nixos/pkgsets/emacs/rust.nix

{ config, lib, pkgs, ... }:

with lib;

let
  rustEnv = pkgs.symlinkJoin {
    name = "rustEnv";
    paths = config.machine.pkgsets.rustpkgs.pkgwrap;
  };
in mkIf (elem "emacs::rust" config.machine.pkgs) {
  programs.emacs.init.usePackage.rust-mode = {
    enable = true;
    hook = [ ''(rust-mode . (lambda () (cargo-minor-mode)))'' ]
           ++ (if (elem "emacs::lsp" config.machine.pkgs)
               then [''(rust-mode . (lambda () (lsp)))'']
               else [''(rust-mode . (lambda () (racer-mode)))'']);
    mode = [ ''("\\.rs\\'" . rust-mode)'' ];
    command = [ "rust-mode" ];
    bindLocal = optionalAttrs (elem "emacs::company" config.machine.pkgs) { rust-mode-map = {
      "<tab>" = "company-indent-or-complete-common";
    };};
    config = ''
      (setq rust-rustfmt-bin "${rustEnv}/bin/rustfmt")
      (setq rust-format-on-save t)
    '';
  };

  programs.emacs.init.usePackage.cargo = {
    enable = true;
    defer = true;
  };

  programs.emacs.init.usePackage.racer = {
    enable = true;
    defer = true;
    hook = [
      ''(racer-mode . (lambda () (eldoc-mode)))''
    ] ++ optional (elem "emacs::company" config.machine.pkgs)  ''(racer-mode . (lambda () (company-mode)))'';

    config = ''
      (setq racer-rust-src-path "${rustEnv}/lib/rustlib/src/rust/src")
      (setq racer-cmd "${rustEnv}/bin/racer")
    '';
  };
}