[MacPorts] #51619: qt5.depends_component procedure

[MacPorts]

#51619: qt5.depends_component procedure
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  Reporter:  RJVB          |      Owner:  mkae
      Type:  enhancement   |     Status:  assigned
  Priority:  Normal        |  Milestone:
 Component:  ports         |    Version:
Resolution:                |   Keywords:
      Port:  qt5, qt5-kde  |
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Comment (by RJVB):

 Replying to [comment:20 ctreleaven]:
 > To state the obvious, variants suck.  You all know why...only one
 variant can be the default.

 Among mutually conflicting variants, yes. More in general, only one set of
 variants can be the default.

 It would also suck if users would have to add a variant to all KF5 ports
 they might want to install (including all 60+ frameworks), or if they
 would have to use a variant to force non-KF5 ports to install against
 port:qt5-kde .

 BTW, what happens when you do

 `default_variants +foo`

 before variant foo has been defined? Will that still work, or does the
 statement have to come after the variant has been defined?


 > Thus the need for {{{require_active_variants}}} ...

 ... actually goes a bit beyond that. It can be used for any combination of
 variants required. `port:kf5-digikam` for instance requires `opencv
 +qt5+contrib`, and only +qt5 conflicts with one of the port's other
 variants.

 > Thus we only serve binaries for the default--which is pretty important
 for something as large as Qt.

 Those are actually the main arguments why Marko and I were almost relieved
 when it became clear that we'd better prepare a dedicated `port:qt5-kde`.
 It would make dependencies easier (and allow ports to express a preference
 rather than a hard requirement), but also allow the build bots to provide
 a binary build.

 > As an aside, the current implementation of {{{require_active_variants}}}
 isn't very friendly to novice users.  The word "error" is repeated several
 time while masking the actual polite message to just reinstall port foo
 with variant +bar.  My mythtv-* ports need {{{require_active_variants}}}
 and numerous times users have been convinced that the port is broken when
 they get this result.

 I suppose you're entitled to feel welcome to change the message based on
 the feedback you've gotten!

--
Ticket URL: <https://trac.macports.org/ticket/51619#comment:22>
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