#597340 dpkg-gencontrol: implicit substvar at the end of every field

Package:
dpkg-dev
Source:
dpkg
Submitter:
Raphaël Hertzog
Date:
2026-06-07 01:17:01 UTC
Severity:
wishlist
#597340#5
Date:
2010-09-18 19:23:51 UTC
From:
To:
Package: dpkg-dev
Version: 1.15.8.5
Severity: wishlist

Every time that debhelper needs to adjust a dependency it provides a new
substvar and the maintainer needs to put it in the right field. I was
thinking that we could avoid the second half if some specific substvars
was added at the end of every field.

dpkg-gencontrol could be modified to always append the value of
${implicit:<fieldname>} at the end of the corresponding field. Maybe
we should even support multiple substvars (say
${implicit:<fieldname>:<origin>}) so that there's no coordination problem
if multiple tools want to add something at the end of the same field.

This would even make it possible for debhelper to add dependencies that
are not at all present in debian/control, like for example Breaks... this
would have been handy for example when several dh_* tools have stopped
doing their work on the assumption that the triggerized version of
the postinst snippet was available on the system. With a break, it could
ensure that the relevant package had been upgraded...

With such a system, the ${misc:Depends} that we are currently adding
everywhere would not have been needed.

CCing -devel and Joey Hess to have some input on this idea. Do you think
it would be useful ? Do you have comments and suggestions ?

Cheers,
#597340#10
Date:
2010-09-18 19:45:14 UTC
From:
To:
Raphaël Hertzog wrote:

Note this would mean that for depends fields, the content of the
substvar would need to start with ", ".

It seems like a good idea, it would reduce clutter if misc:Depends did
not need to be manually listed. I don't know if debhelper's perl:Depends
and python:Depends could be sanely made implicit.
#597340#15
Date:
2010-09-19 20:50:12 UTC
From:
To:
Raphaël Hertzog wrote:

I'm uncomfortable with the idea of (even more?) build-time package
settings being hidden away outside of debian/control. :-/
#597340#20
Date:
2010-09-19 21:07:44 UTC
From:
To:
On the flip side, it means less possibilities of mistakes for debhelper
users, a simpler learning curve to newbies who don't have to know about
substvars right from the start, etc.

But I can understand your feeling and we will probably need options to
disable this behaviour in some cases.

Cheers,
#597340#25
Date:
2010-09-20 09:08:42 UTC
From:
To:
I'm at least as uncomfortable with new options as I am with new magic.
dpkg-source has way too many options already.

Cheers,
Julien
#597340#30
Date:
2026-06-07 01:14:09 UTC
From:
To:
Version: 1.23.0

This got somehow implemented with the implicit substvars defined in
deb-substvars(5) by the $= operator. I don't think further implicitness
would be wise here, so the current support seems sufficient to me. And
I'm thus closing this report now.

Thanks,
Guillem