action_sheet: Add and use PageRoot

Without this, the upcoming resolve/unresolve feature would have a
bug where certain error dialogs would fail to appear. (Specifically
the ones that explain to the user that a topic has changed between
opening the action sheet and pressing the resolve/unresolve button.)

Author: chrisbobbe

lib/widgets/action_sheet.dart

@@ -24,6 +24,7 @@ import 'emoji_reaction.dart';
 import 'icons.dart';
 import 'inset_shadow.dart';
 import 'message_list.dart';
+import 'page.dart';
 import 'store.dart';
 import 'text.dart';
 import 'theme.dart';
@@ -163,11 +164,15 @@ class ActionSheetCancelButton extends StatelessWidget {
 }
 
 /// Show a sheet of actions you can take on a topic.
+///
+/// Needs a [PageRoot] ancestor.
 void showTopicActionSheet(BuildContext context, {
   required int channelId,
   required TopicName topic,
 }) {
-  final store = PerAccountStoreWidget.of(context);
+  final pageRootContext = PageRoot.contextOf(context);
+
+  final store = PerAccountStoreWidget.of(pageRootContext);
   final subscription = store.subscriptions[channelId];
 
   final optionButtons = <ActionSheetMenuItemButton>[];
@@ -237,7 +242,7 @@ void showTopicActionSheet(BuildContext context, {
       currentVisibilityPolicy: visibilityPolicy,
       newVisibilityPolicy: to,
       narrow: TopicNarrow(channelId, topic),
-      pageContext: context);
+      pageContext: pageRootContext);
   }));
 
   if (optionButtons.isEmpty) {
@@ -250,7 +255,7 @@ void showTopicActionSheet(BuildContext context, {
     return;
   }
 
-  _showActionSheet(context, optionButtons: optionButtons);
+  _showActionSheet(pageRootContext, optionButtons: optionButtons);
 }
 
 class UserTopicUpdateButton extends ActionSheetMenuItemButton {
@@ -374,35 +379,36 @@ class UserTopicUpdateButton extends ActionSheetMenuItemButton {
 
 /// Show a sheet of actions you can take on a message in the message list.
 ///
-/// Must have a [MessageListPage] ancestor.
+/// Must have a [MessageListPage] ancestor and a [PageRoot] ancestor.
 void showMessageActionSheet({required BuildContext context, required Message message}) {
-  final store = PerAccountStoreWidget.of(context);
+  final pageRootContext = PageRoot.contextOf(context);
+  final store = PerAccountStoreWidget.of(pageRootContext);
 
   // The UI that's conditioned on this won't live-update during this appearance
   // of the action sheet (we avoid calling composeBoxControllerOf in a build
   // method; see its doc).
   // So we rely on the fact that isComposeBoxOffered for any given message list
   // will be constant through the page's life.
-  final messageListPage = MessageListPage.ancestorOf(context);
+  final messageListPage = MessageListPage.ancestorOf(pageRootContext);
   final isComposeBoxOffered = messageListPage.composeBoxController != null;
 
   final isMessageRead = message.flags.contains(MessageFlag.read);
   final markAsUnreadSupported = store.connection.zulipFeatureLevel! >= 155; // TODO(server-6)
   final showMarkAsUnreadButton = markAsUnreadSupported && isMessageRead;
 
   final optionButtons = [
-    ReactionButtons(message: message, pageContext: context),
-    StarButton(message: message, pageContext: context),
+    ReactionButtons(message: message, pageContext: pageRootContext),
+    StarButton(message: message, pageContext: pageRootContext),
     if (isComposeBoxOffered)
-      QuoteAndReplyButton(message: message, pageContext: context),
+      QuoteAndReplyButton(message: message, pageContext: pageRootContext),
     if (showMarkAsUnreadButton)
-      MarkAsUnreadButton(message: message, pageContext: context),
-    CopyMessageTextButton(message: message, pageContext: context),
-    CopyMessageLinkButton(message: message, pageContext: context),
-    ShareButton(message: message, pageContext: context),
+      MarkAsUnreadButton(message: message, pageContext: pageRootContext),
+    CopyMessageTextButton(message: message, pageContext: pageRootContext),
+    CopyMessageLinkButton(message: message, pageContext: pageRootContext),
+    ShareButton(message: message, pageContext: pageRootContext),
   ];
 
-  _showActionSheet(context, optionButtons: optionButtons);
+  _showActionSheet(pageRootContext, optionButtons: optionButtons);
 }
 
 abstract class MessageActionSheetMenuItemButton extends ActionSheetMenuItemButton {

lib/widgets/message_list.dart

@@ -277,7 +277,7 @@ class _MessageListPageState extends State<MessageListPage> implements MessageLis
             narrow: ChannelNarrow(streamId)))));
     }
 
-    return Scaffold(
+    return PageRoot(child: Scaffold(
       appBar: ZulipAppBar(
         buildTitle: (willCenterTitle) =>
           MessageListAppBarTitle(narrow: narrow, willCenterTitle: willCenterTitle),
@@ -318,7 +318,7 @@ class _MessageListPageState extends State<MessageListPage> implements MessageLis
                 ))),
             if (ComposeBox.hasComposeBox(narrow))
               ComposeBox(key: _composeBoxKey, narrow: narrow)
-          ])));
+          ]))));
   }
 }
 

lib/widgets/page.dart

@@ -3,6 +3,30 @@ import 'package:flutter/material.dart';
 
 import 'store.dart';
 
+/// An [InheritedWidget] for near the root of a page's widget subtree,
+/// providing its [BuildContext].
+///
+/// Useful when needing a context that persists through the page's lifespan,
+/// e.g. for a show-action-sheet function
+/// whose buttons use a context to close the sheet
+/// or show an error dialog / snackbar asynchronously.
+///
+/// (In this scenario, it would be buggy to use the context of the element
+/// that was long-pressed,
+/// if the element can unmount as part of handling a Zulip event.)
+class PageRoot extends InheritedWidget {
+  const PageRoot({super.key, required super.child});
+
+  @override
+  bool updateShouldNotify(covariant PageRoot oldWidget) => false;
+
+  static BuildContext contextOf(BuildContext context) {
+    final element = context.getElementForInheritedWidgetOfExactType<PageRoot>();
+    assert(element != null, 'No PageRoot ancestor');
+    return element!;
+  }
+}
+
 /// A page route that always builds the same widget.
 ///
 /// This is useful for making the route more transparent for a test to inspect.
@@ -42,7 +66,8 @@ mixin AccountPageRouteMixin<T extends Object?> on PageRoute<T> {
       accountId: accountId,
       placeholder: loadingPlaceholderPage ?? const LoadingPlaceholderPage(),
       routeToRemoveOnLogout: this,
-      child: super.buildPage(context, animation, secondaryAnimation));
+      child: PageRoot(
+        child: super.buildPage(context, animation, secondaryAnimation)));
   }
 }
 

test/widgets/action_sheet_test.dart

@@ -21,11 +21,11 @@ import 'package:zulip/model/narrow.dart';
 import 'package:zulip/model/store.dart';
 import 'package:zulip/model/typing_status.dart';
 import 'package:zulip/widgets/action_sheet.dart';
+import 'package:zulip/widgets/app.dart';
 import 'package:zulip/widgets/app_bar.dart';
 import 'package:zulip/widgets/compose_box.dart';
 import 'package:zulip/widgets/content.dart';
 import 'package:zulip/widgets/emoji.dart';
-import 'package:zulip/widgets/home.dart';
 import 'package:zulip/widgets/icons.dart';
 import 'package:zulip/widgets/inbox.dart';
 import 'package:zulip/widgets/message_list.dart';
@@ -160,9 +160,13 @@ void main() {
         ]);
       }
 
-      await tester.pumpWidget(TestZulipApp(accountId: eg.selfAccount.id,
-        child: const HomePage()));
+      // ZulipApp instead of TestZulipApp so that we can push a route to the nav,
+      // exercising HomePage.buildRoute which (via AccountPageRouteMixin)
+      // makes a PageRoot, which the action sheet needs.
+      await tester.pumpWidget(ZulipApp());
       await tester.pump();
+
+      // If this fails, adjust setup so the inbox page is visible.
       check(find.byType(InboxPageBody)).findsOne();
 
       await tester.longPress(find.text(topic));