We find it immensely useful to program our packages (technically, "derivations"):
It's trivial to combine multiple packages into one, e.g. via the 'nixpkgs.buildEnv' function. We use this to define a package called 'tools', containing shells, linters, differs, VCS, converters, data processors, etc. Our devs only need to install one package; and if they find something useful enough to share with the team, they can add it to that 'tools' package.
This approach is also modular/compositional: we define a 'minimal-tools' package containing bash, coreutils, git, diffutils, sed, grep, archivers, compressors, etc. which is enough for most shell scripts. Our 'tools' package is defined using that 'minimal-tools' package, plus a bunch of more-interactive tools like process monitors, download managers, etc. The reason we made this modular is so each of our projects can include that 'minimal-tools' package in their development environments, alongside project-specific tooling like interpreters (NodeJS, Python, JVM, etc.), compilers, code formatters, etc. (depending on the whole 'tools' package felt like bloat, and was easy to avoid)
(Outside of work, my personal NixOS config takes this even further; defining different packages for e.g. media tools, development tools, document tools, audio tools, etc. and splitting those into separate packages for gui/cli tools. That's not particularly "useful in practice"; I just like to keep my system config organised!)
Another very common way of programming with packages is to override their definitions. For example, we override the whole of Nixpkgs to use the 'jre11_headless' JVM. This is done by the following 'overlay' function (all of the dependency-propagation happens automatically, since Nixpkgs uses laziness):
Overriding is also useful for individual packages, e.g. if we want to alter something deep down a dependency chain. It's also useful for applying patches or running a "fixup" script to the source, without having to e.g. fork a git repo.
It's trivial to combine multiple packages into one, e.g. via the 'nixpkgs.buildEnv' function. We use this to define a package called 'tools', containing shells, linters, differs, VCS, converters, data processors, etc. Our devs only need to install one package; and if they find something useful enough to share with the team, they can add it to that 'tools' package.
This approach is also modular/compositional: we define a 'minimal-tools' package containing bash, coreutils, git, diffutils, sed, grep, archivers, compressors, etc. which is enough for most shell scripts. Our 'tools' package is defined using that 'minimal-tools' package, plus a bunch of more-interactive tools like process monitors, download managers, etc. The reason we made this modular is so each of our projects can include that 'minimal-tools' package in their development environments, alongside project-specific tooling like interpreters (NodeJS, Python, JVM, etc.), compilers, code formatters, etc. (depending on the whole 'tools' package felt like bloat, and was easy to avoid)
(Outside of work, my personal NixOS config takes this even further; defining different packages for e.g. media tools, development tools, document tools, audio tools, etc. and splitting those into separate packages for gui/cli tools. That's not particularly "useful in practice"; I just like to keep my system config organised!)
Another very common way of programming with packages is to override their definitions. For example, we override the whole of Nixpkgs to use the 'jre11_headless' JVM. This is done by the following 'overlay' function (all of the dependency-propagation happens automatically, since Nixpkgs uses laziness):
Overriding is also useful for individual packages, e.g. if we want to alter something deep down a dependency chain. It's also useful for applying patches or running a "fixup" script to the source, without having to e.g. fork a git repo.