Add a way for the extensions hook to know what assembly it hooks to

[nohwnd]

Summary

Automatic extension registration via hook is limited does not tell the extension into which dll it registers.

This forces mstest to call GetEntryAssembly which is null in native aot.

public static void AddExtensions(ITestApplicationBuilder testApplicationBuilder, string[] arguments) => 
    testApplicationBuilder.AddMSTest(() => [Assembly.GetEntryAssembly()!]);

Look for a way to provide the hooking binary to the hook, so it can use it in a fashion similar to Assembly.GetEntryAssembly(), but without it being null in native aot.

This is also an api that is used by all extensions so it is possibly hard to change.

Background and Motivation

Proposed Feature

Alternative Designs

Similar issue and the aot reasoning is mentioned in #4312 but providing arbitrary assemblies externall is not a goal of this change. Instead the api should just answer the question:

I am installing as extension into a dll, what is that dll?

[Evangelink]

I would instead push strongly to have explicit Program.cs and registration. The auto-generated is to me only a "temporary" solution to ease transition from VSTest. This is a common .NET pattern and by making things explicit and available to the devs it's simplifying many scenario (even the simple is main even reached before a crash)

[nohwnd]

I do agree with you (As I said in the original issue). But even the automatic temporary solution could work more correctly, instead of us "guessing" what the dll that we are registering into is.

[Youssef1313]

Note: xUnit has this part too deep from the entry point.

https://github.com/xunit/xunit/blob/018bb24c6117d0d28b7225bf6da9120b8e189164/src/xunit.v3.runner.inproc.console/TestingPlatform/TestPlatformTestFramework.cs#L240

So even with an explicit entry point, the only way to change the assembly in xUnit is calling Assembly.SetEntryAssembly(myAssembly) at the beginning of entry point.

[Evangelink]

I would vote for closing this issue for now, we can revisit if we get requests.