[Python-modules-team] Bug#694280: ipython-doc: missing Breaks+Replaces: ipython (<< 0.12.1+dfsg)

[Andreas Beckmann]

Package: ipython-doc
Version: 0.12.1+dfsg-1
Severity: serious
User: treinen at debian.org
Usertags: edos-file-overwrite

Architecture: amd64
Distribution: squeeze->wheezy (partial) upgrade

Hi,

automatic installation tests of packages that share a file and at the
same time do not conflict by their package dependency relationships has
detected the following problem:

  Selecting previously deselected package ipython.
  Unpacking ipython (from .../ipython_0.10-2_all.deb) ...

  Processing triggers for python-central ...
  Setting up ipython (0.10-2) ...
  Processing triggers for python-support ...

  Selecting previously deselected package ipython-doc.
  Unpacking ipython-doc (from .../ipython-doc_0.13.1-1_all.deb) ...
  dpkg: error processing /var/cache/apt/archives/ipython-doc_0.13.1-1_all.deb (--unpack):
   trying to overwrite '/usr/share/doc/ipython/examples/core/example-gnuplot.py', which is also in package ipython 0.10-2


This is a serious bug as it makes installation/upgrade fail, and
violates sections 7.6.1 and 10.1 of the policy.

As this problem can be demonstrated during partial upgrades from squeeze
to wheezy (but not within squeeze or wheezy itself), this indicates a
missing or insufficiently versioned Replaces+Breaks relationship.
But since this particular upgrade ordering is not forbidden by any
dependency relationship, it is possible that apt (or $PACKAGE_MANAGER)
will use this erroneus path on squeeze->wheezy upgrades.

Here is a list of files that are known to be shared by both packages
(according to the Contents files for squeeze and wheezy on amd64, which
may be slightly out of sync):

usr/share/doc/ipython/examples/core/example-embed-short.py
usr/share/doc/ipython/examples/core/example-gnuplot.py
usr/share/doc/ipython/examples/core/ipython-sh.desktop
usr/share/doc/ipython/examples/core/ipython.desktop
usr/share/doc/ipython/examples/core/ipython_here_shell_extension.reg
usr/share/doc/ipython/examples/core/leo_bridge_demo.leo.gz
usr/share/doc/ipython/examples/core/seteditor.py


The examples were recently moved around:

  ipython (0.12.1+dfsg-1) unstable; urgency=low 
   * move all examples to ipython-doc


The following relationships are currently defined:

  Package: ipython-doc
  Replaces: ipython-notebook (<< 0.12.1-1)
  Depends: ipython, libjs-sphinxdoc (>= 1.0)
  Breaks: ipython-notebook (<< 0.12.1-1)
  Conflicts: n/a

The following relationships should be added for a clean takeover of
these files
(http://www.debian.org/doc/debian-policy/ch-relationships.html#s-replaces):

  Package:  ipython-doc
  Breaks:   ipython (<< 0.12.1+dfsg)
  Replaces: ipython (<< 0.12.1+dfsg)

Alternatively to the Breaks, the Depends could be made versioned
(the Replaces is still needed):

  Package:  ipython-doc
  Depends:  ipython (= $(source:Version})
  Replaces: ipython (<< 0.12.1+dfsg)


Cheers,

Andreas

PS: for more information about the detection of file overwrite errors
of this kind see http://edos.debian.net/file-overwrites/.
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