Dependency Injection: Keyed services returned for non-keyed resolution

[kmcclellan]

Description

The relatively new feature of keyed services seems to have a bug. I would not expect a keyed service to be returned from the non-keyed call to IServiceProvider.GetServices<T>() extension method.

Reproduction Steps

using Microsoft.Extensions.DependencyInjection;

var services = new ServiceCollection();
services.AddKeyedTransient<TestProcessor>("test123");

await using var provider = services.BuildServiceProvider();

for (var i = 0; i < 10; i++)
{
    var processors = new List<TestProcessor>();

    // Common pattern for combining both specific and global logic.
    processors.AddRange(provider.GetKeyedServices<TestProcessor>("test123"));
    processors.AddRange(provider.GetServices<TestProcessor>());

    // Only a single processor is registered, so this should always be 1?
    Console.WriteLine("Processor count: {0}", processors.Count);

    // Not sure why the delay makes a difference, but it does.
    await Task.Delay(1);
}

sealed class TestProcessor
{
}

Expected behavior

The number of processors resolved should be consistent with each invocation. The number of processors resolved should equal one.

Actual behavior

Processor count: 1
Processor count: 1
Processor count: 1
Processor count: 1
Processor count: 2
Processor count: 2
Processor count: 2
Processor count: 2
Processor count: 2
Processor count: 2

Regression?

Does not appear to be a regression (reproducible with Microsoft.Extensions.DependencyInjection v8.0.0).

Known Workarounds

No response

Configuration

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net9.0</TargetFramework>
    <Nullable>enable</Nullable>
    <ImplicitUsings>enable</ImplicitUsings>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="9.0.2" />
  </ItemGroup>

</Project>

.NET SDK 9.0.102
Windows 11 10.0.26100

Other information

No response

[dotnet-policy-service]

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

[KalleOlaviNiemitalo]

This seems a duplicate of #111795. Workaround:

AppContext.SetSwitch("Microsoft.Extensions.DependencyInjection.DisableDynamicEngine", true);