[Nix-dev] What about causing hard failures when trying to install superseded packages?

[Eelco Dolstra]

Hi,

Marc Weber wrote:

> Lluís Batlle and I both missed that qemu_kvm replaces kvm* packages for
> quite a while.
> 
> So what about causing hard failures when trying to install old packages
> unless you explicitly enable them?
> 
> 
> deprecatePackage = name : msg: pkg: if ! getConfig ["ignoreDeprecation" name] false && ! getConfig ["ignoreDeprecation" "all"] false
>   then throw msg
>   else pkg;
> 
> deprecatePackage "kvm-88" "use XY instead" { ..
> };

Another possibility: add a meta.replaces attribute that tells nix-env that a
package is an upgrade to a package with another name.  For instance, for
qemu-kvm, we would have:

  meta.replaces = [ "kvm" ];

IIRC Michael Raskin objected to this on the grounds that somebody might write
meta.replaces = [ "*" ], but that seems a case of Just Don't Do That :-)

-- 
Eelco Dolstra | http://www.st.ewi.tudelft.nl/~dolstra/