I am trying to migrating my old drag and drop script to Godot 3 and found "input_event, mouse_entered and mouse_exited" for Area2D in not connecting.
Except CollisionObject2D events other events are working fine for Area2D.
The Script was working fine in **Godot 2.***.
Following is the sample code I used to test.
var dd = get_node("Area2D").connect("input_event",self,"_on_Area2D_input_event")
func _on_Area2D_input_event( viewport, event, shape_idx ):