commands: allow to write non-bash scripts

modules/commands.nix

@@ -7,6 +7,10 @@ let
   # environment.
   strOrPackage = import ../nix/strOrPackage.nix { inherit lib pkgs; };
 
+  writeDefaultShellScript = import ../nix/writeDefaultShellScript.nix {
+    inherit (pkgs) lib writeTextFile bash;
+  };
+
   pad = str: num:
     if num > 0 then
       pad "${str} " (num - 1)
@@ -18,7 +22,12 @@ let
     assert lib.assertMsg (cmd.command == null || cmd.name != cmd.command) "[[commands]]: ${toString cmd.name} cannot be set to both the `name` and the `command` attributes. Did you mean to use the `package` attribute?";
     assert lib.assertMsg (cmd.package != null || (cmd.command != null && cmd.command != "")) "[[commands]]: ${name} expected either a command or package attribute.";
     if cmd.package == null then
-      pkgs.writeShellScriptBin cmd.name cmd.command
+      writeDefaultShellScript
+        {
+          name = cmd.name;
+          text = cmd.command;
+          binPrefix = true;
+        }
     else
       cmd.package;
 
@@ -117,7 +126,15 @@ let
       type = types.nullOr types.str;
       default = null;
       description = ''
-        If defined, it will define a script for the command.
+        If defined, it will add a script with the name of the command, and the
+        content of this value.
+
+        By default it generates a bash script, unless a different shebang is
+        provided.
+      '';
+      example = ''
+        #!/usr/bin/env python
+        print("Hello")
       '';
     };
 

nix/writeDefaultShellScript.nix

@@ -0,0 +1,26 @@
+{ lib, writeTextFile, bash }:
+
+/*
+ * Similar to writeShellScript, except that a default shebang can be provided
+ *
+ * Either the script already has a shebang, or one will be provided for it.
+ */
+{ name
+, text
+, defaultShebang ? "#!${bash}/bin/bash\nset -euo pipefail\n"
+, checkPhase ? null
+, binPrefix ? false
+}:
+let
+  script =
+    if lib.hasPrefix "#!" then text
+    else "${defaultShebang}\n${text}";
+in
+writeTextFile (
+  {
+    inherit name text;
+    executable = true;
+  }
+  // (lib.optionalAttrs (checkPhase != null) { inherit checkPhase; })
+  // (lib.optionalAttrs binPrefix { destination = "/bin/${name}"; })
+)

tests/commands.nix

@@ -0,0 +1,53 @@
+{ pkgs, devshell }:
+{
+  # Basic devshell usage
+  commands-1 =
+    let
+      shell = devshell.mkShell {
+        devshell.name = "commands-1";
+        commands = [
+          {
+            name = "bash-script";
+            category = "hello";
+            help = "Prints hello-bash";
+            command = ''
+              echo "hello-bash"
+            '';
+          }
+          {
+            name = "python-script";
+            category = "hello";
+            help = "Prints hello-python";
+            command = ''
+              #!/usr/bin/env python3
+              print("hello-python")
+            '';
+          }
+          {
+            package = "git";
+          }
+        ];
+      };
+    in
+    pkgs.runCommand "devshell-1" { } ''
+      # Load the devshell
+      source ${shell}
+
+      menu
+
+      # Checks that all the commands are available
+      type -p bash-script
+      type -p python-script
+      type -p git
+
+      [[ $(bash-script) == hello-bash ]]
+
+      # Check that the shebang is correct. We can't execute it inside of the
+      # sandbox because /usr/bin/env doesn't exist.
+      #
+      # Ideally it would be rewritten with patchShebang.
+      [[ $(head -n1 "$(type -p python-script)") == "#!/usr/bin/env python3" ]]
+
+      touch $out
+    '';
+}

tests/default.nix

@@ -6,6 +6,7 @@ let
   attrs = { inherit pkgs devshell; };
 in
 { recurseForDerivations = true; }
+// (import ./commands.nix attrs)
 // (import ./devshell.nix attrs)
 // (import ./git-hooks.nix attrs)
 // (import ./modules-docs.nix attrs)