[setup topic/libsolv] Does "obsoletes:" work?

[Ken Brown]

On 10/23/2017 7:38 AM, Jon Turney wrote:
> On 21/10/2017 21:18, Ken Brown wrote:
>> On 10/20/2017 6:24 PM, Ken Brown wrote:
>>> Have you ever tested the "obsoletes:" feature of setup/libsolv?  I 
>>> tried adding an "obsoletes:" line to setup.ini, and it didn't seem to 
>>> have any effect.
> 
> It seems I tested it back in May, so it might well have broken since :)
> 
> Here's a very small test repo I've been using for some tests:
> http://www.dronecode.org.uk/cygwin/test/x86_64/
> 
> But yes, your patch looks like it's needed for it to work correctly...
> 
>> It turns out that it *is* working (after a minor fix, attached), but 
>> not always as I expect.  Suppose A requires B and C obsoletes B.  Then 
>> the "obsoletes" statement appears to have no effect.  If I remove the 
>> dependence of A on B, then setup does propose uninstalling B and 
>> installing C.
>>
>> I guess the issue is that libsolv interprets "C obsoletes B" as 
>> "uninstall B and install C", and it won't uninstall B while something 
>> requires it.
> 
> The 'targeted' vs. 'untargeted' distinction is relevant here? Perhaps we 
> are doing the wrong one?

Maybe.  I've read and re-read the discussion of this in 
libsolv-bindings.txt, and I'm still not sure I understand it.

But here's a simpler case where "obsoletes" isn't working as I expect. 
Using your test repo, in which A requires C and obsoletes B, I start 
with none of the packages installed.  I choose B for installation 
(either interactively or on the command line), and B gets installed.  If 
I now run setup a second time, A and C get installed and B gets uninstalled.

I expected A and C to be installed on the first run.  I don't think this 
has anything to do with targeted vs. untargeted, because that 
distinction is only relevant for updating installed packages.

Ken