[MacPorts] #68662: Ensure the default dependency is active, not a path-based alternative

[MacPorts]

#68662: Ensure the default dependency is active, not a path-based alternative
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  Reporter:  ryandesign     |      Owner:  admin@…
      Type:  defect         |     Status:  new
  Priority:  Normal         |  Milestone:
 Component:  buildbot/mpbb  |    Version:
Resolution:                 |   Keywords:
      Port:                 |
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Comment (by ryandesign):

 Well then limit my remarks to those `path:`-based depspecs that do refer
 to files installed by ports, i.e. most cases.

 If we say that icu dependents must not use `path:`-based depspecs, that
 makes life much more difficult for the maintainer of the icu ports who
 might like to test building a variety of ports against a new version of
 icu-devel to verify they still work before updating the icu port.

 We don't intend the buildbot to exactly mirror what happens on a user
 system. If we did, we wouldn't bother deactivating all but essential deps
 before a build. But we do that to avoid the pretty common problem that
 some ports can't build with certain other ports active, or that some ports
 might opportunistically use other ports that they don't declare
 dependencies on. By having only the declared deps active on the buildbot,
 we avoid a whole set of build problems, and can then publish binaries
 which users use, and then they won't experience those problem either. This
 is good for the user. We could have the buildbot do the same for
 `path:`-based deps to avoid the inevitable situation where ports that were
 presumed to be drop-in replacements turn out not to be. Consider any
 number of cases where a new version of software may behave differently
 from the old version in some way that causes a build failure for another
 port.

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Ticket URL: <https://trac.macports.org/ticket/68662#comment:3>
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