[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.

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.
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[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