> On Dec 7, 2016, at 11:04 AM, Joshua Root <j...@macports.org> wrote: > > On 2016-12-8 03:07 , Ryan Schmidt wrote: >> >>> On Dec 7, 2016, at 4:20 AM, René J.V. Bertin <rjvber...@gmail.com> wrote: >>> >>> 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 ${pv}, and thus on port:python35? Are those >>> declaration scopes somehow evaluated outside of the loop? That hypothesis >>> is supported by the error that's raised when I unset pdv and pv immediately >>> after the loop. > > This is almost exactly the same situation as: > > foreach foo {bar baz} { > proc p_$foo {} { > puts $foo > } > } > p_bar > p_baz > > Try it in tclsh. (Variants are slightly different only in that they > automagically bring all global variables into scope. Thus you get pv with its > current value instead of a "no such variable" error.) > >>> 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. >> >> The boost port shows a typical example of using "eval" and "subst" to ensure >> the variable values are substituted immediately. > > That sounds overly complicated (there should be almost no reason to use eval, > ever.) Quotes instead of braces would allow variable substitution in the > variant body.
I agree, it sounds overly complicated to me too, but it is at least a block of code that has been tested by someone and added to many ports and seems to work.
