Re: [PATCH 0/3] Make pulseaudio a DISTRO_FEATURE

[Phil Blundell <philb@gnu.org>]

On Wed, 2011-11-23 at 16:33 +0000, Paul Eggleton wrote:
> On Wednesday 23 November 2011 16:59:56 Koen Kooi wrote:
> > We also agreed that the current behaviour should be retained, so needing to
> > add pulse to distro features would go against that. Having said that, I
> > personally would dislike having negative ('nopulseaudio') entries to
> > address that. Feedback needed :)
> 
> I don't see how we can achieve this without making a huge mess. I'm happy to 
> be proven wrong, but I would really like us to figure this stuff out soon so we 
> can get the actual problem here fixed.

Agreed.  This problem (or variants of it) comes up fairly frequently: we
had a similar amount of grief when ipv4 and ipv6 became DISTRO_FEATURES
and everybody who wasn't paying attention found that they suddenly had
no networking.  But I think it is basically insoluble in the general
case without any extra stateful mechanics: we need to either:

a) decide that what we have today, or at some other arbitrary point, is
the "base configuration" and any departure from that (including
removals) will now be a DISTRO_FEATURE.  This means accepting things
like "nopulseaudio" which are, admittedly, ugly; or

b) introduce some sort of concept of "feature epochs", where the DISTRO
gets to declare what epoch it is expecting and the compatibility code
then backfills DISTRO_FEATURES to take account of things that were
enabled by default in past epochs but have since been removed.  This
introduces a certain extra maintenance burden but it means that DISTROs
will no longer get unpleasant surprises; or

c) just live with the status quo and accept that things will break when
features are turned off.

My personal preference would be for (b) but I could live with (a) just
as well.

p.