[Rd] recent changes to r-devel with package date checking?

[Ivan Krylov]

On Thu, 26 Mar 2026 20:46:46 -0500
Dirk Eddelbuettel <edd using debian.org> wrote:

> Are we really only talking about parsing an RFC 822 date into an ISO
> date or is there more going here? If it is this, why can the date
> (coming in with a regularized format) not be converted as needed?

R needs the "Built" date to differ between binary builds of the same
version of the source package for approximately the same purpose as why
the +b1 suffix is added to version numbers in Debian when rebuilding
without changing the source. R uses the date as a proxy for
binary-level dependencies (e.g. cached S4 classes [1] or ABI issues
with LinkingTo [2]) that "disappear" upon re-installation from source.

Interestingly, Debian rules for binNMUs [3] seem to fulfil this already:

> The only file in the source package which is modified by the binNMU
> is debian/changelog, which gets a new entry for the new version.

In other words, when a binNMU happens, the Built: date is updated,
which is what R cares about.

So, e.g., r-cran-libcoin (1.0-9-1+b1) in bookworm has

Built: R 4.2.1; x86_64-pc-linux-gnu; 'Sun, 18 Sep 2022 22:43:49 +0000'; unix

with the binNMU timestamp from changelog.Debian.amd64 and not the
source package timestamp from changelog.Debian. Actually, I see this
for all r-cran-* packages with binNMUs that I have installed:

dpkg -l | \
 awk '
  ($1=="ii" && $2 ~ /^r-cran-/ && $3 ~ /\+b/){
   sub("r-cran-","",$2); print $2
  }
 ' | while read pkg; do
  srcDate=$(dpkg-parsechangelog \
   -l /usr/share/doc/r-cran-"$pkg"/changelog.Debian.gz -S Date)
  binDate=$(dpkg-parsechangelog \
   -l /usr/share/doc/r-cran-"$pkg"/changelog.Debian.amd64.gz -S Date)
  pkgDesc=$(dpkg -L r-cran-"$pkg" | grep '/DESCRIPTION$')
  grep -q "^Built:.*$srcDate" $pkgDesc && echo "$pkg has source date"
  grep -q "^Built:.*$binDate" $pkgDesc && echo "$pkg has binary date"
done

So, while Simon's fix in r89726 avoided the immediate breakage, the
dates patched in by the Debian build system should be safe to use as
well. r-cran.mk would just need to use something like:

builttime := $(shell dpkg-parsechangelog -l$(CURDIR)/debian/changelog -S Timestamp)
builttimeR := $(shell date -u -d @$(builttime) +"%Y-%m-%d %H:%M:%S UTC")
builttimeStamp := "--built-timestamp=\"$(builttimeR)\""

instead of the RFC 5322 format.

-- 
Best regards,
Ivan

[1]
https://stat.ethz.ch/pipermail/r-devel/2022-September/081971.html
Also discussed in
https://stat.ethz.ch/pipermail/r-devel/2023-August/082769.html
https://stat.ethz.ch/pipermail/r-devel/2025-January/083779.html

[2]
https://stat.ethz.ch/pipermail/r-package-devel/2025q1/011376.html

[3]
https://wiki.debian.org/binNMU