[Pkg-rust-maintainers] Bug#946465: librust-rand+alloc-dev: does not find upgrade path from buster to bullseye

[Andreas Beckmann]

Package: librust-rand+alloc-dev
Version: 0.6.4-2
Severity: serious
User: debian-qa at lists.debian.org
Usertags: piuparts

Hi,

during a test with piuparts I noticed your package fails to upgrade from
'buster'.
It installed fine in 'buster', then the upgrade to 'bullseye' fails.

>From the attached log (scroll to the bottom...):

  Starting 2 pkgProblemResolver with broken count: 2
  Investigating (0) librust-rand-core-0.2+alloc-dev:amd64 < 0.2.2-1+b1 @ii mK Ib >
  Broken librust-rand-core-0.2+alloc-dev:amd64 Depends on librust-rand-core-0.2-dev:amd64 < 0.2.2-1+b1 @ii mR > (= 0.2.2-1+b1)
    Considering librust-rand-core-0.2-dev:amd64 3 as a solution to librust-rand-core-0.2+alloc-dev:amd64 0
    Removing librust-rand-core-0.2+alloc-dev:amd64 rather than change librust-rand-core-0.2-dev:amd64
  Investigating (0) librust-rand-core-0.4-dev:amd64 < none -> 0.4.2-1 @un uN Ib >
  Broken librust-rand-core-0.4-dev:amd64 Breaks on librust-rand-core-dev:amd64 < 0.3.0-1 @ii mK > (< 0.4.3-~~)
    Considering librust-rand-core-dev:amd64 -1 as a solution to librust-rand-core-0.4-dev:amd64 -1
    Holding Back librust-rand-core-0.4-dev:amd64 rather than change librust-rand-core-dev:amd64
  Investigating (1) librust-rand-pcg-0.1-dev:amd64 < none -> 0.1.2-1+b1 @un uN Ib >
  Broken librust-rand-pcg-0.1-dev:amd64 Depends on librust-rand-core-0.4+default-dev:amd64 < none @un H >
    Considering librust-rand-core-0.4-dev:amd64 -1 as a solution to librust-rand-pcg-0.1-dev:amd64 -1
    Holding Back librust-rand-pcg-0.1-dev:amd64 rather than change librust-rand-core-0.4+default-dev:amd64
  Investigating (2) librust-rand-dev:amd64 < 0.5.5-2 -> 0.6.4-2 @ii umU Ib >
  Broken librust-rand-dev:amd64 Depends on librust-rand-pcg-0.1+default-dev:amd64 < none @un H >
    Considering librust-rand-pcg-0.1-dev:amd64 -1 as a solution to librust-rand-dev:amd64 1
    Re-Instated librust-rand-core-0.4-dev:amd64
    Re-Instated librust-rand-pcg-0.1-dev:amd64
    Re-Instated librust-rand-dev:amd64
  Investigating (2) librust-rand-core-0.4-dev:amd64 < none -> 0.4.2-1 @un uN Ib >
  Broken librust-rand-core-0.4-dev:amd64 Breaks on librust-rand-core-dev:amd64 < 0.3.0-1 @ii mK > (< 0.4.3-~~)
    Considering librust-rand-core-dev:amd64 -1 as a solution to librust-rand-core-0.4-dev:amd64 -1
    Holding Back librust-rand-core-0.4-dev:amd64 rather than change librust-rand-core-dev:amd64
  Investigating (3) librust-rand-pcg-0.1-dev:amd64 < none -> 0.1.2-1+b1 @un uN Ib >
  Broken librust-rand-pcg-0.1-dev:amd64 Depends on librust-rand-core-0.4+default-dev:amd64 < none @un H >
    Considering librust-rand-core-0.4-dev:amd64 -1 as a solution to librust-rand-pcg-0.1-dev:amd64 -1
    Holding Back librust-rand-pcg-0.1-dev:amd64 rather than change librust-rand-core-0.4+default-dev:amd64
  Investigating (4) librust-rand-dev:amd64 < 0.5.5-2 -> 0.6.4-2 @ii umU Ib >
  Broken librust-rand-dev:amd64 Depends on librust-rand-pcg-0.1+default-dev:amd64 < none @un H >
    Considering librust-rand-pcg-0.1-dev:amd64 -1 as a solution to librust-rand-dev:amd64 1
    Removing librust-rand-dev:amd64 rather than change librust-rand-pcg-0.1+default-dev:amd64
  Investigating (5) librust-rand+alloc-dev:amd64 < 0.5.5-2 -> 0.6.4-2 @ii pumU Ib >
  Broken librust-rand+alloc-dev:amd64 Depends on librust-rand-dev:amd64 < 0.5.5-2 | 0.6.4-2 @ii umR > (= 0.6.4-2)
    Considering librust-rand-dev:amd64 1 as a solution to librust-rand+alloc-dev:amd64 10000
  Done
  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+alloc-dev : Depends: librust-rand-dev (= 0.6.4-2)
  E: Unable to correct problems, you have held broken packages.

Similar errors happen in several other rust packages, too,
but this one has the most rdepends.

I can't spot immediately how the correct upgrade path should look like,
there are too many virtual packages involved. And probably this involves
substituting a currently installed package for another one as well.
Fixing this (and similar) bug(s) will probably need some Breaks to be
added to some packages.


cheers,

Andreas
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