systemd.services.caddy.serviceConfig.StateDirectory = "foobar"; - breaks nixos-rebuild

[eliasp]

Describe the bug

On 21.11 I used to have in my configuration:

systemd.services.caddy.serviceConfig = {
  StateDirectory = "caddy";
  Environment = "HOME=%S/caddy";
};

IIRC I did this, because otherwise Caddy would try to use / as its home directory.
When upgrading from 21.11 to 22.05 this broke, as StateDirectory = "caddy"; is now set by the caddy module itself:

$ nixos-rebuild --upgrade build
unpacking channels...
building Nix...
building the system configuration...
error: value is a string while a list was expected

       at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/lib/systemd-unit-options.nix:26:14:

           25|         if isList (head defs'')
           26|         then concatLists defs''
             |              ^
           27|         else mergeEqualOption loc defs';
(use '--show-trace' to show detailed location information)

Full trace using `--show-trace`:

unpacking channels...
building Nix...
building the system configuration...
error: value is a string while a list was expected
   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/lib/systemd-unit-options.nix:26:14:

       25|         if isList (head defs'')
       26|         then concatLists defs''
         |              ^
       27|         else mergeEqualOption loc defs';

   … while evaluating 'merge'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/lib/systemd-unit-options.nix:20:18:

       19|     name = "systemd option";
       20|     merge = loc: defs:
         |                  ^
       21|       let

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:782:59:

      781|       if isDefined then
      782|         if all (def: type.check def.value) defsFinal then type.merge loc defsFinal
         |                                                           ^
      783|         else let allInvalid = filter (def: ! type.check def.value) defsFinal;

   … while evaluating the attribute 'value'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:793:27:

      792|     optionalValue =
      793|       if isDefined then { value = mergedValue; }
         |                           ^
      794|       else {};

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/types.nix:432:22:

      431|       merge = loc: defs:
      432|         mapAttrs (n: v: v.value) (filterAttrs (n: v: v ? value) (zipAttrsWith (name: defs:
         |                      ^
      433|             (mergeDefinitions (loc ++ [name]) elemType defs).optionalValue

   … from call site

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/lib/systemd-lib.nix:118:55:

      117|   attrsToSection = as:
      118|     concatStrings (concatLists (mapAttrsToList (name: value:
         |                                                       ^
      119|       map (x: ''

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/attrsets.nix:356:16:

      355|   mapAttrsToList = f: attrs:
      356|     map (name: f name attrs.${name}) (attrNames attrs);
         |                ^
      357|

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/attrsets.nix:356:10:

      355|   mapAttrsToList = f: attrs:
      356|     map (name: f name attrs.${name}) (attrNames attrs);
         |          ^
      357|

   … from call site

   … while evaluating 'attrsToSection'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/lib/systemd-lib.nix:117:20:

      116|
      117|   attrsToSection = as:
         |                    ^
      118|     concatStrings (concatLists (mapAttrsToList (name: value:

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/lib/systemd-lib.nix:367:13:

      366|           ${optionalString (def ? stopIfChanged && !def.stopIfChanged) "X-StopIfChanged=false"}
      367|           ${attrsToSection def.serviceConfig}
         |             ^
      368|         '';

   … while evaluating the attribute 'value'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:581:44:

      580|       defnsByName' = byName "config" (module: value:
      581|           [{ inherit (module) file; inherit value; }]
         |                                            ^
      582|         ) configs;

   … while evaluating 'dischargeProperties'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:832:25:

      831|   */
      832|   dischargeProperties = def:
         |                         ^
      833|     if def._type or "" == "merge" then

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:761:137:

      760|         defs' = concatMap (m:
      761|           map (value: { inherit (m) file; inherit value; }) (builtins.addErrorContext "while evaluating definitions from `${m.file}':" (dischargeProperties m.value))
         |                                                                                                                                         ^
      762|         ) defs;

   … while evaluating definitions from `/nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/boot/systemd.nix':

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:760:28:

      759|         # Process mkMerge and mkIf properties.
      760|         defs' = concatMap (m:
         |                            ^
      761|           map (value: { inherit (m) file; inherit value; }) (builtins.addErrorContext "while evaluating definitions from `${m.file}':" (dischargeProperties m.value))

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:760:17:

      759|         # Process mkMerge and mkIf properties.
      760|         defs' = concatMap (m:
         |                 ^
      761|           map (value: { inherit (m) file; inherit value; }) (builtins.addErrorContext "while evaluating definitions from `${m.file}':" (dischargeProperties m.value))

   … while evaluating the attribute 'values'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:873:7:

      872|     in {
      873|       values = concatMap (def: if getPrio def == highestPrio then [(strip def)] else []) defs;
         |       ^
      874|       inherit highestPrio;

   … while evaluating the attribute 'values'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:774:9:

      773|       in {
      774|         values = defs''';
         |         ^
      775|         inherit (defs'') highestPrio;

   … while evaluating the attribute 'mergedValue'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:780:5:

      779|     # Type-check the remaining definitions, and merge them. Or throw if no definitions.
      780|     mergedValue =
         |     ^
      781|       if isDefined then

   … while evaluating the option `systemd.units.caddy.service.text':

   … while evaluating the attribute 'value'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:746:9:

      745|     in warnDeprecation opt //
      746|       { value = builtins.addErrorContext "while evaluating the option `${showOption loc}':" value;
         |         ^
      747|         inherit (res.defsFinal') highestPrio;

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:296:72:

      295|           # For definitions that have an associated option
      296|           declaredConfig = mapAttrsRecursiveCond (v: ! isOption v) (_: v: v.value) options;
         |                                                                        ^
      297|

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/attrsets.nix:401:20:

      400|               then recurse (path ++ [name]) value
      401|               else f (path ++ [name]) value;
         |                    ^
      402|         in mapAttrs g;

   … while evaluating 'g'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/attrsets.nix:398:19:

      397|           g =
      398|             name: value:
         |                   ^
      399|             if isAttrs value && cond value

   … from call site

   … while evaluating the attribute 'text' of the derivation 'unit-caddy.service'

   at /nix/store/5dwy7n9m6l518wfccm9l7k8qj8lcxqks-nixos-22.05.956.6f637542ed0/nixos/pkgs/stdenv/generic/make-derivation.nix:278:7:

      277|     // (lib.optionalAttrs (attrs ? name || (attrs ? pname && attrs ? version)) {
      278|       name =
         |       ^
      279|         let

   … while evaluating the attribute 'buildCommand' of the derivation 'system-units'

   at /nix/store/5dwy7n9m6l518wfccm9l7k8qj8lcxqks-nixos-22.05.956.6f637542ed0/nixos/pkgs/stdenv/generic/make-derivation.nix:278:7:

      277|     // (lib.optionalAttrs (attrs ? name || (attrs ? pname && attrs ? version)) {
      278|       name =
         |       ^
      279|         let

   … while evaluating 'check'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/types.nix:394:15:

      393|       name = "path";
      394|       check = x: isCoercibleToString x && builtins.substring 0 1 (toString x) == "/";
         |               ^
      395|       merge = mergeEqualOption;

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:782:22:

      781|       if isDefined then
      782|         if all (def: type.check def.value) defsFinal then type.merge loc defsFinal
         |                      ^
      783|         else let allInvalid = filter (def: ! type.check def.value) defsFinal;

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:782:17:

      781|       if isDefined then
      782|         if all (def: type.check def.value) defsFinal then type.merge loc defsFinal
         |                 ^
      783|         else let allInvalid = filter (def: ! type.check def.value) defsFinal;

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:782:12:

      781|       if isDefined then
      782|         if all (def: type.check def.value) defsFinal then type.merge loc defsFinal
         |            ^
      783|         else let allInvalid = filter (def: ! type.check def.value) defsFinal;

   … while evaluating the attribute 'mergedValue'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:780:5:

      779|     # Type-check the remaining definitions, and merge them. Or throw if no definitions.
      780|     mergedValue =
         |     ^
      781|       if isDefined then

   … while evaluating the option `environment.etc.systemd/system.source':

   … while evaluating the attribute 'value'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:746:9:

      745|     in warnDeprecation opt //
      746|       { value = builtins.addErrorContext "while evaluating the option `${showOption loc}':" value;
         |         ^
      747|         inherit (res.defsFinal') highestPrio;

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:296:72:

      295|           # For definitions that have an associated option
      296|           declaredConfig = mapAttrsRecursiveCond (v: ! isOption v) (_: v: v.value) options;
         |                                                                        ^
      297|

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/attrsets.nix:401:20:

      400|               then recurse (path ++ [name]) value
      401|               else f (path ++ [name]) value;
         |                    ^
      402|         in mapAttrs g;

   … while evaluating 'g'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/attrsets.nix:398:19:

      397|           g =
      398|             name: value:
         |                   ^
      399|             if isAttrs value && cond value

   … from call site

   … while evaluating 'escapeShellArg'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/strings.nix:316:20:

      315|   */
      316|   escapeShellArg = arg: "'${replaceStrings ["'"] ["'\\''"] (toString arg)}'";
         |                    ^
      317|

   … from call site

   … while evaluating 'concatMapStringsSep'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/strings.nix:111:5:

      110|     # List of input strings
      111|     list: concatStringsSep sep (map f list);
         |     ^
      112|

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/etc/etc.nix:54:43:

       53|     mkdir -p "$out/etc"
       54|     ${concatMapStringsSep "\n" (etcEntry: escapeShellArgs [
         |                                           ^
       55|       "makeEtcEntry"

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/etc/etc.nix:54:33:

       53|     mkdir -p "$out/etc"
       54|     ${concatMapStringsSep "\n" (etcEntry: escapeShellArgs [
         |                                 ^
       55|       "makeEtcEntry"

   … from call site

   … while evaluating 'concatMapStringsSep'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/strings.nix:111:5:

      110|     # List of input strings
      111|     list: concatStringsSep sep (map f list);
         |     ^
      112|

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/etc/etc.nix:54:7:

       53|     mkdir -p "$out/etc"
       54|     ${concatMapStringsSep "\n" (etcEntry: escapeShellArgs [
         |       ^
       55|       "makeEtcEntry"

   … while evaluating the attribute 'buildCommand' of the derivation 'etc'

   at /nix/store/5dwy7n9m6l518wfccm9l7k8qj8lcxqks-nixos-22.05.956.6f637542ed0/nixos/pkgs/stdenv/generic/make-derivation.nix:278:7:

      277|     // (lib.optionalAttrs (attrs ? name || (attrs ? pname && attrs ? version)) {
      278|       name =
         |       ^
      279|         let

   … while evaluating the attribute 'value'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:581:44:

      580|       defnsByName' = byName "config" (module: value:
      581|           [{ inherit (module) file; inherit value; }]
         |                                            ^
      582|         ) configs;

   … while evaluating 'atDepth'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/attrsets.nix:60:17:

       59|       len = length attrPath;
       60|       atDepth = n:
         |                 ^
       61|         if n == len

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/attrsets.nix:63:39:

       62|         then value
       63|         else { ${elemAt attrPath n} = atDepth (n + 1); };
         |                                       ^
       64|     in atDepth 0;

   … while evaluating the attribute 'value'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/types.nix:461:58:

      460|         # Push down position info.
      461|         (map (def: mapAttrs (n: v: { inherit (def) file; value = v; }) def.value) defs);
         |                                                          ^
      462|       emptyValue = { value = {}; };

   … while evaluating 'dischargeProperties'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:832:25:

      831|   */
      832|   dischargeProperties = def:
         |                         ^
      833|     if def._type or "" == "merge" then

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:761:137:

      760|         defs' = concatMap (m:
      761|           map (value: { inherit (m) file; inherit value; }) (builtins.addErrorContext "while evaluating definitions from `${m.file}':" (dischargeProperties m.value))
         |                                                                                                                                         ^
      762|         ) defs;

   … while evaluating definitions from `/nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/etc/etc.nix':

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:760:28:

      759|         # Process mkMerge and mkIf properties.
      760|         defs' = concatMap (m:
         |                            ^
      761|           map (value: { inherit (m) file; inherit value; }) (builtins.addErrorContext "while evaluating definitions from `${m.file}':" (dischargeProperties m.value))

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:760:17:

      759|         # Process mkMerge and mkIf properties.
      760|         defs' = concatMap (m:
         |                 ^
      761|           map (value: { inherit (m) file; inherit value; }) (builtins.addErrorContext "while evaluating definitions from `${m.file}':" (dischargeProperties m.value))

   … while evaluating the attribute 'values'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:873:7:

      872|     in {
      873|       values = concatMap (def: if getPrio def == highestPrio then [(strip def)] else []) defs;
         |       ^
      874|       inherit highestPrio;

   … while evaluating the attribute 'values'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:774:9:

      773|       in {
      774|         values = defs''';
         |         ^
      775|         inherit (defs'') highestPrio;

   … while evaluating the attribute 'optionalValue.value'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:792:5:

      791|
      792|     optionalValue =
         |     ^
      793|       if isDefined then { value = mergedValue; }

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/types.nix:455:29:

      454|       merge = loc: defs:
      455|         zipAttrsWith (name: defs:
         |                             ^
      456|           let merged = mergeDefinitions (loc ++ [name]) elemType defs;

   … from call site

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/attrsets.nix:518:24:

      517|     let f = attrPath:
      518|       zipAttrsWith (n: values:
         |                        ^
      519|         let here = attrPath ++ [n]; in

   … from call site

   … while evaluating the attribute 'value'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:581:44:

      580|       defnsByName' = byName "config" (module: value:
      581|           [{ inherit (module) file; inherit value; }]
         |                                            ^
      582|         ) configs;

   … while evaluating 'dischargeProperties'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:832:25:

      831|   */
      832|   dischargeProperties = def:
         |                         ^
      833|     if def._type or "" == "merge" then

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:761:137:

      760|         defs' = concatMap (m:
      761|           map (value: { inherit (m) file; inherit value; }) (builtins.addErrorContext "while evaluating definitions from `${m.file}':" (dischargeProperties m.value))
         |                                                                                                                                         ^
      762|         ) defs;

   … while evaluating definitions from `/nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/etc/etc-activation.nix':

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:760:28:

      759|         # Process mkMerge and mkIf properties.
      760|         defs' = concatMap (m:
         |                            ^
      761|           map (value: { inherit (m) file; inherit value; }) (builtins.addErrorContext "while evaluating definitions from `${m.file}':" (dischargeProperties m.value))

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:760:17:

      759|         # Process mkMerge and mkIf properties.
      760|         defs' = concatMap (m:
         |                 ^
      761|           map (value: { inherit (m) file; inherit value; }) (builtins.addErrorContext "while evaluating definitions from `${m.file}':" (dischargeProperties m.value))

   … while evaluating the attribute 'values'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:873:7:

      872|     in {
      873|       values = concatMap (def: if getPrio def == highestPrio then [(strip def)] else []) defs;
         |       ^
      874|       inherit highestPrio;

   … while evaluating the attribute 'values'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:774:9:

      773|       in {
      774|         values = defs''';
         |         ^
      775|         inherit (defs'') highestPrio;

   … while evaluating the attribute 'mergedValue'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:780:5:

      779|     # Type-check the remaining definitions, and merge them. Or throw if no definitions.
      780|     mergedValue =
         |     ^
      781|       if isDefined then

   … while evaluating the option `system.activationScripts.etc.text':

   … while evaluating the attribute 'value'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:746:9:

      745|     in warnDeprecation opt //
      746|       { value = builtins.addErrorContext "while evaluating the option `${showOption loc}':" value;
         |         ^
      747|         inherit (res.defsFinal') highestPrio;

   … while evaluating anonymous lambda

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/modules.nix:296:72:

      295|           # For definitions that have an associated option
      296|           declaredConfig = mapAttrsRecursiveCond (v: ! isOption v) (_: v: v.value) options;
         |                                                                        ^
      297|

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/attrsets.nix:401:20:

      400|               then recurse (path ++ [name]) value
      401|               else f (path ++ [name]) value;
         |                    ^
      402|         in mapAttrs g;

   … while evaluating 'g'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/attrsets.nix:398:19:

      397|           g =
      398|             name: value:
         |                   ^
      399|             if isAttrs value && cond value

   … from call site

   … while evaluating the attribute 'text'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/activation/activation-script.nix:9:5:

        8|   addAttributeName = mapAttrs (a: v: v // {
        9|     text = ''
         |     ^
       10|       #### Activation script snippet ${a}:

   … while evaluating 'id'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/trivial.nix:14:5:

       13|     # The value to return
       14|     x: x;
         |     ^
       15|

   … from call site

   … while evaluating 'textClosureMap'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/lib/strings-with-deps.nix:75:35:

       74|
       75|   textClosureMap = f: predefined: names:
         |                                   ^
       76|     concatStringsSep "\n" (map f (textClosureList predefined names));

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/activation/activation-script.nix:49:9:

       48|
       49|       ${textClosureMap id (withDrySnippets) (attrNames withDrySnippets)}
         |         ^
       50|

   … while evaluating 'systemActivationScript'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/activation/activation-script.nix:20:33:

       19|
       20|   systemActivationScript = set: onlyDry: let
         |                                 ^
       21|     set' = mapAttrs (_: v: if isString v then (noDepEntry v) // { supportsDryActivation = false; } else v) set;

   … from call site

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/activation/activation-script.nix:137:18:

      136|       apply = set: set // {
      137|         script = systemActivationScript set false;
         |                  ^
      138|       };

   … while evaluating the attribute 'system.activationScripts.script'

   at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/system/activation/activation-script.nix:137:9:

      136|       apply = set: set // {
      137|         script = systemActivationScript set false;
         |         ^
      138|       };

   … while evaluating the attribute 'activationScript' of the derivation 'nixos-system-web-prod-f2f8-22.05.956.6f637542ed0'

   at /nix/store/5dwy7n9m6l518wfccm9l7k8qj8lcxqks-nixos-22.05.956.6f637542ed0/nixos/pkgs/stdenv/generic/make-derivation.nix:278:7:

      277|     // (lib.optionalAttrs (attrs ? name || (attrs ? pname && attrs ? version)) {
      278|       name =
         |       ^
      279|         let

So I simply dropped this from my configuration, but I feel like this should be handled better nonetheless, to:

• not expose those low-level and hard to understand internals to the user
• either provide a more meaningful error message or support changing this value

Steps To Reproduce

Steps to reproduce the behavior:

1. Set services.caddy.enable = true;
2. Set systemd.services.caddy.serviceConfig.StateDirectory = "foobar";
3. Execute nixos-rebuild build

Expected behavior

• Caddy using StateDirectory = "foobar" for its service unit
• nixos-rebuild build not failing with a hard to understand error message

Additional context

Add any other context about the problem here.

Notify maintainers

I'm not sure whether @aanderse (who did the mentioned change in the caddy module) is the right person to address here, as this could also be caused further down the line (e.g. in the systemd module) - I couldn't actually figure this out.

Metadata

[user@system:~]$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 5.10.118, NixOS, 21.11 (Porcupine), 21.11.337814.5986ddf62ab`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3.3`
 - channels(root): `"nixos-22.05.956.6f637542ed0"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[roberth]

#158602 improves the error message a bit:

nix-repl> (nixos { services.caddy.enable = true; systemd.services.caddy.serviceConfig = {  StateDirectory = "caddy";  Environment = "HOME=%S/caddy";}; fileSystems."/".device = "x"; boot.loader.grub.enable = false; }).config.system.build.toplevel

error: The definitions for systemd unit options should be either all lists, representing repeatable options, or all non-lists, but for the option systemd.services.caddy.serviceConfig.StateDirectory, the definitions are a mix of list and non-list
       - In `nixpkgs/nixos/modules/services/web-servers/caddy/default.nix':
           [
             "caddy"
           ]
       - In `nixpkgs/pkgs/top-level/all-packages.nix': "caddy"

To make this not an error, we should add proper NixOS options for all systemd settings, formalizing the knowledge that StateDirectory always behaves like a set.

cc @NixOS/systemd

[eliasp]

With #158602 having been merged, I'd consider this "fixed".