I hit an issue today when using the Microsoft.Z3.x64 package in a .NET 5.0 project and running the tests for my project on mac. Specifically it throws the following exception when running the tests.

Error Message:
   System.DllNotFoundException : Unable to load shared library 'libz3' or one of its dependencies. In order to help diagnose loading problems, consider setting the DYLD_PRINT_LIBRARIES environment variable: dlopen(liblibz3, 1): image not found

After probing about in MyTestProject/bin/x64/Debug/net5.0/runtimes I noticed that the z3lib.dylib was under a folder called macos and that the MyTestProject.deps.json file was pointing to this location for the macos rid. However, checking with the Microsoft documentation on which runtime identifiers are officially supported it seems that macos is not a well known value. Instead osx-x64 is the base rid for mac, as detailed here.

Also running dotnet --info on my machine reveals my specific rid to be:

Runtime Environment:
 OS Name:     Mac OS X
 OS Version:  11.0
 OS Platform: Darwin
 RID:         osx.11.0-x64
 Base Path:   /usr/local/share/dotnet/sdk/5.0.102/

It seems that NuGet generates the MyProject.deps.json rid mappings based on the folder structure in the NuGet package and that the package is installed at ~/.nuget/packages/microsoft.z3.x64/4.8.10/. Inspecting that location showed again that under the runtimes folder there was a macos folder which contained the libz3.dylib file. If I copied / renamed this folder to osx-x64, and then re-ran the tests in my project it was properly able to locate liibz3.dylib.

Therefore, I think the fix is to ensure that when the nuget package is created the libz3.dylib file is placed under osx-x64 rather than macos.

I've attempted a fix here, but I'm not completely certain I've identified the right places to ensure that the packaging is now done correctly.