[Blazor] Maui windows apps can't find _framework/blazor.modules.json

[javiercn]

For some reason the apps fail to find the file and as a result initializers don't load. It works fine in other platforms like Android

[gerneio]

This isn't working for me on Android or Windows MAUI currently (unable to test iOS). Neither beforeStart or afterStarted initializers are working (as described here). Using latest net7.0 workloads:

> dotnet workload list

Installed Workload Id      Manifest Version       Installation Source
--------------------------------------------------------------------------------
android                    33.0.46/7.0.100        SDK 7.0.200, VS 17.5.33530.505
ios                        16.2.2054/7.0.100      SDK 7.0.200, VS 17.5.33530.505
maccatalyst                16.2.2054/7.0.100      SDK 7.0.200, VS 17.5.33530.505
maui-android               7.0.81/7.0.100         VS 17.5.33530.505
wasm-tools                 7.0.5/7.0.100          VS 17.5.33530.505
maui-windows               7.0.81/7.0.100         VS 17.5.33530.505
maui-maccatalyst           7.0.81/7.0.100         VS 17.5.33530.505
maui-ios                   7.0.81/7.0.100         VS 17.5.33530.505

Note that I tried this both with putting the {ASSEMBLY NAME}.lib.module.js file under the MAUI project wwwroot folder, as well as under an RCL's wwwroot folder, but same results either way. I do see that the {MAUI_PROJECT}.modules.json file is being created in the output wwwroot folder (which also means I'm naming those files correctly).

Ultimately, after stepping through the _framework/blazor.webview.js for a bit, what I found was that these initializers are supposed to be loaded via the importInitializersAsync JS method, which uses the _framework/blazor.modules.json to determine which JS files needs to be run as initializers. On Android, using CDT and looking at the network tab, I can see that the _framework/blazor.modules.json file is returned as an empty array (same for the Windows app). Both network requests have a status code of 200.

Just wanted to add my experiences, as well as inquire if there are any plausible workarounds? Really what I'm after is the ability to trigger a JS specific workload BEFORE Blazor.Start() is called, or at least before any of the .NET ecosystem is loaded. However, when using the MAUI BlazorWebView, Blazor.Start() is called automatically therefore the autostart=false mechanism can't be used as in WASM.

[ghost]

Thanks for contacting us.

We're moving this issue to the .NET 8 Planning milestone for future evaluation / consideration. We would like to keep this around to collect more feedback, which can help us with prioritizing this work. We will re-evaluate this issue, during our next planning meeting(s).
If we later determine, that the issue has no community involvement, or it's very rare and low-impact issue, we will close it - so that the team can focus on more important and high impact issues.
To learn more about what to expect next and how this issue will be handled you can read more about our triage process here.

[vnbaaij]

@mkArtakMSFT, @javiercn We are running into this when using the Blazor Fluent UI library in A Blazor Hybrid project (see microsoft/fluentui-blazor#404 (comment)). Any indication on if/when/how this is solved? And are there known workarounds (besides building your own Microsoft.AspNetCore.Components.WebView :))?

[vnbaaij]

@mkArtakMSFT, @javiercn, one of our contributors has created a nice workaround for this. See https://github.com/microsoft/fluentui-blazor#tempory-workaround-for-maui-issues for the details.

[LuohuaRain]

is this PR relevant?
dotnet/aspnetcore#48594

[hml-coder]

Issue also exists with RCL component hosted in BlazorWebView in Windows Forms and Wpf projects. Workaround mentioned by @vnbaaij is required.

[Jarek300]

Is this problem fixed in .NET 8?

Do Blazor JS module initializers work in NET 8 in Blazor Hybrid? Is loading file wwwroot/{AppName}.lib.module.js in Blazor hybrid / BlazorWebView fixed?

[Zhanglirong-Winnie]

Verified this issue with Visual Studio Enterprise 17.9.0 Preview 2. Can repro this issue.

[javiercn]

This should be fixed in #18953

[datvm]

@javiercn Hi when is this fix released? And when it is released, do the old projects that use the workaround need to remove it? We have tons of MAUI projects that is currently using the initializersLoader.webview.js workaround

[BretJohnson]

This indeed does look to be fixed in .NET9. With .NET9, you should not use the workaround https://github.com/microsoft/fluentui-blazor?tab=readme-ov-file#temporary-workaround-for-mauiwpfwindows-forms-issues, for Blazor Fluent UI, and in fact things won't work if you do since now the modules file is named _framework/blazor.modules.json and the workaround has it look for <app-name>.modules.json, which is no longer generated.