File conflict when upgrading package

[Zbigniew Jędrzejewski-Szmek]

On Mon, Nov 18, 2013 at 01:31:32PM -0800, Adam Williamson wrote:
> On Mon, 2013-11-18 at 00:44 +0100, Mattias Ellert wrote:
> > sön 2013-11-17 klockan 22:12 +0100 skrev Sandro Mani:
> > > Upgrading from xflr5-6.09.05-4.fc21.x86_64 to xflr5-6.09.05-5.fc21.x86_64 however fails with
> > > Transaction check error:
> > >     file /usr/share/applications/xflr5.desktop from install of xflr5-6.09.05-5.fc21.x86_64 conflicts with file from
> > > package xflr5-6.09.05-4.fc21.x86_64
> > 
> > You are replacing a directory with an ordinary file. The requires a
> > %pretrans script. %pretrans scripts must be written in lua:
> > 
> > %pretrans -p <lua>
> > st = posix.stat("%{_datadir}/applications/%{name}.desktop")
> > if st and st.type == "directory" then
> >   os.execute("rm -rf %{_datadir}/applications/%{name}.desktop")
> > end
> 
> We had more or less this conversation a couple of months back in the
> context of unbundling webapps. At the time it became clear we really
> don't have any best practice for lua snippets for these cases (file ->
> directory, directory -> file). I was hoping someone was gonna come up
> with something, but no-one has. I've seen different snippets of vastly
> different complexity suggested by different people...
I think that putting work-arounds for this in multiple packages (where
multiple means more than one), is insane from a software engineering
point-of-view. If rpm has trouble with this case bacause it makes it
hard to implement a transaction, then there's no way that instead
individual packagers are going to implement it in package
scripts. There's just no way that all those snippets are all going to
work correctly, *and* it wastes a *lot* of maintainer time. This must
be fixed in rpm.

Zbyszek