treewide: use optionalString instead of 'then ""'

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 ''

nixos/modules/services/continuous-integration/jenkins/default.nix

@@ -210,9 +210,7 @@ in {
 
       preStart =
         let replacePlugins =
-              if cfg.plugins == null
+              optionalString (cfg.plugins != null) (
-              then ""
-              else
                 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}

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" ''

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 ""
+      optionalString (v != null)
-      else generators.mkKeyValueDefault {
+      (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).

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 \
+          --${optionalString (!cfg.collectors.status) "no-"}collector.status \
-          --${if cfg.collectors.version == true then "" else "no-"}collector.version \
+          --${optionalString (!cfg.collectors.version) "no-"}collector.version \
-          --${if cfg.collectors.node == true then "" else "no-"}collector.node \
+          --${optionalString (!cfg.collectors.node) "no-"}collector.node \
-          --${if cfg.collectors.cluster == true then "" else "no-"}collector.cluster \
+          --${optionalString (!cfg.collectors.cluster) "no-"}collector.cluster \
-          --${if cfg.collectors.resources == true then "" else "no-"}collector.resources \
+          --${optionalString (!cfg.collectors.resources) "no-"}collector.resources \
-          --${if cfg.collectors.config == true then "" else "no-"}collector.config \
+          --${optionalString (!cfg.collectors.config) "no-"}collector.config \
           %d/configFile \
           ${toString cfg.port} ${cfg.listenAddress}
       '';

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 ""
+        lib.optionalString (v != null) (generators.mkKeyValueDefault {} "=" k v);
-        else generators.mkKeyValueDefault {} "=" k v;
     } cfg.settings);
   need_CAP_NET_BIND_SERVICE = cfg.settings.identd_port != 0 && cfg.settings.identd_port < 1024;
 in

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

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 ""
+    lib.optionalString (length nonchars != 0)
-    else substring (head nonchars).ind (add 1 (sub (last nonchars).ind (head nonchars).ind)) str;
+      (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:

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}
+    ${optionalString (cfg.hostName != "") "host=${cfg.hostName}"}
-    ${if cfg.password == "" then "" else "serverpassword="+cfg.password}
+    ${optionalString (cfg.password != "") "serverpassword=${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}
+    ${optionalString (cfg.registerName != "") "registerName=${cfg.registerName}"}
-    ${if cfg.registerPassword == "" then "" else "registerPassword="+cfg.registerPassword}
+    ${optionalString (cfg.registerPassword == "") "registerPassword=${cfg.registerPassword}"}
-    ${if cfg.registerUrl      == "" then "" else "registerUrl="+cfg.registerUrl}
+    ${optionalString (cfg.registerUrl != "") "registerUrl=${cfg.registerUrl}"}
-    ${if cfg.registerHostname == "" then "" else "registerHostname="+cfg.registerHostname}
+    ${optionalString (cfg.registerHostname != "") "registerHostname=${cfg.registerHostname}"}
 
     certrequired=${boolToString cfg.clientCertRequired}
-    ${if cfg.sslCert == "" then "" else "sslCert="+cfg.sslCert}
+    ${optionalString (cfg.sslCert != "") "sslCert=${cfg.sslCert}"}
-    ${if cfg.sslKey  == "" then "" else "sslKey="+cfg.sslKey}
+    ${optionalString (cfg.sslKey != "") "sslKey=${cfg.sslKey}"}
-    ${if cfg.sslCa   == "" then "" else "sslCA="+cfg.sslCa}
+    ${optionalString (cfg.sslCa != "") "sslCA=${cfg.sslCa}"}
 
-    ${lib.optionalString (cfg.dbus != null) "dbus=${cfg.dbus}"}
+    ${optionalString (cfg.dbus != null) "dbus=${cfg.dbus}"}
 
     ${cfg.extraConfig}
   '';

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}"'';
+  maybeString = prefix: x: optionalString (x != null) ''${prefix} "${x}"'';
-  maybeToString = prefix: x: if x == null then "" else ''${prefix} ${toString x}'';
+  maybeToString = prefix: x: optionalString (x != null) ''${prefix} ${toString x}'';
   forEach = pre: l: concatMapStrings (x: pre + x + "\n") l;
 
 

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 ""
+          ${optionalString (interfaces != []) (concatStrings (map (i: "--interface=\"${i}\"") interfaces))} \
-            else (concatStrings (map (i: "--interface=\"${i}\"")
-                                     interfaces))} \
           -h "${hostKey}" \
           ${optionalString (!syslog) "--no-syslog" } \
           ${if passwordAuthentication then "--password" else "--no-password" } \

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 =

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) "";
       };

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

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/";

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

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

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
+        optionalString (val != null)
-          then ""
+            (if (item.optional)
-          else 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;

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 ""
+      font = lib.optionalString (cfg.font != null) (
-        else (if lib.last (lib.splitString "." cfg.font) == "pf2"
+             if lib.last (lib.splitString "." cfg.font) == "pf2"
              then cfg.font
              else "${convertedFont}");
     });

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}";

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:") +
+    (lib.optionalString (aspell != null) "${aspell}/bin:") +
-    (if tex == null then "" else "${tex}/bin:") +
+    (lib.optionalString (tex != null) "${tex}/bin:") +
-    (if netpbm == null then "" else "${lib.getBin netpbm}/bin:") +
+    (lib.optionalString (netpbm != null) "${lib.getBin netpbm}/bin:") +
-    (if imagemagick == null then "" else "${imagemagick}/bin:");
+    (lib.optionalString (imagemagick != null) "${imagemagick}/bin:");
 
   enableParallelBuilding = true;
 

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;

pkgs/applications/networking/browsers/chromium/default.nix

@@ -134,9 +134,7 @@ let
     };
   };
 
-  suffix = if (channel == "stable" || channel == "ungoogled-chromium")
+  suffix = lib.optionalString (channel != "stable" && channel != "ungoogled-chromium") ("-" + channel);
-    then ""
-    else "-" + channel;
 
   sandboxExecutableName = chromium.browser.passthru.sandboxExecutableName;
 

pkgs/applications/networking/browsers/microsoft-edge/browser.nix

@@ -46,13 +46,9 @@ let
              then baseName
              else baseName + "-" + channel;
 
-  iconSuffix = if channel == "stable"
+  iconSuffix = lib.optionalString (channel != "stable") "_${channel}";
-               then ""
-               else "_${channel}";
 
-  desktopSuffix = if channel == "stable"
+  desktopSuffix = lib.optionalString (channel != "stable") "-${channel}";
-                  then ""
-                  else "-${channel}";
 in
 
 stdenv.mkDerivation rec {

pkgs/applications/office/libreoffice/default.nix

@@ -395,7 +395,7 @@ in
   dontWrapQtApps = true;
 
   configureFlags = [
-    (if withHelp then "" else "--without-help")
+    (lib.optionalString (!withHelp) "--without-help")
     "--with-boost=${getDev boost}"
     "--with-boost-libdir=${getLib boost}/lib"
     "--with-beanshell-jar=${bsh}"

pkgs/applications/science/logic/hol_light/default.nix

@@ -2,8 +2,7 @@
 
 let
   load_num =
-    if num == null then "" else
+    lib.optionalString (num != null) ''
-    ''
       -I ${num}/lib/ocaml/${ocaml.version}/site-lib/num \
       -I ${num}/lib/ocaml/${ocaml.version}/site-lib/top-num \
       -I ${num}/lib/ocaml/${ocaml.version}/site-lib/stublibs \

pkgs/applications/science/math/sage/sage-tests.nix

@@ -19,7 +19,7 @@ let
   runAllTests = files == null;
   testArgs = if runAllTests then "--all" else testFileList;
   patienceSpecifier = lib.optionalString longTests "--long";
-  timeSpecifier = if timeLimit == null then "" else "--short ${toString timeLimit}";
+  timeSpecifier = lib.optionalString (timeLimit != null) "--short ${toString timeLimit}";
   relpathToArg = relpath: lib.escapeShellArg "${src}/${relpath}"; # paths need to be absolute
   testFileList = lib.concatStringsSep " " (map relpathToArg files);
 in

pkgs/applications/version-management/sapling/default.nix

@@ -38,7 +38,7 @@ let
   #
   # See https://github.com/NixOS/nixpkgs/pull/198311#issuecomment-1326894295
   myCargoSetupHook = rustPlatform.cargoSetupHook.overrideAttrs (old: {
-    cargoConfig = if stdenv.isDarwin then "" else old.cargoConfig;
+    cargoConfig = lib.optionalString (!stdenv.isDarwin) old.cargoConfig;
   });
 
   src = fetchFromGitHub {

pkgs/applications/window-managers/sway/wrapper.nix

@@ -28,7 +28,7 @@ let
        export DBUS_SESSION_BUS_ADDRESS
        exec ${sway}/bin/sway "$@"
      else
-       exec ${if !dbusSupport then "" else "${dbus}/bin/dbus-run-session"} ${sway}/bin/sway "$@"
+       exec ${lib.optionalString dbusSupport "${dbus}/bin/dbus-run-session"} ${sway}/bin/sway "$@"
      fi
    '';
 in symlinkJoin {

pkgs/build-support/bintools-wrapper/default.nix

@@ -59,12 +59,12 @@ let
   bintoolsVersion = lib.getVersion bintools;
   bintoolsName = lib.removePrefix targetPrefix (lib.getName bintools);
 
-  libc_bin = if libc == null then "" else getBin libc;
+  libc_bin = lib.optionalString (libc != null) (getBin libc);
-  libc_dev = if libc == null then "" else getDev libc;
+  libc_dev = lib.optionalString (libc != null) (getDev libc);
-  libc_lib = if libc == null then "" else getLib libc;
+  libc_lib = lib.optionalString (libc != null) (getLib libc);
-  bintools_bin = if nativeTools then "" else getBin bintools;
+  bintools_bin = lib.optionalString (!nativeTools) (getBin bintools);
   # The wrapper scripts use 'cat' and 'grep', so we may need coreutils.
-  coreutils_bin = if nativeTools then "" else getBin coreutils;
+  coreutils_bin = lib.optionalString (!nativeTools) (getBin coreutils);
 
   # See description in cc-wrapper.
   suffixSalt = replaceStrings ["-" "."] ["_" "_"] targetPlatform.config;
@@ -103,7 +103,7 @@ in
 stdenv.mkDerivation {
   pname = targetPrefix
     + (if name != "" then name else "${bintoolsName}-wrapper");
-  version = if bintools == null then "" else bintoolsVersion;
+  version = lib.optionalString (bintools != null) bintoolsVersion;
 
   preferLocalBuild = true;
 
@@ -265,7 +265,7 @@ stdenv.mkDerivation {
     # install the wrapper, you get tools like objdump (same for any
     # binaries of libc).
     + optionalString (!nativeTools) ''
-      printWords ${bintools_bin} ${if libc == null then "" else libc_bin} > $out/nix-support/propagated-user-env-packages
+      printWords ${bintools_bin} ${lib.optionalString (libc != null) libc_bin} > $out/nix-support/propagated-user-env-packages
     ''
 
     ##
@@ -381,7 +381,7 @@ stdenv.mkDerivation {
     # for substitution in utils.bash
     expandResponseParams = "${expand-response-params}/bin/expand-response-params";
     shell = getBin shell + shell.shellPath or "";
-    gnugrep_bin = if nativeTools then "" else gnugrep;
+    gnugrep_bin = lib.optionalString (!nativeTools) gnugrep;
     wrapperName = "BINTOOLS_WRAPPER";
     inherit dynamicLinker targetPrefix suffixSalt coreutils_bin;
     inherit bintools_bin libc_bin libc_dev libc_lib;

pkgs/build-support/cc-wrapper/default.nix

@@ -75,14 +75,14 @@ let
   ccVersion = lib.getVersion cc;
   ccName = lib.removePrefix targetPrefix (lib.getName cc);
 
-  libc_bin = if libc == null then "" else getBin libc;
+  libc_bin = optionalString (libc != null) (getBin libc);
-  libc_dev = if libc == null then "" else getDev libc;
+  libc_dev = optionalString (libc != null) (getDev libc);
-  libc_lib = if libc == null then "" else getLib libc;
+  libc_lib = optionalString (libc != null) (getLib libc);
   cc_solib = getLib cc
     + optionalString (targetPlatform != hostPlatform) "/${targetPlatform.config}";
 
   # The wrapper scripts use 'cat' and 'grep', so we may need coreutils.
-  coreutils_bin = if nativeTools then "" else getBin coreutils;
+  coreutils_bin = optionalString (!nativeTools) (getBin coreutils);
 
   # The "suffix salt" is a arbitrary string added in the end of env vars
   # defined by cc-wrapper's hooks so that multiple cc-wrappers can be used
@@ -164,7 +164,7 @@ assert nativePrefix == bintools.nativePrefix;
 stdenv.mkDerivation {
   pname = targetPrefix
     + (if name != "" then name else "${ccName}-wrapper");
-  version = if cc == null then "" else ccVersion;
+  version = optionalString (cc != null) ccVersion;
 
   preferLocalBuild = true;
 
@@ -600,10 +600,10 @@ stdenv.mkDerivation {
     # for substitution in utils.bash
     expandResponseParams = "${expand-response-params}/bin/expand-response-params";
     shell = getBin shell + shell.shellPath or "";
-    gnugrep_bin = if nativeTools then "" else gnugrep;
+    gnugrep_bin = optionalString (!nativeTools) gnugrep;
     # stdenv.cc.cc should not be null and we have nothing better for now.
     # if the native impure bootstrap is gotten rid of this can become `inherit cc;` again.
-    cc = if nativeTools then "" else cc;
+    cc = optionalString (!nativeTools) cc;
     wrapperName = "CC_WRAPPER";
     inherit suffixSalt coreutils_bin bintools;
     inherit libc_bin libc_dev libc_lib;

pkgs/build-support/docker/default.nix

@@ -594,7 +594,7 @@ rec {
           nativeBuildInputs = [ jshon pigz jq moreutils ];
           # Image name must be lowercase
           imageName = lib.toLower name;
-          imageTag = if tag == null then "" else tag;
+          imageTag = lib.optionalString (tag != null) tag;
           inherit fromImage baseJson;
           layerClosure = writeReferencesToFile layer;
           passthru.buildArgs = args;

pkgs/build-support/fetchgithub/default.nix

@@ -24,7 +24,7 @@ let
     position = "${position.file}:${toString position.line}";
   };
   passthruAttrs = removeAttrs args [ "owner" "repo" "rev" "fetchSubmodules" "forceFetchGit" "private" "githubBase" "varPrefix" ];
-  varBase = "NIX${if varPrefix == null then "" else "_${varPrefix}"}_GITHUB_PRIVATE_";
+  varBase = "NIX${lib.optionalString (varPrefix != null) "_${varPrefix}"}_GITHUB_PRIVATE_";
   useFetchGit = fetchSubmodules || (leaveDotGit == true) || deepClone || forceFetchGit || (sparseCheckout != []);
   # We prefer fetchzip in cases we don't need submodules as the hash
   # is more stable in that case.

pkgs/build-support/kernel/make-initrd-ng.nix

@@ -72,7 +72,7 @@ in
   ${if makeUInitrd then "uInitrdCompression" else null} = uInitrdCompression;
 
   passAsFile = ["contents"];
-  contents = lib.concatMapStringsSep "\n" ({ object, symlink, ... }: "${object}\n${if symlink == null then "" else symlink}") contents + "\n";
+  contents = lib.concatMapStringsSep "\n" ({ object, symlink, ... }: "${object}\n${lib.optionalString (symlink != null) symlink}") contents + "\n";
 
   nativeBuildInputs = [makeInitrdNGTool cpio] ++ lib.optional makeUInitrd ubootTools ++ lib.optional strip binutils;
 

pkgs/build-support/nix-gitignore/default.nix

@@ -66,7 +66,7 @@ in rec {
       handleSlashPrefix = l:
         let
           split = (match "^(/?)(.*)" l);
-          findSlash = l: if (match ".+/.+" l) != null then "" else l;
+          findSlash = l: lib.optionalString ((match ".+/.+" l) == null) l;
           hasSlash = mapAroundCharclass findSlash l != l;
         in
           (if (elemAt split 0) == "/" || hasSlash

pkgs/build-support/rust/build-rust-crate/configure-crate.nix

@@ -21,7 +21,7 @@
 , verbose
 , workspace_member }:
 let version_ = lib.splitString "-" crateVersion;
-    versionPre = if lib.tail version_ == [] then "" else lib.elemAt version_ 1;
+    versionPre = lib.optionalString (lib.tail version_ != []) (lib.elemAt version_ 1);
     version = lib.splitVersion (lib.head version_);
     rustcOpts = lib.foldl' (opts: opt: opts + " " + opt)
         (if release then "-C opt-level=3" else "-C debuginfo=2")

pkgs/build-support/vm/default.nix

@@ -468,7 +468,7 @@ rec {
 
         echo "installing RPMs..."
         PATH=/usr/bin:/bin:/usr/sbin:/sbin $chroot /mnt \
-          rpm -iv --nosignature ${if runScripts then "" else "--noscripts"} $rpms
+          rpm -iv --nosignature ${lib.optionalString (!runScripts) "--noscripts"} $rpms
 
         echo "running post-install script..."
         eval "$postInstall"

pkgs/data/sgml+xml/stylesheets/xslt/docbook-xsl/default.nix

@@ -3,7 +3,7 @@
 let
 
   common = { pname, sha256, suffix ? "" }: let
-    legacySuffix = if suffix == "-nons" then "" else "-ns";
+    legacySuffix = lib.optionalString (suffix != "-nons") "-ns";
     self = stdenv.mkDerivation rec {
       inherit pname;
       version = "1.79.2";

pkgs/development/compilers/purescript/purescript/default.nix

@@ -7,10 +7,7 @@ let
   dynamic-linker = stdenv.cc.bintools.dynamicLinker;
 
   patchelf = libPath :
-    if stdenv.isDarwin
+    lib.optionalString (!stdenv.isDarwin) ''
-      then ""
-      else
-        ''
           chmod u+w $PURS
           patchelf --interpreter ${dynamic-linker} --set-rpath ${libPath} $PURS
           chmod u-w $PURS

pkgs/development/interpreters/acl2/libipasirglucose4/default.nix

@@ -24,7 +24,7 @@ stdenv.mkDerivation rec {
 
   postBuild = ''
     $CXX -shared -o ${libname} \
-        ${if stdenv.cc.isClang then "" else "-Wl,-soname,${libname}"} \
+        ${lib.optionalString (!stdenv.cc.isClang) "-Wl,-soname,${libname}"} \
         ipasirglucoseglue.o libipasirglucose4.a
   '';
 

pkgs/development/interpreters/python/mk-python-derivation.nix

@@ -118,7 +118,7 @@ let
 
     optionalLocation = let
         pos = builtins.unsafeGetAttrPos (if attrs ? "pname" then "pname" else "name") attrs;
-      in if pos == null then "" else " at ${pos.file}:${toString pos.line}:${toString pos.column}";
+      in lib.optionalString (pos != null) " at ${pos.file}:${toString pos.line}:${toString pos.column}";
 
     leftPadName = name: against: let
         len = lib.max (lib.stringLength name) (lib.stringLength against);

pkgs/development/interpreters/python/wrapper.nix

@@ -42,7 +42,7 @@ let
             if [ -f "$prg" ]; then
               rm -f "$out/bin/$prg"
               if [ -x "$prg" ]; then
-                makeWrapper "$path/bin/$prg" "$out/bin/$prg" --set NIX_PYTHONPREFIX "$out" --set NIX_PYTHONEXECUTABLE ${pythonExecutable} --set NIX_PYTHONPATH ${pythonPath} ${if permitUserSite then "" else ''--set PYTHONNOUSERSITE "true"''} ${lib.concatStringsSep " " makeWrapperArgs}
+                makeWrapper "$path/bin/$prg" "$out/bin/$prg" --set NIX_PYTHONPREFIX "$out" --set NIX_PYTHONEXECUTABLE ${pythonExecutable} --set NIX_PYTHONPATH ${pythonPath} ${lib.optionalString (!permitUserSite) ''--set PYTHONNOUSERSITE "true"''} ${lib.concatStringsSep " " makeWrapperArgs}
               fi
             fi
           done

pkgs/development/libraries/ffmpeg/generic.nix

@@ -330,7 +330,7 @@ assert buildPostproc -> buildAvutil;
 assert buildSwscale -> buildAvutil;
 
 stdenv.mkDerivation (finalAttrs: {
-  pname = "ffmpeg" + (if ffmpegVariant == "small" then "" else "-${ffmpegVariant}");
+  pname = "ffmpeg" + (optionalString (ffmpegVariant != "small") "-${ffmpegVariant}");
   inherit version;
 
   src = fetchgit {

pkgs/development/libraries/opencv/tests.nix

@@ -39,7 +39,7 @@ let
     "stitching"
     "video"
   ] ++ lib.optionals (!stdenv.isAarch64 && enableGStreamer) [ "gapi" ];
-  testRunner = if stdenv.isDarwin then "" else "${lib.getExe xvfb-run} -a ";
+  testRunner = lib.optionalString (!stdenv.isDarwin) "${lib.getExe xvfb-run} -a ";
   testsPreparation = ''
     touch $out
     # several tests want a write access, so we have to copy files

pkgs/development/libraries/qt-4.x/4.8/default.nix

@@ -173,9 +173,9 @@ stdenv.mkDerivation rec {
     "-make" "libs" "-make" "tools" "-make" "translations"
     "-no-phonon" "-no-webkit" "-no-multimedia" "-audio-backend"
   ]) ++ [
-    "-${if demos then "" else "no"}make" "demos"
+    "-${lib.optionalString (!demos) "no"}make" "demos"
-    "-${if examples then "" else "no"}make" "examples"
+    "-${lib.optionalString (!examples) "no"}make" "examples"
-    "-${if docs then "" else "no"}make" "docs"
+    "-${lib.optionalString (!docs) "no"}make" "docs"
   ] ++ lib.optional developerBuild "-developer-build"
     ++ lib.optionals stdenv.hostPlatform.isDarwin [ platformFlag "unsupported/macx-clang-libc++" ]
     ++ lib.optionals stdenv.hostPlatform.isWindows [ platformFlag "win32-g++-4.6" ];

pkgs/development/mobile/titaniumenv/build-app.nix

@@ -158,8 +158,7 @@ stdenv.mkDerivation ({
 
   installPhase = ''
     ${if target == "android" then ''
-      ${if release then ""
+      ${lib.optionalString (!release) ''
-      else ''
         cp "$(ls build/android/bin/*.apk | grep -v '\-unsigned.apk')" $out
       ''}
 

pkgs/development/python-modules/azure-common/default.nix

@@ -23,7 +23,7 @@ buildPythonPackage rec {
     azure-nspkg
   ] ++ lib.optionals (!isPy3k) [ setuptools ]; # need for namespace lookup
 
-  postInstall = if isPy3k then "" else ''
+  postInstall = lib.optionalString (!isPy3k) ''
     echo "__import__('pkg_resources').declare_namespace(__name__)" >> "$out/lib/${python.libPrefix}"/site-packages/azure/__init__.py
   '';
 

pkgs/development/python-modules/azure-mgmt-common/default.nix

@@ -26,7 +26,7 @@ buildPythonPackage rec {
     msrestazure
   ];
 
-  postInstall = if isPy3k then "" else ''
+  postInstall = pkgs.lib.optionalString (!isPy3k) ''
     echo "__import__('pkg_resources').declare_namespace(__name__)" >> "$out/lib/${python.libPrefix}"/site-packages/azure/mgmt/__init__.py
     echo "__import__('pkg_resources').declare_namespace(__name__)" >> "$out/lib/${python.libPrefix}"/site-packages/azure/__init__.py
   '';

pkgs/development/python-modules/tensorflow/bin.nix

@@ -53,7 +53,7 @@ in buildPythonPackage {
   disabled = pythonAtLeast "3.11";
 
   src = let
-    pyVerNoDot = lib.strings.stringAsChars (x: if x == "." then "" else x) python.pythonVersion;
+    pyVerNoDot = lib.strings.stringAsChars (x: lib.optionalString (x != ".") x) python.pythonVersion;
     platform = if stdenv.isDarwin then "mac" else "linux";
     unit = if cudaSupport then "gpu" else "cpu";
     key = "${platform}_py_${pyVerNoDot}_${unit}";

pkgs/development/ruby-modules/bundled-common/default.nix

@@ -70,11 +70,12 @@ let
       assert gemFiles.gemdir != null; "cp -a ${gemFiles.gemdir}/* $out/") #*/
   );
 
-  maybeCopyAll = pkgname: if pkgname == null then "" else
+  maybeCopyAll = pkgname: lib.optionalString (pkgname != null) (
     let
       mainGem = gems.${pkgname} or (throw "bundlerEnv: gem ${pkgname} not found");
     in
-    copyIfBundledByPath mainGem;
+      copyIfBundledByPath mainGem
+  );
 
   # We have to normalize the Gemfile.lock, otherwise bundler tries to be
   # helpful by doing so at run time, causing executables to immediately bail

pkgs/development/ruby-modules/gem/default.nix

@@ -224,7 +224,7 @@ stdenv.mkDerivation ((builtins.removeAttrs attrs ["source"]) // {
     pushd $out/${ruby.gemPath}
     find doc/ -iname created.rid -delete -print
     find gems/*/ext/ extensions/ \( -iname Makefile -o -iname mkmf.log -o -iname gem_make.out \) -delete -print
-    ${if keepGemCache then "" else "rm -fvr cache"}
+    ${lib.optionalString (!keepGemCache) "rm -fvr cache"}
     popd
 
     # write out metadata and binstubs

pkgs/development/tools/misc/distcc/default.nix

@@ -26,7 +26,7 @@ let
       configureFlagsArray=( CFLAGS="-O2 -fno-strict-aliasing"
                             CXXFLAGS="-O2 -fno-strict-aliasing"
           --mandir=$out/share/man
-                            ${if sysconfDir == "" then "" else "--sysconfdir=${sysconfDir}"}
+                            ${lib.optionalString (sysconfDir != "") "--sysconfdir=${sysconfDir}"}
                             ${lib.optionalString static "LDFLAGS=-static"}
                             ${lib.withFeature (static == true || popt == null) "included-popt"}
                             ${lib.withFeature (avahi != null) "avahi"}

pkgs/os-specific/linux/kernel/manual-config.nix

@@ -397,10 +397,11 @@ stdenv.mkDerivation ({
   meta = {
     description =
       "The Linux kernel" +
-      (if kernelPatches == [] then "" else
+      (lib.optionalString (kernelPatches != []) (
         " (with patches: "
         + lib.concatStringsSep ", " (map (x: x.name) kernelPatches)
-        + ")");
+        + ")"
+      ));
     license = lib.licenses.gpl2Only;
     homepage = "https://www.kernel.org/";
     maintainers = lib.teams.linux-kernel.members ++ [