[MacPorts] #53250: buildbot: weird handling of conflicting dependencies

[MacPorts]

#53250: buildbot: weird handling of conflicting dependencies
----------------------+-----------------
 Reporter:  mojca     |      Owner:
     Type:  defect    |     Status:  new
 Priority:  Normal    |  Milestone:
Component:  ports     |    Version:
 Keywords:  buildbot  |       Port:
----------------------+-----------------
 See
 https://build.macports.org/builders/ports-10.12_x86_64-builder/builds/17760

 The port `qt55-qttools` fails to build because `qt5-qtbase` gets pulled in
 somehow instead of `qt55-qtbase` and dependencies fail to activate:

 {{{
 Can't install qt55-qtxmlpatterns because conflicting ports are active:
 qt5-qtbase
 }}}

 While this is probably a bug in one of qt-related ports that warrants a
 separate ticket, I really don't like the fact that our buildbot reports
 success after only checking whether packages have already been compiled:

 {{{
 Installing dependency (1 of 49) 'libiconv' with variants '' ... [OK]
 ...
 Installing dependency (46 of 49) 'qt5-qtbase' with variants '' ... [OK]
 Installing dependency (47 of 49) 'qt55-qtxmlpatterns' with variants '' ...
 [OK]
 Installing dependency (48 of 49) 'qt55-qtdeclarative' with variants '' ...
 [OK]
 Installing dependency (49 of 49) 'qt55-sqlite-plugin' with variants '' ...
 [OK]
 }}}

 Before the recently introduced changes this would report:
 {{{
 Installing dependency (47 of 49) 'qt55-qtxmlpatterns' with variants '' ...
 [FAIL]
 }}}

--
Ticket URL: <https://trac.macports.org/ticket/53250>
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