ci: improvements in scripting and testing

flake.nix

@@ -2,16 +2,11 @@
   description = "Skynet Discord Bot";
 
   inputs = {
-    nixpkgs.url = "nixpkgs/nixos-23.05";
+    nixpkgs.url = "nixpkgs/nixos-unstable";
     naersk.url = "github:nix-community/naersk";
     utils.url = "github:numtide/flake-utils";
   };
 
-  /*
-  sudo nano /etc/nix/nix.conf
-  trusted-users = {username}
-  */
-
   nixConfig = {
     extra-substituters = "https://nix-cache.skynet.ie/skynet-cache";
     extra-trusted-public-keys = "skynet-cache:zMFLzcRZPhUpjXUy8SF8Cf7KGAZwo98SKrzeXvdWABo=";
@@ -25,20 +20,35 @@
   }:
     utils.lib.eachDefaultSystem (
       system: let
-        pkgs = nixpkgs.legacyPackages."${system}";
-        naersk-lib = naersk.lib."${system}";
+        pkgs = (import nixpkgs) {inherit system;};
+        naersk' = pkgs.callPackage naersk {};
         package_name = "skynet_discord_bot";
         desc = "Skynet Discord Bot";
+        buildInputs = with pkgs; [
+          openssl
+          pkg-config
+          rustfmt
+        ];
       in rec {
-        # `nix build`
-        packages."${package_name}" = naersk-lib.buildPackage {
-          pname = "${package_name}";
-          root = ./.;
-
-          buildInputs = with pkgs; [
-            openssl
-            pkg-config
-          ];
+        packages = {
+          # For `nix build` & `nix run`:
+          default = naersk'.buildPackage {
+            pname = "${package_name}";
+            src = ./.;
+            buildInputs = buildInputs;
+          };
+          # Run `nix build .#fmt` to run tests
+          fmt = naersk'.buildPackage {
+            src = ./.;
+            mode = "fmt";
+            buildInputs = buildInputs;
+          };
+          # Run `nix build .#clippy` to lint code
+          clippy = naersk'.buildPackage {
+            src = ./.;
+            mode = "clippy";
+            buildInputs = buildInputs;
+          };
         };
 
         defaultPackage = packages."${package_name}";
@@ -52,7 +62,7 @@
 
         # `nix develop`
         devShell = pkgs.mkShell {
-          nativeBuildInputs = with pkgs; [rustc cargo pkg-config openssl];
+          nativeBuildInputs = with pkgs; [rustc cargo pkg-config openssl rustfmt];
         };
 
         nixosModule = {