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.

20 files changed, 90 insertions, 5 deletions

diff --git a/nixos/modules/programs/gnupg.nix b/nixos/modules/programs/gnupg.nix
index 06f49182e4df1..fe5d7bd834b22 100644
--- a/nixos/modules/programs/gnupg.nix
+++ b/nixos/modules/programs/gnupg.nix
@@ -71,6 +71,7 @@ in
       type = types.nullOr (types.enum pkgs.pinentry.flavors);
       example = "gnome3";
       default = defaultPinentryFlavor;
+      defaultText = literalDocBook ''matching the configured desktop environment'';
       description = ''
         Which pinentry interface to use. If not null, the path to the
         pinentry binary will be passed to gpg-agent via commandline and
diff --git a/nixos/modules/services/audio/mpdscribble.nix b/nixos/modules/services/audio/mpdscribble.nix
index 57d3ef77b34ed..333ffb709410a 100644
--- a/nixos/modules/services/audio/mpdscribble.nix
+++ b/nixos/modules/services/audio/mpdscribble.nix
@@ -128,6 +128,10 @@ in {
           mpdCfg.credentials).passwordFile
       else
         null;
+      defaultText = literalDocBook ''
+        The first password file with read access configured for MPD when using a local instance,
+        otherwise <literal>null</literal>.
+      '';
       type = types.nullOr types.str;
       description = ''
         File containing the password for the mpd daemon.
diff --git a/nixos/modules/services/cluster/kubernetes/addons/dns.nix b/nixos/modules/services/cluster/kubernetes/addons/dns.nix
index 34943fddd3d10..10f45db7883f4 100644
--- a/nixos/modules/services/cluster/kubernetes/addons/dns.nix
+++ b/nixos/modules/services/cluster/kubernetes/addons/dns.nix
@@ -1,4 +1,4 @@
-{ config, pkgs, lib, ... }:
+{ config, options, pkgs, lib, ... }:
 
 with lib;
 
@@ -23,6 +23,10 @@ in {
           take 3 (splitString "." config.services.kubernetes.apiserver.serviceClusterIpRange
         ))
       ) + ".254";
+      defaultText = literalDocBook ''
+        The <literal>x.y.z.254</literal> IP of
+        <literal>config.${options.services.kubernetes.apiserver.serviceClusterIpRange}</literal>.
+      '';
       type = types.str;
     };
 
diff --git a/nixos/modules/services/cluster/kubernetes/kubelet.nix b/nixos/modules/services/cluster/kubernetes/kubelet.nix
index 4c00e162efa85..3a15984c23053 100644
--- a/nixos/modules/services/cluster/kubernetes/kubelet.nix
+++ b/nixos/modules/services/cluster/kubernetes/kubelet.nix
@@ -36,6 +36,7 @@ let
       key = mkOption {
         description = "Key of taint.";
         default = name;
+        defaultText = literalDocBook "Name of this submodule.";
         type = str;
       };
       value = mkOption {
diff --git a/nixos/modules/services/computing/slurm/slurm.nix b/nixos/modules/services/computing/slurm/slurm.nix
index 02dfe2fe882f0..aa0be8726f0ec 100644
--- a/nixos/modules/services/computing/slurm/slurm.nix
+++ b/nixos/modules/services/computing/slurm/slurm.nix
@@ -281,6 +281,10 @@ in
         type = types.path;
         internal = true;
         default = etcSlurm;
+        defaultText = literalDocBook ''
+          Directory created from generated config files and
+          <literal>config.${opt.extraConfigPaths}</literal>.
+        '';
         description = ''
           Path to directory with slurm config files. This option is set by default from the
           Slurm module and is meant to make the Slurm config file available to other modules.
diff --git a/nixos/modules/services/games/quake3-server.nix b/nixos/modules/services/games/quake3-server.nix
index 1dc01260e8fad..175af4a838289 100644
--- a/nixos/modules/services/games/quake3-server.nix
+++ b/nixos/modules/services/games/quake3-server.nix
@@ -71,6 +71,7 @@ in {
       baseq3 = mkOption {
         type = types.either types.package types.path;
         default = defaultBaseq3;
+        defaultText = literalDocBook "Manually downloaded Quake 3 installation directory.";
         example = "/var/lib/q3ds";
         description = ''
           Path to the baseq3 files (pak*.pk3). If this is on the nix store (type = package) all .pk3 files should be saved
diff --git a/nixos/modules/services/misc/gitweb.nix b/nixos/modules/services/misc/gitweb.nix
index 13396bf2eb028..a1180716e36bb 100644
--- a/nixos/modules/services/misc/gitweb.nix
+++ b/nixos/modules/services/misc/gitweb.nix
@@ -47,6 +47,7 @@ in
         $highlight_bin = "${pkgs.highlight}/bin/highlight";
         ${cfg.extraConfig}
       '';
+      defaultText = literalDocBook "generated config file";
       type = types.path;
       readOnly = true;
       internal = true;
diff --git a/nixos/modules/services/misc/matrix-synapse.nix b/nixos/modules/services/misc/matrix-synapse.nix
index 90e2dbfafa15a..df9217cc52776 100644
--- a/nixos/modules/services/misc/matrix-synapse.nix
+++ b/nixos/modules/services/misc/matrix-synapse.nix
@@ -403,6 +403,29 @@ in {
             database = cfg.database_name;
           };
         }.${cfg.database_type};
+        defaultText = literalDocBook ''
+          <variablelist>
+            <varlistentry>
+              <term>using sqlite3</term>
+              <listitem>
+                <programlisting>
+                  { database = "''${config.${opt.dataDir}}/homeserver.db"; }
+                </programlisting>
+              </listitem>
+            </varlistentry>
+            <varlistentry>
+              <term>using psycopg2</term>
+              <listitem>
+                <programlisting>
+                  psycopg2 = {
+                    user = config.${opt.database_user};
+                    database = config.${opt.database_name};
+                  }
+                </programlisting>
+              </listitem>
+            </varlistentry>
+          </variablelist>
+        '';
         description = ''
           Arguments to pass to the engine.
         '';
diff --git a/nixos/modules/services/misc/rippled.nix b/nixos/modules/services/misc/rippled.nix
index 67768a97bfb6a..f6ec0677774b3 100644
--- a/nixos/modules/services/misc/rippled.nix
+++ b/nixos/modules/services/misc/rippled.nix
@@ -401,6 +401,7 @@ in
       config = mkOption {
         internal = true;
         default = pkgs.writeText "rippled.conf" rippledCfg;
+        defaultText = literalDocBook "generated config file";
       };
     };
   };
diff --git a/nixos/modules/services/monitoring/thanos.nix b/nixos/modules/services/monitoring/thanos.nix
index da626788d827c..9e93d8dbb0efd 100644
--- a/nixos/modules/services/monitoring/thanos.nix
+++ b/nixos/modules/services/monitoring/thanos.nix
@@ -83,6 +83,9 @@ let
   mkArgumentsOption = cmd: mkOption {
     type = types.listOf types.str;
     default = argumentsOf cmd;
+    defaultText = literalDocBook ''
+      calculated from <literal>config.services.thanos.${cmd}</literal>
+    '';
     description = ''
       Arguments to the <literal>thanos ${cmd}</literal> command.
 
diff --git a/nixos/modules/services/networking/firewall.nix b/nixos/modules/services/networking/firewall.nix
index b5b46fe6042cd..ff023a888f268 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 8c44687a38224..e37e324019e81 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 {
diff --git a/nixos/modules/services/web-apps/keycloak.nix b/nixos/modules/services/web-apps/keycloak.nix
index fac8e08b35975..e08f6dcabd2f5 100644
--- a/nixos/modules/services/web-apps/keycloak.nix
+++ b/nixos/modules/services/web-apps/keycloak.nix
@@ -140,6 +140,7 @@ in
           lib.mkOption {
             type = lib.types.port;
             default = dbPorts.${cfg.database.type};
+            defaultText = lib.literalDocBook "default port of selected database";
             description = ''
               Port of the database to connect to.
             '';
diff --git a/nixos/modules/services/web-apps/nextcloud.nix b/nixos/modules/services/web-apps/nextcloud.nix
index 04ec7888950d5..dfc80bbbf4286 100644
--- a/nixos/modules/services/web-apps/nextcloud.nix
+++ b/nixos/modules/services/web-apps/nextcloud.nix
@@ -499,6 +499,7 @@ in {
     occ = mkOption {
       type = types.package;
       default = occ;
+      defaultText = literalDocBook "generated script";
       internal = true;
       description = ''
         The nextcloud-occ program preconfigured to target this Nextcloud instance.
diff --git a/nixos/modules/services/web-servers/lighttpd/collectd.nix b/nixos/modules/services/web-servers/lighttpd/collectd.nix
index 3f262451c2cb7..5f091591daf91 100644
--- a/nixos/modules/services/web-servers/lighttpd/collectd.nix
+++ b/nixos/modules/services/web-servers/lighttpd/collectd.nix
@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.lighttpd.collectd;
+  opt = options.services.lighttpd.collectd;
 
   collectionConf = pkgs.writeText "collection.conf" ''
     datadir: "${config.services.collectd.dataDir}"
@@ -29,6 +30,9 @@ in
     collectionCgi = mkOption {
       type = types.path;
       default = defaultCollectionCgi;
+      defaultText = literalDocBook ''
+        <literal>config.${options.services.collectd.package}</literal> configured for lighttpd
+      '';
       description = ''
         Path to collection.cgi script from (collectd sources)/contrib/collection.cgi
         This option allows to use a customized version
diff --git a/nixos/modules/services/x11/display-managers/default.nix b/nixos/modules/services/x11/display-managers/default.nix
index 3adb50c678e4e..58e4fe04f3737 100644
--- a/nixos/modules/services/x11/display-managers/default.nix
+++ b/nixos/modules/services/x11/display-managers/default.nix
@@ -279,6 +279,9 @@ in
             defaultSessionFromLegacyOptions
           else
             null;
+        defaultText = literalDocBook ''
+          Taken from display manager settings or window manager settings, if either is set.
+        '';
         example = "gnome";
         description = ''
           Graphical session to pre-select in the session chooser (only effective for GDM, LightDM and SDDM).
diff --git a/nixos/modules/system/activation/activation-script.nix b/nixos/modules/system/activation/activation-script.nix
index 8dbfe393f109b..154b6127b27f5 100644
--- a/nixos/modules/system/activation/activation-script.nix
+++ b/nixos/modules/system/activation/activation-script.nix
@@ -142,6 +142,7 @@ in
       readOnly = true;
       internal = true;
       default = systemActivationScript (removeAttrs config.system.activationScripts [ "script" ]) true;
+      defaultText = literalDocBook "generated activation script";
     };
 
     system.userActivationScripts = mkOption {
diff --git a/nixos/modules/system/boot/plymouth.nix b/nixos/modules/system/boot/plymouth.nix
index 4b8194d2f85c1..78ae8e9d20b77 100644
--- a/nixos/modules/system/boot/plymouth.nix
+++ b/nixos/modules/system/boot/plymouth.nix
@@ -1,4 +1,4 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
@@ -7,6 +7,7 @@ let
   inherit (pkgs) plymouth nixos-icons;
 
   cfg = config.boot.plymouth;
+  opt = options.boot.plymouth;
 
   nixosBreezePlymouth = pkgs.plasma5Packages.breeze-plymouth.override {
     logoFile = cfg.logo;
@@ -71,6 +72,11 @@ in
 
       themePackages = mkOption {
         default = lib.optional (cfg.theme == "breeze") nixosBreezePlymouth;
+        defaultText = literalDocBook ''
+          A NixOS branded variant of the breeze theme when
+          <literal>config.${opt.theme} == "breeze"</literal>, otherwise
+          <literal>[ ]</literal>.
+        '';
         type = types.listOf types.package;
         description = ''
           Extra theme packages for plymouth.
diff --git a/nixos/modules/tasks/filesystems/zfs.nix b/nixos/modules/tasks/filesystems/zfs.nix
index 65364801c32aa..a9100da1aa401 100644
--- a/nixos/modules/tasks/filesystems/zfs.nix
+++ b/nixos/modules/tasks/filesystems/zfs.nix
@@ -112,6 +112,7 @@ in
         readOnly = true;
         type = types.bool;
         default = inInitrd || inSystem;
+        defaultText = literalDocBook "<literal>true</literal> if ZFS filesystem support is enabled";
         description = "True if ZFS filesystem support is enabled";
       };
 
diff --git a/nixos/modules/virtualisation/cri-o.nix b/nixos/modules/virtualisation/cri-o.nix
index 38766113f3916..cf51100015033 100644
--- a/nixos/modules/virtualisation/cri-o.nix
+++ b/nixos/modules/virtualisation/cri-o.nix
@@ -71,6 +71,10 @@ in
     package = mkOption {
       type = types.package;
       default = crioPackage;
+      defaultText = literalDocBook ''
+        <literal>pkgs.cri-o</literal> built with
+        <literal>config.${opt.extraPackages}</literal>.
+      '';
       internal = true;
       description = ''
         The final CRI-O package (including extra packages).