Bug#1028093: warn about python*-dev dependencies breaking cross compilation

[Helmut Grohne <helmut@subdivi.de>]

Package: lintian
Version: 2.115.3
Severity: wishlist
X-Debbugs-Cc: Joe Nahmias <joe@nahmias.net>, Jelmer Vernooij <jelmer@debian.org>

Hi,

Joe noticed a repetitive cross build failure. Can we turn that into a
lintian check?

Preconditions
 * A source package builds an architecture-dependent binary package.
 * The package Build-Depends: python([0-9.]*|3?(-all))-dev without any
   :native or :any qualifier.

The assumption is that in this case, the package very likely builds a
Python extension module. For doing so, it needs a build architecture
Python interpreter and a host architecture Python development package.
This dependency however will cause both components to be installed for
the host architecture and for the Python interpreter this tends to fail
postinst.

Instead, it should be Build-Depends: &:native, lib& (where "&" is the
package name previously used). The :native qualifier will cause the
interpretr to be installed for the build architecture and the second
dependency will pull the host architecture development package. For
native builds, there is no difference as the first package depends on
the second.

This transformation is quite mechanical, affects many packages and helps
cross building a lot. I suppose that this could be automated by the
janitor.

Thanks for considering

Helmut