External dependencies
It can happen that you need some library that is not packaged. PyPI has ten times more modules than Fedora has packages. The same for Rubygems.org, Crates.io…
External dependencies allow you to install a package using the native package manager. I.e. not dnf or rpm, but rather using pip, gem, etc.
Right now it is possible to do that only for BuildRequires. Run-time Requires will need more co-operation with DNF and rpm.
This feature is disabled by default. It can be enabled using:
config_opts['external_buildrequires'] = True
Modules
PyPI
BuildRequires: external:pypi:foo - this will run pip3 --install foo
Crate
BuildRequires: external:crate:foo - this will run cargo install foo
Others
Do you miss other languages here? File an issue and let us know which language you want to add. There are two requirements. The native package manager needs to be available in Fedora. And the manager has to have --root or something similar which let you allow to install the files in the different root path. That is because we run this tool in bootstrap chroot.
How it works
When we find the external:: prefix in BuildRequires then Mock install the native package manager in bootstrap buildroot. E.g., for external:pypi:foo mock will install pip3 and run pip3 install --root MOCK_CHROOT foo.
To satisfy rpm dependencies Mock calls create-fake-rpm and creates a fake rpm package that provides external:pypi:foo and installs it in chroot.
All this is logged in root.log and usually start with the line Installing dependencies to satisfy external:*
As of now, this feature requires bootstrap chroot enabled and requires create-fake-rpm to be present (package) in the target chroot.
Available since 2.7