Upgrade to version 8.0.2 failed to resolve IMvxMessenger on start

[nicolgit]

🔙 Regression

After upgrading from 7.x to version 8.0.2 the app throws a Failed to resolve first ViewModel

Old (and correct) behavior

App starts up normally.

Current behavior

on start throw the following exception

{MvvmCross.Exceptions.MvxException}	MvvmCross.Exceptions.MvxException
Exception: "Failed to construct and initialize ViewModel for type CaledosLab.Runner.Commons.ViewModels.MainPageViewModel from locator MvxDefaultViewModelLocator - check InnerException for more information"

  at MvvmCross.ViewModels.MvxViewModelLoader.LoadViewModel (MvvmCross.ViewModels.MvxViewModelRequest request, MvvmCross.ViewModels.IMvxBundle savedState, MvvmCross.Navigation.EventArguments.IMvxNavigateEventArgs navigationArgs) [0x00044] in /_/MvvmCross/ViewModels/MvxViewModelLoader.cs:74 
  at MvvmCross.Navigation.MvxNavigationService.Navigate (System.Type viewModelType, MvvmCross.ViewModels.IMvxBundle presentationBundle, System.Threading.CancellationToken cancellationToken) [0x00019] in /_/MvvmCross/Navigation/MvxNavigationService.cs:454 
  at MvvmCross.Navigation.MvxNavigationService.Navigate[TViewModel] (MvvmCross.ViewModels.IMvxBundle presentationBundle, System.Threading.CancellationToken cancellationToken) [0x00000] in /_/MvvmCross/Navigation/MvxNavigationService.cs:501 
  at CaledosLab.Runner.Commons.ViewModels.CaledosAppStart.NavigateToFirstViewModel (System.Object hint) [0x00018] in C:\Caledos\code\Runner\CaledosLab.Runner.Commons.ViewModels\App.cs:53 

InnerException	{MvvmCross.Exceptions.MvxException}	MvvmCross.Exceptions.MvxException
Message "Problem creating viewModel of type MainPageViewModel"

  at MvvmCross.ViewModels.MvxDefaultViewModelLocator.Load (System.Type viewModelType, MvvmCross.ViewModels.IMvxBundle parameterValues, MvvmCross.ViewModels.IMvxBundle savedState, MvvmCross.Navigation.EventArguments.IMvxNavigateEventArgs navigationArgs) [0x00029] in /_/MvvmCross/ViewModels/MvxDefaultViewModelLocator.cs:32 
  at MvvmCross.ViewModels.MvxViewModelLoader.LoadViewModel (MvvmCross.ViewModels.MvxViewModelRequest request, MvvmCross.ViewModels.IMvxBundle savedState, MvvmCross.Navigation.EventArguments.IMvxNavigateEventArgs navigationArgs) [0x00031] in /_/MvvmCross/ViewModels/MvxViewModelLoader.cs:70 

InnerException	{MvvmCross.Exceptions.MvxIoCResolveException}	MvvmCross.Exceptions.MvxIoCResolveException
Message	"Problem creating viewModel of type MainPageViewModel"	string
  at MvvmCross.ViewModels.MvxDefaultViewModelLocator.Load (System.Type viewModelType, MvvmCross.ViewModels.IMvxBundle parameterValues, MvvmCross.ViewModels.IMvxBundle savedState, MvvmCross.Navigation.EventArguments.IMvxNavigateEventArgs navigationArgs) [0x00029] in /_/MvvmCross/ViewModels/MvxDefaultViewModelLocator.cs:32 
  at MvvmCross.ViewModels.MvxViewModelLoader.LoadViewModel (MvvmCross.ViewModels.MvxViewModelRequest request, MvvmCross.ViewModels.IMvxBundle savedState, MvvmCross.Navigation.EventArguments.IMvxNavigateEventArgs navigationArgs) [0x00031] in /_/MvvmCross/ViewModels/MvxViewModelLoader.cs:70 

Reproduction steps

the exception raises here(***)

public class App : MvvmCross.ViewModels.MvxApplication
    {
        public override void Initialize()
        {
            CreatableTypes()
                .EndingWith("Service")
                .AsInterfaces()
                .RegisterAsLazySingleton();
            
            InitializeAppConfiguration();
            InitializeAppText();

            RegisterCustomAppStart<CaledosAppStart>();
        }

        private void InitializeAppConfiguration()
        {
            var languageManager = new LanguageManager();
            Mvx.IoCProvider.RegisterSingleton<ILanguageManager>(languageManager);
        }

        private void InitializeAppText()
        {
            TextLoader.Instance.LoadJsonFromResource("Shared.json", "Shared");                        
        }
    }

public class CaledosAppStart : MvxAppStart
    {
        public CaledosAppStart(IMvxApplication application, IMvxNavigationService navigationService) : base(application, navigationService)
        {
        }

        protected override async Task NavigateToFirstViewModel(object hint = null)
        {
            try
            {
                await NavigationService.Navigate<MainPageViewModel>();
            }
            catch (System.Exception e)
            {

                throw; (***)
            }
            
        }
    }

Configuration

Version: 8.0.2

Platform:

• 🤖 Android

[Cheesebaron]

Comment out stuff in your MainPageViewModel constructor untill you find out which dependency fails resolving.

[nicolgit]

@Cheesebaron thank you for the hint, the constructor crashes on the following row:

token = Mvx.IoCProvider.Resolve<IMvxMessenger>().Subscribe<UserMessage>(OnUserMessage);

any idea?

[Cheesebaron]

I think I've seen other issues with regards to MvxMessenger breaking in other issues, where they just downgraded that package to 8.0.1.

[nicolgit]

downgraded MvxMessenger to 8.0.1 but the issue is the same :-(

[nicolgit]

Any Idea to unlock the situation? do you think it is better to rollback to 7 and wait for a future MVVM release?

[tvone-timmoore]

With Mvx 8.0.2, WPF, .NET 5.

I'm having a similar problem when trying to publish a message from code called from MvxAppStart.NavigateToFirstViewModel() and the MvxMessenger is getting stuck waiting for the UI Thread.

I'm processing the command line args to load a file and navigate to the correct viewmodel, the same code works when selecting a load button after the UI shows.

This previously worked with Mvx 7 and lower.

[Edit] Will raise a new bug as it's not quite the same.

[entdark]

I'm having a similar problem when trying to publish a message from code called from MvxAppStart.NavigateToFirstViewModel() and the MvxMessenger is getting stuck waiting for the UI Thread.

Could it be related to #4364?

[tvone-timmoore]

I'm having a similar problem when trying to publish a message from code called from MvxAppStart.NavigateToFirstViewModel() and the MvxMessenger is getting stuck waiting for the UI Thread.

Could it be related to #4364?

Thanks @entdark, yes is could be related that #4364, I've added my comment to that bug.

I've just started to have a look at MvvmCross 8 code to see why it is blocking in 8 but not 7.

[ivmirx]

Same here, but it happens only on iOS and only in release builds, I was able to catch it only by catching an exception in static void Main(string[] args) and logging it via the WiFi console in Xcode:

MvvmCross.Exceptions.MvxIoCResolveException: Failed to resolve type MvvmCross.Plugin.Messenger.IMvxMessenger
  at MvvmCross.IoC.MvxIoCContainer.Resolve (System.Type type) <0x105051f74 + 0x00148> in …
  at MvvmCross.IoC.MvxIoCContainer.Resolve[T] () <0x105051f10 + 0x0002f> in …
  at MvvmCross.IoC.MvxIoCProvider.Resolve[T] () <0x10505614c + 0x00033> in …
  at MyApp.Core.State..ctor (MyApp.Core.IDatabaseService databaseService, Plugin.StoreReview.Abstractions.IStoreReview storeReview) <0x105903658 + 0x0024f> in …
  at MyApp.Core.App.Initialize () <0x1058f8e4c + 0x00093> in …
  at MvvmCross.Core.MvxSetup.InitializeApp (MvvmCross.Plugin.IMvxPluginMa<…>

Looks like a race condition that does not happen in slower debugging-enabled builds. Linker settings do not affect the crash.

[ivmirx]

Solved the problem by adding this to App.Initialize() before registering any of my singletons and calling RegisterAppStart<…>():

var pluginManager = Mvx.IoCProvider.Resolve<IMvxPluginManager>();
pluginManager.EnsurePluginLoaded<MvvmCross.Plugin.Messenger.Plugin>(true);

[entdark]

Could that be related: AppRopio/AppRopio.Mobile@2e19235?
I fixed it by using ToList() that forced to iterate through all the items in IEnumerable. I did not pay much attention to that back then but now looking to the source I see this:

MvvmCross/MvvmCross/Core/MvxSetup.cs

Line 396 in c67b773

.AsParallel()

And since it is using AsParallel() it is not waiting for result when iterating through all the plugins when loading them. So the app initialization happens faster than all the plugins get loaded.

[entdark]

By the way, there is no point in AsParallel() if it's executed in foreach. It has to be ForAll(item => {}) extension for the parallel query.

[entdark]

My hypothesis was wrong about parallel query (or maybe not - I will get to that topic later). But I found out another thing: that method returns false for type MvvmCross.Plugin.Messenger.Plugin:

MvvmCross/MvvmCross/Core/MvxSetup.cs

Line 430 in c67b773

if (TypeContainsPluginAttribute(type))

Even worse: if to try to load all possible attributes manually it still finds 0.
So MvxMessenger never gets loaded.
If that condition is commented out then things go fine.
I am reminding that it happens in Release builds only.

[entdark]

Solved the problem by adding this to App.Initialize() before registering any of my singletons and calling RegisterAppStart<…>():

Seems like the proper place would be overriden App.LoadPlugins(IMvxPluginManager pluginManager):

MvvmCross/MvvmCross/ViewModels/MvxApplication.cs

Line 35 in c67b773

public virtual void LoadPlugins(IMvxPluginManager pluginManager)

[entdark]

@ivmirx

[ValonK]

I tried the workaround mentioned earlier, but unfortunately, it didnt work for me. Additionally, I've completely removed MvxMessenger from the project. However, I'm still encountering the issue when running the app in Release Mode on iOS (stuck on splash screen then crashes), while Android works correctly.

We haven't transitioned our app to MAUI yet, so we're currently stuck using Xamarin.Forms with MvvmCross 8.0.2. (7.1.2) works correctly.

The iOS logs haven't provided any useful insights. Has anyone found a solution for this problem?

MvvmCross 8.0.2
MvvmCross.Forms 8.0.2