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Using a special command (nix-shell) whenever I needed to do development things (e.g. Rust builds) was not my idea of fun.Funny you should mention that, because that's exactly what got me using Nix everywhere :). I've always hated installing tools and libraries globally—what if I need a different version for a future project?—so I like tools that sandbox as much as possible like virtualenv, cargo, cabal... etc. But these tools are all language-specific and have their own limitations (especially around native libraries and dependencies written in other languages).
nix-shell gives me the equivalent of virtualenv that works for everything. I can have a single sandboxed environment even if my project uses a bunch of different languages and I can manage everything in a reproducible, low-overhead fashion. No more worrying about making a mess by installing tools or packages globally.
Then, once I got really used to that, I spent some time setting up direnv[1] and lorri[2]—both of which are themselves managed with Nix, of course!—so that my environment gets automatically configured as soon as I enter a project directory without needing to call nix-shell explicitly. To be honest, the experience is still a bit rough, but it works well enough day-to-day that I have my reproducible sandbox cake and eat it in an mostly frictionless way too :).
[1]: https://direnv.net/
[2]: https://github.com/target/lorri