Re: Conditional Recommends

[Carsten Hey <carsten@debian.org>]

* Josselin Mouette [2011-05-21 13:24 +0200]:
> Therefore, I’m wondering whether it would be possible to extend the
> syntax of Recommends to allow for conditional dependencies. For example,
> in this case:
>         Package: A
>         Recommends: A-plugin-B {B}

The following would be more general:

        Package: A
        Recommends: !B | A-plugin-B


If we have had this syntax a lot earlier, for example "Build-Conflicts:
X" could have been written as "Build-Depends: !X".  But we already
invented all those fields and the number of additional use cases for
exclamation marks as negation in package relationship fields seems to be
rather limited.


With above exclamation mark syntax, we could also express "weak
conflicts", e.g.:

        Package: X
        Recommends: !Y

Apt would remove Y by default if X gets installed, but users could
overwrite this.


Is there any need for such a weak conflict, e.g., to get rid of gcc-4.4
if gcc-4.5 gets installed?  Apt's autoremove feature presumably already
handles most of these cases.

If we add conditional recommends and there is a need for weak conflicts,
I think we should choose a syntax that allows us to express both.


Regards
Carsten