aspnetcore: .NET 8 preview7 Blazor WASM AAD authentication ends with There was an error trying to log you in: '"undefined" is not valid JSON'

Same issue on .NET 8 and I have tried adding both to the trimmer exception. Pushing this to .NET 9 is unacceptable. This has been going on long enough. It’s been years now.

In the 8.0.0 release:

• This issue appears to be a regression from #44981 (cc @javiercn).
• It results in a “LogInFailed” UI without any visible notifications.
• No errors are logged in the browser console or in the RemoteAuthenticatorView.LogInFailed context (notably, downgrading MSAL to 7.0.13 yields an error: "undefined" is not valid JSON).
• Disabling trimming for Microsoft.Authentication.WebAssembly.Msal when publishing the app resolves the issue immediately.

I believe this should not be classified as “technical debt” for future “.NET 9 Planning”, but rather recognized as a regression that could potentially cause significant issues for users.

I can confirm. The issue is solved in our case by mentioning only one root assembly:

<ItemGroup>
    <TrimmerRootAssembly Include="Microsoft.AspNetCore.Components.WebAssembly.Authentication" />
</ItemGroup>

I experienced the same issue when upgrading to .NET 8.0 with Azure B2C. I had to add the following to get it to work.

  <ItemGroup>
    <TrimmerRootAssembly Include="Microsoft.Authentication.WebAssembly.Msal" />
    <TrimmerRootAssembly Include="Microsoft.AspNetCore.Components.WebAssembly.Authentication" />
  </ItemGroup>

Specifying just Microsoft.Authentication.WebAssembly.Msal alone did not work for me.

Thanks for contacting us.

We’re moving this issue to the .NET 9 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.

@czlatea Doesn’t work for me; tried both and just Authentication in both Client and Server projects using .net 8

Something that caught me out was I also needed to clear cache after adding

<ItemGroup>
    <TrimmerRootAssembly Include="Microsoft.Authentication.WebAssembly.Msal" />
    <TrimmerRootAssembly Include="Microsoft.AspNetCore.Components.WebAssembly.Authentication" />
  </ItemGroup>

Edit: This actually didn’t fix it.

Using Net8.0, TrimmerRootAssembly does not fix the issue. Please help.

@kyleherzog Sorry for the confusion. Actually I do have both the MSAL and WebAssembly.Authentication rooted and it is probably the Microsoft.AspNetCore.Components.WebAssembly.Authentication which is the important one for this symptom.