NuGet Product(s) Involved

dotnet.exe

The Elevator Pitch

The dotnet CLI would like to compile and distribute itself as a Native AOT application (dotnet/sdk#49667), to take advantage of faster startup times and eliminate unnecessary CoreCLR startup overhead. To do this, we need our partner libraries and tools to be AOT/Trimming compatible. While doing initial testing we found that several libraries that we use report trimming warnings, and we'd like to request that a future version of those libraries be made trim-compatible.

The namespaces that we use that would need to be compatible are:

• NuGet.Client
• NuGet.Common
• NuGet.Configuration
• NuGet.ContentModel
• NuGet.Credentials
• NuGet.DependencyResolver
• NuGet.Frameworks
• NuGet.LibraryModel
• NuGet.Packaging
• NuGet.Packaging.Core
• NuGet.Packaging.Signing
• NuGet.ProjectModel
• NuGet.Protocol
• NuGet.Protocol.Core.Types
• NuGet.Repositories
• NuGet.RuntimeModel
• NuGet.Versioning

I took a look at NuGet.Client myself, and broadly saw three areas of work while investigating the impact of marking libraries "IsAotCompatible=true":

• Assembly loads to get dll version information for NuGet libraries themselves
• Json serialization that is reflection-based instead of source-generated
• A complex version-property setting scheme that uses a delegate for the PackArgs type that I didn't see a good way to work around

In addition, I believe that making these libraries Trimming-compatible would require having a new .NET-specific TFM. While that would make ifdefs, etc more cumbersome, I think it might be a blessing in disguise as that would mean you could potentially limit any breaking API changes to the new TFM only.

There may be more items, however, as I am not fully up to speed on the NuGet codebase.

Additional Context and Details

There are some helpful resources that I found:

• .NET Blog post describing how to make libraries AOT-compatible
• List of trimming incompatibilities
• Native AOT docs root
• My hacked-up fork of NuGet.Client demonstrating some of the changes

To sweeten the pot a bit, we need NuGet libraries to be AOT-able in order to make a fully-native tool that can fill the role of dnx - using NuGet APIs to interact with feeds, manage packages, etc. With this, we can make .NET SDK Tools super easy to use, without dragging in the whole SDK payload.