nixos/treewide: Fix incorrectly rendered examples

Many options define their example to be a Nix value without using
literalExample. This sometimes gets rendered incorrectly in the manual,
causing confusion like in https://github.com/NixOS/nixpkgs/issues/25516

This fixes it by using literalExample for such options. The list of
option to fix was determined with this expression:

  let
    nixos = import ./nixos { configuration = {}; };
    lib = import ./lib;
    valid = d: {
      # escapeNixIdentifier from https://github.com/NixOS/nixpkgs/pull/82461
      set = lib.all (n: lib.strings.escapeNixIdentifier n == n) (lib.attrNames d) && lib.all (v: valid v) (lib.attrValues d);
      list = lib.all (v: valid v) d;
    }.${builtins.typeOf d} or true;

    optionList = lib.optionAttrSetToDocList nixos.options;

  in map (opt: {
    file = lib.elemAt opt.declarations 0;
    loc = lib.options.showOption opt.loc;
  }) (lib.filter (opt: if opt ? example then ! valid opt.example else false) optionList)

which when evaluated will output all options that use a Nix identifier
that would need escaping as an attribute name.

nixos/modules/services/amqp/activemq/default.nix

@@ -63,9 +63,11 @@ in {
       javaProperties = mkOption {
         type = types.attrs;
         default = { };
-        example = {
+        example = literalExample ''
+          {
             "java.net.preferIPv4Stack" = "true";
-        };
+          }
+        '';
         apply = attrs: {
           "activemq.base" = "${cfg.baseDir}";
           "activemq.data" = "${cfg.baseDir}/data";

nixos/modules/services/backup/syncoid.nix

@@ -138,7 +138,11 @@ in {
           };
         }));
         default = {};
-        example."pool/test".target = "root@target:pool/test";
+        example = literalExample ''
+          {
+            "pool/test".target = "root@target:pool/test";
+          }
+        '';
         description = "Syncoid commands to run.";
       };
     };

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

@@ -7,33 +7,41 @@ with lib;
   options.services.hadoop = {
     coreSite = mkOption {
       default = {};
-      example = {
+      example = literalExample ''
+        {
           "fs.defaultFS" = "hdfs://localhost";
-      };
+        }
+      '';
       description = "Hadoop core-site.xml definition";
     };
 
     hdfsSite = mkOption {
       default = {};
-      example = {
+      example = literalExample ''
+        {
           "dfs.nameservices" = "namenode1";
-      };
+        }
+      '';
       description = "Hadoop hdfs-site.xml definition";
     };
 
     mapredSite = mkOption {
       default = {};
-      example = {
+      example = literalExample ''
+        {
           "mapreduce.map.cpu.vcores" = "1";
-      };
+        }
+      '';
       description = "Hadoop mapred-site.xml definition";
     };
 
     yarnSite = mkOption {
       default = {};
-      example = {
+      example = literalExample ''
+        {
           "yarn.resourcemanager.ha.id" = "resourcemanager1";
-      };
+        }
+      '';
       description = "Hadoop yarn-site.xml definition";
     };
 

nixos/modules/services/network-filesystems/netatalk.nix

@@ -98,13 +98,14 @@ in
             Set of AFP volumes to export.
             See <literal>man apf.conf</literal> for more information.
           '';
-        example =
+        example = literalExample ''
           { srv =
              { path = "/srv";
                "read only" = true;
                "hosts allow" = "10.1.0.0/16 10.2.1.100 2001:0db8:1234::/48";
              };
-          };
+          }
+        '';
       };
 
       extmap = mkOption {

nixos/modules/services/network-filesystems/rsyncd.nix

@@ -74,13 +74,14 @@ in
             See <command>man rsyncd.conf</command> for options.
           '';
         type = types.attrsOf (types.attrsOf types.str);
-        example =
+        example = literalExample ''
           { srv =
              { path = "/srv";
                "read only" = "yes";
                comment = "Public rsync share.";
              };
-          };
+          }
+        '';
       };
 
       user = mkOption {

nixos/modules/services/network-filesystems/samba.nix

@@ -189,7 +189,7 @@ in
           See <command>man smb.conf</command> for options.
         '';
         type = types.attrsOf (types.attrsOf types.unspecified);
-        example =
+        example = literalExample ''
           { public =
             { path = "/srv/public";
               "read only" = true;
@@ -197,7 +197,8 @@ in
               "guest ok" = "yes";
               comment = "Public samba share.";
             };
-          };
+          }
+        '';
       };
 
     };

nixos/modules/services/networking/3proxy.nix

@@ -334,10 +334,12 @@ in {
           nsrecord = mkOption {
             type = types.attrsOf types.str;
             default = { };
-            example = {
+            example = literalExample ''
+              {
                 "files.local" = "192.168.1.12";
                 "site.local" = "192.168.1.43";
-            };
+              }
+            '';
             description = "Adds static nsrecords.";
           };
         };

nixos/modules/services/networking/dnscache.nix

@@ -61,10 +61,12 @@ in {
           Table of {hostname: server} pairs to use as authoritative servers for hosts (and subhosts).
           If entry for @ is not specified predefined list of root servers is used.
         '';
-        example = {
+        example = literalExample ''
+          {
             "@" = ["8.8.8.8" "8.8.4.4"];
             "example.com" = ["192.168.100.100"];
-        };
+          }
+        '';
       };
 
       forwardOnly = mkOption {

nixos/modules/services/networking/ndppd.nix

@@ -142,7 +142,11 @@ in {
         messages, and respond to them according to a set of rules.
       '';
       default = {};
-      example = { eth0.rules."1111::/64" = {}; };
+      example = literalExample ''
+        {
+          eth0.rules."1111::/64" = {};
+        }
+      '';
     };
   };
 

nixos/modules/services/networking/strongswan.nix

@@ -4,7 +4,7 @@ let
 
   inherit (builtins) toFile;
   inherit (lib) concatMapStringsSep concatStringsSep mapAttrsToList
-                mkIf mkEnableOption mkOption types;
+                mkIf mkEnableOption mkOption types literalExample;
 
   cfg = config.services.strongswan;
 
@@ -79,7 +79,8 @@ in
     connections = mkOption {
       type = types.attrsOf (types.attrsOf types.str);
       default = {};
-      example = {
+      example = literalExample ''
+        {
           "%default" = {
             keyexchange = "ikev2";
             keyingtries = "1";
@@ -91,7 +92,8 @@ in
             leftsubnet = "10.1.0.0/16";
             right      = "%any";
           };
-      };
+        }
+      '';
       description = ''
         A set of connections and their options for the ‘conn xxx’
         sections of the <filename>ipsec.conf</filename> file.

nixos/modules/services/networking/syncthing.nix

@@ -169,12 +169,14 @@ in {
           description = ''
             folders which should be shared by syncthing.
           '';
-          example = {
+          example = literalExample ''
+            {
               "/home/user/sync" = {
                 id = "syncme";
                 devices = [ "bigbox" ];
               };
-          };
+            }
+          '';
           type = types.attrsOf (types.submodule ({ name, ... }: {
             options = {
 

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

@@ -46,9 +46,11 @@ in
         https://www.jetbrains.com/help/youtrack/standalone/YouTrack-Java-Start-Parameters.html
         for more information.
       '';
-      example = {
+      example = literalExample ''
+        {
           "jetbrains.youtrack.overrideRootPassword" = "tortuga";
-      };
+        }
+      '';
       type = types.attrsOf types.str;
     };
 

nixos/modules/virtualisation/containers.nix

@@ -609,9 +609,11 @@ in
             bindMounts = mkOption {
               type = with types; loaOf (submodule bindMountOpts);
               default = {};
-              example = { "/home" = { hostPath = "/home/alice";
+              example = literalExample ''
+                { "/home" = { hostPath = "/home/alice";
                               isReadOnly = false; };
-                        };
+                }
+              '';
 
               description =
                 ''