[Bug 716599] Re: apt can't open package cache under certain circumstances

[Jonathan Thomas]

Ah, sorry forgot about this. At UDS David and I initially discussed it
and did agree that the error was coming from APT. I had to get somewhere
so I quickly came here and sent the bug back to new. We later went
through QApt's code and found that its function for calculating download
used a fetcher that could potentially raise errors. These errors were
not being cleared from APT's error system, so when QApt went to reload
the cache the errors would still be there, tripping up QApt in to
thinking that the cache reload failed.

QApt now discards all errors incurred in its downloadSize() function,
fixing this issue. I'd like to apologize for not giving a decent
explanation for setting the bug back to new, and for forgetting about
the Launchpad bug for this long after UDS.

** Package changed: apt (Ubuntu) => qapt (Ubuntu)

** Changed in: qapt (Ubuntu)
       Status: New => Fix Released

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https://bugs.launchpad.net/bugs/716599

Title:
  apt can't open package cache under certain circumstances

Status in “qapt” package in Ubuntu:
  Fix Released

Bug description:
  Binary package hint: apt

  The problem in apt I'm reporting can be triggered through "Muon
  updater". I originally reported the bug to KDE but the author of Muon
  suggested me reporting the problem here, as it was an apt problem.

  The following is the original bug report about Muon updater
  (https://bugs.kde.org/show_bug.cgi?id=265741):

  ----------------------------------------------------------------

  Version:           0.2 (using KDE 4.6.0) 
  OS:                Linux

  Please bear with me as this is a rather difficult bug to explain and
  reproduce.

  The problem appears when there are pending updates after a repository refresh
  (apt-get update), those updates are not applied and, later, Muon updater is
  opened (it will show the updated packages), the repositories are updated again
  and a newer version of one of the pending packages is found.

  My personal theory is that Muon updater still tries to mark the old packages
  which are now not present in the repositories, as a newer version of them was
  released. Anyway, I don't know Muon internals, so I could be completely wrong.

  Reproducible: Always

  Steps to Reproduce:
  1. Add a frequently update repository to "Software sources" (for example,
  Chromium Daily PPA, https://launchpad.net/~chromium-daily/+archive/ppa).
  2. Reload the repositories (apt-get update).
  3. Hopefully, there will be pending updates. Muon will report them.
  4. Don't reload the repositories until there are newer version of those
  packages (Chromium Daily should publish new packages every day).
  5. Without reloading, open Muon updater. It will show the same old pending
  updates.
  6. Refresh the repositories from Muon updater (Check for Updates).

  Actual Results:  
  Muon updater will show an error dialog (the following is an approximate
  translation from the Spanish version):

  "The package system couldn't be started. Your configuration may be defective.
  Details:
  A file for package $PACKAGE couldn't be located. This could mean that you will
  have to manually fix that package."

  ("El sistema de paquetes no se ha podido iniciar. Su configuración puede estar
  defectuosa.
  Detalles:
  No se pudo localizar un archivo para el paquete $PACKAGE. Esto puede significar
  que necesita arreglar manualmente este paquete.")

  Expected Results:  
  Muon updater should have suggested the newer version of the package as an
  update candidate without showing an error message as the update can be
  performed the next time Muon is opened.

  OS: Linux (x86_64) release 2.6.35-25-generic
  Compiler: cc

  ----------------------------------------------------------------

  The following is the replly of the author of Muon
  (https://bugs.kde.org/show_bug.cgi?id=265741#c1):

  This is an issue with APT itself not being able to open the package cache. I
  would recommend reporting this bug at Launchpad:
  https://bugs.launchpad.net/ubuntu/+source/apt/

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