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crate2nix

Generate Cargo.nix manually

  • ✅ Does not use import from derivation feature from Nix which may lead to disabling build parallelism,
  • 🛠️ but you need to regenerate Cargo.nix whenever you change your dependencies or other config affecting Cargo.lock.

Disregarding whether you use nix with flakes or without, you might want to generate your Cargo.nix file manually. That way you avoid using the import from derivation feature from nix which might disable build parallelism.

Here is a simple example which uses all the defaults and will generate a Cargo.nix file.

If you installed crate2nix locally:

Terminal window
# From the project directory with the Cargo.toml.
crate2nix generate

If you prefer to run it without installation:

Terminal window
# From the project directory with the Cargo.toml.
nix run nixpkgs#crate2nix -- generate

Here is a more elaborate example that uses <nixos-unstable> as the default pkgs path (instead of <nixpkgs>) and specifies both the path to the Cargo.toml file (-f) and the output (-o) file explicitly (usually not needed).

Terminal window
crate2nix generate \
    -n '<nixos-unstable>' \
    -f /some/project/dir/Cargo.toml \
    -o /some/project/dir/Cargo.nix

Use crate2nix help to show all commands and options.

Look at the ./crate2nix/Cargo.nix file of this project for a non-trivial example. (How meta!)