MVP Communication between presenters?

Personally i disagree the way many people choose event bus to solve this kind of problems

It's hard for me to imagine a case when two presenters need to communicate each other, can you provide a real case?

In my opinion if two presenters need to communicate each other then you should merge these two in just one single presenter. Remember that also communication of models object between two use cases is business logic so maybe the scope of the presenter is bigger than you thought initially.

Consider also that if you use collaborators in the right way then you don't need communication between presenters. Data should be provided by collaborators.

The pattern itself doesn't really prescribe how to handle this.

My own preference is a message/event hub where presenters can register interest in certain events. It prevents complex dependency trees and keeps the presenters testable.

For example:

class PresenterA
{
   void HandleProductSelectionChanged(int productId)
   {
      EventHub.Publish(EventType.ProductChanged, productId);
   }
}

class PresenterB
{
    void PresenterB
    {
       EventHub.Register(EventType.ProductChanged, HandleProductChanged);
    }

    public void HandleProductChanged(object state)
    {
       var productId = (int)state;
       var productDetails = LoadProductDetails(productId);
       view.DisplayProductDetails(productDetails);
    }
}

EventHub would keep a list of subscribers to invoke for each event type.

You retain your testability - simply call on HandleProductChanged to see how PresenterB would respond to a new product selection.

The only disadvantage (as with any pattern) is you introduce a level of indirection. If PresenterA directly invoked PresenterB, or PresenterB listened to an event on PresenterA, it is immediately obvious what's going to happen.

In this approach, you would have the extra step seeing EventType.ProductChanged, and then finding which Presenters registered an interest in that event.

In my own experience, that single level of indirection is well worth modularity you get.