dnf replacing yum and dnf-yum
Richard Hughes
hughsient at gmail.com
Wed Apr 8 08:55:43 UTC 2015
On 7 April 2015 at 17:37, Adam Williamson <adamwill at fedoraproject.org> wrote:
> This is easier said than done. We don't have a perfect dependency
> checker and it's not at all easy to write one.
>From someone that's actually written a yum-compatible dependency
checker in C several years ago[1] I can attest that the --skip-broken
flag is really only a work around for repositories being pushed while
broken, or the depsolver being broken by design. We tried using
--skip-broken by default in PackageKit a few years ago and it was
basically a disaster.
A "simple" iterative depsolver like yum has needs so many special
cases that it becomes a maze of code making pretty random decisions,
requiring spurious manual deps added to packages when upgrade issues
were found. Ten years ago cleverer people than me decided that
SAT-based solvers were the only thing that made logical sense, which
is what hawkey uses via the libsolv library. PackageKit in F22 uses
hawkey, and the code is predictable and stable, which is a long way
from what we had with the yum depsolver.
To those mis-remembering how awesome the yum depsolver was: it really wasn't.
Richard
[1] https://github.com/hughsie/zif
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