default $direction="" arguments of Rel_() call are not working

[kirchsth]

Hi @Potherca, @adrianvlupu,

I checked the Rel_() definitions with the default argument $direction=""

!unquoted procedure Rel_($alias1, $alias2, $label, $direction="")
!unquoted procedure Rel_($alias1, $alias2, $label, $techn, $direction="")

and

1. they are not working with default values (if $direction is "" an invalid PlantUML syntax is created, you can test it in sample below)
2. if you use Rel_() with 4 arguments it is not clear if it uses the first or second definition.

I checked all combinations

@startuml
!include https://raw.githubusercontent.com/plantuml-stdlib/C4-PlantUML/master/C4_Container.puml

Person(personAlias, "Label", "Optional Description")
Container(containerAlias, "Label", "Technology", "Optional Description")
 
' C4.puml has two active Rel_ definitions (both with $direction default values)
' !unquoted procedure Rel_($alias1, $alias2, $label, $direction="")
' !unquoted procedure Rel_($alias1, $alias2, $label, $techn, $direction="")

' first Rel_ with $direction default value is not working
' creates "personAlias containerAlias: **Label**" and this produce "Syntax Error?"
' Rel_(personAlias, containerAlias, "Label")

' first Rel_ with concrete $direction is working (and used, means second Rel_ with default value of $direction is ignored)
Rel_(personAlias, containerAlias, "Label", "<-->")

' second Rel_ with $direction default value is not working
' creates "personAlias http containerAlias: **Label**" and this produce "Syntax Error?"
' Rel_(personAlias, containerAlias, "Label", "http")

' second Rel_ with concrete $direction is working (and used)
Rel_(personAlias, containerAlias, "Label", "http", "<<-->>")

' correct Rel_ definitions are without default values 
' !unquoted procedure Rel_($alias1, $alias2, $label, $direction)
' !unquoted procedure Rel_($alias1, $alias2, $label, $techn, $direction)
@enduml

at 2. first definition is used.

Therefore I think we should remove all default values (and extend only the second Rel_ in the future, if required).
Is my assumption correct or have I overseen something?

BR Helmut