[Blazor Hybrid] BlazorWebView ComponentType error blocks XAML Hot Reload updates

[nor0x]

Description

just created a File -> New .NET MAUI Blazor Hybrid app in Visual Studio and started a Debug Build on Windows. XAML Hot-Reload is not working. There are multiple of these logs in the Hot Reload Console.

19:08 04.52 MauiApp24: Hot Reload session started
19:11 14.01 No changes were found.
19:11 24.95 No changes were found.

It seems that only XAML HR is not working for me, changes in .razor files are updated correctly.

Steps to Reproduce

1. Create new MAUI Blazor Hybrid app
2. Debug on Windows or Android
3. Make XAML changes

Link to public reproduction project repository

No response

Version with bug

8.0.7 SR2

Is this a regression from previous behavior?

Not sure, did not test other versions

Last version that worked well

Unknown/Other

Affected platforms

Windows and Android, I was not able test on other platforms

Affected platform versions

• Windows 23H2
• Android

Did you find any workaround?

No response

Relevant log output

My Visual Studio version is:

Microsoft Visual Studio Enterprise 2022 (64-bit) - Preview
Version 17.10.0 Preview 1.0

Thanks for the issue report @nor0x! This issue appears to be a problem with Visual Studio, so we ask that you use the VS feedback tool to report the issue. That way it will get to the routed to the team that owns this experience in VS.

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[drasticactions]

XAML Hot Reload is a Visual Studio feature and isn't something that can be addressed in this repo, you should file this to VSFeedback.

Also, those logs you posted are for C# Hot Reload, not XAML. Those logs are under "Xamarin Hot Reload", which, yes, is confusing and really they should be moved under a single location.

[drasticactions]

Also, checking the newest Visual Studio 17.9 and 17.10 Preview builds, it seems to work correctly for me on Android and Windows,

If you see the Live Visual Tree, then XAML Hot Reload functions. If you can edit properties in Live Property Explorer, it functions. Since you mentioned Razor changes being applied, those occur through the XAML Hot Reload system, so the connection should be working.

I assume that you're changing specific properties to BlazorWebView then and those are not applying. Trying to edit it, ComponentType doesn't seem to like to be changed or modified so if you try and edit code around it then it might protest and not apply changes to the rest. That's something that could be looked at within this repo.

So TL;DR, if you don't see things like Live Visual Tree or Live Property Explorer, or you get yellow bars or errors saying XAML Hot Reload can't start, that should go to VS since it can't be fixed here.

If you are trying to change specific things and those are not applying, then file it here and we can move or modify the issue as needed depending on where the fix has to go: The core control or the underlying system itself.

[nor0x]

thank you for the reply @drasticactions. Indeed there are some logs in the Xamarin Hot Reload panel:

[11:00:52]  (MauiApp24) .NET Project references .NET MAUI.
[11:00:52]  (MauiApp24) WinUI hot reload is in progress.
[11:01:06]  Hot Reload changes cannot be applied due to this error in the XAML:
  D:\Dev\maui\MauiApp24\MainPage.xaml(16,59): Nested types are not supported: Components.Routes.

which is also displayed in the XAML Editor. I can confirm that the Live Visual Tree is filled and changing properties via the Live Property Explorer works fine for me.

In my case nothing is hot-reloaded right now - I tried changing i.e. the BackgroundColor of the ContentPage or the outer Border or Grid

EDIT: Workaround

if I remove ComponentType="{x:Type local:Components}" from the RootComponent during Debug runtime - Hot Reload works fine again

[drasticactions]

Yes, this is "correct" (but not ideal) behavior. If there is any "rude edit" changes in the editor then incremental changes are not applied, so in this condition none of the other changes you make would apply and that's fully expected. The idea here is that you would "fix" the rude edit and then any other changes you made, including your fix to the XAML, would flow through.

But it is also very lame in this context, since here it is a fundamental part of the control and you can't do anything to fix it short of removing it wholesale. If you edit around it then it should work, but you still have the issue of the initial load since that page by default has the BlazorWebView as root, so moving that would invoke that ComponentType, causing the rude edit, meaning you would need to restart the session.

There are future changes being proposed internally to "work around" these kinds of issues to brute force (as in, reload the page wholesale in cases where you can't incrementally edit it for whatever reason), and that should help cases like what you see here. CC @BretJohnson @chabiss

So as it is right now, to me, this isn't a "bug" in that this is expected behavior for what XAML Hot Reload should do in this current situation... but it's a really lame limitation and maybe this is where having better messaging and future tooling changes could help. There are ways for us to "mask" that error and hide it, but you can't edit that field and have it hot reload so you would still need some error to tell you that changes there won't work, but also let other changes through, which could cause weird conditions. That, or update BlazorWebView to support incremental changes, which wouldn't require XAML Hot Reload changes but, IMO, seems less likely to happen.

[nor0x]

thank you for the info and explanation. Interesting to understand what's going on here. For now I'm unblocked by removing the ComponentType during runtime - but it's not nice though. I think this is something that can be handled in a better way by the tooling / framework. Also I don't quite understand why it works for you in a new blank project 🤔