On Nov 27, 2013, at 09:39, Peter Danecek wrote:
> recently when I was upgrading `qgis`, I realised that its dependency on
> `py2?-pyqt4-devel` potentially causes conflicts which are not easily resolved
> by users.
>
> qgis depends on `port:py2?-pyqt4-devel`, while most other ports depend
> explicitly on `port:py2?-pyqt4`. There are few ports (python/py-matplotlib &
> science/gnuradio) which use `path:*` so their dependency is resolved by both.
>
> Now, I imagine that qgis' dependency is due to some specific feature which
> the port requires. Maybe Vincent could confirm this is the case. But I
> imagine that py2?-pyqt4-devel would satisfy the requirements of all other
> dependents of py2?-pyqt4 as well.
>
> So are there any objections to implement such changes?
At present, if there is more than one port that can satisfy a dependency, other
ports should declare a dependency on those ports using a path:-style depspec.
> Side question / discussion:
>
> I have limited understanding of the Macports base, but I wonder if it would
> be to difficult to implement a mechanism which would allow to specify several
> alternative ports instead of the `path:` syntax. What I have in mind is
> something like this:
>
> depends_lib-append {port:py27-pyqt4 port:py27-pyqt4-devel}
>
> in analogy to the license specification. If any of the dependencies in the
> braces exist, this dependency would be satisfied, if not the first is
> installed.
>
> An alternative solution to this generic problem could be to specify in the
> `py2?-pyqt4` port itself that it could be substituted (not "replaced") with a
> (set of) other ports (here: py2?-pyqt4-devel). At the condition that any of
> these ports is already installed, dependents would use that port instead.
> This would avoid to have to change a potentially large set of dependent ports
> in case an alternative port becomes available and I have the impression that
> part of the logic can be shared with `replaced_by`. But again, unfortunately
> I do know to little about base and registry.
You’re talking about https://trac.macports.org/ticket/16336 . Yeah, that would
be nice. Until we have it, though, path:-style dependencies are what we have to
use.
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