[MacPorts] #51619: qt5.depends_component procedure

[MacPorts]

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

Comment (by RJVB):

 I wouldn't commit anything just yet, in any event I won't have an occasion
 to take a detailed look until Monday. OTOH, if this is just to introduce
 qt5.depends_component and you don't mind making adjustments later, then
 fine. There will be more commits on the PortGroup level anyway, including
 for instance a mechanism by which (KF5) ports can express a preference for
 qt5-kde .

 There is discussion going on on the devel ML ("Re: port:libressl vs
 port:openssl, path-style variants and prebuilt binaries") which evokes
 among other things the idea of adaptive depspecs. You should have seen it,
 and that Mojca is apparently rather on the same page as I am concerning
 the depspecs and (automatic) variant.

 > qt5 PG provides qt5kde variant (unless Portfile opts out).

 Doesn't that means you can no longer prevent installing with qt5-kde
 installed? No variant provided means you cannot NOT set it and that seems
 counterproductive (opting out seems of interest only as a way to say "I
 don't work with that port").

 > if qt5kde is not selected
 > > path dependency on Qt component is used so qt5-kde could still satisfy
 dependency

 If that's not done with adaptive depspecs I will have to rectify that in
 the KF5 PG, idem with the preference mechanism. That'd be a shame, for
 functionality that should be provided at the Qt5 PG level.

 > every Qt component (e.g. qt5*-qtmultimedia) explicitly depends on
 qt5*-qtbase (not a path dependency)

 Not the qt5-kde-* ports; those evidently depend on qt5-kde (including the
 stub qt5-kde-qtbase port).

--
Ticket URL: <https://trac.macports.org/ticket/51619#comment:29>
MacPorts <https://www.macports.org/>
Ports system for macOS