Nightly Rust development with Nix

This one took a while to get simple enough; enjoy!

Background

While getting started with Bevy I wanted to make sure I had an easily reproducible development environment by using only Nix as the package manager. However, the latest version of Bevy was not compatible with stable Rust, so looked into Nix development environments for the nightly version. Unfortunately the instructions I could find either recommended using Rustup (that is, involving another package manager and probably sacrificing reproducibility), were “left as an exercise to the reader”-style vague, or looked complex to maintain. I also wanted to start out with stable integration with JetBrains IDEA, my IDE of choice, so that when I upgrade any part of the setup it would have a good chance to Just Keep Working™.

I tried starting from a standard Nix shell, but nightly Rust integration seemed like it would need one of the aforementioned complex setups or some third party involvement. I didn’t want to add another framework, but finally caved and started using one. This happily turned out to be the right choice.

Prerequisites

• Nix
• devenv (pkgs.devenv)
• direnv (programs.direnv.enable = true in NixOS)
• Optionally RustRover (pkgs.jetbrains.rust-rover) or JetBrains IDEA Ultimate (pkgs.jetbrains.idea-ultimate) with the official Rust plugin¹

Setup

1. Go to your project directory
2. Run devenv init to create devenv and direnv configuration
3. Run devenv inputs add fenix github:nix-community/fenix --follows nixpkgs to add nightly Rust support

4. Add the following in devenv.nix:

   languages.rust = {
     channel = "nightly";
     components = [
       "cargo"
       "rust-src"
       "rustc"
     ];
     enable = true;
   };
   

At this point cargo --version and rustc --version should print -nightly version numbers, and you can run cargo init to start the Rust journey.

Optional IDE setup

Start your IDE inside the project directory² to have all the tools you just installed available on the path. In Languages & Frameworks → Rust, you can now set the relevant paths for the project:

• Toolchain location: [path to project]/.devenv/profile/bin
• Standard library: [path to project]/.devenv/profile/lib/rustlib/src/rust/library

This should be enough to build and run the code, and to follow references to Rust core, within the IDE.

1. I’ve only tested this with IDEA, but it should work similarly in RustRover. ↩

2. I use nohup idea-ultimate nosplash . &>/dev/null & disown to be able to use the shell immediately after starting IDEA. ↩