On Friday 05 February 2010 04:43:05 Hideki Yamane wrote: > > This is true in general, although it's perhaps worth noting that a rare > > pre- depends on a priority required package like debconf by a priority > > optional or extra package isn't likely to cause any trouble. > > Yes, it is true in general but I want to know the example for that :) > For example, if I have foobar package and it says "Pre-Depends: > debconf", what would happen?
Short answer: nothing, it would work fine in practice. Long answer: Debconf would be required to be fully unpacked and configured before foobar could even be unpacked. But, since debconf is priority "required", and is already depended on by so many other packages that it's infeasible that it won't already be completely installed, the pre-depends would be a no-op. In the rare case that debconf wasn't already installed, it would simply be unpacked and configured first, which might slow down the resolver (and hence installation) but otherwise would be no problem. However, it is possible that you can dream up a bizarre corner case where you are pre-depending on a specific version, your doing a big dist-upgrade, the foobar package has a pre-depends and so do a bunch of other packages that are intertwined in foobar's dependency graph, and the whole thing explodes in a big unresolvable mess. The last paragraph is incredibly unlikely for just foobar pre-depending on debconf that's you'd have to come up with some silly scenerio to show it breaking, but if pre-depends were used all over the place on lots of packages, that kind of scenerio could happen really quickly, which is why they are generally to be avoided. I think the general idea is: 1) Don't use pre-depends. 2) No, really, don't use pre-depends. 2) Don't use pre-depends unless it's the best technical solution. =)
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