Subsequent mainframe overrides prior one without notice

[jeffkowalski]

The following script,

@startuml
mainframe frame1
node node1
mainframe frame2
node node2
@enduml

yields in

I would have expected a warning about the re-definition, or better, a diagram like this:

[arnaudroques]

Well, mainframe is really only a decoration (as title, legend...). It works in many diagrams and there is no semantic behind it. For example, you can even have this.

@startuml
mainframe mainframe
title title

nwdiag {
  network dmz {
      address = "210.x.x.x/24"

      web01 [address = "210.x.x.1"];
      web02 [address = "210.x.x.2"];
  }
}
@enduml

So we cannot have two mainframes decoration in a single diagram. We could display an error message on that case, but we prefer to be lazy on this one.