Auto injecting struct fields about go-inject

[Monnoroch]

Option number one:

AutoInjectModule(new(MyServer),
  // This argument is a mapping of field names to annotations.
  // Omitted fields imply inject.AutoInject annotation.
  struct {
    AuthClient Auth
    FrontendClient Frontend
  }{}
) 

This method implies that the user defines how to provide a type, not the type's author. This method makes it possible and natural to separate the type and the module for providing it into two separate libraries and encourages to have multiple modules for providing the same type for different purposes.

This method requires the user to know the internals of the type and the user's code will break when they change.

[Monnoroch]

Option number two (thanks @GeniyX):

type MyServer struct {
  AuthClient grpc.Client
  // ${Field}Annotation field declares the annotation for the ${Field} field.
  // Omitting this field implies inject.AutoInject annotation.
  AuthClientAnnotation Auth
  FrontendClient grpc.Client
  FrontendClientAnnotation Frontend
}

Optionally, allow annotation fields to be private, which is possible.

This method implies that there is only one canonical way to provide a type, that the type's author pre-defined for everyone. It's still possible to write a custom provider to override this though.

This method is consistent with annotation providers, that have to be named ProvideAnnotaionXxx as opposed to ProvideXxx in normal providers.

[Monnoroch]

Option number three:

/// Implement this interface to make the type auto-injectable.
type AutoInjectable interface {
   /// Returns a mapping of field names to annotations.
   /// Omitted fields imply inject.AutoInject annotation.
   /// Not implementing this method implies all fields having inject.AutoInject annotation.
   ProvideAutoInjectAnnotations() interface{}
}

func (self MyServer) ProvideAutoInjectAnnotations() interface{} {
  return struct {
    AuthClient Auth
    FrontendClient Frontend
  }{}
}

This method implies that there is only one canonical way to provide a type, that the type's author pre-defined for everyone. It's still possible to write a custom provider to override this though.

This method can be used together with the first method: the interface implementation will define the default way to provide the type and the user will be able to override specific fields.

[Monnoroch]

It was decided to implement (1) as the most generic approach and (3) for non-general-purpose libraries.