Re: Bug#501866: Missing dependancy - libpango1.0-common.prerm uses defoma-app in pkg defoma

[Sven Joachim <svenjoac@gmx.de>]

On 2008-10-16 13:35 +0200, Raphael Hertzog wrote:

> On Thu, 16 Oct 2008, Sven Joachim wrote:
>> On 2008-10-15 17:20 +0200, Josselin Mouette wrote:
>> > Frankly, I’m tempted to reassign this to dpkg; Policy §7.2 is very clear
>> > on the relationship between prerm scripts and Depends. 
>> 
>> I think reassigning would be OK.  Maybe also raising the severity to
>> important.
>
> I'm not quite sure this is the right thing to do, quoting policy:
>     A Depends field takes effect only when a package is to be configured. It
>     does not prevent a package being on the system in an unconfigured state
>     while its dependencies are unsatisfied, and it is possible to replace a
>     package whose dependencies are satisfied and which is properly
>     installed with a different version whose dependencies are not and
>     cannot be satisfied; 
>
> So there's no guaranty in the prerm script. You can only rely on essential
> packages being unpacked.

If this is not going to change, it should be documented in the Policy.

>> > Dpkg needs to ensure that all dependencies *and their own dependencies*
>> > are in a clean, installed state when running the prerm script. It
>> > correctly does it for postinst already.
>
> I don't think this is reasonable. You are asking to change all Depends
> into Pre-Depends.

Not quite, since prerm scripts are only called during removals and
upgrades, and if the package being removed or upgraded had been
installed correctly, the dependencies should be fulfilled during the run
of the prerm script.  However, this cannot be guaranteed in all cases,
e.g. if there are circular dependencies.

Sven