[Pkg-rust-maintainers] Bug#967954: Bug#967954: debcargo: generated ranged build-deps result in "BD-uninstallable" on debian buildd network

[Daniel Kahn Gillmor]

On Wed 2020-08-12 13:59:05 +0100, peter green wrote:
> It has been said in the past by the release team that the current
> autobuilder behaviour of only considering the first option for a
> build-dependency is by design to improve the determinism of the
> autobuilding process. I don't think you will persuade them to change
> it.

Judging by a conversation on #debian-buildd, that seems to be correct
(though there are of course many other ways for non-determinism to
potentially sneak in, not least of which are different versions of
build-deps).

> The proper fix IMO would be to add support for version ranges to
> dependencies in dpkg

I agree that this seems promising -- we'd then need to have debcargo
unwind a bunch of its extensive Provides: tags to take advantage of it,
but that doesn't sound too ugly.  it's possible that introducing ranges
into build-dependencies would be a problem for dpkg for other reasons
though.  I'm Cc'ing Guillem here to see whether he has any thoughts on
the matter.

For the purposes of resolving #967954, we really only need to worry
about ranged dependencies in the build-depends, not in any of the other
dependency fields (though obviously if it's simpler to do ranges across
all of them then that's fine too).

> but even if you can get the dpkg developers to agree to do that it
> would not be a quick solution as any change to dependency metadata
> takes a long time to trickle down to the many tools used in Debian.

I don't care so much about how long it takes as long as we're moving in
the right direction.  If it takes two years, the best to start doing
this change is two years ago.  the second best time is the present :P

     --dkg
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