Unsustainable debian/rules as official build entry point?

[Guillem Jover <guillem@debian.org>]

Hi!

So, dpkg 1.19.0 and 1.19.0.1 had a bug where the build target was not
being called when building packages.

Apparently this caused mass build failures, all due to packages (or
their helpers) being very Debian policy non-compliant! These are all
MUST requirements. Stuff like:

  - binary-targets are the only thing required to build a package, and
    the needed build-targets must be depended on by the binary-targets.
  - build-targets must not require root privs, but must be able to be
    run with root privs (via binary-target invocation).
  - debian/rules must not assume any pre-existing environment variable,
    as it still needs to be runnable as debian/rules.

From what I've been told (thanks Niels and Helmut! :), we have lots of
packages in the archive that FTBFS due to, at least:

  - debhelper compat levels < 9 not recursing into debian/rules to
    call the build target.
  - dh-elpa's test failing when executed as root.
  - debian/rules assuming DEB_*_MULTIARCH being present w/o defining it.

The first will just solve itself as people upgrade compat, the second
does really need fixing (although might get shadowed again with the
upcoming R³ support), the last is a recurring problem.


Given the above, and that these are clear regressions, it seems
obvious to me that we are (collectively) not checking/using debian/rules
as the official build entry point interface.

And I've got to question whether we should keep supporting it or just
declare dpkg-buildpackage to be that entry point.


Using debian/rules as the official build entry point has the beauty
that it makes source packages be somewhat self-contained (although
they will still require dpkg-dev tools internally), has perhaps less
interface surface than dpkg-buildpackage provides, and does not tie
it to a specific implementation (dpkg in this case).

Using dpkg-buildpackage as the official build entry point would allow
for much debian/rules refactoring and reduction, and optimizations. We
could predefine multiple environment variables from data sources
dpkg-buildpackage has already needed to parse, or to get a defined and
cleaner environment (see recent LC_ALL=C.UTF-8 thread). It could allow
us to make packaging easier by possbly (and conditionally) reversing the
current inside-out build nature, where the bulk of the building logic is
inside debian/rules via some helper, and even perhaps reduce the need
for a helper, making packaging easier. Etc.


In the past there's been quite strong opposition to switching the
official build entry point from debian/rules to dpkg-buildpackage
(well, even to debian/rules being a Makefile! :). But it seems obvious
that the current situation is not very sustainable. So if there's
still opposition, it might make sense for those opposing to at least
try to attest the conformance of that interface from time to time, and
file bugs etc.? Thoughts?

Thanks,
Guillem