nixos/mailhog: add setSendmail option for sendmail setuid wrapper.

This might be used in dev environments, where `sendmail` is the prefered
mail transport.

maintainers/maintainer-list.nix

@@ -18077,6 +18077,12 @@
     githubId = 61306;
     name = "Rene Treffer";
   };
+  RTUnreal = {
+    email = "unreal+nixpkgs@rtinf.net";
+    github = "RTUnreal";
+    githubId = 22859658;
+    name = "RTUnreal";
+  };
   rubenhoenle = {
     email = "git@hoenle.xyz";
     github = "rubenhoenle";

nixos/modules/services/mail/mailhog.nix

@@ -1,4 +1,9 @@
-{ config, lib, pkgs, ... }:
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
 let
   cfg = config.services.mailhog;
 
@@ -8,17 +13,24 @@ let
       "-smtp-bind-addr :${toString cfg.smtpPort}"
       "-ui-bind-addr :${toString cfg.uiPort}"
       "-storage ${cfg.storage}"
-    ] ++ lib.optional (cfg.storage == "maildir")
-      "-maildir-path $STATE_DIRECTORY"
+    ]
+    ++ lib.optional (cfg.storage == "maildir") "-maildir-path $STATE_DIRECTORY"
     ++ cfg.extraArgs
   );
 
+  mhsendmail = pkgs.writeShellScriptBin "mailhog-sendmail" ''
+    exec ${lib.getExe pkgs.mailhog} sendmail $@
+  '';
 in
 {
   ###### interface
 
   imports = [
-    (lib.mkRemovedOptionModule [ "services" "mailhog" "user" ] "")
+    (lib.mkRemovedOptionModule [
+      "services"
+      "mailhog"
+      "user"
+    ] "")
   ];
 
   options = {
@@ -26,8 +38,15 @@ in
     services.mailhog = {
       enable = lib.mkEnableOption "MailHog, web and API based SMTP testing";
 
+      setSendmail = lib.mkEnableOption "set the system sendmail to mailhogs's" // {
+        default = true;
+      };
+
       storage = lib.mkOption {
-        type = lib.types.enum [ "maildir" "memory" ];
+        type = lib.types.enum [
+          "maildir"
+          "memory"
+        ];
         default = "memory";
         description = "Store mails on disk or in memory.";
       };
@@ -52,13 +71,12 @@ in
 
       extraArgs = lib.mkOption {
         type = lib.types.listOf lib.types.str;
-        default = [];
+        default = [ ];
         description = "List of additional arguments to pass to the MailHog process.";
       };
     };
   };
 
-
   ###### implementation
 
   config = lib.mkIf cfg.enable {
@@ -69,11 +87,21 @@ in
       wantedBy = [ "multi-user.target" ];
       serviceConfig = {
         Type = "exec";
-        ExecStart = "${pkgs.mailhog}/bin/MailHog ${args}";
+        ExecStart = "${lib.getExe pkgs.mailhog} ${args}";
         DynamicUser = true;
         Restart = "on-failure";
         StateDirectory = "mailhog";
       };
     };
+
+    services.mail.sendmailSetuidWrapper = lib.mkIf cfg.setSendmail {
+      program = "sendmail";
+      source = lib.getExe mhsendmail;
+      # Communication happens through the network, no data is written to disk
+      owner = "nobody";
+      group = "nogroup";
+    };
   };
+
+  meta.maintainers = with lib.maintainers; [RTUnreal];
 }