Re: [gentoo-dev] Dependencies default to accept any slot value acceptable (:*), can we default to :0 instead?

[Sergey Popov]

08.12.2013 20:54, Tom Wijsman пишет:
> Hello fellow developers
>
> == Situation ==
>
> When specifying a dependency like cat/pkg it will default to cat/pkg:*
> which is defined in `man 5 ebuild` as:
>
>     * Indicates  that  any  slot value is acceptable. In addition,
>       for runtime dependencies, indicates that the package will not
>       break if the matched package is uninstalled and replaced by a
>       different matching package in a different slot.
>
> This default reflects different behavior than what we use slots for,
> besides allowing side-by-side installations we rather use it to
> specifically depend on a new major version. (eg. dev-libs/glib).
>
> Let's say I want to a add a new major version of cat/pkg to the Portage
> tree, introducing it in the same SLOT="0" isn't an option. This gives
> us two options, one is SLOT="2", the other is to create cat/pkg2 or so.
>
> Creating a new SLOT is the most sane thing going forward; but, as the
> default (:*) depends on any SLOT, this needs a half thousand commits to
> fix up reverse dependencies. Thus, instead a new package is made. [1]
>
> When our defaults force us down such path, that can't be good and it
> affects the quality of our Portage tree; so, this makes me wonder, can
> we change the default from :* to :0? What do you think?
>
>  [1] https://bugs.gentoo.org/show_bug.cgi?id=493652
>      "media-libs/libsdl2: should be a SLOT=2 of media-libs/libsdl"
>
> == Task ==
>
> If we agree we do this; in order to change :* to :0, we need to change
> the PMS to cover this change and implement it in the package managers.
>
> Before we do that, we need to evaluate how practical this is to apply.
> While we are trying to fix the default behavior, what would changing
> the default from :* to :0 break?
>
> One thing that directly comes to mind is that dependencies that have no
> SLOT="0" ebuild present would need us to manually specify a specific
> SLOT; given that this is a not so common situation, the amount of
> commits needed here is low.
>
> Another thing that comes to mind is that we need to check what to do
> with packages were the highest available version does not belong to
> SLOT="0"; technically, restricting these to SLOT="0" will not cause
> breakage, it might however cause some blockers. We'll have to look
> closer into how we can alleviate this result.
>
> Is there anything else we need to take into account?
>
> == Summary ==
>
> Situation:
>
>     Defaulting to :* on SLOT-less dependencies makes it hard to add a
>     new SLOT to a package, using :0 instead would not make this a
>     problem and not require to fix up all reverse dependencies.
>
> Task:
>
>     Check results, correct some exceptions, update PMS, implement it.
>
> Thank you in advance for participating in this discussion.
>

In short - please do NOT do this. More complicated answer - you break
the whole idea of slots. When user types 'emerge cat/foo' it means now -
"i want cat/foo, whatever versions it will be(depending on mask,
keywords, etc, etc)". Your proposal changes this behaviour drastically,
and reasons for such changes are not worth it.

-- 
Best regards, Sergey Popov
Gentoo developer
Gentoo Desktop Effects project lead
Gentoo Qt project lead
Gentoo Proxy maintainers project lead