IL3000 error in MsQuicApi..cctor when publishing AOT

[euju-ms]

Describe the bug

When publishing an app that uses HttpClient, it results in IL3000.

System.Net.Quic.MsQuicApi..cctor(): 'System.Reflection.Assembly.Location.get' always returns an empty string for assemblies embedded in a single-file app. If the path to the app directory is needed, consider calling 'System.AppContext.BaseDirectory'.

To Reproduce

Here's a repo that contains the minimal repro console app: https://github.com/euju-ms/MsQuicApiError

1. Download the source code then open MsQuicApiError.sln from VisualStudio
2. Publish the project MsQuicApiError using Properties\PublishProfiles\FolderProflie.pubxml, then observe the error.

Exceptions (if any)

Further technical details

• Include the output of dotnet --info

.NET SDK:
 Version:           9.0.100
 Commit:            59db016f11
 Workload version:  9.0.100-manifests.c6f19616
 MSBuild version:   17.12.7+5b8665660

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.23786
 OS Platform: Windows
 RID:         win-x64
 Base Path:   C:\Program Files\dotnet\sdk\9.0.100\

.NET workloads installed:
 [aspire]
   Installation Source: VS 17.12.35506.116
   Manifest Version:    8.2.2/8.0.100
   Manifest Path:       C:\Program Files\dotnet\sdk-manifests\8.0.100\microsoft.net.sdk.aspire\8.2.2\WorkloadManifest.json
   Install Type:              Msi

Configured to use loose manifests when installing new manifests.

Host:
  Version:      9.0.0
  Architecture: x64
  Commit:       9d5a6a9aa4

.NET SDKs installed:
  3.1.426 [C:\Program Files\dotnet\sdk]
  6.0.136 [C:\Program Files\dotnet\sdk]
  6.0.321 [C:\Program Files\dotnet\sdk]
  6.0.428 [C:\Program Files\dotnet\sdk]
  7.0.120 [C:\Program Files\dotnet\sdk]
  7.0.410 [C:\Program Files\dotnet\sdk]
  8.0.111 [C:\Program Files\dotnet\sdk]
  8.0.307 [C:\Program Files\dotnet\sdk]
  9.0.100 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.26 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 8.0.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 9.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.26 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 8.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 9.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.32 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 5.0.17 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.26 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 8.0.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 9.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
  x86   [C:\Program Files (x86)\dotnet]
    registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
  Not set

global.json file:
  c:\Users\euju\RiderProjects\OSClient\global.json

Learn more:
  https://aka.ms/dotnet/info

Download .NET:
  https://aka.ms/dotnet/download

• The IDE (VS / VS Code/ VS4Mac) you're running on, and its versionz

Microsoft Visual Studio Enterprise 2022 (64-bit) - Current
Version 17.12.0

[euju-ms]

By the way, if I change the TargetPlatform to net9.0 then publish, then the publish succeeds.

[MIRIMIRIM]

I also experienced the same warning, but I didn't use HttpClient. And dotnet version are 8.0.404 and 9.0.100, TargetFramework is also net8.0

[dozer75]

I did get the same as well when I tried to include HttpClient and set it up in a project using AOT... Isn't HttpClient AOT compatible because of Quic dependency in .NET 8? I can verify that it does work in .NET 9, but in my current assignment we're not supposed to use non LTS .NET versions...

The message is not that intuitive either so the AOT build warnings could certainly get some improvements...

[acraven]

We have been experiencing this when building an AOT console app (to deploy as an AWS lambda function) since the release of 8.0.404. I don't recall us using HttpClient in our builds that were failing (due to MSBuildShowWarningsAsErrors), but we did produce a min-repro which was almost identical to the OP's. We have not seen the problem with 9.0.

We are faced with the following choices:
a) Pin the SDK we build on to 8.0.403 and hope this is resolved before we need an 8.x.x security patch.
b) Upgrade to 9.0 and use an STS build until the next LTS build is released.
c) Ignore the IL3000 warning and hope this does not produce a runtime error.

We've chosen option a) for the time being.

[ByronAP]

"OS Version: 10.0.23786" isn't MS QUIC only supported on Windows 11

[Evangelink]

We have a similar issue on MSTest, one of our acceptance test is starting to fail with the exact same error. Targeting net9.0 is also not triggering an issue.

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/ncl
See info in area-owners.md if you want to be subscribed.

[MichalStrehovsky]

This is a bug in the warning suppression:

runtime/src/libraries/System.Net.Quic/src/System/Net/Quic/Internal/MsQuicApi.cs

Lines 86 to 93 in 9cb3b72

	#pragma warning disable IL3000 // Avoid accessing Assembly file path when publishing as a single file
	// Windows ships msquic in the assembly directory next to System.Net.Quic, so load that.
	// For single-file deployments, the assembly location is an empty string so we fall back
	// to AppContext.BaseDirectory which is the directory containing the single-file executable.
	string path = typeof(MsQuicApi).Assembly.Location is string assemblyLocation && !string.IsNullOrEmpty(assemblyLocation)
	? System.IO.Path.GetDirectoryName(assemblyLocation)!
	: AppContext.BaseDirectory;
	#pragma warning restore IL3000

This suppresses the warning for the Roslyn analyzer when building the repo, but not in the output IL that the AOT compiler looks at.

This needs to use the UnconditionalSuppressMessageAttribute to do suppression (and drop the pragma suppression).

As for workarounds, the only thing that can be done is suppressing the warning with NoWarn and then remembering to remove the suppression once this is fixed.

[MichalStrehovsky]

Out of curiosity, why do we need to do this? I would expect DllImportSearchPath.AssemblyDirectory to have this behavior in a single-file-safe manner. Also, why do we only need this in .NET 8? (It took a while finding this place because neither main nor release/9.0 seem to have this modified probing logic)

[rzikm]

We are working on a fix, in the meantime, suppressing the warning or pinning to a previous SDK version (e.g. via global.json) is probably the best available workaround.