declaring variants/subports in loops and loop variables

[René J.V. Bertin]

Hi,

See https://trac.macports.org/ticket/53022#comment:2

I'm still waiting for the final verdict from the ticket reporter, but it seems that issue was one of those cases where I shouldn't have used a loop variable in the declaration scope of a variant (nor subport):

{{{
set pythonversions {3.4 3.5}
foreach pdv ${pythonversions} {
    set pv [join [lrange [split ${pdv} .] 0 1] ""]
    # snip
    variant python${pv} description "Add bindings for Python ${pdv}" {
        depends_libs-append port:python${pv}
        # snip
    }
}
}}}

Why is it that this makes both the +python34 and +python35 variants depend on the last value of ${pv}, and thus on port:python35? Are those declaration scopes somehow evaluated outside of the loop? That hypothesis is supported by the error that's raised when I unset pdv and pv immediately after the loop.

If so, is there a cleaner and not much more complex way to do loop-based variant/subport declaration such that at least the loop variables are undefined outside of the loop? Unsetting the variables works but isn't very elegant and too easy to forget. 

R.