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

[Ken Brown]

On 10/24/2017 4:09 PM, Jon Turney wrote:
> 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.

OK, so maybe there's no real problem here.  In any case, the situation 
is unlikely to happen often -- the user has to intentionally choose to 
install an obsolete package.

I think we might have reached the point where more widespread testing 
would be useful.  If it would help, I could put together a patch series 
containing the various (sometimes revised) patches we've discussed recently.

Ken