Hi, On Thu, 22 Dec 2016 15:01:44 +0100 Johannes Schauer <jo...@debian.org> wrote: > On Mon, 17 Oct 2016 07:20:43 +0800 Paul Wise <p...@debian.org> wrote: > > * Use python-apt to do the resolution and emit `apt install pkg=1.2.3` > > commands? > > I don't see a way to achieve this with python-apt. Even when manually > iterating > through the given dependency string and checking which package in the apt > cache > satisfies the dependency, the solution would not always be correct. Here is an > example in which this approach would fail: > > Suppose there are the packages A, B, C and D. A depends on D and D conflicts > with C. Now the wants the following resolved: > > 'A | B, C' > > With the algorithm sketched above, A and C would be picked for installation > but > the solution would be invalid because A and C conflict via D. To avoid this > situation, the code has to traverse all dependency trees which would in turn > lead to the implementation of a full-fledged resolver. Certainly this is not > desired.
on IRC, juliank informed me that this approach is already implemented in
python-apt. Specifically, try to do:
$ python3 -c "import apt.debfile; a = apt.debfile.DebPackage();
a.satisfy_depends_str('nginx-light | apache2, nginx-full'); a.check();
print(a.required_changes)"
(['nginx-full'], [], [])
That result is clearly wrong because it failed to satisfy the first alternative
(nginx-light and nginx-full conflict).
On the other hand, if I hand the problem to the script I presented in my last
email, then I get a correct list including apache2 and nginx-full.
Thanks!
cheers, josch
signature.asc
Description: signature
