5.5 List Attributes

All properties have some optional attributes. Which attributes can be used depends on the type of the property. Attributes can either be single value attributes or they can have multiple values. In the latter case, we call them list attributes.

All list attributes are marked as such in the syntax reference. When using an attribute inside a property context, it is important to understand whether it is a list attribute or not. In many cases, the attribute name already indicates that the attribute may have a list of values. E. g. flags or limits.

The multiple values of the list attributes can either be specified as a comma separated list or by using multiple attribute statements in the same context. In this example, the task has the flags f1, f2 and f3 assigned. The second flags attribute does not override the first value. It will append the new ones to the old list.

task "T1" {
  flags f1
  flags f2, f3
}

Special care needs to be taken when list attributes are inherited by the enclosing property or by the parent scenario.

task "T2" {
  flags f1
  task "T3" {
    flags f2
  }
}

In this example, task T3 has the flags f1 and f2 assigned.

The same works for scenarios as well. Even though the syntax may not look like inheritance is at play, the scenario s2 inherits all values from s1.

project "List attributes" 2014-04-06 +1m {
  scenario s1 "S1" {
    scenario s2 "S2"
  }
}
task "T4" {
  s1:flags f1
  s2:flags f2
}

In scenario s2 the task T4 has the flags f1 and f2 assigned.

Sometimes this inheritance is not desired. In these cases, you can explicitly purge the attribute list before assigning new values. Here, task T6 only has the flag f2 assigned.

task "T5" {
  flags f1
  task "T6" {
    purge flags
    flags f2
  }
}