nixpkgs/lib/types.nix

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# Definitions related to run-time type checking. Used in particular
# to type-check NixOS configurations.
let lib = import ./default.nix; in
with lib.lists;
with lib.attrsets;
with lib.options;
with lib.trivial;
with lib.modules;
rec {
isType = type: x: (x._type or "") == type;
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typeOf = x: x._type or "";
setType = typeName: value: value // {
_type = typeName;
};
# name (name of the type)
# check (check the config value)
# merge (default merge function)
# docPath (path concatenated to the option name contained in the option set)
isOptionType = isType "option-type";
mkOptionType =
{ name
, check ? (x: true)
, merge ? mergeDefaultOption
, merge' ? args: merge
, docPath ? lib.id
}:
{ _type = "option-type";
inherit name check merge merge' docPath;
};
types = rec {
unspecified = mkOptionType {
name = "unspecified";
};
bool = mkOptionType {
name = "boolean";
check = builtins.isBool;
merge = fold lib.or false;
};
int = mkOptionType {
name = "integer";
check = builtins.isInt;
};
string = mkOptionType {
name = "string";
check = builtins.isString;
merge = lib.concatStrings;
};
# Like string, but add newlines between every value. Useful for
# configuration file contents.
lines = mkOptionType {
name = "string";
check = builtins.isString;
merge = lib.concatStringsSep "\n";
};
envVar = mkOptionType {
name = "environment variable";
inherit (string) check;
merge = lib.concatStringsSep ":";
};
attrs = mkOptionType {
name = "attribute set";
check = isAttrs;
merge = fold lib.mergeAttrs {};
};
# derivation is a reserved keyword.
package = mkOptionType {
name = "derivation";
check = isDerivation;
};
path = mkOptionType {
name = "path";
# Hacky: there is no isPath primop.
check = x: builtins.unsafeDiscardStringContext (builtins.substring 0 1 (toString x)) == "/";
};
# drop this in the future:
list = builtins.trace "types.list is deprecated; use types.listOf instead" types.listOf;
listOf = elemType: mkOptionType {
name = "list of ${elemType.name}s";
check = value: isList value && all elemType.check value;
merge = defs: map (def: elemType.merge [def]) (concatLists defs);
docPath = path: elemType.docPath (path + ".*");
};
attrsOf = elemType: mkOptionType {
name = "attribute set of ${elemType.name}s";
check = x: isAttrs x && all elemType.check (lib.attrValues x);
merge = lib.zipAttrsWith (name: elemType.merge' { inherit name; });
docPath = path: elemType.docPath (path + ".<name>");
};
# List or attribute set of ...
loaOf = elemType:
let
convertIfList = defIdx: def:
if isList def then
listToAttrs (
flip imap def (elemIdx: elem:
{ name = "unnamed-${toString defIdx}.${toString elemIdx}"; value = elem; }))
else
def;
listOnly = listOf elemType;
attrOnly = attrsOf elemType;
in mkOptionType {
name = "list or attribute set of ${elemType.name}s";
check = x:
if isList x then listOnly.check x
else if isAttrs x then attrOnly.check x
else false;
merge = defs: attrOnly.merge (imap convertIfList defs);
docPath = path: elemType.docPath (path + ".<name?>");
};
uniq = elemType: mkOptionType {
inherit (elemType) name check docPath;
merge = list:
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if length list == 1 then
head list
else
throw "Multiple definitions of ${elemType.name}. Only one is allowed for this option.";
};
none = elemType: mkOptionType {
inherit (elemType) name check docPath;
merge = list:
throw "No definitions are allowed for this option.";
};
nullOr = elemType: mkOptionType {
inherit (elemType) docPath;
name = "null or ${elemType.name}";
check = x: builtins.isNull x || elemType.check x;
merge = defs:
if all isNull defs then null
else if any isNull defs then
throw "Some but not all values are null."
else elemType.merge defs;
};
functionTo = elemType: mkOptionType {
name = "function that evaluates to a(n) ${elemType.name}";
check = builtins.isFunction;
merge = fns:
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args: elemType.merge (map (fn: fn args) fns);
};
submodule = opts: mkOptionType rec {
name = "submodule";
check = x: isAttrs x || builtins.isFunction x;
# FIXME: make error messages include the parent attrpath.
merge = merge' {};
merge' = args: defs:
let
coerce = def: if builtins.isFunction def then def else { config = def; };
modules = (toList opts) ++ map coerce defs;
in (evalModules modules args).config;
};
# Obsolete alternative to configOf. It takes its option
# declarations from the options attribute of containing option
# declaration.
optionSet = mkOptionType {
name = /* builtins.trace "types.optionSet is deprecated; use types.submodule instead" */ "option set";
};
};
}