"A fatal error has occurred loading the metadata for 'System.Private.CoreLib.dll' and debugging needs to be terminated." when debugging 11.0 WASM browser project

[jinzhao1127]

REGRESSION INFO: Works well on 10.0/9.0/8.0

INSTALL STEPS:

1. Clean Win11 x64 25h2 ENU
2. Install the VS 18.3
3. Install the .NET 11.0 Preview 1 SDK: https://aka.ms/dotnet/11.0.1xx/daily/dotnet-sdk-win-x64.exe
4. Add feed

Platform

• Windows
• macOS
• Linux

Repro Steps

1. Install WebAssembly Browser App template via command:
   dotnet workload install wasm-experimental
2. Run dotnet new wasmbrowser -o WasmBrowser to create a wasm browser project
3. Open the project in VS
4. Run the project (F5)

Actual Result
Failed to run the project with error "A fatal error has occurred loading the metadata for 'System.Private.CoreLib.dll'"

Note

1. This issue does not repro on Ctrl + F5
2. This issue does not reproduce on 10.0/9.0/8.0 wasm browser project.
3. This issue does not repro on Blazor web project.

Error Log

A fatal error has occurred loading the metadata for 'System.Private.CoreLib.dll' and debugging needs to be terminated. The operation failed because the debugger could not get the metadata.

[oroztocil]

@akoeplinger Do you know if this could be an incomplete code flow issue?

[akoeplinger]

According to @thaystg this is under investigation and related to the new debugger.

[thaystg]

Hello, the issue is related to something that was changed on .net11
On .net10 we have the .dll files in the bin folder, now I only see the .wasm files.
The .dll files are used by the debugger to load the metadata, can you keep the .dll files when the app is compiled in debug mode?

[thaystg]

.net10

.net11

[ilonatommy]

@maraf, it looks like dotnet/runtime#120330 might have caused it.

- <_WasmNativeAssetFileNames>;@(WasmNativeAsset->'%(FileName)%(Extension)');</_WasmNativeAssetFileNames>
+ <_WasmNativeAssetFileNames>;@(WasmNativeAsset->'%(FileName)%(Extension)');@(WasmAssembliesFinal->'%(FileName)%(Extension)');</_WasmNativeAssetFileNames>

When WasmNativeWorkload=true the framework assemblies are added to @(WasmAssembliesFinal) and then removed from ReferenceCopyLocalPaths so they don't get copied to the bin directory.
WasmNativeWorkload is set to true for net11:
https://github.com/dotnet/runtime/blob/facd688567d1acf67f4264537e8c1917f5b2deeb/src/mono/nuget/Microsoft.NET.Workload.Mono.Toolchain.Current.Manifest/WorkloadManifest.targets.in#L41

The temporary workaround is to set

<WasmNativeWorkload>false</WasmNativeWorkload>

in the project. @maraf, should we change WorkloadManifest.targets.in for debug mode?

[maraf]

I'll take a look why we are removing items from ReferenceCopyLocalPaths.
Having workload working for Debug builds is important.

[ilonatommy]

@jinzhao1127, could you please check the same scenario with

<WasmNativeWorkload>false</WasmNativeWorkload>

added to csproj?
Does it help? Can you debug?

[jinzhao1127]

@jinzhao1127, could you please check the same scenario with

<WasmNativeWorkload>false</WasmNativeWorkload>

added to csproj? Does it help? Can you debug?

@ilonatommy It does not help. After adding <WasmNativeWorkload>false</WasmNativeWorkload> in csproj file, it will require to reload the project , when F5 to debug the project, the browser does not launch.