Using rust libraries with esy

esy is a package manager for Reason and OCaml. It's however possible to pull-in rust packages, if needed. Support for rust packages isn't natively available, there OCaml ecosystem does seem to bind to rust packages occasionally. If you wish to do so too, then here's how you can do it with esy.

1. Create an esy manifest (package.json or esy.json) with esy-rustup package.

{
  "dependencies": {
    "esy-rustup": "^1.51.1"
  }
}

On newer MacOS, 1.75 is the recommended version, which is not published on NPM. You could use the github repository formula directly with,

  "resolutions": {
    "esy-rustup": "esy-packages/esy-rustup:esy.json#bd83f59efa55da39ba49b155d867e8ae55e3df1"
  }
}

2. Run cargo init to initialize a rust project

3. Run, esy cargo run to run the hello world program.

4. If you're using ocaml-rust, you'll also need to set OCAML_WHERE_PATH because of how ocaml-rust configures ocaml toolchain.

  "esy": {
    "buildEnv": {
      "OCAML_WHERE_PATH": "#{ocaml.lib}/ocaml",
    },
  }

4. Optionally add #{self.root}/target/debug to exportedEnv and run the program with esy x rust-ocaml-with-esy

{
    "exportedEnv": {
      "PATH": {
        "scope": "global",
        "val": "#{self.root}/target/debug:$PATH"
      }
    }
}

Adding dependencies

cargo add doesn't work with esy it hits the network and violates esy's sandbox assumptions. To workaround this,

1. add crate to Cargo.toml manually

[dependencies]
rand = "0.8.5"

2. Run esy cargo vendor

3. Build the project esy (which would run esy b cargo build)