Merge pull request #148785 from pennae/more-option-doc-staticizing

treewide: more defaultText for options

lib/modules.nix

@@ -614,6 +614,8 @@ rec {
         definitions = map (def: def.value) res.defsFinal;
         files = map (def: def.file) res.defsFinal;
         inherit (res) isDefined;
+        # This allows options to be correctly displayed using `${options.path.to.it}`
+        __toString = _: showOption loc;
       };
 
   # Merge definitions of a value of a given type.

nixos/modules/config/networking.nix

@@ -1,12 +1,13 @@
 # /etc files related to networking, such as /etc/services.
 
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
 
   cfg = config.networking;
+  opt = options.networking;
 
   localhostMultiple = any (elem "localhost") (attrValues (removeAttrs cfg.hosts [ "127.0.0.1" "::1" ]));
 
@@ -78,6 +79,7 @@ in
       httpProxy = lib.mkOption {
         type = types.nullOr types.str;
         default = cfg.proxy.default;
+        defaultText = literalExpression "config.${opt.proxy.default}";
         description = ''
           This option specifies the http_proxy environment variable.
         '';
@@ -87,6 +89,7 @@ in
       httpsProxy = lib.mkOption {
         type = types.nullOr types.str;
         default = cfg.proxy.default;
+        defaultText = literalExpression "config.${opt.proxy.default}";
         description = ''
           This option specifies the https_proxy environment variable.
         '';
@@ -96,6 +99,7 @@ in
       ftpProxy = lib.mkOption {
         type = types.nullOr types.str;
         default = cfg.proxy.default;
+        defaultText = literalExpression "config.${opt.proxy.default}";
         description = ''
           This option specifies the ftp_proxy environment variable.
         '';
@@ -105,6 +109,7 @@ in
       rsyncProxy = lib.mkOption {
         type = types.nullOr types.str;
         default = cfg.proxy.default;
+        defaultText = literalExpression "config.${opt.proxy.default}";
         description = ''
           This option specifies the rsync_proxy environment variable.
         '';
@@ -114,6 +119,7 @@ in
       allProxy = lib.mkOption {
         type = types.nullOr types.str;
         default = cfg.proxy.default;
+        defaultText = literalExpression "config.${opt.proxy.default}";
         description = ''
           This option specifies the all_proxy environment variable.
         '';

nixos/modules/config/system-path.nix

@@ -41,12 +41,17 @@ let
       pkgs.zstd
     ];
 
-    defaultPackages = map (pkg: setPrio ((pkg.meta.priority or 5) + 3) pkg)
-      [ pkgs.nano
-        pkgs.perl
-        pkgs.rsync
-        pkgs.strace
-      ];
+  defaultPackageNames =
+    [ "nano"
+      "perl"
+      "rsync"
+      "strace"
+    ];
+  defaultPackages =
+    map
+      (n: let pkg = pkgs.${n}; in setPrio ((pkg.meta.priority or 5) + 3) pkg)
+      defaultPackageNames;
+  defaultPackagesText = "[ ${concatMapStringsSep " " (n: "pkgs.${n}") defaultPackageNames } ]";
 
 in
 
@@ -73,6 +78,11 @@ in
       defaultPackages = mkOption {
         type = types.listOf types.package;
         default = defaultPackages;
+        defaultText = literalDocBook ''
+          these packages, with their <literal>meta.priority</literal> numerically increased
+          (thus lowering their installation priority):
+          <programlisting>${defaultPackagesText}</programlisting>
+        '';
         example = [];
         description = ''
           Set of default packages that aren't strictly necessary

nixos/modules/hardware/system-76.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 let
-  inherit (lib) mkOption mkEnableOption types mkIf mkMerge optional versionOlder;
+  inherit (lib) literalExpression mkOption mkEnableOption types mkIf mkMerge optional versionOlder;
   cfg = config.hardware.system76;
+  opt = options.hardware.system76;
 
   kpkgs = config.boot.kernelPackages;
   modules = [ "system76" "system76-io" ] ++ (optional (versionOlder kpkgs.kernel.version "5.5") "system76-acpi");
@@ -60,6 +61,7 @@ in {
 
       firmware-daemon.enable = mkOption {
         default = cfg.enableAll;
+        defaultText = literalExpression "config.${opt.enableAll}";
         example = true;
         description = "Whether to enable the system76 firmware daemon";
         type = types.bool;
@@ -67,6 +69,7 @@ in {
 
       kernel-modules.enable = mkOption {
         default = cfg.enableAll;
+        defaultText = literalExpression "config.${opt.enableAll}";
         example = true;
         description = "Whether to make the system76 out-of-tree kernel modules available";
         type = types.bool;
@@ -74,6 +77,7 @@ in {
 
       power-daemon.enable = mkOption {
         default = cfg.enableAll;
+        defaultText = literalExpression "config.${opt.enableAll}";
         example = true;
         description = "Whether to enable the system76 power daemon";
         type = types.bool;

nixos/modules/misc/version.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.system.nixos;
+  opt = options.system.nixos;
 in
 
 {
@@ -53,6 +54,7 @@ in
     stateVersion = mkOption {
       type = types.str;
       default = cfg.release;
+      defaultText = literalExpression "config.${opt.release}";
       description = ''
         Every once in a while, a new NixOS release may change
         configuration defaults in a way incompatible with stateful

nixos/modules/programs/captive-browser.nix

@@ -3,6 +3,18 @@
 with lib;
 let
   cfg = config.programs.captive-browser;
+  browserDefault = chromium: concatStringsSep " " [
+    ''env XDG_CONFIG_HOME="$PREV_CONFIG_HOME"''
+    ''${chromium}/bin/chromium''
+    ''--user-data-dir=''${XDG_DATA_HOME:-$HOME/.local/share}/chromium-captive''
+    ''--proxy-server="socks5://$PROXY"''
+    ''--host-resolver-rules="MAP * ~NOTFOUND , EXCLUDE localhost"''
+    ''--no-first-run''
+    ''--new-window''
+    ''--incognito''
+    ''-no-default-browser-check''
+    ''http://cache.nixos.org/''
+  ];
 in
 {
   ###### interface
@@ -26,18 +38,8 @@ in
       # the options below are the same as in "captive-browser.toml"
       browser = mkOption {
         type = types.str;
-        default = concatStringsSep " " [
-          ''env XDG_CONFIG_HOME="$PREV_CONFIG_HOME"''
-          ''${pkgs.chromium}/bin/chromium''
-          ''--user-data-dir=''${XDG_DATA_HOME:-$HOME/.local/share}/chromium-captive''
-          ''--proxy-server="socks5://$PROXY"''
-          ''--host-resolver-rules="MAP * ~NOTFOUND , EXCLUDE localhost"''
-          ''--no-first-run''
-          ''--new-window''
-          ''--incognito''
-          ''-no-default-browser-check''
-          ''http://cache.nixos.org/''
-        ];
+        default = browserDefault pkgs.chromium;
+        defaultText = literalExpression (browserDefault "\${pkgs.chromium}");
         description = ''
           The shell (/bin/sh) command executed once the proxy starts.
           When browser exits, the proxy exits. An extra env var PROXY is available.

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

nixos/modules/programs/zsh/zsh.nix

@@ -1,6 +1,6 @@
 # This module defines global configuration for the zshell.
 
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
@@ -9,6 +9,7 @@ let
   cfge = config.environment;
 
   cfg = config.programs.zsh;
+  opt = options.programs.zsh;
 
   zshAliases = concatStringsSep "\n" (
     mapAttrsFlatten (k: v: "alias ${k}=${escapeShellArg v}")
@@ -147,6 +148,7 @@ in
 
       enableGlobalCompInit = mkOption {
         default = cfg.enableCompletion;
+        defaultText = literalExpression "config.${opt.enableCompletion}";
         description = ''
           Enable execution of compinit call for all interactive zsh shells.
 

nixos/modules/security/acme.nix

@@ -2,6 +2,7 @@
 with lib;
 let
   cfg = config.security.acme;
+  opt = options.security.acme;
 
   # Used to calculate timer accuracy for coalescing
   numCerts = length (builtins.attrNames cfg.certs);
@@ -485,6 +486,7 @@ let
       email = mkOption {
         type = types.nullOr types.str;
         default = cfg.email;
+        defaultText = literalExpression "config.${opt.email}";
         description = "Contact email address for the CA to be able to reach you.";
       };
 

nixos/modules/security/dhparams.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 let
-  inherit (lib) mkOption types;
+  inherit (lib) literalExpression mkOption types;
   cfg = config.security.dhparams;
+  opt = options.security.dhparams;
 
   bitType = types.addCheck types.int (b: b >= 16) // {
     name = "bits";
@@ -13,6 +14,7 @@ let
     options.bits = mkOption {
       type = bitType;
       default = cfg.defaultBitSize;
+      defaultText = literalExpression "config.${opt.defaultBitSize}";
       description = ''
         The bit size for the prime that is used during a Diffie-Hellman
         key exchange.

nixos/modules/services/audio/mpdscribble.nix

@@ -1,10 +1,11 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.mpdscribble;
   mpdCfg = config.services.mpd;
+  mpdOpt = options.services.mpd;
 
   endpointUrls = {
     "last.fm" = "http://post.audioscrobbler.com";
@@ -108,6 +109,11 @@ in {
         mpdCfg.network.listenAddress
       else
         "localhost");
+      defaultText = literalExpression ''
+        if config.${mpdOpt.network.listenAddress} != "any"
+        then config.${mpdOpt.network.listenAddress}
+        else "localhost"
+      '';
       type = types.str;
       description = ''
         Host for the mpdscribble daemon to search for a mpd daemon on.
@@ -122,6 +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.
@@ -132,6 +142,7 @@ in {
 
     port = mkOption {
       default = mpdCfg.network.port;
+      defaultText = literalExpression "config.${mpdOpt.network.port}";
       type = types.port;
       description = ''
         Port for the mpdscribble daemon to search for a mpd daemon on.

nixos/modules/services/backup/tarsnap.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, utils, ... }:
+{ config, lib, options, pkgs, utils, ... }:
 
 with lib;
 
 let
   gcfg = config.services.tarsnap;
+  opt = options.services.tarsnap;
 
   configFile = name: cfg: ''
     keyfile ${cfg.keyfile}
@@ -59,12 +60,13 @@ in
       };
 
       archives = mkOption {
-        type = types.attrsOf (types.submodule ({ config, ... }:
+        type = types.attrsOf (types.submodule ({ config, options, ... }:
           {
             options = {
               keyfile = mkOption {
                 type = types.str;
                 default = gcfg.keyfile;
+                defaultText = literalExpression "config.${opt.keyfile}";
                 description = ''
                   Set a specific keyfile for this archive. This defaults to
                   <literal>"/root/tarsnap.key"</literal> if left unspecified.
@@ -87,6 +89,9 @@ in
               cachedir = mkOption {
                 type = types.nullOr types.path;
                 default = "/var/cache/tarsnap/${utils.escapeSystemdPath config.keyfile}";
+                defaultText = literalExpression ''
+                  "/var/cache/tarsnap/''${utils.escapeSystemdPath config.${options.keyfile}}"
+                '';
                 description = ''
                   The cache allows tarsnap to identify previously stored data
                   blocks, reducing archival time and bandwidth usage.

nixos/modules/services/cluster/hadoop/default.nix

@@ -1,6 +1,7 @@
-{ config, lib, pkgs, ...}:
+{ config, lib, options, pkgs, ...}:
 let
   cfg = config.services.hadoop;
+  opt = options.services.hadoop;
 in
 with lib;
 {
@@ -44,6 +45,14 @@ with lib;
         "mapreduce.map.env" = "HADOOP_MAPRED_HOME=${cfg.package}/lib/${cfg.package.untarDir}";
         "mapreduce.reduce.env" = "HADOOP_MAPRED_HOME=${cfg.package}/lib/${cfg.package.untarDir}";
       };
+      defaultText = literalExpression ''
+        {
+          "mapreduce.framework.name" = "yarn";
+          "yarn.app.mapreduce.am.env" = "HADOOP_MAPRED_HOME=''${config.${opt.package}}/lib/''${config.${opt.package}.untarDir}";
+          "mapreduce.map.env" = "HADOOP_MAPRED_HOME=''${config.${opt.package}}/lib/''${config.${opt.package}.untarDir}";
+          "mapreduce.reduce.env" = "HADOOP_MAPRED_HOME=''${config.${opt.package}}/lib/''${config.${opt.package}.untarDir}";
+        }
+      '';
       type = types.attrsOf types.anything;
       example = literalExpression ''
         options.services.hadoop.mapredSite.default // {
@@ -98,6 +107,9 @@ with lib;
 
     log4jProperties = mkOption {
       default = "${cfg.package}/lib/${cfg.package.untarDir}/etc/hadoop/log4j.properties";
+      defaultText = literalExpression ''
+        "''${config.${opt.package}}/lib/''${config.${opt.package}.untarDir}/etc/hadoop/log4j.properties"
+      '';
       type = types.path;
       example = literalExpression ''
         "''${pkgs.hadoop}/lib/''${pkgs.hadoop.untarDir}/etc/hadoop/log4j.properties";

nixos/modules/services/cluster/kubernetes/addons/dashboard.nix

@@ -1,9 +1,10 @@
-{ config, pkgs, lib, ... }:
+{ config, options, pkgs, lib, ... }:
 
 with lib;
 
 let
   cfg = config.services.kubernetes.addons.dashboard;
+  opt = options.services.kubernetes.addons.dashboard;
 in {
   imports = [
     (mkRenamedOptionModule [ "services" "kubernetes" "addons" "dashboard" "enableRBAC" ] [ "services" "kubernetes" "addons" "dashboard" "rbac" "enable" ])
@@ -28,6 +29,9 @@ in {
             description = "Whether to enable role based access control is enabled for kubernetes dashboard";
             type = types.bool;
             default = elem "RBAC" config.services.kubernetes.apiserver.authorizationMode;
+            defaultText = literalExpression ''
+              elem "RBAC" config.${options.services.kubernetes.apiserver.authorizationMode}
+            '';
           };
 
           clusterAdmin = mkOption {
@@ -54,6 +58,14 @@ in {
         finalImageTag = cfg.version;
         sha256 = "01xrr4pwgr2hcjrjsi3d14ifpzdfbxzqpzxbk2fkbjb9zkv38zxy";
       };
+      defaultText = literalExpression ''
+        {
+          imageName = "k8s.gcr.io/kubernetes-dashboard-amd64";
+          imageDigest = "sha256:0ae6b69432e78069c5ce2bcde0fe409c5c4d6f0f4d9cd50a17974fea38898747";
+          finalImageTag = config.${opt.version};
+          sha256 = "01xrr4pwgr2hcjrjsi3d14ifpzdfbxzqpzxbk2fkbjb9zkv38zxy";
+        };
+      '';
     };
   };
 

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;
     };
 

nixos/modules/services/cluster/kubernetes/apiserver.nix

@@ -1,9 +1,10 @@
-  { config, lib, pkgs, ... }:
+  { config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   top = config.services.kubernetes;
+  otop = options.services.kubernetes;
   cfg = top.apiserver;
 
   isRBACEnabled = elem "RBAC" cfg.authorizationMode;
@@ -84,6 +85,7 @@ in
     clientCaFile = mkOption {
       description = "Kubernetes apiserver CA file for client auth.";
       default = top.caFile;
+      defaultText = literalExpression "config.${otop.caFile}";
       type = nullOr path;
     };
 
@@ -138,6 +140,7 @@ in
       caFile = mkOption {
         description = "Etcd ca file.";
         default = top.caFile;
+        defaultText = literalExpression "config.${otop.caFile}";
         type = types.nullOr types.path;
       };
     };
@@ -157,6 +160,7 @@ in
     featureGates = mkOption {
       description = "List set of feature gates";
       default = top.featureGates;
+      defaultText = literalExpression "config.${otop.featureGates}";
       type = listOf str;
     };
 
@@ -175,6 +179,7 @@ in
     kubeletClientCaFile = mkOption {
       description = "Path to a cert file for connecting to kubelet.";
       default = top.caFile;
+      defaultText = literalExpression "config.${otop.caFile}";
       type = nullOr path;
     };
 

nixos/modules/services/cluster/kubernetes/controller-manager.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   top = config.services.kubernetes;
+  otop = options.services.kubernetes;
   cfg = top.controllerManager;
 in
 {
@@ -30,6 +31,7 @@ in
     clusterCidr = mkOption {
       description = "Kubernetes CIDR Range for Pods in cluster.";
       default = top.clusterCidr;
+      defaultText = literalExpression "config.${otop.clusterCidr}";
       type = str;
     };
 
@@ -44,6 +46,7 @@ in
     featureGates = mkOption {
       description = "List set of feature gates";
       default = top.featureGates;
+      defaultText = literalExpression "config.${otop.featureGates}";
       type = listOf str;
     };
 
@@ -67,6 +70,7 @@ in
         service account's token secret.
       '';
       default = top.caFile;
+      defaultText = literalExpression "config.${otop.caFile}";
       type = nullOr path;
     };
 

nixos/modules/services/cluster/kubernetes/default.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.kubernetes;
+  opt = options.services.kubernetes;
 
   defaultContainerdSettings = {
     version = 2;
@@ -87,6 +88,7 @@ let
       description = "${prefix} certificate authority file used to connect to kube-apiserver.";
       type = types.nullOr types.path;
       default = cfg.caFile;
+      defaultText = literalExpression "config.${opt.caFile}";
     };
 
     certFile = mkOption {

nixos/modules/services/cluster/kubernetes/kubelet.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   top = config.services.kubernetes;
+  otop = options.services.kubernetes;
   cfg = top.kubelet;
 
   cniConfig =
@@ -35,6 +36,7 @@ let
       key = mkOption {
         description = "Key of taint.";
         default = name;
+        defaultText = literalDocBook "Name of this submodule.";
         type = str;
       };
       value = mkOption {
@@ -76,12 +78,14 @@ in
     clusterDomain = mkOption {
       description = "Use alternative domain.";
       default = config.services.kubernetes.addons.dns.clusterDomain;
+      defaultText = literalExpression "config.${options.services.kubernetes.addons.dns.clusterDomain}";
       type = str;
     };
 
     clientCaFile = mkOption {
       description = "Kubernetes apiserver CA file for client authentication.";
       default = top.caFile;
+      defaultText = literalExpression "config.${otop.caFile}";
       type = nullOr path;
     };
 
@@ -148,6 +152,7 @@ in
     featureGates = mkOption {
       description = "List set of feature gates";
       default = top.featureGates;
+      defaultText = literalExpression "config.${otop.featureGates}";
       type = listOf str;
     };
 

nixos/modules/services/cluster/kubernetes/proxy.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   top = config.services.kubernetes;
+  otop = options.services.kubernetes;
   cfg = top.proxy;
 in
 {
@@ -31,6 +32,7 @@ in
     featureGates = mkOption {
       description = "List set of feature gates";
       default = top.featureGates;
+      defaultText = literalExpression "config.${otop.featureGates}";
       type = listOf str;
     };
 

nixos/modules/services/cluster/kubernetes/scheduler.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   top = config.services.kubernetes;
+  otop = options.services.kubernetes;
   cfg = top.scheduler;
 in
 {
@@ -27,6 +28,7 @@ in
     featureGates = mkOption {
       description = "List set of feature gates";
       default = top.featureGates;
+      defaultText = literalExpression "config.${otop.featureGates}";
       type = listOf str;
     };
 

nixos/modules/services/computing/slurm/slurm.nix

@@ -1,10 +1,11 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
 
   cfg = config.services.slurm;
+  opt = options.services.slurm;
   # configuration file can be generated by http://slurm.schedmd.com/configurator.html
 
   defaultUser = "slurm";
@@ -90,6 +91,7 @@ in
         storageUser = mkOption {
           type = types.str;
           default = cfg.user;
+          defaultText = literalExpression "config.${opt.user}";
           description = ''
             Database user name.
           '';
@@ -154,6 +156,7 @@ in
       controlAddr = mkOption {
         type = types.nullOr types.str;
         default = cfg.controlMachine;
+        defaultText = literalExpression "config.${opt.controlMachine}";
         example = null;
         description = ''
           Name that ControlMachine should be referred to in establishing a
@@ -279,6 +282,10 @@ 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.

nixos/modules/services/continuous-integration/buildbot/master.nix

@@ -1,11 +1,12 @@
 # NixOS module for Buildbot continous integration server.
 
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.buildbot-master;
+  opt = options.services.buildbot-master;
 
   python = cfg.package.pythonModule;
 
@@ -152,6 +153,7 @@ in {
 
       buildbotDir = mkOption {
         default = "${cfg.home}/master";
+        defaultText = literalExpression ''"''${config.${opt.home}}/master"'';
         type = types.path;
         description = "Specifies the Buildbot directory.";
       };

nixos/modules/services/continuous-integration/buildbot/worker.nix

@@ -1,11 +1,12 @@
 # NixOS module for Buildbot Worker.
 
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.buildbot-worker;
+  opt = options.services.buildbot-worker;
 
   python = cfg.package.pythonModule;
 
@@ -77,6 +78,7 @@ in {
 
       buildbotDir = mkOption {
         default = "${cfg.home}/worker";
+        defaultText = literalExpression ''"''${config.${opt.home}}/worker"'';
         type = types.path;
         description = "Specifies the Buildbot directory.";
       };

nixos/modules/services/continuous-integration/gocd-agent/default.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.gocd-agent;
+  opt = options.services.gocd-agent;
 in {
   options = {
     services.gocd-agent = {
@@ -98,6 +99,15 @@ in {
           "-Dcruise.console.publish.interval=10"
           "-Djava.security.egd=file:/dev/./urandom"
         ];
+        defaultText = literalExpression ''
+          [
+            "-Xms''${config.${opt.initialJavaHeapSize}}"
+            "-Xmx''${config.${opt.maxJavaHeapMemory}}"
+            "-Djava.io.tmpdir=/tmp"
+            "-Dcruise.console.publish.interval=10"
+            "-Djava.security.egd=file:/dev/./urandom"
+          ]
+        '';
         description = ''
           Specifies startup command line arguments to pass to Go.CD agent
           java process.

nixos/modules/services/continuous-integration/gocd-server/default.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.gocd-server;
+  opt = options.services.gocd-server;
 in {
   options = {
     services.gocd-server = {
@@ -106,6 +107,20 @@ in {
           "-Dcruise.server.port=${toString cfg.port}"
           "-Dcruise.server.ssl.port=${toString cfg.sslPort}"
         ];
+        defaultText = literalExpression ''
+          [
+            "-Xms''${config.${opt.initialJavaHeapSize}}"
+            "-Xmx''${config.${opt.maxJavaHeapMemory}}"
+            "-Dcruise.listen.host=''${config.${opt.listenAddress}}"
+            "-Duser.language=en"
+            "-Djruby.rack.request.size.threshold.bytes=30000000"
+            "-Duser.country=US"
+            "-Dcruise.config.dir=''${config.${opt.workDir}}/conf"
+            "-Dcruise.config.file=''${config.${opt.workDir}}/conf/cruise-config.xml"
+            "-Dcruise.server.port=''${toString config.${opt.port}}"
+            "-Dcruise.server.ssl.port=''${toString config.${opt.sslPort}}"
+          ]
+        '';
 
         description = ''
           Specifies startup command line arguments to pass to Go.CD server

nixos/modules/services/databases/hbase.nix

@@ -1,14 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, options, lib, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.hbase;
-
-  defaultConfig = {
-    "hbase.rootdir" = "file://${cfg.dataDir}/hbase";
-    "hbase.zookeeper.property.dataDir" = "${cfg.dataDir}/zookeeper";
-  };
+  opt = options.services.hbase;
 
   buildProperty = configAttr:
     (builtins.concatStringsSep "\n"
@@ -23,7 +19,7 @@ let
 
   configFile = pkgs.writeText "hbase-site.xml"
     ''<configuration>
-        ${buildProperty (defaultConfig // cfg.settings)}
+        ${buildProperty (opt.settings.default // cfg.settings)}
       </configuration>
     '';
 
@@ -96,7 +92,16 @@ in {
 
       settings = mkOption {
         type = with lib.types; attrsOf (oneOf [ str int bool ]);
-        default = defaultConfig;
+        default = {
+          "hbase.rootdir" = "file://${cfg.dataDir}/hbase";
+          "hbase.zookeeper.property.dataDir" = "${cfg.dataDir}/zookeeper";
+        };
+        defaultText = literalExpression ''
+          {
+            "hbase.rootdir" = "file://''${config.${opt.dataDir}}/hbase";
+            "hbase.zookeeper.property.dataDir" = "''${config.${opt.dataDir}}/zookeeper";
+          }
+        '';
         description = ''
           configurations in hbase-site.xml, see <link xlink:href="https://github.com/apache/hbase/blob/master/hbase-server/src/test/resources/hbase-site.xml"/> for details.
         '';

nixos/modules/services/databases/neo4j.nix

@@ -4,6 +4,7 @@ with lib;
 
 let
   cfg = config.services.neo4j;
+  opt = options.services.neo4j;
   certDirOpt = options.services.neo4j.directories.certificates;
   isDefaultPathOption = opt: isOption opt && opt.type == types.path && opt.highestPrio >= 1500;
 
@@ -256,6 +257,7 @@ in {
       certificates = mkOption {
         type = types.path;
         default = "${cfg.directories.home}/certificates";
+        defaultText = literalExpression ''"''${config.${opt.directories.home}}/certificates"'';
         description = ''
           Directory for storing certificates to be used by Neo4j for
           TLS connections.
@@ -280,6 +282,7 @@ in {
       data = mkOption {
         type = types.path;
         default = "${cfg.directories.home}/data";
+        defaultText = literalExpression ''"''${config.${opt.directories.home}}/data"'';
         description = ''
           Path of the data directory. You must not configure more than one
           Neo4j installation to use the same data directory.
@@ -305,6 +308,7 @@ in {
       imports = mkOption {
         type = types.path;
         default = "${cfg.directories.home}/import";
+        defaultText = literalExpression ''"''${config.${opt.directories.home}}/import"'';
         description = ''
           The root directory for file URLs used with the Cypher
           <literal>LOAD CSV</literal> clause. Only meaningful when
@@ -321,6 +325,7 @@ in {
       plugins = mkOption {
         type = types.path;
         default = "${cfg.directories.home}/plugins";
+        defaultText = literalExpression ''"''${config.${opt.directories.home}}/plugins"'';
         description = ''
           Path of the database plugin directory. Compiled Java JAR files that
           contain database procedures will be loaded if they are placed in
@@ -432,6 +437,7 @@ in {
           baseDirectory = mkOption {
             type = types.path;
             default = "${cfg.directories.certificates}/${name}";
+            defaultText = literalExpression ''"''${config.${opt.directories.certificates}}/''${name}"'';
             description = ''
               The mandatory base directory for cryptographic objects of this
               policy. This path is only automatically generated when this
@@ -493,6 +499,7 @@ in {
           revokedDir = mkOption {
             type = types.path;
             default = "${config.baseDirectory}/revoked";
+            defaultText = literalExpression ''"''${config.${options.baseDirectory}}/revoked"'';
             description = ''
               Path to directory of CRLs (Certificate Revocation Lists) in
               PEM format. Must be an absolute path. The existence of this
@@ -528,6 +535,7 @@ in {
           trustedDir = mkOption {
             type = types.path;
             default = "${config.baseDirectory}/trusted";
+            defaultText = literalExpression ''"''${config.${options.baseDirectory}}/trusted"'';
             description = ''
               Path to directory of X.509 certificates in PEM format for
               trusted parties. Must be an absolute path. The existence of this

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

nixos/modules/services/games/terraria.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg   = config.services.terraria;
+  opt   = options.services.terraria;
   worldSizeMap = { small = 1; medium = 2; large = 3; };
   valFlag = name: val: optionalString (val != null) "-${name} \"${escape ["\\" "\""] (toString val)}\"";
   boolFlag = name: val: optionalString val "-${name}";
@@ -36,7 +37,7 @@ in
         type        = types.bool;
         default     = false;
         description = ''
-          If enabled, starts a Terraria server. The server can be connected to via <literal>tmux -S ${cfg.dataDir}/terraria.sock attach</literal>
+          If enabled, starts a Terraria server. The server can be connected to via <literal>tmux -S ''${config.${opt.dataDir}}/terraria.sock attach</literal>
           for administration by users who are a part of the <literal>terraria</literal> group (use <literal>C-b d</literal> shortcut to detach again).
         '';
       };

nixos/modules/services/hardware/tcsd.nix

@@ -1,11 +1,12 @@
 # tcsd daemon.
 
-{ config, pkgs, lib, ... }:
+{ config, options, pkgs, lib, ... }:
 
 with lib;
 let
 
   cfg = config.services.tcsd;
+  opt = options.services.tcsd;
 
   tcsdConf = pkgs.writeText "tcsd.conf" ''
     port = 30003
@@ -83,6 +84,7 @@ in
 
       platformCred = mkOption {
         default = "${cfg.stateDir}/platform.cert";
+        defaultText = literalExpression ''"''${config.${opt.stateDir}}/platform.cert"'';
         type = types.path;
         description = ''
           Path to the platform credential for your TPM. Your TPM
@@ -96,6 +98,7 @@ in
 
       conformanceCred = mkOption {
         default = "${cfg.stateDir}/conformance.cert";
+        defaultText = literalExpression ''"''${config.${opt.stateDir}}/conformance.cert"'';
         type = types.path;
         description = ''
           Path to the conformance credential for your TPM.
@@ -104,6 +107,7 @@ in
 
       endorsementCred = mkOption {
         default = "${cfg.stateDir}/endorsement.cert";
+        defaultText = literalExpression ''"''${config.${opt.stateDir}}/endorsement.cert"'';
         type = types.path;
         description = ''
           Path to the endorsement credential for your TPM.

nixos/modules/services/logging/journalbeat.nix

@@ -5,14 +5,10 @@ with lib;
 let
   cfg = config.services.journalbeat;
 
-  lt6 = builtins.compareVersions cfg.package.version "6" < 0;
-
   journalbeatYml = pkgs.writeText "journalbeat.yml" ''
     name: ${cfg.name}
     tags: ${builtins.toJSON cfg.tags}
 
-    ${optionalString lt6 "journalbeat.cursor_state_file: /var/lib/${cfg.stateDir}/cursor-state"}
-
     ${cfg.extraConfig}
   '';
 
@@ -57,17 +53,7 @@ in
 
       extraConfig = mkOption {
         type = types.lines;
-        default = optionalString lt6 ''
-          journalbeat:
-            seek_position: cursor
-            cursor_seek_fallback: tail
-            write_cursor_state: true
-            cursor_flush_period: 5s
-            clean_field_names: true
-            convert_to_numbers: false
-            move_metadata_to_field: journal
-            default_type: journal
-        '';
+        default = "";
         description = "Any other configuration options you want to add";
       };
 

nixos/modules/services/mail/rspamd.nix

@@ -5,6 +5,7 @@ with lib;
 let
 
   cfg = config.services.rspamd;
+  opt = options.services.rspamd;
   postfixCfg = config.services.postfix;
 
   bindSocketOpts = {options, config, ... }: {
@@ -285,8 +286,8 @@ in
               bindSockets = [{
                 socket = "/run/rspamd/rspamd.sock";
                 mode = "0660";
-                owner = "${cfg.user}";
-                group = "${cfg.group}";
+                owner = "''${config.${opt.user}}";
+                group = "''${config.${opt.group}}";
               }];
             };
             controller = {

nixos/modules/services/misc/airsonic.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.airsonic;
+  opt = options.services.airsonic;
 in {
   options = {
 
@@ -78,7 +79,7 @@ in {
         description = ''
           List of paths to transcoder executables that should be accessible
           from Airsonic. Symlinks will be created to each executable inside
-          ${cfg.home}/transcoders.
+          ''${config.${opt.home}}/transcoders.
         '';
       };
 

nixos/modules/services/misc/etcd.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.etcd;
+  opt = options.services.etcd;
 
 in {
 
@@ -24,6 +25,7 @@ in {
     advertiseClientUrls = mkOption {
       description = "Etcd list of this member's client URLs to advertise to the rest of the cluster.";
       default = cfg.listenClientUrls;
+      defaultText = literalExpression "config.${opt.listenClientUrls}";
       type = types.listOf types.str;
     };
 
@@ -42,12 +44,14 @@ in {
     initialAdvertisePeerUrls = mkOption {
       description = "Etcd list of this member's peer URLs to advertise to rest of the cluster.";
       default = cfg.listenPeerUrls;
+      defaultText = literalExpression "config.${opt.listenPeerUrls}";
       type = types.listOf types.str;
     };
 
     initialCluster = mkOption {
       description = "Etcd initial cluster configuration for bootstrapping.";
       default = ["${cfg.name}=http://127.0.0.1:2380"];
+      defaultText = literalExpression ''["''${config.${opt.name}}=http://127.0.0.1:2380"]'';
       type = types.listOf types.str;
     };
 
@@ -96,18 +100,21 @@ in {
     peerCertFile = mkOption {
       description = "Cert file to use for peer to peer communication";
       default = cfg.certFile;
+      defaultText = literalExpression "config.${opt.certFile}";
       type = types.nullOr types.path;
     };
 
     peerKeyFile = mkOption {
       description = "Key file to use for peer to peer communication";
       default = cfg.keyFile;
+      defaultText = literalExpression "config.${opt.keyFile}";
       type = types.nullOr types.path;
     };
 
     peerTrustedCaFile = mkOption {
       description = "Certificate authority file to use for peer to peer communication";
       default = cfg.trustedCaFile;
+      defaultText = literalExpression "config.${opt.trustedCaFile}";
       type = types.nullOr types.path;
     };
 

nixos/modules/services/misc/exhibitor.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.exhibitor;
+  opt = options.services.exhibitor;
   exhibitorConfig = ''
     zookeeper-install-directory=${cfg.baseDir}/zookeeper
     zookeeper-data-directory=${cfg.zkDataDir}
@@ -165,6 +166,7 @@ in
       zkDataDir = mkOption {
         type = types.str;
         default = "${cfg.baseDir}/zkData";
+        defaultText = literalExpression ''"''${config.${opt.baseDir}}/zkData"'';
         description = ''
           The Zookeeper data directory
         '';
@@ -172,6 +174,7 @@ in
       zkLogDir = mkOption {
         type = types.path;
         default = "${cfg.baseDir}/zkLogs";
+        defaultText = literalExpression ''"''${config.${opt.baseDir}}/zkLogs"'';
         description = ''
           The Zookeeper logs directory
         '';

nixos/modules/services/misc/gitea.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.gitea;
+  opt = options.services.gitea;
   gitea = cfg.package;
   pg = config.services.postgresql;
   useMysql = cfg.database.type == "mysql";
@@ -51,6 +52,7 @@ in
       log = {
         rootPath = mkOption {
           default = "${cfg.stateDir}/log";
+          defaultText = literalExpression ''"''${config.${opt.stateDir}}/log"'';
           type = types.str;
           description = "Root path for log files.";
         };
@@ -84,6 +86,11 @@ in
         port = mkOption {
           type = types.port;
           default = (if !usePostgresql then 3306 else pg.port);
+          defaultText = literalExpression ''
+            if config.${opt.database.type} != "postgresql"
+            then 3306
+            else config.${options.services.postgresql.port}
+          '';
           description = "Database host port.";
         };
 
@@ -130,6 +137,7 @@ in
         path = mkOption {
           type = types.str;
           default = "${cfg.stateDir}/data/gitea.db";
+          defaultText = literalExpression ''"''${config.${opt.stateDir}}/data/gitea.db"'';
           description = "Path to the sqlite3 database file.";
         };
 
@@ -166,6 +174,7 @@ in
         backupDir = mkOption {
           type = types.str;
           default = "${cfg.stateDir}/dump";
+          defaultText = literalExpression ''"''${config.${opt.stateDir}}/dump"'';
           description = "Path to the dump files.";
         };
       };
@@ -199,6 +208,7 @@ in
         contentDir = mkOption {
           type = types.str;
           default = "${cfg.stateDir}/data/lfs";
+          defaultText = literalExpression ''"''${config.${opt.stateDir}}/data/lfs"'';
           description = "Where to store LFS files.";
         };
       };
@@ -212,6 +222,7 @@ in
       repositoryRoot = mkOption {
         type = types.str;
         default = "${cfg.stateDir}/repositories";
+        defaultText = literalExpression ''"''${config.${opt.stateDir}}/repositories"'';
         description = "Path to the git repositories.";
       };
 

nixos/modules/services/misc/gitlab.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, utils, ... }:
+{ config, lib, options, pkgs, utils, ... }:
 
 with lib;
 
 let
   cfg = config.services.gitlab;
+  opt = options.services.gitlab;
 
   ruby = cfg.packages.gitlab.ruby;
 
@@ -309,6 +310,7 @@ in {
       backup.path = mkOption {
         type = types.str;
         default = cfg.statePath + "/backup";
+        defaultText = literalExpression ''config.${opt.statePath} + "/backup"'';
         description = "GitLab path for backups.";
       };
 
@@ -554,6 +556,7 @@ in {
         defaultForProjects = mkOption {
           type = types.bool;
           default = cfg.registry.enable;
+          defaultText = literalExpression "config.${opt.registry.enable}";
           description = "If GitLab container registry should be enabled by default for projects.";
         };
         issuer = mkOption {

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;

nixos/modules/services/misc/gogs.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.gogs;
+  opt = options.services.gogs;
   configFile = pkgs.writeText "app.ini" ''
     APP_NAME = ${cfg.appName}
     RUN_USER = ${cfg.user}
@@ -129,6 +130,7 @@ in
         path = mkOption {
           type = types.str;
           default = "${cfg.stateDir}/data/gogs.db";
+          defaultText = literalExpression ''"''${config.${opt.stateDir}}/data/gogs.db"'';
           description = "Path to the sqlite3 database file.";
         };
       };
@@ -142,6 +144,7 @@ in
       repositoryRoot = mkOption {
         type = types.str;
         default = "${cfg.stateDir}/repositories";
+        defaultText = literalExpression ''"''${config.${opt.stateDir}}/repositories"'';
         description = "Path to the git repositories.";
       };
 

nixos/modules/services/misc/headphones.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
@@ -7,6 +7,7 @@ let
   name = "headphones";
 
   cfg = config.services.headphones;
+  opt = options.services.headphones;
 
 in
 
@@ -29,6 +30,7 @@ in
       configFile = mkOption {
         type = types.path;
         default = "${cfg.dataDir}/config.ini";
+        defaultText = literalExpression ''"''${config.${opt.dataDir}}/config.ini"'';
         description = "Path to config file.";
       };
       host = mkOption {

nixos/modules/services/misc/matrix-appservice-discord.nix

@@ -1,4 +1,4 @@
-{ config, pkgs, lib, ... }:
+{ config, options, pkgs, lib, ... }:
 
 with lib;
 
@@ -7,6 +7,7 @@ let
   registrationFile = "${dataDir}/discord-registration.yaml";
   appDir = "${pkgs.matrix-appservice-discord}/${pkgs.matrix-appservice-discord.passthru.nodeAppDir}";
   cfg = config.services.matrix-appservice-discord;
+  opt = options.services.matrix-appservice-discord;
   # TODO: switch to configGen.json once RFC42 is implemented
   settingsFile = pkgs.writeText "matrix-appservice-discord-settings.json" (builtins.toJSON cfg.settings);
 
@@ -74,6 +75,7 @@ in {
       url = mkOption {
         type = types.str;
         default = "http://localhost:${toString cfg.port}";
+        defaultText = literalExpression ''"http://localhost:''${toString config.${opt.port}}"'';
         description = ''
           The URL where the application service is listening for HS requests.
         '';

nixos/modules/services/misc/matrix-synapse.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.matrix-synapse;
+  opt = options.services.matrix-synapse;
   pg = config.services.postgresql;
   usePostgresql = cfg.database_type == "psycopg2";
   logConfigFile = pkgs.writeText "log_config.yaml" cfg.logConfig;
@@ -197,7 +198,7 @@ in {
       tls_certificate_path = mkOption {
         type = types.nullOr types.str;
         default = null;
-        example = "${cfg.dataDir}/homeserver.tls.crt";
+        example = "/var/lib/matrix-synapse/homeserver.tls.crt";
         description = ''
           PEM encoded X509 certificate for TLS.
           You can replace the self-signed certificate that synapse
@@ -209,7 +210,7 @@ in {
       tls_private_key_path = mkOption {
         type = types.nullOr types.str;
         default = null;
-        example = "${cfg.dataDir}/homeserver.tls.key";
+        example = "/var/lib/matrix-synapse/homeserver.tls.key";
         description = ''
           PEM encoded private key for TLS. Specify null if synapse is not
           speaking TLS directly.
@@ -218,7 +219,7 @@ in {
       tls_dh_params_path = mkOption {
         type = types.nullOr types.str;
         default = null;
-        example = "${cfg.dataDir}/homeserver.tls.dh";
+        example = "/var/lib/matrix-synapse/homeserver.tls.dh";
         description = ''
           PEM dh parameters for ephemeral keys
         '';
@@ -408,6 +409,29 @@ in {
             database = cfg.database_name;
           };
         }.${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.
         '';

nixos/modules/services/misc/mediatomb.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
@@ -6,6 +6,7 @@ let
 
   gid = config.ids.gids.mediatomb;
   cfg = config.services.mediatomb;
+  opt = options.services.mediatomb;
   name = cfg.package.pname;
   pkg = cfg.package;
   optionYesNo = option: if option then "yes" else "no";
@@ -261,6 +262,7 @@ in {
       dataDir = mkOption {
         type = types.path;
         default = "/var/lib/${name}";
+        defaultText = literalExpression ''"/var/lib/''${config.${opt.package}.pname}"'';
         description = ''
           The directory where Gerbera/Mediatomb stores its state, data, etc.
         '';
@@ -277,13 +279,13 @@ in {
       user = mkOption {
         type = types.str;
         default = "mediatomb";
-        description = "User account under which ${name} runs.";
+        description = "User account under which the service runs.";
       };
 
       group = mkOption {
         type = types.str;
         default = "mediatomb";
-        description = "Group account under which ${name} runs.";
+        description = "Group account under which the service runs.";
       };
 
       port = mkOption {
@@ -340,7 +342,7 @@ in {
         type = types.bool;
         default = false;
         description = ''
-          Allow ${name} to create and use its own config file inside the <literal>dataDir</literal> as
+          Allow the service to create and use its own config file inside the <literal>dataDir</literal> as
           configured by <option>services.mediatomb.dataDir</option>.
           Deactivated by default, the service then runs with the configuration generated from this module.
           Otherwise, when enabled, no service configuration is generated. Gerbera/Mediatomb then starts using

nixos/modules/services/misc/moonraker.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 with lib;
 let
   pkg = pkgs.moonraker;
   cfg = config.services.moonraker;
+  opt = options.services.moonraker;
   format = pkgs.formats.ini {
     # https://github.com/NixOS/nixpkgs/pull/121613#issuecomment-885241996
     listToValue = l:
@@ -31,6 +32,7 @@ in {
       configDir = mkOption {
         type = types.path;
         default = cfg.stateDir + "/config";
+        defaultText = literalExpression ''config.${opt.stateDir} + "/config"'';
         description = ''
           The directory containing client-writable configuration files.
 

nixos/modules/services/misc/mwlib.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.mwlib;
+  opt = options.services.mwlib;
   pypkgs = pkgs.python27Packages;
 
   inherit (pypkgs) python mwlib;
@@ -46,6 +47,9 @@ in
 
       qserve = mkOption {
         default = [ "${cfg.qserve.address}:${toString cfg.qserve.port}" ];
+        defaultText = literalExpression ''
+          [ "''${config.${opt.qserve.address}}:''${toString config.${opt.qserve.port}}"
+        ]'';
         type = types.listOf types.str;
         description = "Register qserve instance.";
       }; # nserve.qserve
@@ -96,6 +100,7 @@ in
     nslave = {
       enable = mkOption {
         default = cfg.qserve.enable;
+        defaultText = literalExpression "config.${opt.qserve.enable}";
         type = types.bool;
         description = ''
           Pulls new jobs from exactly one qserve instance
@@ -127,7 +132,7 @@ in
           You have to enable it, or use your own way for serving files
           and set the http.url option accordingly.
           '';
-        type = types.submodule ({
+        type = types.submodule ({ config, options, ... }: {
           options = {
             enable = mkOption {
               default = true;
@@ -148,7 +153,8 @@ in
             }; # nslave.http.address
 
             url = mkOption {
-              default = "http://localhost:${toString cfg.nslave.http.port}/cache";
+              default = "http://localhost:${toString config.port}/cache";
+              defaultText = literalExpression ''"http://localhost:''${toString config.${options.port}}/cache"'';
               type = types.str;
               description = ''
                 Specify URL for accessing generated files from cache.

nixos/modules/services/misc/rippled.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.rippled;
+  opt = options.services.rippled;
 
   b2i = val: if val then "1" else "0";
 
@@ -165,6 +166,7 @@ let
         description = "Location to store the database.";
         type = types.path;
         default = cfg.databasePath;
+        defaultText = literalExpression "config.${opt.databasePath}";
       };
 
       compression = mkOption {
@@ -177,6 +179,7 @@ let
         description = "Enable automatic purging of older ledger information.";
         type = types.nullOr (types.addCheck types.int (v: v > 256));
         default = cfg.ledgerHistory;
+        defaultText = literalExpression "config.${opt.ledgerHistory}";
       };
 
       advisoryDelete = mkOption {
@@ -398,6 +401,7 @@ in
       config = mkOption {
         internal = true;
         default = pkgs.writeText "rippled.conf" rippledCfg;
+        defaultText = literalDocBook "generated config file";
       };
     };
   };

nixos/modules/services/misc/sickbeard.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
@@ -7,6 +7,7 @@ let
   name = "sickbeard";
 
   cfg = config.services.sickbeard;
+  opt = options.services.sickbeard;
   sickbeard = cfg.package;
 
 in
@@ -39,6 +40,7 @@ in
       configFile = mkOption {
         type = types.path;
         default = "${cfg.dataDir}/config.ini";
+        defaultText = literalExpression ''"''${config.${opt.dataDir}}/config.ini"'';
         description = "Path to config file.";
       };
       port = mkOption {

nixos/modules/services/misc/sourcehut/builds.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 let
   cfg = config.services.sourcehut;
+  opt = options.services.sourcehut;
   scfg = cfg.builds;
   rcfg = config.services.redis;
   iniKey = "builds.sr.ht";
@@ -38,6 +39,7 @@ in
     statePath = mkOption {
       type = types.path;
       default = "${cfg.statePath}/buildsrht";
+      defaultText = literalExpression ''"''${config.${opt.statePath}}/buildsrht"'';
       description = ''
         State path for builds.sr.ht.
       '';
@@ -61,7 +63,7 @@ in
               rev = "ff96a0fa5635770390b184ae74debea75c3fd534";
               ref = "nixos-unstable";
           };
-          image_from_nixpkgs = pkgs_unstable: (import ("${pkgs.sourcehut.buildsrht}/lib/images/nixos/image.nix") {
+          image_from_nixpkgs = pkgs_unstable: (import ("''${pkgs.sourcehut.buildsrht}/lib/images/nixos/image.nix") {
             pkgs = (import pkgs_unstable {});
           });
         in

nixos/modules/services/misc/sourcehut/dispatch.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 let
   cfg = config.services.sourcehut;
+  opt = options.services.sourcehut;
   cfgIni = cfg.settings;
   scfg = cfg.dispatch;
   iniKey = "dispatch.sr.ht";
@@ -38,6 +39,7 @@ in
     statePath = mkOption {
       type = types.path;
       default = "${cfg.statePath}/dispatchsrht";
+      defaultText = literalExpression ''"''${config.${opt.statePath}}/dispatchsrht"'';
       description = ''
         State path for dispatch.sr.ht.
       '';

nixos/modules/services/misc/sourcehut/git.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 let
   cfg = config.services.sourcehut;
+  opt = options.services.sourcehut;
   scfg = cfg.git;
   iniKey = "git.sr.ht";
 
@@ -41,6 +42,7 @@ in
     statePath = mkOption {
       type = types.path;
       default = "${cfg.statePath}/gitsrht";
+      defaultText = literalExpression ''"''${config.${opt.statePath}}/gitsrht"'';
       description = ''
         State path for git.sr.ht.
       '';

nixos/modules/services/misc/sourcehut/hg.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 let
   cfg = config.services.sourcehut;
+  opt = options.services.sourcehut;
   scfg = cfg.hg;
   iniKey = "hg.sr.ht";
 
@@ -40,6 +41,7 @@ in
     statePath = mkOption {
       type = types.path;
       default = "${cfg.statePath}/hgsrht";
+      defaultText = literalExpression ''"''${config.${opt.statePath}}/hgsrht"'';
       description = ''
         State path for hg.sr.ht.
       '';

nixos/modules/services/misc/sourcehut/hub.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 let
   cfg = config.services.sourcehut;
+  opt = options.services.sourcehut;
   cfgIni = cfg.settings;
   scfg = cfg.hub;
   iniKey = "hub.sr.ht";
@@ -38,6 +39,7 @@ in
     statePath = mkOption {
       type = types.path;
       default = "${cfg.statePath}/hubsrht";
+      defaultText = literalExpression ''"''${config.${opt.statePath}}/hubsrht"'';
       description = ''
         State path for hub.sr.ht.
       '';

nixos/modules/services/misc/sourcehut/lists.nix

@@ -1,11 +1,12 @@
 # Email setup is fairly involved, useful references:
 # https://drewdevault.com/2018/08/05/Local-mail-server.html
 
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 let
   cfg = config.services.sourcehut;
+  opt = options.services.sourcehut;
   cfgIni = cfg.settings;
   scfg = cfg.lists;
   iniKey = "lists.sr.ht";
@@ -42,6 +43,7 @@ in
     statePath = mkOption {
       type = types.path;
       default = "${cfg.statePath}/listssrht";
+      defaultText = literalExpression ''"''${config.${opt.statePath}}/listssrht"'';
       description = ''
         State path for lists.sr.ht.
       '';

nixos/modules/services/misc/sourcehut/man.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 let
   cfg = config.services.sourcehut;
+  opt = options.services.sourcehut;
   cfgIni = cfg.settings;
   scfg = cfg.man;
   iniKey = "man.sr.ht";
@@ -38,6 +39,7 @@ in
     statePath = mkOption {
       type = types.path;
       default = "${cfg.statePath}/mansrht";
+      defaultText = literalExpression ''"''${config.${opt.statePath}}/mansrht"'';
       description = ''
         State path for man.sr.ht.
       '';

nixos/modules/services/misc/sourcehut/meta.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 let
   cfg = config.services.sourcehut;
+  opt = options.services.sourcehut;
   cfgIni = cfg.settings;
   scfg = cfg.meta;
   iniKey = "meta.sr.ht";
@@ -39,6 +40,7 @@ in
     statePath = mkOption {
       type = types.path;
       default = "${cfg.statePath}/metasrht";
+      defaultText = literalExpression ''"''${config.${opt.statePath}}/metasrht"'';
       description = ''
         State path for meta.sr.ht.
       '';

nixos/modules/services/misc/sourcehut/paste.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 let
   cfg = config.services.sourcehut;
+  opt = options.services.sourcehut;
   cfgIni = cfg.settings;
   scfg = cfg.paste;
   iniKey = "paste.sr.ht";
@@ -39,6 +40,7 @@ in
     statePath = mkOption {
       type = types.path;
       default = "${cfg.statePath}/pastesrht";
+      defaultText = literalExpression ''"''${config.${opt.statePath}}/pastesrht"'';
       description = ''
         State path for pastesrht.sr.ht.
       '';

nixos/modules/services/misc/sourcehut/todo.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 let
   cfg = config.services.sourcehut;
+  opt = options.services.sourcehut;
   cfgIni = cfg.settings;
   scfg = cfg.todo;
   iniKey = "todo.sr.ht";
@@ -39,6 +40,7 @@ in
     statePath = mkOption {
       type = types.path;
       default = "${cfg.statePath}/todosrht";
+      defaultText = literalExpression ''"''${config.${opt.statePath}}/todosrht"'';
       description = ''
         State path for todo.sr.ht.
       '';

nixos/modules/services/misc/subsonic.nix

@@ -1,8 +1,11 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
-let cfg = config.services.subsonic; in {
+let
+  cfg = config.services.subsonic;
+  opt = options.services.subsonic;
+in {
   options = {
     services.subsonic = {
       enable = mkEnableOption "Subsonic daemon";
@@ -97,7 +100,7 @@ let cfg = config.services.subsonic; in {
         description = ''
           List of paths to transcoder executables that should be accessible
           from Subsonic. Symlinks will be created to each executable inside
-          ${cfg.home}/transcoders.
+          ''${config.${opt.home}}/transcoders.
         '';
       };
     };

nixos/modules/services/misc/zoneminder.nix

@@ -171,7 +171,7 @@ in {
         example = "/storage/tank";
         description = ''
           ZoneMinder can generate quite a lot of data, so in case you don't want
-          to use the default ${home}, you can override the path here.
+          to use the default ${defaultDir}, you can override the path here.
         '';
       };
 

nixos/modules/services/monitoring/grafana.nix

@@ -404,6 +404,7 @@ in {
       path = mkOption {
         description = "Database path.";
         default = "${cfg.dataDir}/data/grafana.db";
+        defaultText = literalExpression ''"''${config.${opt.dataDir}}/data/grafana.db"'';
         type = types.path;
       };
 

nixos/modules/services/monitoring/graphite.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.graphite;
+  opt = options.services.graphite;
   writeTextOrNull = f: t: mapNullable (pkgs.writeTextDir f) t;
 
   dataDir = cfg.dataDir;
@@ -171,6 +172,13 @@ in {
             directories:
                 - ${dataDir}/whisper
         '';
+        defaultText = literalExpression ''
+          '''
+            whisper:
+              directories:
+                - ''${config.${opt.dataDir}}/whisper
+          '''
+        '';
         example = ''
           allowed_origins:
             - dashboard.example.com
@@ -312,12 +320,14 @@ in {
 
       seyrenUrl = mkOption {
         default = "http://localhost:${toString cfg.seyren.port}/";
+        defaultText = literalExpression ''"http://localhost:''${toString config.${opt.seyren.port}}/"'';
         description = "Host where seyren is accessible.";
         type = types.str;
       };
 
       graphiteUrl = mkOption {
         default = "http://${cfg.web.listenAddress}:${toString cfg.web.port}";
+        defaultText = literalExpression ''"http://''${config.${opt.web.listenAddress}}:''${toString config.${opt.web.port}}"'';
         description = "Host where graphite service runs.";
         type = types.str;
       };

nixos/modules/services/monitoring/parsedmarc.nix

@@ -1,7 +1,8 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 let
   cfg = config.services.parsedmarc;
+  opt = options.services.parsedmarc;
   ini = pkgs.formats.ini {};
 in
 {
@@ -80,6 +81,9 @@ in
         datasource = lib.mkOption {
           type = lib.types.bool;
           default = cfg.provision.elasticsearch && config.services.grafana.enable;
+          defaultText = lib.literalExpression ''
+            config.${opt.provision.elasticsearch} && config.${options.services.grafana.enable}
+          '';
           apply = x: x && cfg.provision.elasticsearch;
           description = ''
             Whether the automatically provisioned Elasticsearch

nixos/modules/services/monitoring/smartd.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
@@ -8,6 +8,7 @@ let
        + optionalString (config.networking.domain != null) ".${config.networking.domain}";
 
   cfg = config.services.smartd;
+  opt = options.services.smartd;
 
   nm = cfg.notifications.mail;
   nw = cfg.notifications.wall;
@@ -211,6 +212,7 @@ in
 
         autodetected = mkOption {
           default = cfg.defaults.monitored;
+          defaultText = literalExpression "config.${opt.defaults.monitored}";
           type = types.separatedString " ";
           description = ''
             Like <option>services.smartd.defaults.monitored</option>, but for the

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.
 

nixos/modules/services/monitoring/uptime.nix

@@ -1,8 +1,9 @@
-{ config, pkgs, lib, ... }:
+{ config, options, pkgs, lib, ... }:
 let
-  inherit (lib) mkOption mkEnableOption mkIf mkMerge types optional;
+  inherit (lib) literalExpression mkOption mkEnableOption mkIf mkMerge types optional;
 
   cfg = config.services.uptime;
+  opt = options.services.uptime;
 
   configDir = pkgs.runCommand "config" { preferLocalBuild = true; }
   (if cfg.configFile != null then ''
@@ -52,7 +53,10 @@ in {
 
     enableWebService = mkEnableOption "the uptime monitoring program web service";
 
-    enableSeparateMonitoringService = mkEnableOption "the uptime monitoring service" // { default = cfg.enableWebService; };
+    enableSeparateMonitoringService = mkEnableOption "the uptime monitoring service" // {
+      default = cfg.enableWebService;
+      defaultText = literalExpression "config.${opt.enableWebService}";
+    };
 
     nodeEnv = mkOption {
       description = "The node environment to run in (development, production, etc.)";

nixos/modules/services/monitoring/zabbix-proxy.nix

@@ -1,7 +1,8 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 let
   cfg = config.services.zabbixProxy;
+  opt = options.services.zabbixProxy;
   pgsql = config.services.postgresql;
   mysql = config.services.mysql;
 
@@ -103,6 +104,11 @@ in
         port = mkOption {
           type = types.int;
           default = if cfg.database.type == "mysql" then mysql.port else pgsql.port;
+          defaultText = literalExpression ''
+            if config.${opt.database.type} == "mysql"
+            then config.${options.services.mysql.port}
+            else config.${options.services.postgresql.port}
+          '';
           description = "Database host port.";
         };
 

nixos/modules/services/monitoring/zabbix-server.nix

@@ -1,7 +1,8 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 let
   cfg = config.services.zabbixServer;
+  opt = options.services.zabbixServer;
   pgsql = config.services.postgresql;
   mysql = config.services.mysql;
 
@@ -95,6 +96,11 @@ in
         port = mkOption {
           type = types.int;
           default = if cfg.database.type == "mysql" then mysql.port else pgsql.port;
+          defaultText = literalExpression ''
+            if config.${opt.database.type} == "mysql"
+            then config.${options.services.mysql.port}
+            else config.${options.services.postgresql.port}
+          '';
           description = "Database host port.";
         };
 

nixos/modules/services/networking/amuled.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.amule;
+  opt = options.services.amule;
   user = if cfg.user != null then cfg.user else "amule";
 in
 
@@ -26,6 +27,9 @@ in
       dataDir = mkOption {
         type = types.str;
         default = "/home/${user}/";
+        defaultText = literalExpression ''
+          "/home/''${config.${opt.user}}/"
+        '';
         description = ''
           The directory holding configuration, incoming and temporary files.
         '';

nixos/modules/services/networking/ergo.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 let
   cfg = config.services.ergo;
+  opt = options.services.ergo;
 
-  inherit (lib) mkEnableOption mkIf mkOption optionalString types;
+  inherit (lib) literalExpression mkEnableOption mkIf mkOption optionalString types;
 
   configFile = pkgs.writeText "ergo.conf" (''
 ergo {
@@ -92,6 +93,7 @@ in {
       group = mkOption {
         type = types.str;
         default = cfg.user;
+        defaultText = literalExpression "config.${opt.user}";
         description = "The group as which to run the Ergo node.";
       };
 

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 =
           ''

nixos/modules/services/networking/jibri/default.nix

@@ -132,7 +132,7 @@ in
         pkgs.writeScript "finalize_recording.sh" ''''''
         #!/bin/sh
         RECORDINGS_DIR=$1
-        ${pkgs.rclone}/bin/rclone copy $RECORDINGS_DIR RCLONE_REMOTE:jibri-recordings/ -v --log-file=/var/log/jitsi/jibri/recording-upload.txt
+        ''${pkgs.rclone}/bin/rclone copy $RECORDINGS_DIR RCLONE_REMOTE:jibri-recordings/ -v --log-file=/var/log/jitsi/jibri/recording-upload.txt
         exit 0
         '''''';
       '';

nixos/modules/services/networking/ntopng.nix

@@ -1,10 +1,11 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
 
   cfg = config.services.ntopng;
+  opt = options.services.ntopng;
   redisCfg = config.services.redis;
 
   configFile = if cfg.configText != "" then
@@ -35,8 +36,8 @@ in
           collection tool.
 
           With the default configuration, ntopng monitors all network
-          interfaces and displays its findings at http://localhost:${toString
-          cfg.http-port}. Default username and password is admin/admin.
+          interfaces and displays its findings at http://localhost:''${toString
+          config.${opt.http-port}}. Default username and password is admin/admin.
 
           See the ntopng(8) manual page and http://www.ntop.org/products/ntop/
           for more info.

nixos/modules/services/networking/quassel.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.quassel;
+  opt = options.services.quassel;
   quassel = cfg.package;
   user = if cfg.user != null then cfg.user else "quassel";
 in
@@ -63,6 +64,9 @@ in
 
       dataDir = mkOption {
         default = "/home/${user}/.config/quassel-irc.org";
+        defaultText = literalExpression ''
+          "/home/''${config.${opt.user}}/.config/quassel-irc.org"
+        '';
         type = types.str;
         description = ''
           The directory holding configuration files, the SQlite database and the SSL Cert.

nixos/modules/services/networking/quorum.nix

@@ -1,9 +1,10 @@
-{ config, pkgs, lib, ... }:
+{ config, options, pkgs, lib, ... }:
 let
 
   inherit (lib) mkEnableOption mkIf mkOption literalExpression types optionalString;
 
   cfg = config.services.quorum;
+  opt = options.services.quorum;
   dataDir = "/var/lib/quorum";
   genesisFile = pkgs.writeText "genesis.json" (builtins.toJSON cfg.genesis);
   staticNodesFile = pkgs.writeText "static-nodes.json" (builtins.toJSON cfg.staticNodes);
@@ -23,6 +24,7 @@ in {
       group = mkOption {
         type = types.str;
         default = cfg.user;
+        defaultText = literalExpression "config.${opt.user}";
         description = "The group as which to run quorum.";
       };
 

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 {

nixos/modules/services/networking/wasabibackend.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 let
   cfg = config.services.wasabibackend;
+  opt = options.services.wasabibackend;
 
-  inherit (lib) mkEnableOption mkIf mkOption optionalAttrs optionalString types;
+  inherit (lib) literalExpression mkEnableOption mkIf mkOption optionalAttrs optionalString types;
 
   confOptions = {
       BitcoinRpcConnectionString = "${cfg.rpc.user}:${cfg.rpc.password}";
@@ -103,6 +104,7 @@ in {
       group = mkOption {
         type = types.str;
         default = cfg.user;
+        defaultText = literalExpression "config.${opt.user}";
         description = "The group as which to run the wasabibackend node.";
       };
     };

nixos/modules/services/networking/wireguard.nix

@@ -1,10 +1,11 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
 
   cfg = config.networking.wireguard;
+  opt = options.networking.wireguard;
 
   kernel = config.boot.kernelPackages;
 
@@ -438,6 +439,7 @@ in
         type = types.bool;
         # 2019-05-25: Backwards compatibility.
         default = cfg.interfaces != {};
+        defaultText = literalExpression "config.${opt.interfaces} != { }";
         example = true;
       };
 

nixos/modules/services/networking/wpa_supplicant.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, utils, ... }:
+{ config, lib, options, pkgs, utils, ... }:
 
 with lib;
 
@@ -8,6 +8,7 @@ let
     else pkgs.wpa_supplicant;
 
   cfg = config.networking.wireless;
+  opt = options.networking.wireless;
 
   # Content of wpa_supplicant.conf
   generatedConfig = concatStringsSep "\n" (
@@ -421,6 +422,7 @@ in {
       dbusControlled = mkOption {
         type = types.bool;
         default = lib.length cfg.interfaces < 2;
+        defaultText = literalExpression "length config.${opt.interfaces} < 2";
         description = ''
           Whether to enable the DBus control interface.
           This is only needed when using NetworkManager or connman.

nixos/modules/services/search/kibana.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.kibana;
+  opt = options.services.kibana;
 
   ge7 = builtins.compareVersions cfg.package.version "7" >= 0;
   lt6_6 = builtins.compareVersions cfg.package.version "6.6" < 0;
@@ -130,6 +131,9 @@ in {
           This defaults to the singleton list [ca] when the <option>ca</option> option is defined.
         '';
         default = if cfg.elasticsearch.ca == null then [] else [ca];
+        defaultText = literalExpression ''
+          if config.${opt.elasticsearch.ca} == null then [ ] else [ ca ]
+        '';
         type = types.listOf types.path;
       };
 

nixos/modules/services/security/privacyidea.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.privacyidea;
+  opt = options.services.privacyidea;
 
   uwsgi = pkgs.uwsgi.override { plugins = [ "python3" ]; };
   python = uwsgi.python3;
@@ -112,6 +113,7 @@ in
       encFile = mkOption {
         type = types.str;
         default = "${cfg.stateDir}/enckey";
+        defaultText = literalExpression ''"''${config.${opt.stateDir}}/enckey"'';
         description = ''
           This is used to encrypt the token data and token passwords
         '';
@@ -120,6 +122,7 @@ in
       auditKeyPrivate = mkOption {
         type = types.str;
         default = "${cfg.stateDir}/private.pem";
+        defaultText = literalExpression ''"''${config.${opt.stateDir}}/private.pem"'';
         description = ''
           Private Key for signing the audit log.
         '';
@@ -128,6 +131,7 @@ in
       auditKeyPublic = mkOption {
         type = types.str;
         default = "${cfg.stateDir}/public.pem";
+        defaultText = literalExpression ''"''${config.${opt.stateDir}}/public.pem"'';
         description = ''
           Public key for checking signatures of the audit log.
         '';

nixos/modules/services/security/tor.nix

@@ -1,10 +1,11 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with builtins;
 with lib;
 
 let
   cfg = config.services.tor;
+  opt = options.services.tor;
   stateDir = "/var/lib/tor";
   runDir = "/run/tor";
   descriptionGeneric = option: ''
@@ -799,6 +800,11 @@ in
           options.SOCKSPort = mkOption {
             description = descriptionGeneric "SOCKSPort";
             default = if cfg.settings.HiddenServiceNonAnonymousMode == true then [{port = 0;}] else [];
+            defaultText = literalExpression ''
+              if config.${opt.settings}.HiddenServiceNonAnonymousMode == true
+              then [ { port = 0; } ]
+              else [ ]
+            '';
             example = [{port = 9090;}];
             type = types.listOf (optionSOCKSPort true);
           };

nixos/modules/services/security/vault.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.vault;
+  opt = options.services.vault;
 
   configFile = pkgs.writeText "vault.hcl" ''
     listener "tcp" {
@@ -83,6 +84,11 @@ in
       storagePath = mkOption {
         type = types.nullOr types.path;
         default = if cfg.storageBackend == "file" then "/var/lib/vault" else null;
+        defaultText = literalExpression ''
+          if config.${opt.storageBackend} == "file"
+          then "/var/lib/vault"
+          else null
+        '';
         description = "Data directory for file backend";
       };
 

nixos/modules/services/torrent/peerflix.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.peerflix;
+  opt = options.services.peerflix;
 
   configFile = pkgs.writeText "peerflix-config.json" ''
     {
@@ -32,6 +33,7 @@ in {
     downloadDir = mkOption {
       description = "Peerflix temporary download directory.";
       default = "${cfg.stateDir}/torrents";
+      defaultText = literalExpression ''"''${config.${opt.stateDir}}/torrents"'';
       type = types.path;
     };
   };

nixos/modules/services/torrent/rtorrent.nix

@@ -1,10 +1,11 @@
-{ config, pkgs, lib, ... }:
+{ config, options, pkgs, lib, ... }:
 
 with lib;
 
 let
 
   cfg = config.services.rtorrent;
+  opt = options.services.rtorrent;
 
 in {
   options.services.rtorrent = {
@@ -21,6 +22,7 @@ in {
     downloadDir = mkOption {
       type = types.str;
       default = "${cfg.dataDir}/download";
+      defaultText = literalExpression ''"''${config.${opt.dataDir}}/download"'';
       description = ''
         Where to put downloaded files.
       '';

nixos/modules/services/torrent/transmission.nix

@@ -4,6 +4,7 @@ with lib;
 
 let
   cfg = config.services.transmission;
+  opt = options.services.transmission;
   inherit (config.environment) etc;
   apparmor = config.security.apparmor;
   rootDir = "/run/transmission";
@@ -47,11 +48,13 @@ in
           options.download-dir = mkOption {
             type = types.path;
             default = "${cfg.home}/${downloadsDir}";
+            defaultText = literalExpression ''"''${config.${opt.home}}/${downloadsDir}"'';
             description = "Directory where to download torrents.";
           };
           options.incomplete-dir = mkOption {
             type = types.path;
             default = "${cfg.home}/${incompleteDir}";
+            defaultText = literalExpression ''"''${config.${opt.home}}/${incompleteDir}"'';
             description = ''
               When enabled with
               services.transmission.home
@@ -147,6 +150,7 @@ in
           options.watch-dir = mkOption {
             type = types.path;
             default = "${cfg.home}/${watchDir}";
+            defaultText = literalExpression ''"''${config.${opt.home}}/${watchDir}"'';
             description = "Watch a directory for torrent files and add them to transmission.";
           };
           options.watch-dir-enabled = mkOption {

nixos/modules/services/video/epgstation/default.nix

@@ -1,9 +1,10 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
   cfg = config.services.epgstation;
+  opt = options.services.epgstation;
 
   username = config.users.users.epgstation.name;
   groupname = config.users.users.epgstation.group;
@@ -72,6 +73,7 @@ in
     socketioPort = mkOption {
       type = types.port;
       default = cfg.port + 1;
+      defaultText = literalExpression "config.${opt.port} + 1";
       description = ''
         Socket.io port for EPGStation to listen on.
       '';
@@ -80,6 +82,7 @@ in
     clientSocketioPort = mkOption {
       type = types.port;
       default = cfg.socketioPort;
+      defaultText = literalExpression "config.${opt.socketioPort}";
       description = ''
         Socket.io port that the web client is going to connect to. This may be
         different from <option>socketioPort</option> if EPGStation is hidden
@@ -183,6 +186,9 @@ in
         in {
           type = types.str;
           default = "http+unix://${replaceStrings ["/"] ["%2F"] sockPath}";
+          defaultText = literalExpression ''
+            "http+unix://''${replaceStrings ["/"] ["%2F"] config.${options.services.mirakurun.unixSocket}}"
+          '';
           example = "http://localhost:40772";
           description = "URL to connect to Mirakurun.";
         });

nixos/modules/services/video/unifi-video.nix

@@ -1,7 +1,8 @@
-{ config, lib, pkgs, utils, ... }:
+{ config, lib, options, pkgs, utils, ... }:
 with lib;
 let
   cfg = config.services.unifi-video;
+  opt = options.services.unifi-video;
   mainClass = "com.ubnt.airvision.Main";
   cmd = ''
     ${pkgs.jsvc}/bin/jsvc \
@@ -164,6 +165,7 @@ in
       pidFile = mkOption {
         type = types.path;
         default = "${cfg.dataDir}/unifi-video.pid";
+        defaultText = literalExpression ''"''${config.${opt.dataDir}}/unifi-video.pid"'';
         description = "Location of unifi-video pid file.";
       };
 

nixos/modules/services/web-apps/discourse.nix

@@ -4,6 +4,7 @@ let
   json = pkgs.formats.json {};
 
   cfg = config.services.discourse;
+  opt = options.services.discourse;
 
   # Keep in sync with https://github.com/discourse/discourse_docker/blob/master/image/base/Dockerfile#L5
   upstreamPostgresqlVersion = lib.getVersion pkgs.postgresql_13;
@@ -327,6 +328,7 @@ in
         useSSL = lib.mkOption {
           type = lib.types.bool;
           default = cfg.redis.host != "localhost";
+          defaultText = lib.literalExpression ''config.${opt.redis.host} != "localhost"'';
           description = ''
             Connect to Redis with SSL.
           '';
@@ -399,6 +401,7 @@ in
           domain = lib.mkOption {
             type = lib.types.str;
             default = cfg.hostname;
+            defaultText = lib.literalExpression "config.${opt.hostname}";
             description = ''
               HELO domain to use for outgoing mail.
             '';

nixos/modules/services/web-apps/galene.nix

@@ -1,8 +1,9 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 let
   cfg = config.services.galene;
+  opt = options.services.galene;
   defaultstateDir = "/var/lib/galene";
   defaultrecordingsDir = "${cfg.stateDir}/recordings";
   defaultgroupsDir = "${cfg.stateDir}/groups";
@@ -88,6 +89,7 @@ in
       recordingsDir = mkOption {
         type = types.str;
         default = defaultrecordingsDir;
+        defaultText = literalExpression ''"''${config.${opt.stateDir}}/recordings"'';
         example = "/var/lib/galene/recordings";
         description = "Recordings directory.";
       };
@@ -95,6 +97,7 @@ in
       dataDir = mkOption {
         type = types.str;
         default = defaultdataDir;
+        defaultText = literalExpression ''"''${config.${opt.stateDir}}/data"'';
         example = "/var/lib/galene/data";
         description = "Data directory.";
       };
@@ -102,6 +105,7 @@ in
       groupsDir = mkOption {
         type = types.str;
         default = defaultgroupsDir;
+        defaultText = literalExpression ''"''${config.${opt.stateDir}}/groups"'';
         example = "/var/lib/galene/groups";
         description = "Web server directory.";
       };

nixos/modules/services/web-apps/hedgedoc.nix

@@ -33,7 +33,7 @@ in
       type = types.listOf types.str;
       default = [];
       description = ''
-        Groups to which the user ${name} should be added.
+        Groups to which the service user should be added.
       '';
     };
 

nixos/modules/services/web-apps/invidious.nix

@@ -225,6 +225,7 @@ in
       port = lib.mkOption {
         type = types.port;
         default = options.services.postgresql.port.default;
+        defaultText = lib.literalExpression "options.services.postgresql.port.default";
         description = ''
           The port of the database Invidious should use.
 

nixos/modules/services/web-apps/keycloak.nix

@@ -1,7 +1,8 @@
-{ config, pkgs, lib, ... }:
+{ config, options, pkgs, lib, ... }:
 
 let
   cfg = config.services.keycloak;
+  opt = options.services.keycloak;
 in
 {
   options.services.keycloak = {
@@ -139,6 +140,7 @@ in
           lib.mkOption {
             type = lib.types.port;
             default = dbPorts.${cfg.database.type};
+            defaultText = lib.literalDocBook "default port of selected database";
             description = ''
               Port of the database to connect to.
             '';
@@ -147,6 +149,7 @@ in
       useSSL = lib.mkOption {
         type = lib.types.bool;
         default = cfg.database.host != "localhost";
+        defaultText = lib.literalExpression ''config.${opt.database.host} != "localhost"'';
         description = ''
           Whether the database connection should be secured by SSL /
           TLS.

nixos/modules/services/web-apps/matomo.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 with lib;
 let
   cfg = config.services.matomo;
@@ -12,10 +12,7 @@ let
   phpExecutionUnit = "phpfpm-${pool}";
   databaseService = "mysql.service";
 
-  fqdn =
-    let
-      join = hostName: domain: hostName + optionalString (domain != null) ".${domain}";
-     in join config.networking.hostName config.networking.domain;
+  fqdn = if config.networking.domain != null then config.networking.fqdn else config.networking.hostName;
 
 in {
   imports = [
@@ -81,9 +78,14 @@ in {
       hostname = mkOption {
         type = types.str;
         default = "${user}.${fqdn}";
+        defaultText = literalExpression ''
+          if config.${options.networking.domain} != null
+          then "${user}.''${config.${options.networking.fqdn}}"
+          else "${user}.''${config.${options.networking.hostName}}"
+        '';
         example = "matomo.yourdomain.org";
         description = ''
-          URL of the host, without https prefix. By default, this is ${user}.${fqdn}, but you may want to change it if you
+          URL of the host, without https prefix. You may want to change it if you
           run Matomo on a different URL than matomo.yourdomain.
         '';
       };

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.

nixos/modules/services/web-apps/peertube.nix

@@ -1,7 +1,8 @@
-{ lib, pkgs, config, ... }:
+{ lib, pkgs, config, options, ... }:
 
 let
   cfg = config.services.peertube;
+  opt = options.services.peertube;
 
   settingsFormat = pkgs.formats.json {};
   configFile = settingsFormat.generate "production.json" cfg.settings;
@@ -153,6 +154,11 @@ in {
       host = lib.mkOption {
         type = lib.types.str;
         default = if cfg.database.createLocally then "/run/postgresql" else null;
+        defaultText = lib.literalExpression ''
+          if config.${opt.database.createLocally}
+          then "/run/postgresql"
+          else null
+        '';
         example = "192.168.15.47";
         description = "Database host address or unix socket.";
       };
@@ -193,12 +199,22 @@ in {
       host = lib.mkOption {
         type = lib.types.nullOr lib.types.str;
         default = if cfg.redis.createLocally && !cfg.redis.enableUnixSocket then "127.0.0.1" else null;
+        defaultText = lib.literalExpression ''
+          if config.${opt.redis.createLocally} && !config.${opt.redis.enableUnixSocket}
+          then "127.0.0.1"
+          else null
+        '';
         description = "Redis host.";
       };
 
       port = lib.mkOption {
         type = lib.types.nullOr lib.types.port;
         default = if cfg.redis.createLocally && cfg.redis.enableUnixSocket then null else 6379;
+        defaultText = lib.literalExpression ''
+          if config.${opt.redis.createLocally} && config.${opt.redis.enableUnixSocket}
+          then null
+          else 6379
+        '';
         description = "Redis port.";
       };
 
@@ -212,6 +228,7 @@ in {
       enableUnixSocket = lib.mkOption {
         type = lib.types.bool;
         default = cfg.redis.createLocally;
+        defaultText = lib.literalExpression "config.${opt.redis.createLocally}";
         description = "Use Unix socket.";
       };
     };

nixos/modules/services/web-apps/pgpkeyserver-lite.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
@@ -6,6 +6,7 @@ let
 
   cfg = config.services.pgpkeyserver-lite;
   sksCfg = config.services.sks;
+  sksOpt = options.services.sks;
 
   webPkg = cfg.package;
 
@@ -37,6 +38,7 @@ in
 
       hkpAddress = mkOption {
         default = builtins.head sksCfg.hkpAddress;
+        defaultText = literalExpression "head config.${sksOpt.hkpAddress}";
         type = types.str;
         description = "
           Wich ip address the sks-keyserver is listening on.
@@ -45,6 +47,7 @@ in
 
       hkpPort = mkOption {
         default = sksCfg.hkpPort;
+        defaultText = literalExpression "config.${sksOpt.hkpPort}";
         type = types.int;
         description = "
           Which port the sks-keyserver is listening on.

nixos/modules/services/web-apps/zabbix.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 let
 
@@ -6,6 +6,7 @@ let
   inherit (lib) literalExpression mapAttrs optionalString versionAtLeast;
 
   cfg = config.services.zabbixWeb;
+  opt = options.services.zabbixWeb;
   fpm = config.services.phpfpm.pools.zabbix;
 
   user = "zabbix";
@@ -82,6 +83,11 @@ in
             if cfg.database.type == "mysql" then config.services.mysql.port
             else if cfg.database.type == "pgsql" then config.services.postgresql.port
             else 1521;
+          defaultText = literalExpression ''
+            if config.${opt.database.type} == "mysql" then config.${options.services.mysql.port}
+            else if config.${opt.database.type} == "pgsql" then config.${options.services.postgresql.port}
+            else 1521
+          '';
           description = "Database host port.";
         };
 

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

nixos/modules/services/x11/display-managers/default.nix

@@ -7,13 +7,14 @@
 # (e.g., KDE, Gnome or a plain xterm), and optionally the *window
 # manager* (e.g. kwin or twm).
 
-{ config, lib, pkgs, ... }:
+{ config, lib, options, pkgs, ... }:
 
 with lib;
 
 let
 
   cfg = config.services.xserver;
+  opt = options.services.xserver;
   xorg = pkgs.xorg;
 
   fontconfig = config.fonts.fontconfig;
@@ -147,6 +148,7 @@ in
       xauthBin = mkOption {
         internal = true;
         default = "${xorg.xauth}/bin/xauth";
+        defaultText = literalExpression ''"''${pkgs.xorg.xauth}/bin/xauth"'';
         description = "Path to the <command>xauth</command> program used by display managers.";
       };
 
@@ -278,6 +280,9 @@ 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).
@@ -337,11 +342,12 @@ in
 
       # Configuration for automatic login. Common for all DM.
       autoLogin = mkOption {
-        type = types.submodule {
+        type = types.submodule ({ config, options, ... }: {
           options = {
             enable = mkOption {
               type = types.bool;
-              default = cfg.displayManager.autoLogin.user != null;
+              default = config.user != null;
+              defaultText = literalExpression "config.${options.user} != null";
               description = ''
                 Automatically log in as <option>autoLogin.user</option>.
               '';
@@ -355,7 +361,7 @@ in
               '';
             };
           };
-        };
+        });
 
         default = {};
         description = ''