rust-flake

A simple way to enable nix package, overlay and devShell creation for Rust projects!

The idea is to be a very simple flake to get a devshell and builder for rust projects that already use the rust-toolchain.toml file. The rust-overlay is great for this, but it doesn't output a nice package or devShells output. To enable a nice devShell, it should only require following the flake example below. A rust-toolchain.toml file is required, and is common in many rust projects.

Below is a simple example. See the example/ directory for a full directory of this example. example2 has a more complex example with merging into another flake output attribute set.

Right now this only handles simple rust projects and slightly less simple rust workspaces. If you need more specific setup, then this flake is not for you.

Example

# ./flake.nix
{
  inputs.rust-flake.url = "github:KaiSforza/rust-flake";
  outputs =
    inputs:
    let
      inherit (inputs.rust-flake.lib) rust-flake rust-flakes;
    in
    rust-flakes [
      (rust-flake {
        root = ./.;
      })
    ];
}

# ./rust-toolchain.toml
[toolchain]
channel = "stable"

This will create a few things:

• packages.${system}.default - the main package from the Cargo.toml file in ./..
  • packages.${system}.${name} - If the is-default argument is false, it will create a separate name package.
• devShells.${system}.default - A devshell containing all of the build and run dependencies specified. Defaults to including a working rust-overlay toolchain based on the toml file. This toolchain includes the rust-src and rust-analyzer by default, but can be extended.
• overlays.${system}.default - A collection of all the packages in this flake that you can use as an overlay in another flake.

Options to rust-flake function

root

The root directory of the rust crate, should usually be ./.. This is the only required setting.

repo-root = root

The root for files that are required in the root of the repository. Only needed if you are using a large mono-repo with different toolchain files, or if the toolchain file is in a separate directory.

workspace = false

If the project is a workspace, set this to true to use the workspace.* values instead of the root values from the TOML file. The name-override will also have to be set, as workspace.package.name is not available.

pkgs-overrides = final: prev: {}

Overrides for the package,

extra-files = [ ]

By default, Cargo.toml, Cargo.lock and src/ are included. Use this if you need other files or directories.

deps-build = final: prev: [ ]

Extra packages to include. Should be a function that will take final and prev arguments like an overlay function. Gets added to nativeBuildInputs and to the devshell.

deps-run = final: prev: [ ]

Extra packages that are needed at runtime. Should be a function that will take final and prev arguments like an overlay function. Gets added to buildInputs and to the devshell.

is-default = true

Will use the package name default instead of the cargo projects name or name-override.

toolchain = repo-root + /rust-toolchain.toml

The toolchain file to use, useful for

toolchain-overrides = { }

Overrides for the toolchain in general. Will affect both the builder toolchain as well as the devshell toolchain.

dev-overrides = {extensions = ["rust-src" "rust-analyzer"];}

Overrides for just the devshell, having these in the builder causes the toolchain to become a runtime dependency, so it's only added by default to the devshell.

name-override = (cargoToml.package.name)

Allows overriding the name from the Cargo.toml file.

Special situations

Different systems

Use the nix-systems flakes and set this to override the systems that rust-flake will create outputs for:

{
  # ...
  inputs.systems.url = "github:nix-systems/default-linux";
  inputs.rust-flakes.inputs.systems.follows = "systems";
  # ...
}

This will only create outputs for x86_64-linux and aarch64-linux, not *-darwin.