[Nix-dev] Preference for building from source

[Juho Östman]

Does nixpkgs have a policy on building packages preferably from source?
I have noticed the nix scripts of a few packages fetch a binary package
instead of building from source, even though a source should also be
available, for example Eclipse and Gradle. Is this a conscious decision,
or were these packages too difficult to build for the moment?

As for me, I think packages should be built from source whenever it is
possible. It allows using the nix script as a base for customisation and
alternative versions and confirms that the source can be compiled and
corresponds to the binary package.

Sometimes source packages include pre-built dependencies. These should
also be replaced with distribution-built versions, if such are
available. The reasons are the same: allowing customisation and linking
to an alternative version, and confirming that the dependency is built
using the public source code.