Bug#753002: perl: deprecated modules and Replaces entries

[Niko Tyni]

Package: perl
Version: 5.20.0-1

We had a discussion with Jonas on IRC about the Replaces/Provides/Breaks
dance we're doing with separately packaged modules, and a question
about the Replaces entries with deprecated modules came up.

For instance, 5.20.0-1 is doing this for Module::Build :

Recommends: libmodule-build-perl
Breaks: libmodule-build-perl (<< 0.420500)
Replaces: libmodule-build-perl

(note that we don't Provide libmodule-build-perl anymore because it's
 now deprecated and will be removed in 5.22.)

I'm not quite sure if the Replaces is correct here. I assume it's
for policy 7.6.2 ("Replacing whole packages, forcing their removal"):

  Second, Replaces allows the packaging system to resolve which package
  should be removed when there is a conflict (see Conflicting binary
  packages - Conflicts, Section 7.4).

although I'm not quite sure if Breaks and Conflicts are synonymous here.

Clearly, if it comes to a choice between removing libmodule-build-perl
or perl-modules, the former should be preferred. But what we really
want in this case is an upgrade of libmodule-build-perl (unlike in the
non-deprecated case, where it's fine to remove the separate package.)

So I wonder if we should drop the Replaces too.

This probably needs some testing. Keeping the Replaces is perhaps
the more conservative approach, as we did a successful 5.18 transition
where for instance libmodule-pluggable-perl was handled the way
libmodule-build-perl currently is.
-- 
Niko Tyni   ntyni at debian.org