[Pkg-rust-maintainers] Bug#936029: apt fails to resolve multiple levels of provides

[Ximin Luo]

Package: apt
Version: 1.8.3
Severity: important

Dear Maintainer,

apt is having trouble resolving the (correct) dependencies of a certain rust package:

$ sudo apt install librust-rand+default-dev
[..]
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 librust-rand+default-dev : Depends: librust-rand-dev (= 0.6.4-2)
                            Depends: librust-rand+std-dev (= 0.6.4-2)
E: Unable to correct problems, you have held broken packages.
exit code 100

A manual workaround is to supply the dependencies being complained about explicitly:

$ sudo apt install librust-rand+default-dev librust-rand-dev
[..]
The following additional packages will be installed:
[..]
0 upgraded, 25 newly installed, 0 to remove and 101 not upgraded.
Need to get 964 kB/1,280 kB of archives.
After this operation, 10.3 MB of additional disk space will be used.
Do you want to continue? [Y/n] ^C

However this of course can't be done on the buildds, and is preventing
rust-debcargo from building, though strangely it has succeeded on some
architectures:

https://buildd.debian.org/status/package.php?p=rust-debcargo

Note that the dose3 checker succeeds, which is why the builds are being
attempted in the first place, as opposed to being stuck on BD-Uninstallable.

X

-- System Information:
Debian Release: bullseye/sid
  APT prefers testing
  APT policy: (990, 'testing'), (500, 'unstable-debug'), (500, 'testing-debug'), (500, 'stable'), (300, 'unstable'), (100, 'experimental'), (1, 'experimental-debug')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.0-5-amd64 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_PROPRIETARY_MODULE, TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE
Locale: LANG=en_GB.utf8, LC_CTYPE=en_GB.utf8 (charmap=UTF-8), LANGUAGE=en_GB:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages apt depends on:
ii  adduser                 3.118
ii  debian-archive-keyring  2019.1
ii  gpgv                    2.2.17-3
ii  libapt-pkg5.0           1.8.3
ii  libc6                   2.28-10
ii  libgcc1                 1:9.2.1-4
ii  libgnutls30             3.6.9-4
ii  libseccomp2             2.4.1-2
ii  libstdc++6              9.2.1-4

Versions of packages apt recommends:
ii  ca-certificates  20190110

Versions of packages apt suggests:
pn  apt-doc         <none>
ii  aptitude        0.8.11-7
ii  dpkg-dev        1.19.7
ii  gnupg           2.2.17-3
ii  gnupg2          2.2.17-3
ii  powermgmt-base  1.36
ii  synaptic        0.84.6+b1

-- no debconf information