treewide: use optionalString instead of 'then ""'

53 files changed, 101 insertions, 116 deletions

diff --git a/nixos/modules/services/backup/borgbackup.nix b/nixos/modules/services/backup/borgbackup.nix
index 0da70112d48d..3b44f097ab79 100644
--- a/nixos/modules/services/backup/borgbackup.nix
+++ b/nixos/modules/services/backup/borgbackup.nix
@@ -33,7 +33,7 @@ let
     }
     trap on_exit EXIT
 
-    archiveName="${if cfg.archiveBaseName == null then "" else cfg.archiveBaseName + "-"}$(date ${cfg.dateFormat})"
+    archiveName="${optionalString (cfg.archiveBaseName != null) (cfg.archiveBaseName + "-")}$(date ${cfg.dateFormat})"
     archiveSuffix="${optionalString cfg.appendFailedSuffix ".failed"}"
     ${cfg.preHook}
   '' + optionalString cfg.doInit ''
diff --git a/nixos/modules/services/continuous-integration/jenkins/default.nix b/nixos/modules/services/continuous-integration/jenkins/default.nix
index a9a587b41e88..e4d54b0cb0f4 100644
--- a/nixos/modules/services/continuous-integration/jenkins/default.nix
+++ b/nixos/modules/services/continuous-integration/jenkins/default.nix
@@ -210,9 +210,7 @@ in {
 
       preStart =
         let replacePlugins =
-              if cfg.plugins == null
-              then ""
-              else
+              optionalString (cfg.plugins != null) (
                 let pluginCmds = lib.attrsets.mapAttrsToList
                       (n: v: "cp ${v} ${cfg.home}/plugins/${n}.jpi")
                       cfg.plugins;
@@ -220,7 +218,7 @@ in {
                   rm -r ${cfg.home}/plugins || true
                   mkdir -p ${cfg.home}/plugins
                   ${lib.strings.concatStringsSep "\n" pluginCmds}
-                '';
+                '');
         in ''
           rm -rf ${cfg.home}/war
           ${replacePlugins}
diff --git a/nixos/modules/services/misc/cgminer.nix b/nixos/modules/services/misc/cgminer.nix
index fced106cb325..81eb42cbc5de 100644
--- a/nixos/modules/services/misc/cgminer.nix
+++ b/nixos/modules/services/misc/cgminer.nix
@@ -11,7 +11,7 @@ let
     mapAttrsToList (n: v: ''"${n}": "${(concatStringsSep "," (map convType v))}"'')
       (foldAttrs (n: a: [n] ++ a) [] cfg.hardware);
   mergedConfig = with builtins;
-    mapAttrsToList (n: v: ''"${n}":  ${if isBool v then "" else ''"''}${convType v}${if isBool v then "" else ''"''}'')
+    mapAttrsToList (n: v: ''"${n}":  ${if isBool v then (convType v) else ''"${convType v}"''}'')
       cfg.config;
 
   cgminerConfig = pkgs.writeText "cgminer.conf" ''
diff --git a/nixos/modules/services/misc/sourcehut/default.nix b/nixos/modules/services/misc/sourcehut/default.nix
index d4391bc49e31..580a009a0ad3 100644
--- a/nixos/modules/services/misc/sourcehut/default.nix
+++ b/nixos/modules/services/misc/sourcehut/default.nix
@@ -8,13 +8,13 @@ let
   settingsFormat = pkgs.formats.ini {
     listToValue = concatMapStringsSep "," (generators.mkValueStringDefault {});
     mkKeyValue = k: v:
-      if v == null then ""
-      else generators.mkKeyValueDefault {
+      optionalString (v != null)
+      (generators.mkKeyValueDefault {
         mkValueString = v:
           if v == true then "yes"
           else if v == false then "no"
           else generators.mkValueStringDefault {} v;
-      } "=" k v;
+      } "=" k v);
   };
   configIniOfService = srv: settingsFormat.generate "sourcehut-${srv}-config.ini"
     # Each service needs access to only a subset of sections (and secrets).
diff --git a/nixos/modules/services/monitoring/prometheus/exporters/pve.nix b/nixos/modules/services/monitoring/prometheus/exporters/pve.nix
index e02acad3ecd1..f95412efd7dd 100644
--- a/nixos/modules/services/monitoring/prometheus/exporters/pve.nix
+++ b/nixos/modules/services/monitoring/prometheus/exporters/pve.nix
@@ -104,12 +104,12 @@ in
       LoadCredential = "configFile:${computedConfigFile}";
       ExecStart = ''
         ${cfg.package}/bin/pve_exporter \
-          --${if cfg.collectors.status == true then "" else "no-"}collector.status \
-          --${if cfg.collectors.version == true then "" else "no-"}collector.version \
-          --${if cfg.collectors.node == true then "" else "no-"}collector.node \
-          --${if cfg.collectors.cluster == true then "" else "no-"}collector.cluster \
-          --${if cfg.collectors.resources == true then "" else "no-"}collector.resources \
-          --${if cfg.collectors.config == true then "" else "no-"}collector.config \
+          --${optionalString (!cfg.collectors.status) "no-"}collector.status \
+          --${optionalString (!cfg.collectors.version) "no-"}collector.version \
+          --${optionalString (!cfg.collectors.node) "no-"}collector.node \
+          --${optionalString (!cfg.collectors.cluster) "no-"}collector.cluster \
+          --${optionalString (!cfg.collectors.resources) "no-"}collector.resources \
+          --${optionalString (!cfg.collectors.config) "no-"}collector.config \
           %d/configFile \
           ${toString cfg.port} ${cfg.listenAddress}
       '';
diff --git a/nixos/modules/services/networking/biboumi.nix b/nixos/modules/services/networking/biboumi.nix
index 1428856764e6..d44a46b35a29 100644
--- a/nixos/modules/services/networking/biboumi.nix
+++ b/nixos/modules/services/networking/biboumi.nix
@@ -8,8 +8,7 @@ let
   settingsFile = pkgs.writeText "biboumi.cfg" (
     generators.toKeyValue {
       mkKeyValue = k: v:
-        if v == null then ""
-        else generators.mkKeyValueDefault {} "=" k v;
+        lib.optionalString (v != null) (generators.mkKeyValueDefault {} "=" k v);
     } cfg.settings);
   need_CAP_NET_BIND_SERVICE = cfg.settings.identd_port != 0 && cfg.settings.identd_port < 1024;
 in
diff --git a/nixos/modules/services/networking/cjdns.nix b/nixos/modules/services/networking/cjdns.nix
index 5a19475161fd..80085da92702 100644
--- a/nixos/modules/services/networking/cjdns.nix
+++ b/nixos/modules/services/networking/cjdns.nix
@@ -239,7 +239,7 @@ in
       after = [ "network-online.target" ];
       bindsTo = [ "network-online.target" ];
 
-      preStart = if cfg.confFile != null then "" else ''
+      preStart = optionalString (cfg.confFile == null) ''
         [ -e /etc/cjdns.keys ] && source /etc/cjdns.keys
 
         if [ -z "$CJDNS_PRIVATE_KEY" ]; then
diff --git a/nixos/modules/services/networking/libreswan.nix b/nixos/modules/services/networking/libreswan.nix
index 785729d8f742..b8a3d6c8fdb5 100644
--- a/nixos/modules/services/networking/libreswan.nix
+++ b/nixos/modules/services/networking/libreswan.nix
@@ -14,8 +14,8 @@ let
     nonchars = filter (x : !(elem x.value chars))
                (imap0 (i: v: {ind = i; value = v;}) (stringToCharacters str));
   in
-    if length nonchars == 0 then ""
-    else substring (head nonchars).ind (add 1 (sub (last nonchars).ind (head nonchars).ind)) str;
+    lib.optionalString (length nonchars != 0)
+      (substring (head nonchars).ind (add 1 (sub (last nonchars).ind (head nonchars).ind)) str);
   indent = str: concatStrings (concatMap (s: ["  " (trim [" " "\t"] s) "\n"]) (splitString "\n" str));
   configText = indent (toString cfg.configSetup);
   connectionText = concatStrings (mapAttrsToList (n: v:
diff --git a/nixos/modules/services/networking/murmur.nix b/nixos/modules/services/networking/murmur.nix
index ebade7aa8e40..37a1ff8b2d34 100644
--- a/nixos/modules/services/networking/murmur.nix
+++ b/nixos/modules/services/networking/murmur.nix
@@ -19,8 +19,8 @@ let
     welcometext="${cfg.welcometext}"
     port=${toString cfg.port}
 
-    ${if cfg.hostName == "" then "" else "host="+cfg.hostName}
-    ${if cfg.password == "" then "" else "serverpassword="+cfg.password}
+    ${optionalString (cfg.hostName != "") "host=${cfg.hostName}"}
+    ${optionalString (cfg.password != "") "serverpassword=${cfg.password}"}
 
     bandwidth=${toString cfg.bandwidth}
     users=${toString cfg.users}
@@ -32,17 +32,17 @@ let
     bonjour=${boolToString cfg.bonjour}
     sendversion=${boolToString cfg.sendVersion}
 
-    ${if cfg.registerName     == "" then "" else "registerName="+cfg.registerName}
-    ${if cfg.registerPassword == "" then "" else "registerPassword="+cfg.registerPassword}
-    ${if cfg.registerUrl      == "" then "" else "registerUrl="+cfg.registerUrl}
-    ${if cfg.registerHostname == "" then "" else "registerHostname="+cfg.registerHostname}
+    ${optionalString (cfg.registerName != "") "registerName=${cfg.registerName}"}
+    ${optionalString (cfg.registerPassword == "") "registerPassword=${cfg.registerPassword}"}
+    ${optionalString (cfg.registerUrl != "") "registerUrl=${cfg.registerUrl}"}
+    ${optionalString (cfg.registerHostname != "") "registerHostname=${cfg.registerHostname}"}
 
     certrequired=${boolToString cfg.clientCertRequired}
-    ${if cfg.sslCert == "" then "" else "sslCert="+cfg.sslCert}
-    ${if cfg.sslKey  == "" then "" else "sslKey="+cfg.sslKey}
-    ${if cfg.sslCa   == "" then "" else "sslCA="+cfg.sslCa}
+    ${optionalString (cfg.sslCert != "") "sslCert=${cfg.sslCert}"}
+    ${optionalString (cfg.sslKey != "") "sslKey=${cfg.sslKey}"}
+    ${optionalString (cfg.sslCa != "") "sslCA=${cfg.sslCa}"}
 
-    ${lib.optionalString (cfg.dbus != null) "dbus=${cfg.dbus}"}
+    ${optionalString (cfg.dbus != null) "dbus=${cfg.dbus}"}
 
     ${cfg.extraConfig}
   '';
diff --git a/nixos/modules/services/networking/nsd.nix b/nixos/modules/services/networking/nsd.nix
index 09f3bdc7ae07..6db728e7aa5a 100644
--- a/nixos/modules/services/networking/nsd.nix
+++ b/nixos/modules/services/networking/nsd.nix
@@ -137,8 +137,8 @@ let
   '';
 
   yesOrNo = b: if b then "yes" else "no";
-  maybeString = prefix: x: if x == null then "" else ''${prefix} "${x}"'';
-  maybeToString = prefix: x: if x == null then "" else ''${prefix} ${toString x}'';
+  maybeString = prefix: x: optionalString (x != null) ''${prefix} "${x}"'';
+  maybeToString = prefix: x: optionalString (x != null) ''${prefix} ${toString x}'';
   forEach = pre: l: concatMapStrings (x: pre + x + "\n") l;
 
 
diff --git a/nixos/modules/services/networking/ssh/lshd.nix b/nixos/modules/services/networking/ssh/lshd.nix
index af64969c2fcd..129e42055514 100644
--- a/nixos/modules/services/networking/ssh/lshd.nix
+++ b/nixos/modules/services/networking/ssh/lshd.nix
@@ -165,9 +165,7 @@ in
         ${lsh}/sbin/lshd --daemonic \
           --password-helper="${lsh}/sbin/lsh-pam-checkpw" \
           -p ${toString portNumber} \
-          ${if interfaces == [] then ""
-            else (concatStrings (map (i: "--interface=\"${i}\"")
-                                     interfaces))} \
+          ${optionalString (interfaces != []) (concatStrings (map (i: "--interface=\"${i}\"") interfaces))} \
           -h "${hostKey}" \
           ${optionalString (!syslog) "--no-syslog" } \
           ${if passwordAuthentication then "--password" else "--no-password" } \
diff --git a/nixos/modules/services/scheduling/fcron.nix b/nixos/modules/services/scheduling/fcron.nix
index f1d2f462a755..47bd358f979d 100644
--- a/nixos/modules/services/scheduling/fcron.nix
+++ b/nixos/modules/services/scheduling/fcron.nix
@@ -6,7 +6,7 @@ let
 
   cfg = config.services.fcron;
 
-  queuelen = if cfg.queuelen == null then "" else "-q ${toString cfg.queuelen}";
+  queuelen = optionalString (cfg.queuelen != null) "-q ${toString cfg.queuelen}";
 
   # Duplicate code, also found in cron.nix. Needs deduplication.
   systemCronJobs =
diff --git a/nixos/modules/services/web-apps/invidious.nix b/nixos/modules/services/web-apps/invidious.nix
index e875be47fb91..8823da010014 100644
--- a/nixos/modules/services/web-apps/invidious.nix
+++ b/nixos/modules/services/web-apps/invidious.nix
@@ -62,7 +62,7 @@ let
         port = cfg.database.port;
         # Blank for unix sockets, see
         # https://github.com/will/crystal-pg/blob/1548bb255210/src/pq/conninfo.cr#L100-L108
-        host = if cfg.database.host == null then "" else cfg.database.host;
+        host = lib.optionalString (cfg.database.host != null) cfg.database.host;
         # Not needed because peer authentication is enabled
         password = lib.mkIf (cfg.database.host == null) "";
       };
diff --git a/nixos/modules/services/web-apps/invoiceplane.nix b/nixos/modules/services/web-apps/invoiceplane.nix
index 8be1fd3055d0..f419b75cf70f 100644
--- a/nixos/modules/services/web-apps/invoiceplane.nix
+++ b/nixos/modules/services/web-apps/invoiceplane.nix
@@ -16,7 +16,7 @@ let
     DB_HOSTNAME=${cfg.database.host}
     DB_USERNAME=${cfg.database.user}
     # NOTE: file_get_contents adds newline at the end of returned string
-    DB_PASSWORD=${if cfg.database.passwordFile == null then "" else "trim(file_get_contents('${cfg.database.passwordFile}'), \"\\r\\n\")"}
+    DB_PASSWORD=${optionalString (cfg.database.passwordFile != null) "trim(file_get_contents('${cfg.database.passwordFile}'), \"\\r\\n\")"}
     DB_DATABASE=${cfg.database.name}
     DB_PORT=${toString cfg.database.port}
     SESS_EXPIRATION=864000
diff --git a/nixos/modules/services/web-apps/peertube.nix b/nixos/modules/services/web-apps/peertube.nix
index 4ef2d7dce532..8a1fc3c567cc 100644
--- a/nixos/modules/services/web-apps/peertube.nix
+++ b/nixos/modules/services/web-apps/peertube.nix
@@ -350,7 +350,7 @@ in {
         };
         redis = {
           hostname = "${toString cfg.redis.host}";
-          port = (if cfg.redis.port == null then "" else cfg.redis.port);
+          port = (lib.optionalString (cfg.redis.port != null) cfg.redis.port);
         };
         storage = {
           tmp = lib.mkDefault "/var/lib/peertube/storage/tmp/";
diff --git a/nixos/modules/services/web-servers/lighttpd/cgit.nix b/nixos/modules/services/web-servers/lighttpd/cgit.nix
index 5042fbf1f8f2..e9f42c41183b 100644
--- a/nixos/modules/services/web-servers/lighttpd/cgit.nix
+++ b/nixos/modules/services/web-servers/lighttpd/cgit.nix
@@ -4,7 +4,7 @@ with lib;
 
 let
   cfg = config.services.lighttpd.cgit;
-  pathPrefix = if stringLength cfg.subdir == 0 then "" else "/" + cfg.subdir;
+  pathPrefix = optionalString (stringLength cfg.subdir != 0) ("/" + cfg.subdir);
   configFile = pkgs.writeText "cgitrc"
     ''
       # default paths to static assets
diff --git a/nixos/modules/services/x11/desktop-managers/phosh.nix b/nixos/modules/services/x11/desktop-managers/phosh.nix
index 3cfa6e044b73..e4cd9fd99e40 100644
--- a/nixos/modules/services/x11/desktop-managers/phosh.nix
+++ b/nixos/modules/services/x11/desktop-managers/phosh.nix
@@ -100,7 +100,7 @@ let
     };
   };
 
-  optionalKV = k: v: if v == null then "" else "${k} = ${builtins.toString v}";
+  optionalKV = k: v: optionalString (v != null) "${k} = ${builtins.toString v}";
 
   renderPhocOutput = name: output: let
     modelines = if builtins.isList output.modeline
diff --git a/nixos/modules/system/boot/kernel_config.nix b/nixos/modules/system/boot/kernel_config.nix
index 31e9ec626ca6..e618070f0dc3 100644
--- a/nixos/modules/system/boot/kernel_config.nix
+++ b/nixos/modules/system/boot/kernel_config.nix
@@ -70,11 +70,10 @@ let
       let
         val = if item.freeform != null then item.freeform else item.tristate;
       in
-        if val == null
-          then ""
-          else if (item.optional)
+        optionalString (val != null)
+            (if (item.optional)
             then "${key}? ${mkValue val}\n"
-            else "${key} ${mkValue val}\n";
+            else "${key} ${mkValue val}\n");
 
     mkConf = cfg: concatStrings (mapAttrsToList mkConfigLine cfg);
   in mkConf exprs;
diff --git a/nixos/modules/system/boot/loader/grub/grub.nix b/nixos/modules/system/boot/loader/grub/grub.nix
index 9f80b40d116c..a10dd3d0ca78 100644
--- a/nixos/modules/system/boot/loader/grub/grub.nix
+++ b/nixos/modules/system/boot/loader/grub/grub.nix
@@ -65,8 +65,8 @@ let
         [ coreutils gnused gnugrep findutils diffutils btrfs-progs util-linux mdadm ]
         ++ optional cfg.efiSupport efibootmgr
         ++ optionals cfg.useOSProber [ busybox os-prober ]);
-      font = if cfg.font == null then ""
-        else (if lib.last (lib.splitString "." cfg.font) == "pf2"
+      font = lib.optionalString (cfg.font != null) (
+             if lib.last (lib.splitString "." cfg.font) == "pf2"
              then cfg.font
              else "${convertedFont}");
     });
diff --git a/nixos/modules/system/boot/systemd/user.nix b/nixos/modules/system/boot/systemd/user.nix
index 92e1b087392d..1b6398d2f929 100644
--- a/nixos/modules/system/boot/systemd/user.nix
+++ b/nixos/modules/system/boot/systemd/user.nix
@@ -42,7 +42,7 @@ let
 
   writeTmpfiles = { rules, user ? null }:
     let
-      suffix = if user == null then "" else "-${user}";
+      suffix = optionalString (user != null) "-${user}";
     in
     pkgs.writeTextFile {
       name = "nixos-user-tmpfiles.d${suffix}";
diff --git a/pkgs/applications/editors/texmacs/darwin.nix b/pkgs/applications/editors/texmacs/darwin.nix
index ff090dd3259a..8c74d8c5c8f2 100644
--- a/pkgs/applications/editors/texmacs/darwin.nix
+++ b/pkgs/applications/editors/texmacs/darwin.nix
@@ -47,10 +47,10 @@ stdenv.mkDerivation {
 
   postInstall = "wrapProgram $out/Applications/TeXmacs-${version}/Contents/MacOS/TeXmacs --suffix PATH : " +
     "${ghostscript}/bin:" +
-    (if aspell == null then "" else "${aspell}/bin:") +
-    (if tex == null then "" else "${tex}/bin:") +
-    (if netpbm == null then "" else "${lib.getBin netpbm}/bin:") +
-    (if imagemagick == null then "" else "${imagemagick}/bin:");
+    (lib.optionalString (aspell != null) "${aspell}/bin:") +
+    (lib.optionalString (tex != null) "${tex}/bin:") +
+    (lib.optionalString (netpbm != null) "${lib.getBin netpbm}/bin:") +
+    (lib.optionalString (imagemagick != null) "${imagemagick}/bin:");
 
   enableParallelBuilding = true;
 
diff --git a/pkgs/applications/editors/vscode/vscodium.nix b/pkgs/applications/editors/vscode/vscodium.nix
index 3e66c7e6abd0..b434279621d1 100644
--- a/pkgs/applications/editors/vscode/vscodium.nix
+++ b/pkgs/applications/editors/vscode/vscodium.nix
@@ -22,7 +22,7 @@ let
     armv7l-linux = "0m1v24gg2dy79hgrz37gysgrazg8vkr1gkp52j6m6y76vi0l8249";
   }.${system} or throwSystem;
 
-  sourceRoot = if stdenv.isDarwin then "" else ".";
+  sourceRoot = lib.optionalString (!stdenv.isDarwin) ".";
 in
   callPackage ./generic.nix rec {
     inherit sourceRoot commandLineArgs useVSCodeRipgrep;
diff --git a/pkgs/applications/networking/browsers/chromium/default.nix b/pkgs/applications/networking/browsers/chromium/default.nix
index 77f4def41f33..a5e6855e9637 100644
--- a/pkgs/applications/networking/browsers/chromium/default.nix
+++ b/pkgs/applications/networking/browsers/chromium/default.nix
@@ -134,9 +134,7 @@ let
     };
   };
 
-  suffix = if (channel == "stable" || channel == "ungoogled-chromium")
-    then ""
-    else "-" + channel;
+  suffix = lib.optionalString (channel != "stable" && channel != "ungoogled-chromium") ("-" + channel);
 
   sandboxExecutableName = chromium.browser.passthru.sandboxExecutableName;
 
diff --git a/pkgs/applications/networking/browsers/microsoft-edge/browser.nix b/pkgs/applications/networking/browsers/microsoft-edge/browser.nix
index 2af28bb8dd06..7f72a42ffe0d 100644
--- a/pkgs/applications/networking/browsers/microsoft-edge/browser.nix
+++ b/pkgs/applications/networking/browsers/microsoft-edge/browser.nix
@@ -46,13 +46,9 @@ let
              then baseName
              else baseName + "-" + channel;
 
-  iconSuffix = if channel == "stable"
-               then ""
-               else "_${channel}";
+  iconSuffix = lib.optionalString (channel != "stable") "_${channel}";
 
-  desktopSuffix = if channel == "stable"
-                  then ""
-                  else "-${channel}";
+  desktopSuffix = lib.optionalString (channel != "stable") "-${channel}";
 in
 
 stdenv.mkDerivation rec {
diff --git a/pkgs/applications/office/libreoffice/default.nix b/pkgs/applications/office/libreoffice/default.nix
index 25e8f18998e2..518167cb33d1 100644
--- a/