Bug#987615: perl-base: please ship modules used by usrmerge in perl-base

[Dimitri John Ledkov]

On Wed, 28 Apr 2021 at 18:46, Niko Tyni <ntyni at debian.org> wrote:
>
> On Mon, Apr 26, 2021 at 03:26:02PM +0100, Dimitri John Ledkov wrote:
> > Package: perl-base
> > Version: 5.30.3-4
> > Severity: normal
> >
> > Dear Maintainer,
> >
> > usrmerge will be needed to be installed upon upgrades to bookworm to
> > convert systems to merged /usr. It would be helpful for small installs
> > to be able to perform that without installing the larger perl package.
>
> Thanks for raising this early. I'm copying the usrmerge maintainer.
>
> > Please consider moving things that usrmerge & libfile-find-rule-perl
> > use from per/perl-modules to perl-base.
>
> I understand the concern, but I'm hesitant to do this. See below.
>
> > In bookworm+1 you may drop these things from perl-base and add breaks
> > on usrmerge.
>
> Quoting the Debian policy:
>
>   Maintainers should take great care in adding any programs, interfaces,
>   or functionality to essential packages. Packages may assume that
>   functionality provided by essential packages is always available without
>   declaring explicit dependencies, which means that removing functionality
>   from the Essential set is very difficult and is almost never done. Any
>   capability added to an essential package therefore creates an obligation
>   to support that capability as part of the Essential set in perpetuity.
>

How about splitting perl-modules and have perl-modules &
perl-modules-bits-and-pieces which will not be essential; perl-modules
will depend on; but also usrmerge will be able to depend on
"perl-base, perl-modules-bits-and-pieces | perl-modules" ?
And later it will be able to collapse back into perl-modules.

> Have other avenues been investigated? How critical is the
> libfile-find-rule-perl dependency - would it be hard to replace it with
> something that's already in the Essential set, for instance piping from
> find(1) ? Could autodie usage be replaced with explicit error handling?
>

In Ubuntu, a choice was made to simply vendor copies of the needed
modules in the usrmerge package to reduce its dependencies. I'm not
advocating for Debian to make a similar choice.

> Is Perl the right language to implement the migration in the first
> place? A small binary with minimal external dependencies would seem
> preferable.

Yes it is the right language. The implementation is concise and
correct, and it is tricky to get right.

-- 
Regards,

Dimitri.