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+---
+title: "cargo2nix: Dramatically simpler Rust inside Nix"
+date: 2020-10-05
+layout: post
+lang: en
+ref: cargo2nix-dramatically-simpler-rust-in-nix
+---
+
+In the same vein of my earlier post on
+[swift2nix]({% post_url 2020-10-05-swift2nix-run-swift-inside-nix-builds %}), I
+was able to quickly prototype a Rust and Cargo variation of it:
+[cargo2nix][cargo2nix].
+
+
+The inital prototype is even smaller than swift2nix: it has only
+[37 lines of code][37-lines].
+
+[cargo2nix]: https://git.euandreh.xyz/cargo2nix/about/
+[37-lines]: https://git.euandreh.xyz/cargo2nix/tree/default.nix?id=472dde8898296c8b6cffcbd10b3b2c3ba195846d
+
+Here's how to use it (snippet taken from the repo's README):
+
+```nix
+let
+  niv-sources = import ./nix/sources.nix;
+  pkgs = import niv-sources.nixpkgs { };
+  src = pkgs.nix-gitignore.gitignoreSource [ ] ./.;
+  cargo2nix = pkgs.callPackage niv-sources.cargo2nix {
+    lockfile = ./Cargo.lock;
+  };
+in pkgs.stdenv.mkDerivation {
+  inherit src;
+  name = "swift-test";
+  buildInputs = with pkgs; [ cargo ];
+  phases = [ "unpackPhase" "buildPhase" ];
+  buildPhase = ''
+    # Setup dependencies path to satisfy Cargo
+    mkdir .cargo/ vendor/
+    ln -s ${cargo2nix.env.cargo-config} .cargo/config
+    ln -s ${cargo2nix.env.vendor} vendor
+
+    # Run the tests
+    cargo test
+    touch $out
+  '';
+}
+```
+
+That `cargo test` part on line 20 is what I have been fighting with every
+"\*2nix" available for Rust out there. I don't want to bash any of them, all I
+want is to have full control of what Cargo commands to run, and the "*2nix" tool
+should only setup the environment for me. Just let me run Cargo however I want,
+no need to parameterize how the tool runs Cargo for me, or even replicate Cargo
+commands by calling the Rust compiler directly.
+
+Sure it doesn't support private registries or Git dependencies, but how
+much bigger does it has to be to support it? Also, it doesn't support those
+**yet**, there's no reason why for extending it to support them. I just haven't
+needed it yet, so I haven't added. Patches welcome.
+
+The layout of the `vendor/` directory is more explicit and public: whatever the
+command `cargo vendor` returns. However I haven't checked if the shape of the
+`.cargo-checksum.json` is specified, or internal to Cargo.
+
+Try out the demo (also taken from the repo's README):
+
+```shell
+pushd "$(mktemp -d)"
+git clone https://git.euandreh.xyz/cargo2nix-demo
+cd cargo2nix-demo/
+nix-build
+```
+
+Report back if you wish. Again, patches welcome.