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