Native embedding: Consuming ResourceDictionary throws ArgumentNullException on iOS and Android

[davidbritch]

Description

In a .NET for iOS/Android app, that uses .NET MAUI native embedding, attempting to consume a ResourceDictionary throws an ArgumentNullException with the message: Value cannot be null (Parameter 'key').

This doesn't happen on Windows, but at the same time Windows appears to make no effort to consume the RD (iOS + Android at least apply the values in the RD).

        // Create app-level resource dictionary.
        Microsoft.Maui.Controls.Application.Current = new Microsoft.Maui.Controls.Application();
        Microsoft.Maui.Controls.Application.Current.Resources = new MyDictionary();

        NotesPage notesPage = new NotesPage()
        {
            // Set the parent so that the app-level resource dictionary can be located.
            Parent = Microsoft.Maui.Controls.Application.Current
        };

Setting the Parent was necessary in Xamarin.Forms. The exception is still thrown if Parent isn't set.

The stack trace seems to indicate that it's a hot reload issue.

Steps to Reproduce

1. Run the sample on Android or iOS.
2. After a few seconds the ArgumentNullException occurs.

Link to public reproduction project repository

https://github.com/davidbritch/dotnet-maui-issues/tree/main/Embedding-HotReload

Version with bug

.NET 7 GA.

Affected platforms

iOS, Android

Relevant log output

Stack trace:

   at System.ThrowHelper.ThrowArgumentNullException(String name)
   at System.ThrowHelper.ThrowKeyNullException()
   at System.Collections.Concurrent.ConcurrentDictionary`2[[Microsoft.Maui.Dispatching.IDispatcher, Microsoft.Maui, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.XamlHotReload.VisualTreeService.VisualTree.DispatcherVisualTreeContext, Microsoft.Maui.Controls.HotReload.Forms, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].GetOrAdd(IDispatcher key, Func`2 valueFactory)
   at Microsoft.XamlHotReload.VisualTreeService.VisualTree.VisualTreeContextBase.GetDispatcherContext(IDispatcher dispatcher) in /Users/runner/work/1/s/HotReload/Source/Xamarin.HotReload.Xaml/VisualTreeService/VisualTree/VisualTreeContextBase.cs:line 76
   at Microsoft.XamlHotReload.VisualTreeService.VisualTree.FormsVisualTreeContext.<>c__DisplayClass12_0.<SubscribeToVisualTreeChanges>b__0() in /Users/runner/work/1/s/HotReload/Source/Xamarin.HotReload.Xaml/VisualTreeService/VisualTree/FormsVisualTreeContext.cs:line 58
   at Microsoft.XamlHotReload.Utility.DispatcherExtensions.<>c__DisplayClass3_0.<InvokeAsync>b__0() in /Users/runner/work/1/s/HotReload/Source/Microsoft.Maui.Controls.HotReload.Forms/MauiDispatcherExtensions.cs:line 36
   at Microsoft.XamlHotReload.Utility.DispatcherExtensions.<>c__DisplayClass4_0`1[[System.Boolean, System.Private.CoreLib, Version=7.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].<InvokeAsync>b__1() in /Users/runner/work/1/s/HotReload/Source/Microsoft.Maui.Controls.HotReload.Forms/MauiDispatcherExtensions.cs:line 53
--- End of stack trace from previous location ---
   at Microsoft.XamlHotReload.Utility.DispatcherExtensions.Invoke(IDispatcher dispatcher, Action callback) in /Users/runner/work/1/s/HotReload/Source/Microsoft.Maui.Controls.HotReload.Forms/MauiDispatcherExtensions.cs:line 17
   at Microsoft.XamlHotReload.VisualTreeService.VisualTree.FormsVisualTreeContext.SubscribeToVisualTreeChanges() in /Users/runner/work/1/s/HotReload/Source/Xamarin.HotReload.Xaml/VisualTreeService/VisualTree/FormsVisualTreeContext.cs:line 57
   at Microsoft.XamlHotReload.VisualTreeService.VisualTree.FormsVisualTreeContext.<.ctor>b__2_0(EmptyRequestInfo _) in /Users/runner/work/1/s/HotReload/Source/Xamarin.HotReload.Xaml/VisualTreeService/VisualTree/FormsVisualTreeContext.cs:line 30
   at Microsoft.VisualStudio.DesignTools.TapContract.Networking.ProtocolHandler.<>c__DisplayClass34_0`1[[Microsoft.VisualStudio.DesignTools.TapContract.TapOM.EmptyRequestInfo, Microsoft.VisualStudio.DesignTools.TapContract, Version=17.0.0.0, Culture=neutral, PublicKeyToken=null]].<RegisterMessageObserver>b__0(EmptyRequestInfo message)
   at Microsoft.VisualStudio.DesignTools.TapContract.Networking.ProtocolHandler.HandleMessage[EmptyRequestInfo,ResponseWithError](Func`2 callback, Message request)
   at Microsoft.VisualStudio.DesignTools.TapContract.Networking.ProtocolHandler.<>c__DisplayClass35_0`2[[Microsoft.VisualStudio.DesignTools.TapContract.TapOM.EmptyRequestInfo, Microsoft.VisualStudio.DesignTools.TapContract, Version=17.0.0.0, Culture=neutral, PublicKeyToken=null],[Microsoft.VisualStudio.DesignTools.TapContract.TapOM.ResponseWithError, Microsoft.VisualStudio.DesignTools.TapContract, Version=17.0.0.0, Culture=neutral, PublicKeyToken=null]].<RegisterMessageObserver>b__0(Message message)
   at Microsoft.VisualStudio.DesignTools.TapContract.Networking.ProtocolHandler.ProcessInboundMessage(Message message)
   at Microsoft.VisualStudio.DesignTools.TapContract.Networking.ProtocolHandler.<>c__DisplayClass48_0.<OnMessageReceived>b__0()
   at Microsoft.VisualStudio.DesignTools.TapContract.Networking.ProtocolHandler.WaitableActionsList.<>c__DisplayClass8_0.<AddAndSignal>b__0(Boolean isCancelled)
   at Microsoft.VisualStudio.DesignTools.TapContract.Networking.ProtocolHandler.ActionThread(Object list)
   at System.Threading.Thread.StartCallback()

[PureWeen]

@StephaneDelcroix

[ghost]

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.

[egvijayanand]

Have provided a workaround to this issue for the time being, refer to this article.