From 600bb81be151c29b90b99a0516e6e55103bc70c5 Mon Sep 17 00:00:00 2001
From: Paul Schneider <paul@pschneider.fr>
Date: Wed, 19 Aug 2026 17:32:51 +0100
Subject: [PATCH] PostIt: show ViewLocator fallback errors in navigation

---
 src/PostIt/PostIt/App.axaml.cs                    |  8 +++++---
 src/PostIt/PostIt/ViewLocator.cs                  | 14 +++++++++++++-
 src/PostIt/PostIt/ViewModels/MainPageViewModel.cs |  6 +++++-
 3 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/src/PostIt/PostIt/App.axaml.cs b/src/PostIt/PostIt/App.axaml.cs
index 894256fa..91ba662f 100644
--- a/src/PostIt/PostIt/App.axaml.cs
+++ b/src/PostIt/PostIt/App.axaml.cs
@@ -324,10 +324,12 @@ public partial class App : Application
                 $"Template for {vm.GetType().Name} returned <null>.");
         }
 
-        if (view is not Page page)
+        var page = view as Page;
+        if (page is null)
         {
-            throw new InvalidOperationException(
-                $"Template for {vm.GetType().Name} returned {view.GetType().Name}, expected a Page.");
+            // NavigationPage expects Page instances. Wrap any fallback control
+            // (e.g. ViewLocator error TextBlock) into a ContentPage so it can render.
+            page = new ContentPage { Content = view };
         }
 
         page.DataContext = vm;
diff --git a/src/PostIt/PostIt/ViewLocator.cs b/src/PostIt/PostIt/ViewLocator.cs
index 025116d8..fd92c802 100644
--- a/src/PostIt/PostIt/ViewLocator.cs
+++ b/src/PostIt/PostIt/ViewLocator.cs
@@ -21,6 +21,18 @@ public class ViewLocator : IDataTemplate
     }
 
     public Control Build(object? data)
+    {
+        try
+        {
+            return BuildCore(data);
+        }
+        catch (Exception ex)
+        {
+            return new TextBlock { Text = $"ViewLocator threw: {ex}" };
+        }
+    }
+
+    private Control BuildCore(object? data)
     {
         return data switch
         {
@@ -32,7 +44,7 @@ public class ViewLocator : IDataTemplate
             CirclesPageViewModel => _services.GetRequiredService<CirclesPage>(),
             PostAclDialogViewModel => _services.GetRequiredService<PostAclDialog>(),
             null => new TextBlock { Text = "No view for <null>" },
-        _ => new TextBlock { Text = $"No view for {data.GetType().Name}" }
+            _ => new TextBlock { Text = $"No view for {data.GetType().Name}" }
         };
     }
 
diff --git a/src/PostIt/PostIt/ViewModels/MainPageViewModel.cs b/src/PostIt/PostIt/ViewModels/MainPageViewModel.cs
index e3a541ea..e8256df6 100644
--- a/src/PostIt/PostIt/ViewModels/MainPageViewModel.cs
+++ b/src/PostIt/PostIt/ViewModels/MainPageViewModel.cs
@@ -437,7 +437,11 @@ public partial class MainPageViewModel : ViewModelBase
     [RelayCommand(CanExecute = nameof(CanManageAcl))]
     public async Task ManageAcl()
     {
-        if (SelectedPost is null) return;
+        if (SelectedPost is null)
+        {
+            StatusMessage = "Select an existing post before managing ACL.";
+            return;
+        }
         await ((App)App.Current!).PushPageAsync(GetACLViewModel(SelectedPost)).ConfigureAwait(true);
     }