Linker removes needed runtime dependency

[swratten]

Full repro: https://github.com/swratten/docker-test just git clone and docker build

Exception at runtime:

Unhandled Exception: System.TypeLoadException: Could not load type 'Microsoft.Extensions.FileProviders.CompositeFileProvider' from assembly 'Microsoft.AspNetCore.Mvc.Razor.Extensions, Version=2.1.2.0, Culture=neutral
....
at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider provider, Type serviceType)
   at Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService[T](IServiceProvider provider)
   at Microsoft.AspNetCore.Builder.MvcApplicationBuilderExtensions.UseMvc(IApplicationBuilder app, Action`1 configureRoutes)
   at DockerTest.Startup.Configure(IApplicationBuilder app, IHostingEnvironment env) in /app/Startup.cs:line 45

Culprit removed library:

                                                             Before linking (B)   After linking (B)    Size decrease
-----------                                                  -----------          -----------          -----------
Total size of assemblies                                     69,785,560           43,704,832           37.373%   
-----------                                                  -----------          -----------          -----------
...
Microsoft.Extensions.FileProviders.Composite.dll             17,400               0                    100.000%

This is a simple barebones webapi generated through the dotnet cli

My build commands are in the dockerfile:

https://github.com/swratten/docker-test/blob/master/Dockerfile

As suggested at #314 I ran into this previous error, so I added the workaround for that issue

In the meantime, you can work around this by setting the property CrossGenDuringPublish to false.

[vitek-karas]

Even in .NET 7 wepapi projects use libraries which are not yet fully annotated for trimming, so it's possible they don't work. There has been some begining efforts in the ASP.NET repo to start annotating the libraries for trimming, but it's been slow (and difficult).

The dotnet/runtime part of the app should be trimmable, but ASP.NET libraries are a problem currently. I suggest you create a new issue in the dotnet/aspnetcore repo, updated with a project targeting .NET 7.