Generate extensions from CsWin32 that simplify use

[dahall]

@AArnott I've been supporting an alternate, wrapper-based, Win32 library for over a decade, Vanara. Its main purpose is to make Win32 feel more like C# without wrapping it so heavily that following the C++ samples is difficult. I've been working recently on generators that take native API calls and automatically generate extension methods. After years of standing independent from this project, I'm exploring how I could do this extension generation instead for CsWin32. I have a few questions as I get started:

1. I've been through the source for CsWin32 and win32metadata and understand the basic flow. Are there any high-level design docs I can reference? I'm especially interested in the attribute model being used in win32metadata that defines array counts, string lengths, etc. as these are at the heart of providing more usable wrappers/extensions.
2. I didn't find any simple way to inject an alternate generation output into the flow. I'd be interested in developing a syntactically simple way to do this in NativeMethods.txt or via a project variable (e.g. <GeneratorInjector>CsWinExtGen.dll</GeneratorInjector>). This could take the raw, typically unsafe, function or structure and morph it into something less C++ and more C#, and place that in the generation output alongside or replacing the native output.
3. In Vanara, I've provided much richer handles, safehandles, memory handlers, error handlers, and marshaling helpers. I'm interested in exploring how to introduce things like interfaces behind handles or errors in the generator. Can this even fit within the design scope? If so, how do I initiate that discussion? An example would be having something like the following be the base for HRESULT, NTSTATUS, a new Win32Errror (instead of just uint) that would allow for common processing like throwing an exception on failure.

public interface IError
{
   public HRESULT ToHRESULT();
   public bool Failed { get; }
}

Thank you. I look forward to getting involved.

[AArnott]

I'm not actively working on this project anymore. @jevansaks will have to comment on your proposal.

[jevansaks]

1. Attributes in win32metadata are lightly documented here: https://github.com/microsoft/win32metadata/blob/main/docs/projections.md. I'm hoping we can spend some time more rigorously documenting this in the next few months.
2. If you want to process the raw metadata and not use any of cswin32's codegen, I would probably just write your own tool that uses the metadata reading APIs and do it yourself. If you find .NET's metadata reader APIs a bit unfriendly, check out AsmResolver. CsWin32 doesn't have any extensions like that. But with the new CsWin32RunAsBuildTask mode, you can have other source generators work on cswin32's generated source. So that could be a way to extend the output without needing hooks in cswin32 specifically.
3. I'd recommend proposing some of the ideas as new issues on the repo and we can discuss them and get other input from the community.