IL206/ IL2070/IL2090 Linker errors when trimming/AOTing around enums

[blowdart]

Description

When attempting to run an aot/trimming test program I get unexpected trim analysis errors around enums, and around a suppressed line of code.dotnet

Reproduction Steps

See https://github.com/blowdart/idunno.Bluesky/tree/il2070-2090-issue

Clone and run .\trimTest.ps1

Expected behavior

Code compiles, links (respecting suppressions in JsonOptions.cs) and produces trimmed AOT executable.

Actual behavior

Errors on linking

  idunno.TrimmingTest failed with 5 error(s) (9.5s) → trimming\bin\Release\net8.0\win-x64\idunno.TrimmingTest.dll
    Optimizing assemblies for size. This process might take a while.
    G:\idunno.Bluesky\src\idunno.AtProto\JsonOptions.cs(42,13): Trim analysis error IL2026: idunno.AtProto.JsonOptions.CreateDefaultTypeResolver(): Using member 'System.Text.Json.Serialization.Metadata.DefaultJsonTypeInfoResolver.DefaultJsonTypeInfoResolver()' which has 'RequiresUnreferencedCodeAttribute' can break functionality when trimming application code. JSON serialization and deserialization might require types that cannot be statically analyzed. Use the overload that takes a JsonTypeInfo or JsonSerializerContext, or make sure all of the required types are preserved.
    ILLink : Trim analysis error IL2090: System.Text.Json.Serialization.Converters.EnumConverter<T>.ResolveEnumFields(JsonNamingPolicy): 'this' argument does not satisfy 'DynamicallyAccessedMemberTypes.PublicFields' in call to 'System.Type.GetFields(BindingFlags)'. The generic parameter 'T' of 'System.Text.Json.Serialization.Converters.EnumConverter<T>' does not have matching annotations. The source value must declare at least the same requirements as those declared on the target location it is assigned to.
    ILLink : Trim analysis error IL2070: System.Text.Json.Serialization.Converters.EnumConverterFactory.Create(Type, EnumConverterOptions, JsonNamingPolicy, JsonSerializerOptions): 'this' argument does not satisfy 'DynamicallyAccessedMemberTypes.PublicParameterlessConstructor' in call to 'System.Type.MakeGenericType(Type[])'. The parameter 'enumType' of method 'System.Text.Json.Serialization.Converters.EnumConverterFactory.Create(Type, EnumConverterOptions, JsonNamingPolicy, JsonSerializerOptions)' does not have matching annotations. The source value must declare at least the same requirements as those declared on the target location it is assigned to.
    ILLink : Trim analysis error IL2070: System.Text.Json.Serialization.Converters.NullableConverterFactory.GetNullableConverterType(Type): 'this' argument does not satisfy 'DynamicallyAccessedMemberTypes.PublicParameterlessConstructor' in call to 'System.Type.MakeGenericType(Type[])'. The parameter 'valueTypeToConvert' of method 'System.Text.Json.Serialization.Converters.NullableConverterFactory.GetNullableConverterType(Type)' does not have matching annotations. The source value must declare at least the same requirements as those declared on the target location it is assigned to.
    G:\Users\BarryDorrans\.nuget\packages\microsoft.net.illink.tasks\8.0.14\build\Microsoft.NET.ILLink.targets(87,5): error NETSDK1144: Optimizing assemblies for size failed.

Build failed with 5 error(s) and 1 warning(s) in 14.1s

Regression?

No response

Known Workarounds

No response

Configuration

.NET SDK:
 Version:           9.0.201
 Commit:            071aaccdc2
 Workload version:  9.0.200-manifests.5c4e24dc
 MSBuild version:   17.13.13+1c2026462

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.26100
 OS Platform: Windows
 RID:         win-x64
 Base Path:   C:\Program Files\dotnet\sdk\9.0.201\

Host:
  Version:      9.0.3
  Architecture: x64
  Commit:       831d23e561

.NET SDKs installed:
  7.0.302 [C:\Program Files\dotnet\sdk]
  9.0.201 [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 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 8.0.14 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 9.0.3 [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 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 8.0.14 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.NETCore.App 9.0.3 [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 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 8.0.14 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
  Microsoft.WindowsDesktop.App 9.0.3 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
  arm64 [C:\Program Files\dotnet]
    registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\arm64\InstallLocation]
  x86   [C:\Program Files (x86)\dotnet]
    registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
  Not set

global.json file:
  Not found

Other information

@eiriktsarpalis Here's the pared back repo :)

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-text-json, @gregsdennis
See info in area-owners.md if you want to be subscribed.

[eiriktsarpalis]

For the trimmer you need to use UnconditionalSuppressedMessage instead of SuppressMessage.

[blowdart]

Hah, that solves that part of it, but the IL2090 / IL2070 on the enums remains, or do I supress those over every enum as well?

[MichalStrehovsky]

The problem is that this ends up using a .NET 8 ILLink against a .NET 9 System.Text.Json. The .NET 8 ILLink doesn't consider the .NET 9 System.Text.Json trim safe due to the problems I break down below. There's not much the user can do: the warnings only go away if the idunno.TrimmingTest project is updated to .NET 9 (except for the one warning in iDunno, which needs to be fixed in iDunno).

Looks like we don't analyze assemblies that ship OOB in .NET vCurrent with vPrevious ILLink when we build them for vPrevious in dotnet/runtime. Maybe we accidentally override the trim analyzer with the live ILLink analyzer instead of just using the ILLink analyzer that ships with the respective framework version? Cc @dotnet/illink

The issues are:

• System.Text.Json.Serialization.Converters.EnumConverter<T>.ResolveEnumFields requires Do not warn when accessing fields on T constrained to be enum #100814 to not warn and that feature only exists in .NET 9+. The code would be trim safe before that PR too, but that PR is the thing that makes this not warn. Would be fixable by just suppressing the warning under !NET9_0_OR_GREATER in the S.T.Json source (the justification is that public static fields on enums are always preserved).
• The System.Text.Json.Serialization.Converters.EnumConverterFactory.Create and System.Text.Json.Serialization.Converters.NullableConverterFactory.GetNullableConverterType warnings are from Fix warning for MakeGenericType annotation mismatch #104921. We did a mild breaking change in what warning code is generated. That PR also updated the suppression in S.T.Json. We'd also need an ifdef to use the old warning code for < .NET 9.0.

[blowdart]

Well, I can't update the projects to 9, as I specifically want to support 8.

So no trimming it is then.

[MichalStrehovsky]

Well, I can't update the projects to 9, as I specifically want to support 8.

To be clear only the idunno.TrimmingTest project needs to be updated to 9.0 work around this.

[eiriktsarpalis]

@MichalStrehovsky is there anything actionable we can do w.r.t. .NET 8 servicing? Or should I just close this?

[MichalStrehovsky]

@MichalStrehovsky is there anything actionable we can do w.r.t. .NET 8 servicing? Or should I just close this?

This is fixable, the instructions are in my previous comment. But the shiproom is going to ask whether we're sure that's all that's needed to fix and the answer will be we don't know unless the other fix (on the side of how we run illinker analyzer) is also done. I CC'd @dotnet/illink because that's where the expertise is. I can help if needed.

[agocke]

@sbomer can you take a look as well?

[sbomer]

Based on @MichalStrehovsky's analysis I think we should fix this by suppressing the warnings as mentioned. I'm looking into fixing the analyzer version used for OOBs in #114983.