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

[Jon Turney <jon.turney@dronecode.org.uk>]

On 24/10/2017 21:24, Ken Brown wrote:
> 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 was wondering if there might be some scenario where A is in the base 
category, and obsoleted by B, where we'd really want to install B the 
first time on fresh installs, but, yeah, something we'd want to avoid in 
general...

> 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.
Cool, I was going to ask you how far along you were in your test plan :)

I think I've been keeping track of your patches, so I've updated 
topic/libsolv with your patches and rebased onto master.  If that looks 
good to you, I'll do test release.

(I squashed "Fix parsing setup.ini" (for obsoletes) into "Add obsoletes: 
support", and added a missing break; in "Don't override a Skip selection")