diff --git a/lib/types.nix b/lib/types.nix index 4872a676657..f406cb9204b 100644 --- a/lib/types.nix +++ b/lib/types.nix @@ -65,6 +65,11 @@ rec { # definition values and locations (e.g. [ { file = "/foo.nix"; # value = 1; } { file = "/bar.nix"; value = 2 } ]). merge ? mergeDefaultOption + , # Whether this type has a value representing nothingness. If it does, + # this should be a value of the form { value = ; } + # If it doesn't, this should be {} + # This may be used when a value is required for `mkIf false`. This allows the extra laziness in e.g. `lazyAttrsOf`. + emptyValue ? {} , # Return a flat list of sub-options. Used to generate # documentation. getSubOptions ? prefix: {} @@ -88,7 +93,7 @@ rec { functor ? defaultFunctor name }: { _type = "option-type"; - inherit name check merge getSubOptions getSubModules substSubModules typeMerge functor; + inherit name check merge emptyValue getSubOptions getSubModules substSubModules typeMerge functor; description = if description == null then name else description; }; @@ -225,6 +230,7 @@ rec { description = "attribute set"; check = isAttrs; merge = loc: foldl' (res: def: mergeAttrs res def.value) {}; + emptyValue = { value = {}; }; }; # derivation is a reserved keyword. @@ -265,6 +271,7 @@ rec { ) def.value else throw "The option value `${showOption loc}` in `${def.file}` is not a list.") defs))); + emptyValue = { value = {}; }; getSubOptions = prefix: elemType.getSubOptions (prefix ++ ["*"]); getSubModules = elemType.getSubModules; substSubModules = m: listOf (elemType.substSubModules m); @@ -273,7 +280,10 @@ rec { nonEmptyListOf = elemType: let list = addCheck (types.listOf elemType) (l: l != []); - in list // { description = "non-empty " + list.description; }; + in list // { + description = "non-empty " + list.description; + # Note: emptyValue is left as is, because another module may define an element. + }; attrsOf = elemType: mkOptionType rec { name = "attrsOf"; @@ -285,6 +295,7 @@ rec { ) # Push down position info. (map (def: mapAttrs (n: v: { inherit (def) file; value = v; }) def.value) defs))); + emptyValue = { value = {}; }; getSubOptions = prefix: elemType.getSubOptions (prefix ++ [""]); getSubModules = elemType.getSubModules; substSubModules = m: attrsOf (elemType.substSubModules m); @@ -339,6 +350,7 @@ rec { description = "list or attribute set of ${elemType.description}s"; check = x: isList x || isAttrs x; merge = loc: defs: attrOnly.merge loc (convertAllLists loc defs); + emptyValue = { value = {}; }; getSubOptions = prefix: elemType.getSubOptions (prefix ++ [""]); getSubModules = elemType.getSubModules; substSubModules = m: loaOf (elemType.substSubModules m); @@ -350,6 +362,7 @@ rec { name = "uniq"; inherit (elemType) description check; merge = mergeOneOption; + emptyValue = elemType.emptyValue; getSubOptions = elemType.getSubOptions; getSubModules = elemType.getSubModules; substSubModules = m: uniq (elemType.substSubModules m); @@ -367,6 +380,7 @@ rec { else if nrNulls != 0 then throw "The option `${showOption loc}` is defined both null and not null, in ${showFiles (getFiles defs)}." else elemType.merge loc defs; + emptyValue = { value = null; }; getSubOptions = elemType.getSubOptions; getSubModules = elemType.getSubModules; substSubModules = m: nullOr (elemType.substSubModules m); @@ -407,6 +421,7 @@ rec { args.name = last loc; prefix = loc; }).config; + emptyValue = { value = {}; }; getSubOptions = prefix: (evalModules { inherit modules prefix specialArgs; # This is a work-around due to the fact that some sub-modules, @@ -515,6 +530,7 @@ rec { if finalType.check val then val else coerceFunc val; in finalType.merge loc (map (def: def // { value = coerceVal def.value; }) defs); + emptyValue = finalType.emptyValue; getSubOptions = finalType.getSubOptions; getSubModules = finalType.getSubModules; substSubModules = m: coercedTo coercedType coerceFunc (finalType.substSubModules m);