treewide: add literalDocBook text to options with complex defaults

some options have default that are best described in prose, such as
defaults that depend on the system stateVersion, defaults that are
derivations specific to the surrounding context, or those where the
expression is much longer and harder to understand than a simple text
snippet.

2 files changed, 23 insertions, 2 deletions

diff --git a/nixos/modules/services/networking/firewall.nix b/nixos/modules/services/networking/firewall.nix
index b5b46fe6042..ff023a888f2 100644
--- a/nixos/modules/services/networking/firewall.nix
+++ b/nixos/modules/services/networking/firewall.nix
@@ -421,6 +421,7 @@ in
       checkReversePath = mkOption {
         type = types.either types.bool (types.enum ["strict" "loose"]);
         default = kernelHasRPFilter;
+        defaultText = literalDocBook "<literal>true</literal> if supported by the chosen kernel";
         example = "loose";
         description =
           ''
diff --git a/nixos/modules/services/networking/syncthing.nix b/nixos/modules/services/networking/syncthing.nix
index 8c44687a382..e37e324019e 100644
--- a/nixos/modules/services/networking/syncthing.nix
+++ b/nixos/modules/services/networking/syncthing.nix
@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.syncthing;
+  opt = options.services.syncthing;
   defaultUser = "syncthing";
   defaultGroup = defaultUser;
 
@@ -431,7 +432,26 @@ in {
           The path where the settings and keys will exist.
         '';
         default = cfg.dataDir + optionalString cond "/.config/syncthing";
-        defaultText = literalExpression "dataDir${optionalString cond " + \"/.config/syncthing\""}";
+        defaultText = literalDocBook ''
+          <variablelist>
+            <varlistentry>
+              <term><literal>stateVersion >= 19.03</literal></term>
+              <listitem>
+                <programlisting>
+                  config.${opt.dataDir} + "/.config/syncthing"
+                </programlisting>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term>otherwise</term>
+              <listitem>
+                <programlisting>
+                  config.${opt.dataDir}
+                </programlisting>
+              </listitem>
+            </varlistentry>
+          </variablelist>
+        '';
       };
 
       extraFlags = mkOption {