> Consequently, couldn't nix's upgrading routines be modified to call out to pip/cargo/whatever to upgrade things best upgraded by pip/cargo/whatever? No. pip/

> Consequently, couldn't nix's upgrading routines be modified to call out to pip/cargo/whatever to upgrade things best upgraded by pip/cargo/whatever? No. pip/cargo/etc are nondeterministic. Nix packages should not be. Where they are, things often break in bizarre ways. In order to access the Internet, a Nix package must declare the hash of its output - given that pip can produce different output from run to run (it contains a constraint solver which depends on the versions available in the external package repository) this is impossible.