Add option to fail on ambiguous service resolution

[jvmlet]

Problem Statement

Consider the below registrations :

builder.RegisterType<PostalServiceSender>().As<ISender>();
builder.RegisterType<EmailNotifier>().As<ISender>();
builder.RegisterType<AnotherService>();

class AnotherService{
  public AnotherService(ISender sender){
  }
}

It's impossible to determine which sender will be injected into AnotherService

Desired Solution

Please provider an option to fail the ambiguous dependency resolution when creating the container

[tillig]

It's not impossible to determine - last registration made wins. In your example it'll always be the EmailSender. See documentation here.

This is common/well-known behavior for DI containers. We won't be adding an option to fail if there are multiple potential matches.

[jvmlet]

last registration made wins

Well, if its added by assembly scanning?

About common - spring fails such injection

[tillig]

If you need to control it, don't scan. There are trade offs. For example, in an ASP.NET project the order controllers are registered doesn't matter because you never have to resolve one IController, so scanning is great. In other cases you need to control it, so blanket "scan and register as all implemented interfaces" isn't good. Be more strategic with your registration methods.