Resolution of native libraries when using DllImport

[antoinebj]

TL;DR: How can I make DllImport automatically load the right native library from the runtimes/<rid>/native path when it is in a project referred by ProjectReference, similar to what PackageReference enables by adding the appropriate resolution information in deps.json?

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If I create a NuGet package and put native DLLs in runtimes/<rid>/native/, the deps.json file generated for the assembly referencing that package will get runtimeTargets entries for the native libraries, allowing DllImport to find the appropriate DLLs to load. That mechanism is very useful for easily targeting multiple platforms with "Any CPU" despite reliance on native libraries that are each specific to a platform/architecture combination.

Now I would like to unit-test the classes in that package. Usually I put the unit test project in the same solution, make it refer to the project containing the classes to test. Unfortunately, that doesn't bring the mechanisms from PackageReference, as it only uses a ProjectReference. Therefore the deps.json for the unit test assembly doesn't get hints for the native libraries, and when the unit test is run, it complains about not finding the native DLLs.

A workaround would be to have a separate NuGet package containg nothing more than the native libraries, making the project containing .NET code refer to it, similar to what libgit2sharp does. However that's not convenient when updating the native libraries because it requires publishing their package before being able to test their integration in the .NET code.
I know about the NativeLibrary class where one can register a custom resolver, but that seems tedious for true multiplatform. I didn't find a simple way to replicate the RID-based resolution.

Is there any other way? Any thoughts?

[antoinebj]

I also noticed the existence of --additional-deps, but I don't know how to make unit test runners use that parameter.

[benvillalobos]

/cc: @vitek-karas

[vitek-karas]

I can only comment on the runtime side of things:

• If the info is not in .deps.json runtime won't find it - so it's up to SDK to put it there. As you noted this works for PackageReference. I don't know if or how it should for ProjectReference.
• --additional-deps won't help that much, it lets you specify additional .deps.json, but that assumes you have one. So you would have to "hand-craft" one.

[antoinebj]

This has been labeled as a question, which it is indeed, but only because I wouldn't want to make a feature request if there is already an existing solution.
If the conclusion to this question is that there is no simple solution for what I'm trying to do, then I would be inclined to request an improvement in how .deps.json is generated when PackageReference isn't involved, so as to have the same convenience for loading native libraries.

[wasabii]

I second this. Same issue. Building a .NET Core library that includes some native files (from a VCXPROJ). Works fine when I add it to the produced NuGet package: consumers generate .deps.json files referencing the libraries. However, doesn't work in a Console app within the same solution using ProjectReference, nor in a Unit Test. Though, it should. The only issue is that hte generate .deps.json files for those other projects do not fold in the native assets of the ProjectReference.

I would expect to be able to simply include Content (or None) item, and perhaps stick <AssetType>native</AssetType> onto it and have it pulled through.

[wasabii]

Digging into it, DependencyContextBuilder just seems to consider NuGet origins. Would need to fix that, as well as the associated GenerateDeps MSBuild task. And then the MSBuild targets to consider these items.

[rgebee]

Adding to this to say I have the same issue with my project Raylib-cs. Took me a while to notice the .deps.json was not including runtimeTargets so for manual installs it would fail to find the library. I am also not sure how to workaround/fix this issue so any suggestions or more information is appreciated.

[vitek-karas]

@marcpopMSFT I think this is very much an SDK issue.

• SDK needs to communicate information about RID specific assets to the runtime.
• Such communication channel already exists, it's .deps.json (it's basically the main reason why this file exists today)
• SDK will correctly populate .deps.json if the RID specific assets are coming from NuGet packages
• SDK doesn't have mechanisms to define RID specific assets in non-NuGet sources (the project itself, dependent P2P references, ...) - and inherently it doesn't have a mechanism to correctly populate this information into .deps.json

[alexrp]

• SDK doesn't have mechanisms to define RID specific assets in non-NuGet sources (the project itself, dependent P2P references, ...) - and inherently it doesn't have a mechanism to correctly populate this information into .deps.json

FWIW, having a way to do this is essential for parts of vezel-dev/zig-sdk#8 as well.

[marcpopMSFT]

@vitek-karas Isn't this an issue in deps.json creation which from our discussion, the runtime team controls (hence our decision to move it to runtime repo)?