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

[Jon Turney]

On 23/10/2017 18:43, Ken Brown wrote:
> 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.

Yeah, the documentation is a bit impenetrable.

> 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.

I guess I had the opposite expectation (if I ask for A to be installed, 
that's what should happen, because if it insists on upgrading it behind 
my back there's no way to do that...)

The actual behaviour you mention fits what's described there pretty well.