# Nixpkgs/NixOS option handling.
{ lib }:
with lib.trivial;
with lib.lists;
with lib.attrsets;
with lib.strings;
rec {
/* Returns true when the given argument is an option
Type: isOption :: a -> bool
Example:
isOption 1 // => false
isOption (mkOption {}) // => true
*/
isOption = lib.isType "option";
/* Creates an Option attribute set. mkOption accepts an attribute set with the following keys:
All keys default to `null` when not given.
Example:
mkOption { } // => { _type = "option"; }
mkOption { defaultText = "foo"; } // => { _type = "option"; defaultText = "foo"; }
*/
mkOption =
{
# Default value used when no definition is given in the configuration.
default ? null,
# Textual representation of the default, for the manual.
defaultText ? null,
# Example value used in the manual.
example ? null,
# String describing the option.
description ? null,
# Related packages used in the manual (see `genRelatedPackages` in ../nixos/lib/make-options-doc/default.nix).
relatedPackages ? null,
# Option type, providing type-checking and value merging.
type ? null,
# Function that converts the option value to something else.
apply ? null,
# Whether the option is for NixOS developers only.
internal ? null,
# Whether the option shows up in the manual.
visible ? null,
# Whether the option can be set only once
readOnly ? null,
# Deprecated, used by types.optionSet.
options ? null
} @ attrs:
attrs // { _type = "option"; };
/* Creates an Option attribute set for a boolean value option i.e an
option to be toggled on or off:
Example:
mkEnableOption "foo"
=> { _type = "option"; default = false; description = "Whether to enable foo."; example = true; type = { ... }; }
*/
mkEnableOption =
# Name for the created option
name: mkOption {
default = false;
example = true;
description = "Whether to enable ${name}.";
type = lib.types.bool;
};
/* This option accepts anything, but it does not produce any result.
This is useful for sharing a module across different module sets
without having to implement similar features as long as the
values of the options are not accessed. */
mkSinkUndeclaredOptions = attrs: mkOption ({
internal = true;
visible = false;
default = false;
description = "Sink for option definitions.";
type = mkOptionType {
name = "sink";
check = x: true;
merge = loc: defs: false;
};
apply = x: throw "Option value is not readable because the option is not declared.";
} // attrs);
mergeDefaultOption = loc: defs:
let list = getValues defs; in
if length list == 1 then head list
else if all isFunction list then x: mergeDefaultOption loc (map (f: f x) list)
else if all isList list then concatLists list
else if all isAttrs list then foldl' lib.mergeAttrs {} list
else if all isBool list then foldl' lib.or false list
else if all isString list then lib.concatStrings list
else if all isInt list && all (x: x == head list) list then head list
else throw "Cannot merge definitions of `${showOption loc}' given in ${showFiles (getFiles defs)}.";
mergeOneOption = loc: defs:
if defs == [] then abort "This case should never happen."
else if length defs != 1 then
throw "The unique option `${showOption loc}' is defined multiple times, in:\n - ${concatStringsSep "\n - " (getFiles defs)}."
else (head defs).value;
/* "Merge" option definitions by checking that they all have the same value. */
mergeEqualOption = loc: defs:
if defs == [] then abort "This case should never happen."
else foldl' (val: def:
if def.value != val then
throw "The option `${showOption loc}' has conflicting definitions, in ${showFiles (getFiles defs)}."
else
val) (head defs).value defs;
/* Extracts values of all "value" keys of the given list.
Type: getValues :: [ { value :: a } ] -> [a]
Example:
getValues [ { value = 1; } { value = 2; } ] // => [ 1 2 ]
getValues [ ] // => [ ]
*/
getValues = map (x: x.value);
/* Extracts values of all "file" keys of the given list
Type: getFiles :: [ { file :: a } ] -> [a]
Example:
getFiles [ { file = "file1"; } { file = "file2"; } ] // => [ "file1" "file2" ]
getFiles [ ] // => [ ]
*/
getFiles = map (x: x.file);
# Generate documentation template from the list of option declaration like
# the set generated with filterOptionSets.
optionAttrSetToDocList = optionAttrSetToDocList' [];
optionAttrSetToDocList' = prefix: options:
concatMap (opt:
let
docOption = rec {
loc = opt.loc;
name = showOption opt.loc;
description = opt.description or (lib.warn "Option `${name}' has no description." "This option has no description.");
declarations = filter (x: x != unknownModule) opt.declarations;
internal = opt.internal or false;
visible = opt.visible or true;
readOnly = opt.readOnly or false;
type = opt.type.description or null;
}
// optionalAttrs (opt ? example) { example = scrubOptionValue opt.example; }
// optionalAttrs (opt ? default) { default = scrubOptionValue opt.default; }
// optionalAttrs (opt ? defaultText) { default = opt.defaultText; }
// optionalAttrs (opt ? relatedPackages && opt.relatedPackages != null) { inherit (opt) relatedPackages; };
subOptions =
let ss = opt.type.getSubOptions opt.loc;
in if ss != {} then optionAttrSetToDocList' opt.loc ss else [];
in
[ docOption ] ++ optionals docOption.visible subOptions) (collect isOption options);
/* This function recursively removes all derivation attributes from
`x` except for the `name` attribute.
This is to make the generation of `options.xml` much more
efficient: the XML representation of derivations is very large
(on the order of megabytes) and is not actually used by the
manual generator.
*/
scrubOptionValue = x:
if isDerivation x then
{ type = "derivation"; drvPath = x.name; outPath = x.name; name = x.name; }
else if isList x then map scrubOptionValue x
else if isAttrs x then mapAttrs (n: v: scrubOptionValue v) (removeAttrs x ["_args"])
else x;
/* For use in the `example` option attribute. It causes the given
text to be included verbatim in documentation. This is necessary
for example values that are not simple values, e.g., functions.
*/
literalExample = text: { _type = "literalExample"; inherit text; };
# Helper functions.
/* Convert an option, described as a list of the option parts in to a
safe, human readable version.
Example:
(showOption ["foo" "bar" "baz"]) == "foo.bar.baz"
(showOption ["foo" "bar.baz" "tux"]) == "foo.bar.baz.tux"
Placeholders will not be quoted as they are not actual values:
(showOption ["foo" "*" "bar"]) == "foo.*.bar"
(showOption ["foo" "<name>" "bar"]) == "foo.<name>.bar"
Unlike attributes, options can also start with numbers:
(showOption ["windowManager" "2bwm" "enable"]) == "windowManager.2bwm.enable"
*/
showOption = parts: let
escapeOptionPart = part:
let
escaped = lib.strings.escapeNixString part;
in if escaped == "\"${part}\""
then part
else escaped;
in (concatStringsSep ".") (map escapeOptionPart parts);
showFiles = files: concatStringsSep " and " (map (f: "`${f}'") files);
unknownModule = "<unknown-file>";
}