Subject: Re: [alpine-devel] apk and libraries that optionally replace others
To: alpine-devel@lists.alpinelinux.org
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 <CA+T2pCGeMe+LgApEwUju6NL8FCSAPxY7bPCKDHw5Pj3FXZvqCA@mail.gmail.com>
 <CA+T2pCEdamivZ8J1JL7L2p8abgboP6MBdyDjMbdcOs53c2=nxg@mail.gmail.com>
Cc: William Pitcock <nenolod@dereferenced.org>
From: Oliver Smith <ollieparanoid@bitmessage.ch>
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Message-ID: <171bdb07-0c96-7184-e412-99e322c60385@bitmessage.ch>
Date: Wed, 16 May 2018 20:55:00 +0000
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Thanks for the quick and detailed reply! With the solution you have
described, one can reliably make one package always get installed
instead of the other one. I have tried it and it works.

But our use case is slightly different: not all devices need
libdrm-tegra, so we would like all non-tegra devices to depend on the
regular libdrm package. (If we add a higher provider_priority to
libdrm-tegra, then *all* devices will use libdrm-tegra.)

Can this be done with apk as well?

Thanks,
Oliver

William Pitcock:
> Hello,
>
> On Tue, May 15, 2018 at 11:08 PM, William Pitcock
> <nenolod@dereferenced.org> wrote:
>> Hello,
>>
>> On Tue, May 15, 2018 at 3:57 PM, Oliver Smith
>> <ollieparanoid@bitmessage.ch> wrote:
>>> Hey folks,
>>>
>>> in Alpine based postmarketOS we have hit the following use case quite a
>>> few times by now, and we're wondering how to solve it properly:
>>> Packaging "testlib-b" as a _optional_ replacement for "testlib-a".
>>>
>>> Both "testlib-a" and "testlib-b" provide the same soname, which means
>>> abuild will automatically make both binary packages provide
>>> "so:libtestlib.so.1".
>>
>> By default this means that both packages will provide
>> so:libtestlib.so.1 with provider_priority 0.  When provider_priority
>> is 0, it means to skip automatically resolving the provider.  Provider
>> selection is based on a combination of priority and overall "cost" of
>> choosing that provider.  apk will prefer the highest priority provider
>> with the lowest cost (dependency chain length) that can yield a
>> satiable solution.
>>
>>> Now there is a "testapp" package, which has "testlib-a" in makedepends
>>> and links against "libtestlib.so.1". Therefore abuild puts
>>> "so:libtestlib.so.1" in the depends of "testapp". What we would like to
>>> achieve is, that whenever installing "testapp", it pulls in "testlib-a".
>>> But when "testlib-b" is already installed, it uses "testlib-b" instead
>>> of "testlib-a".
>>
>> testlib-b (libdrm) should have provider_priority 1, testlib-a
>> (libdrm-grate) should have provider_priority greater than 1.  The
>> provides field itself should be left alone.  The key is to set a
>> priority on both providers, otherwise APK will treat it as a collision
>> and behave as you describe.
>
> For what it's worth, I am open to adding provider_priority=1 to
> libdrm.  But it's not my package, so I prefer to hear from ncopa who
> maintains it first.  Otherwise, you will need to rebuild the package.
>
> William



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