Consider making ICarterModule.AddRoutes a static abstract method

[mariusz96]

Hi,

Being accustomed to controllers I installed Carter and ran into an issue similar to these when injecting a scoped service into a module's constructor threw an exception:

• Registering modules as Singleton is causing problems #279
• ICarterModule as Singleton services? #288
  .

And I also think that this unknowingly affects many people who inject transient services (ie MediatR library) into a module's constructor.

It appears to me that with an interface like this:

public interface ICarterModuleV2 // Naming things is hard.
{
    static abstract void AddRoutes(IEndpointRouteBuilder app);
}

this could be completely avoided and AddRoutes could still be called through reflection (easy, less efficient) or a source generator (hard, as efficient as hard-coded by a dev).

What do you think? Would this be a worthwhile addition?

EDIT: Turns out there's even a tutorial for this exact source generator: https://dev.to/joaofbantunes/mapping-aspnet-core-minimal-api-endpoints-with-c-source-generators-3faj.

[jchannon]

As #279 says, you shouldn't be injecting services into your classes constructors, minimal API does not work like that. They should be in the RequestDelegate

public class MyModule : ICarterModule
{
    public void AddRoutes(IEndpointRouteBuilder app)
    {

        app.MapGet("/home", IService service => {
          
          var result = service.Foo();
          
          return Results.Ok(result);
        });
   }
}

[mariusz96]

As #279 says, you shuldn't be injecting services into your cla*** constructors, minimal API does not work like that. They sh*uld be in the RequestDelegate

public cla** MyModule : ICarterModule
{
    public void AddRoutes(IEndpointRouteBuilder app)
    {

        app.MapGet("/h*me", IService service => {
          
          var result = service.Foo();
          
          return Results.Ok(result);
        });
   }
}

Yes, I understand that. But with a static abstract method: static abstract void AddRoutes(IEndpointRouteBuilder app), using a dependency injected into a constructor would not even compile. So it would prevent me from making an error and enforce correct usage.

Which is good for a library interface, no?

[jchannon]

I agree but making a method on an interface abstract static is not going to cause a compiler error if a class implements it and injects something into a constructor

…

On Sat, 18 May 2024 at 20:03, Mariusz Stępień ***@***.***> wrote: As #279 <#279> says, you sh*uldn't be injecting services into your cla**** constructors, minimal API does not work like that. They sh*uld be in the RequestDelegate public cla** MyModule : ICarterModule{ public void AddRoutes(IEndpointRouteBuilder app) { app.MapGet("/h*me", IService service => { var result = service.Foo(); return Results.Ok(result); }); }} Yes, I understand that. But with a static abstract method, using a dependency injected into a constructor would not even compile. So it would prevent me from making an error and enforce correct usage. Which is good for a library interface, no? — Reply to this email directly, view it on GitHub <#338 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAAZVJTWIPQE2M3W7RPJZBTZC6QYLAVCNFSM6AAAAABEZGK6J6VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDCMJYHE3TGOBYGQ> . You are receiving this because you commented.Message ID: ***@***.***>

[jchannon]

I've had a play and making the interface have the abstract static method would be an aid to help this.

As it's a breaking change I will do this for .NET9. For now I will add some XML docs as a pointer not to inject dependencies into classes.

What it will look like:

/// <summary>
/// An interface to define HTTP routes
/// </summary>
/// <remarks>Implementations of <see cref="ICarterModule"/> should not inject constructor dependencies. All dependencies should be supplied in the route <see cref="RequestDelegate"/></remarks>
public interface ICarterModule
{
    /// <summary>
    /// Invoked at startup to add routes to the HTTP pipeline
    /// </summary>
    /// <remarks>Implementations of <see cref="ICarterModule"/> should not inject constructor dependencies. All dependencies should be supplied in the route <see cref="RequestDelegate"/></remarks>
    /// <param name="app">An instance of <see cref="IEndpointRouteBuilder"/></param>
    static abstract void AddRoutes(IEndpointRouteBuilder app);
}

[jchannon]

@mariusz96 can you test the latest Carter version, it has an analyzer that warns if you have constructor dependencies 😄