AspNetCoreToSwaggerGenerator and TestServer (CLI): Cannot resolve IApiDescriptionGroupCollectionProvider (.NET Core 2.0)

When executing the new AspNetCoreToSwaggerGenerator against a .NET Core 2.0 via CLI and TestServer, it cannot resolve IApiDescriptionGroupCollectionProvider:

But examining the services object, it clearly has a IApiDescriptionGroupCollectionProvider registration, even with the correct type ($1):

Also this works for the .NET Core 2.1 sample project.

Steps to reproduce:

• Open NSwag.sln
• Select NSwag.ConsoleCore as startup project and select 2.0:

• In project debug settings, use the command line args: run "MyPath\NSwag\samples\WithoutMiddleware\Sample.AspNetCore20\nswag_assembly.nswag"
• Run project with all exceptions enabled (break on all exceptions)

The same works for MyPath\NSwag\samples\WithoutMiddleware\Sample.AspNetCore21\nswag_assembly.nswag

/cc @pranavkm @rynowak any idea why this is happening?

[Ghostbird]

Found that it is the same issue solved here.

When using services.AddMvcCore() instead of services.AddMvC() in Startup.cs:ConfigureServices(), you must do:

services.AddMvcCore().AddApiExplorer()

[adam-ah]

Nice find, @Ghostbird!

For Google’s sake, if you get

InvalidOperationException: API Explorer not registered in DI.

on startup, the solution is to add

services.AddMvcCore().AddApiExplorer();

in public void ConfigureServices(IServiceCollection services)