setup and 'provides:'

[Ken Brown]

On 10/7/2018 6:02 PM, Ken Brown wrote:
> I've been experimenting with setup's support for the 'provides:' tag, and it's
> not behaving the way I expect [*].  I'm not sure if something in setup's
> interface with libsolv needs to be tweaked or if I'm just misunderstanding how
> this should work.  Here's what I tried:
> 
> I created a test repo with packages A, B, and C.  I made A require foo (not a
> package), and I made B and C provide foo.  The attached script does all this
> [**].  I then ran setup and selected A for installation.
> 
> The result was that libsolv simply chose B for installation, and setup showed
> this in the "Confirm" dialog.  What I expected was that libsolv would report a
> problem ("A requires foo but no selected or installed packages provide it"),
> with two possible solutions ("Install B or C").  Is that expectation unreasonable?
> 
> I plan to look into the libsolv sources to see if I can fix this, but I'm hoping
> that someone already knows the answer.

It turns out that this question has been asked before:

https://bugzilla.redhat.com/show_bug.cgi?id=1266761#c3
https://github.com/openSUSE/libsolv/issues/107

AFAICT, libsolv will by default pick the alphabetically first package 
when there are several equally good candidates to meet the requirements. 
  According to the second link I cited, "libsolv offers methods to query 
for the encountered ambiguities after the solving, so that the user can 
be presented with a list of choices and then select different packages."

I may look into this further, but I'm beginning to wonder if it's worth 
the trouble.

Ken