From 8d9636e092779c8ceb4a7b64ed20dbed43101713 Mon Sep 17 00:00:00 2001
From: Alyssa Ross <hi@alyssa.is>
Date: Thu, 9 Jan 2020 19:24:41 +0000
Subject: [PATCH] nixos/mailman: don't set Postfix hashes

It's likely that a user might want to set multiple values for
relay_domains, transport_maps, and local_recipient_maps, and the order
is significant.  This means that there's no good way to set these
across multiple NixOS modules, and they should probably all be set
together in the user's Postfix configuration.

So, rather than setting these in the Mailman module, just make the
Mailman module check that the values it needs to occur somewhere, and
advise the user on what to set if not.
---
 nixos/modules/services/mail/mailman.nix | 26 ++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/nixos/modules/services/mail/mailman.nix b/nixos/modules/services/mail/mailman.nix
index 7eaf11fe4bf9..ba12c9468e0e 100644
--- a/nixos/modules/services/mail/mailman.nix
+++ b/nixos/modules/services/mail/mailman.nix
@@ -161,10 +161,29 @@ in {
 
   config = mkIf cfg.enable {
 
-    assertions = [
-      { assertion = cfg.enable -> config.services.postfix.enable;
+    assertions = let
+      inherit (config.services) postfix;
+
+      requirePostfixHash = optionPath: dataFile:
+        with lib;
+        let
+          expected = "hash:/var/lib/mailman/data/${dataFile}";
+          value = attrByPath optionPath [] postfix;
+        in
+          { assertion = postfix.enable -> isList value && elem expected value;
+            message = ''
+              services.postfix.${concatStringsSep "." optionPath} must contain
+              "${expected}".
+              See <https://mailman.readthedocs.io/en/latest/src/mailman/docs/mta.html>.
+            '';
+          };
+    in [
+      { assertion = postfix.enable;
         message = "Mailman requires Postfix";
       }
+      (requirePostfixHash [ "relayDomains" ] "postfix_domains")
+      (requirePostfixHash [ "config" "transport_maps" ] "postfix_lmtp")
+      (requirePostfixHash [ "config" "local_recipient_maps" ] "postfix_lmtp")
     ];
 
     users.users.mailman = { description = "GNU Mailman"; isSystemUser = true; };
@@ -175,11 +194,8 @@ in {
     };
 
     services.postfix = {
-      relayDomains = [ "hash:/var/lib/mailman/data/postfix_domains" ];
       recipientDelimiter = "+";         # bake recipient addresses in mail envelopes via VERP
       config = {
-        transport_maps = [ "hash:/var/lib/mailman/data/postfix_lmtp" ];
-        local_recipient_maps = [ "hash:/var/lib/mailman/data/postfix_lmtp" ];
         owner_request_special = "no";   # Mailman handles -owner addresses on its own
       };
     };