How to Add a Rust Package to Nix

This is a quick post on how to contribute a Rust binary to nixpkgs. For more info, please check out the official doc.

First of all, if you’ve never added any packags to nixpkgs, you need to add yourself as a maintainer to the maintainers/maintainer-list.nix file. Try keeping the names in sorted order.

Tools are under pkgs/tools. Pick a category that is relevant and add a subdirectory for the Rust package you want to add. For example: if you want to add the fastmod tool, you can add it under pkgs/tools/text/fastmod.

Then you need to add a default.nix file under the subdirectory you just created.

Here’s the content of the default.nix file:

{ stdenv
, fetchFromGitHub
, rustPlatform
, Security
}:

rustPlatform.buildRustPackage rec {
  pname = "fastmod";
  version = "0.4.0";

  src = fetchFromGitHub {
    owner = "facebookincubator";
    repo = pname;
    rev = "v${version}";
    sha256 = "0089a17h0wgan3fs6x1la35lzjs1pib7p81wqkh3zcwvx8ffa8z8";
  };

  cargoSha256 = "02nkxjwfiljndmi0pv98chfsw9vmjzgmp5r14mchpayp4943qk9m";

  buildInputs = stdenv.lib.optional stdenv.isDarwin Security;

  meta = with stdenv.lib; {
    description = "A utility that makes sweeping changes to large, shared code bases";
    homepage = "https://github.com/facebookincubator/fastmod";
    license = licenses.asl20;
    maintainers = with maintainers; [ jduan ];
    platforms = platforms.all;
  };
}

A few things worth noting:

• The fetchFromGitHub function fetches a release of the package from github. The “rev” is a release version.
• Unlike the rev, the version can only contain digits and dots. You want to use 0.4.0 instead of v0.4.0.
• For sha256 and cargoSha256, you can put some random text there and wait for nix-build to tell you the correct SHAs.

Finally, add your package to pkgs/top-level/all-packages.nix.

To test it, you can run the nix-build from the root of the nixpkgs

repo:nix-build -A fastmod default.nix

That’s it! You should see a subdirectory under /nix/store and you can verify the binary by running it.

Now, go to github, open a PR, and have it merged!