DialogStatus.closed] field of the return value can be used
-/// for waiting for the dialog to be closed.
+/// Returns a [DialogStatusController]. Useful for checking if the dialog has
+/// been closed.
 // This API is inspired by [ScaffoldManager.showSnackBar].  We wrap
-// [showDialog]'s return value, a [Future], inside [DialogStatus]
+// [showDialog]'s return value, a [Future], inside [DialogStatusController]
 // whose documentation can be accessed.  This helps avoid confusion when
 // intepreting the meaning of the [Future].
-DialogStatus showErrorDialog({
+DialogStatusController showErrorDialog({
   required BuildContext context,
   required String title,
   String? message,
 }) {
   final zulipLocalizations = ZulipLocalizations.of(context);
   final future = showDialog<void>(
     context: context,
-    builder: (BuildContext context) => AlertDialog(
-      title: Text(title),
-      content: message != null ? Text(message) : null,
-      scrollable: true,
-      actions: [
-        TextButton(
-          onPressed: () => Navigator.pop(context),
-          child: _dialogActionText(zulipLocalizations.errorDialogContinue)),
-      ]));
-  return DialogStatus(future);
+    builder: (BuildContext context) => SingleChildScrollView(
+      child: AlertDialog(
+        title: Text(title),
+        content: message != null ? Text(message) : null,
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.pop(context),
+            child: _dialogActionText(zulipLocalizations.errorDialogContinue)),
+        ])));
+  return DialogStatusController(future);
 }
 
 void showSuggestedActionDialog({
@@ -66,8 +67,7 @@ void showSuggestedActionDialog({
     context: context,
     builder: (BuildContext context) => AlertDialog(
       title: Text(title),
-      content: Text(message),
-      scrollable: true,
+      content: SingleChildScrollView(child: Text(message)),
       actions: [
         TextButton(
           onPressed: () => Navigator.pop(context),