logrotate: default to enable if any rule is active

nixos/doc/manual/from_md/release-notes/rl-2205.section.xml

@@ -865,6 +865,13 @@
           Plugins are automatically repackaged using autoPatchelf.
         </para>
       </listitem>
+      <listitem>
+        <para>
+          <literal>services.logrotate.enable</literal> now defaults to
+          true if any rotate path has been defined, and some paths have
+          been added by default.
+        </para>
+      </listitem>
       <listitem>
         <para>
           The <literal>zrepl</literal> package has been updated from

nixos/doc/manual/release-notes/rl-2205.section.md

@@ -294,6 +294,9 @@ In addition to numerous new and upgraded packages, this release has the followin
 - `services.mattermost.plugins` has been added to allow the declarative installation of Mattermost plugins.
   Plugins are automatically repackaged using autoPatchelf.
 
+- `services.logrotate.enable` now defaults to true if any rotate path has
+  been defined, and some paths have been added by default.
+
 - The `zrepl` package has been updated from 0.4.0 to 0.5:
 
   - The RPC protocol version was bumped; all zrepl daemons in a setup must be updated and restarted before replication can resume.

nixos/modules/services/logging/logrotate.nix

@@ -111,7 +111,10 @@ in
 
   options = {
     services.logrotate = {
-      enable = mkEnableOption "the logrotate systemd service";
+      enable = mkEnableOption "the logrotate systemd service" // {
+        default = foldr (n: a: a || n.enable) false (attrValues cfg.paths);
+        defaultText = literalExpression "cfg.paths != {}";
+      };
 
       paths = mkOption {
         type = with types; attrsOf (submodule pathOpts);