On 06/12/2015 10:28 AM, Radek Holy wrote:
If a package "Requires: foo" and both "bar" and "barbaz" "Provides: foo", they are handled as being equally suitable. DNF/libsolv is not going to prefer packages with shorter names.
Yes, very much agreed here. Please don't add the yum shortest name hack to DNF. This and the rest of the depsolving quirks that choose one provider over the other depending on what else happens to be installed, have made my life quite hard over the years :) Let me try to elaborate. The issue I've had with yum's virtual provider depsolving is that there is currently no way to set a default. A default where it would by default install the package that the maintainer has chosen, but would also allow swapping it out if the user needs to. An example here would be an app that has two backends. One of those backends would be the preferred backend and other one experimantel, and maybe a third one that is for a special use case backend that isn't interesting for the general audience. The way to express this with rpm deps would be to have a virtual provide that all of the backends packages provide, so that the user could choose which one to install. An example here would be PackageKit with different backends. It used to have 2 backends, PackageKit-hawkey and PackageKit-yum (we dropped the different backends from Fedora now, but it was a valid issue in last release). Both of them would have a common virtual provide that PackageKit itself would depend on, to make sure at least one of the backends is installed. With the yum system, yum would pretty much always just pick the shortest name. It _happened_ to be PackageKit-yum, but that was totally an accident. And it made it impossible to change the default without renaming the packages - so in a new release that was supposed to use hawkey, we'd have very little options besides renaming PackageKit-hawkey to PackageKit-h for example to make sure it wins over -yum. What I feel would be a good solution to the problem above would be to have a way to specify the default. I believe this problem is already solved in apt-get with a very nice syntax: the OR syntax: Requires: PackageKit-hawkey | PackageKit-backend ... where PackageKit-backend is a virtual provide that both of the backends satisfy. With the requires above, any of the two would solve the requires, but dnf could use the information to choose the first one as the default when it doesn't have any of the backends already installed. -- Kalev -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct
