[.NET 10] certain [Obsolete] warnings are not reported

[jonathanpeppers]

Version Used: .NET SDK 10.0.100-alpha.1.24573.1

We noticed this from Maestro/codeflow here:

• [main] Update dependencies from dotnet/sdk android#9395

Steps to Reproduce:

1. Call AppDomain.CreateDomain("test") in .NET 10
2. Note that you don't get a SYSLIB0024 warning

Repro: testroslyn.zip

Note that this seems to work fine using net9.0 and a .NET 9 SDK.

Diagnostic Id:

SYSLIB0024: 'AppDomain.CreateDomain(string)' is obsolete: 'Creating and unloading AppDomains is not supported and throws an exception.'

Expected Behavior:

I get a SYSLIB0024 warning.

Actual Behavior:

I get no SYSLIB0024 warning.

Other info:

Note that if I open packs\Microsoft.NETCore.App.Ref\10.0.0-alpha.1.24570.9\ref\net10.0\System.Runtime.dll, it looks correct:

The warning also seems to work fine if I declare an [Obsolete] method within the C# file.

[CyrusNajmabadi]

I don't know what SYSLIB is. But is isn't roslyn :)

[jonathanpeppers]

@CyrusNajmabadi this is if you have [Obsolete(DiagnosticId=" and put SYSLIB0024. Maybe it is any [Obsolete] in a reference assembly?

[jonathanpeppers]

Ok, this works fine, I get a warning if I call it:

[Obsolete]
public void Test()
{
}

This doesn't produce a warning at all:

[Obsolete("whoopsies", DiagnosticId = "SYSLIB0024")]
public void Test()
{
}

[AlekseyTs]

Is it possible that "SYSLIB0024" warning is disabled by default in the new SDK?

@jonathanpeppers What happens if you use a different diagnostic id? For example:

[Obsolete("whoopsies", DiagnosticId = "CustomID_0024")]
public void Test()
{
}

[jonathanpeppers]

When testing this, I found this also produces no warnings:

[Obsolete("whoopsies")]
public void Test()
{
}

What made me notice this issue, warnings related to [SupportedOSPlatformVersion] on Android were also not working in .NET 10. I was hoping whatever the underlying issue was maybe fixed both problems here. [Obsolete] seems more fundamental and reproducible in a console app, though.

[Youssef1313]

I investigated this. It's not a Roslyn bug, but an SDK bug. WarningLevel used to align with the .NET version, and the way the SDK does it is using this:

https://github.com/dotnet/sdk/blob/257517e442d17286d450a5641d10302b3f90ed07/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.Analyzers.targets#L64-L65

Now we are two digit version (10) 😄
So, this trick no longer works. Currently on .NET 10, WarningLevel is calculated as 1 which would take out lots of warnings that have higher level. For example, obsoletion warnings have warning level 2

[Youssef1313]

This is fixed now in SDK and can be closed

[jonathanpeppers]

When Maestro/codeflow makes it to the dotnet/android repo, I'll be able to try it out and close this, thanks!

[AlekseyTs]

@jonathanpeppers I am going to close this issue as fixed. If the problem is still there with updated SDK, please reactivate this issue and attach a complog (https://github.com/jaredpar/complog).