Trying to register additional types in a command interceptor

[0xced]

I'm trying to register an IDbContextFactory<MyContext> from within a command interceptor to make it available to my commands.

Here's my interceptor:

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Spectre.Console.Cli;

public class InjectionInterceptor : ICommandInterceptor
{
    private readonly ITypeRegistrarFrontend _registrar;

    public InjectionInterceptor(ITypeRegistrarFrontend registrar)
    {
        _registrar = registrar ?? throw new ArgumentNullException(nameof(registrar));
    }

    public void Intercept(CommandContext context, CommandSettings settings)
    {
        if (settings is DatabaseSettings databaseSettings)
        {
            var dbContextOptions = new DbContextOptionsBuilder<MyContext>().UseSqlServer(databaseSettings.ConnectionString).Options;
            var dbContextFactory = new PooledDbContextFactory<MyContext>(dbContextOptions);
            _registrar.RegisterInstance<IDbContextFactory<MyContext>>(dbContextFactory);
        }
    }
}

And here's how I'm using it:

var app = new CommandApp();
app.Configure(config =>
{
    // ...
    config.SetInterceptor(new InjectionInterceptor(config.Settings.Registrar));
});
return app.Run(args);

Unfortunately, this doesn't work because the interceptor is called after the type resolver is built.

To workaround this issue I built an abstract AsyncCommand<TSettings> base class with a protected IDbContextFactory<MyContext> DbContextFactory { get; private set; } = null!; property initialized at the very beginning of the ExecuteAsync method. It's not a bad solution but I feel that injecting the IDbContextFactory<MyContext> from the interceptor would have been a cleaner solution.

Is there another way that I could inject my IDbContextFactory<MyContext> without a base class? Would it be possible to call the interceptor before the type resolver is built? (It looks like a chicken and egg problem though. 😕)

[aa-dit-yuh]

Hi @0xced ,
Any guidance exists today?

[nils-a]

No, interceptors are called after the ITypeResolver is built.
Unless you have some strange custom implementation of ITypeRegistrar/ITypeResolver, usage of the registrar is not supported when the resolver has been built.