New dh-r issue (Was: dpkg-gencontrol mystery and ${R:Depends} error)

[Dirk Eddelbuettel <edd@debian.org>]

(tl;dr: Found it, read to end)

I was about to write the following:

  I am spinnig my wheels here, and am a loss.  I was trying to see if I could
  build a quick local repo with just r-base-core and r-recommended (to be used
  in the Docker container for R I maintain), and all of a sudden I noticed that
  the r-api-* field is no longer substituted. In other words, I see the error
  
       dh_gencontrol -O--buildsystem=R
    dpkg-gencontrol: warning: Depends field of package r-cran-lattice: unknown substitution variable ${R:Depends}
    dpkg-gencontrol: warning: Depends field of package r-cran-lattice: unknown substitution variable ${R:Depends}
  
  during builds, and of course the resulting .deb misses the fields.
  
  Things I looked at and tried and excluded:
  
  - It is NOT my pbuilder as I can build one package of yours and I get r-api-3.5
    (I randomly picked r-cran-sourcetools) so things should in fact work
    
  - I used different debian/compat values (9 or 11); no effect
  
  - I used different Build-Depends: settings for debhelper; no effect
  
  - I used different Depends: settings for debhelper (and also added
    Suggests/Recommends); no effect
  
  - I don't think my debian/control etc are broken, but I made a bazillion
    different attempts without any luck.
  
  Pbuilder is otherwise current. I get the same error if I set up a Docker
  container with unstable:
  
    root@09fbf13f719a:/mnt/tmp/cluster-2.0.7-1# dh_gencontrol -O--buildsystem=R                              
    dpkg-gencontrol: warning: Depends field of package r-cran-cluster: unknown substitution variable ${R:Depends}
    dpkg-gencontrol: warning: Depends field of package r-cran-cluster: unknown substitution variable ${R:Depends}
    root@09fbf13f719a:/mnt/tmp/cluster-2.0.7-1# 
  
  I used the r-base-core etc package uploaded to experimental on Monday, and it
  does work with some debian/* setups.
  
  I tested its support for r-api-3.5 weeks ago when I made the first upload to
  experimental. It worked then.  I think we used the same dh-r package all along.
  
  Any ideas?

and I finally noticed that it is a side-effect of 'Priority: recommended'.

If I remove that, or try another package, all is well.

So that would be a dh-r issue.

Could one you who is more familiar with dh-r please look into this? It seems
the ${R:Depends} substitution is also affected by the R package priority
(possibly because it leads to the different install path /usr/lib/R/library/
for these packages rather than /usr/local/lib/R/site-library).

Dirk

-- 
http://dirk.eddelbuettel.com | @eddelbuettel | edd@debian.org