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nixpkgs/pkgs/lib/options.nix

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# Nixpkgs/NixOS option handling.
let lib = import ./default.nix; in
with { inherit (builtins) head tail; };
with import ./trivial.nix;
with import ./lists.nix;
with import ./misc.nix;
with import ./attrsets.nix;
with import ./properties.nix;
with import ./modules.nix;
rec {
inherit (lib) typeOf;
isOption = attrs: (typeOf attrs) == "option";
mkOption = attrs: attrs // {
_type = "option";
# name (this is the name of the attributem it is automatically generated by the traversal)
# default (value used when no definition exists)
# example (documentation)
# description (documentation)
# type (option type, provide a default merge function and ensure type correctness)
# merge (function used to merge definitions into one definition: [ /type/ ] -> /type/)
# apply (convert the option value to ease the manipulation of the option result)
# options (set of sub-options declarations & definitions)
};
# Make the option declaration more user-friendly by adding default
# settings and some verifications based on the declaration content (like
# type correctness).
addOptionMakeUp = {name, recurseInto}: decl:
let
init = {
inherit name;
merge = mergeDefaultOption;
apply = lib.id;
};
mergeFromType = opt:
if decl ? type && decl.type ? merge then
opt // { merge = decl.type.merge; }
else
opt;
addDeclaration = opt: opt // decl;
ensureMergeInputType = opt:
if decl ? type then
opt // {
merge = list:
if all decl.type.check list then
opt.merge list
else
throw "One of the definitions has a bad type.";
}
else opt;
ensureDefaultType = opt:
if decl ? type && decl ? default then
opt // {
default =
if decl.type.check decl.default then
decl.default
else
throw "The default value has a bad type.";
}
else opt;
handleOptionSets = opt:
if decl ? type && decl.type.hasOptions then
let
optionConfig = opts: config:
map (f: applyIfFunction f config)
(decl.options ++ [opts]);
in
opt // {
merge = list:
decl.type.iter
(path: opts:
lib.fix (fixableMergeFun (recurseInto path) (optionConfig opts))
)
opt.name
(opt.merge list);
options = recurseInto (decl.type.docPath opt.name) decl.options;
}
else
opt;
in
foldl (opt: f: f opt) init [
# default settings
mergeFromType
# user settings
addDeclaration
# override settings
ensureMergeInputType
ensureDefaultType
handleOptionSets
];
# Merge a list of options containning different field. This is useful to
# separate the merge & apply fields from the interface.
mergeOptionDecls = opts:
if opts == [] then {}
else if tail opts == [] then
let opt = head opts; in
if opt ? options then
opt // { options = toList opt.options; }
else
opt
else
fold (opt1: opt2:
lib.addErrorContext "opt1 = ${lib.showVal opt1}\nopt2 = ${lib.showVal opt2}" (
# You cannot merge if two options have the same field.
assert opt1 ? default -> ! opt2 ? default;
assert opt1 ? example -> ! opt2 ? example;
assert opt1 ? description -> ! opt2 ? description;
assert opt1 ? merge -> ! opt2 ? merge;
assert opt1 ? apply -> ! opt2 ? apply;
assert opt1 ? type -> ! opt2 ? type;
if opt1 ? options || opt2 ? options then
opt1 // opt2 // {
options =
(toList (attrByPath ["options"] [] opt1))
++ (toList (attrByPath ["options"] [] opt2));
}
else
opt1 // opt2
)) {} opts;
# !!! This function will be removed because this can be done with the
# multiple option declarations.
addDefaultOptionValues = defs: opts: opts //
builtins.listToAttrs (map (defName:
{ name = defName;
value =
let
defValue = builtins.getAttr defName defs;
optValue = builtins.getAttr defName opts;
in
if typeOf defValue == "option"
then
# `defValue' is an option.
if hasAttr defName opts
then builtins.getAttr defName opts
else defValue.default
else
# `defValue' is an attribute set containing options.
# So recurse.
if hasAttr defName opts && isAttrs optValue
then addDefaultOptionValues defValue optValue
else addDefaultOptionValues defValue {};
}
) (attrNames defs));
mergeDefaultOption = list:
if list != [] && tail list == [] then head list
else if all builtins.isFunction list then x: mergeDefaultOption (map (f: f x) list)
else if all isList list then concatLists list
else if all isAttrs list then fold lib.mergeAttrs {} list
else if all (x: true == x || false == x) list then fold lib.or false list
else if all (x: x == toString x) list then lib.concatStrings list
else throw "Cannot merge values.";
mergeTypedOption = typeName: predicate: merge: list:
if all predicate list then merge list
else throw "Expect a ${typeName}.";
mergeEnableOption = mergeTypedOption "boolean"
(x: true == x || false == x) (fold lib.or false);
mergeListOption = mergeTypedOption "list" isList concatLists;
mergeStringOption = mergeTypedOption "string"
(x: if builtins ? isString then builtins.isString x else x + "")
lib.concatStrings;
mergeOneOption = list:
if list == [] then abort "This case should never happen."
else if tail list != [] then throw "Multiple definitions. Only one is allowed for this option."
else head list;
# Handle the traversal of option sets. All sets inside 'opts' are zipped
# and options declaration and definition are separated. If no option are
# declared at a specific depth, then the function recurse into the values.
# Other cases are handled by the optionHandler which contains two
# functions that are used to defined your goal.
# - export is a function which takes two arguments which are the option
# and the list of values.
# - notHandle is a function which takes the list of values are not handle
# by this function.
handleOptionSets = optionHandler@{export, notHandle, ...}: path: opts:
if all isAttrs opts then
lib.zip (attr: opts:
let
recurseInto = name: attrs:
handleOptionSets optionHandler name attrs;
# Compute the path to reach the attribute.
name = if path == "" then attr else path + "." + attr;
# Divide the definitions of the attribute "attr" between
# declaration (isOption) and definitions (!isOption).
test = partition (x: isOption (rmProperties x)) opts;
decls = map rmProperties test.right; defs = test.wrong;
# Make the option declaration more user-friendly by adding default
# settings and some verifications based on the declaration content
# (like type correctness).
opt = addOptionMakeUp
{ inherit name recurseInto; }
(mergeOptionDecls decls);
# Return the list of option sets.
optAttrs = map delayProperties defs;
# return the list of option values.
# Remove undefined values that are coming from evalIf.
optValues = evalProperties defs;
in
if decls == [] then recurseInto name optAttrs
else lib.addErrorContext "while evaluating the option ${name}:" (
export opt optValues
)
) opts
else lib.addErrorContext "while evaluating ${path}:" (notHandle opts);
# Merge option sets and produce a set of values which is the merging of
# all options declare and defined. If no values are defined for an
# option, then the default value is used otherwise it use the merge
# function of each option to get the result.
mergeOptionSets =
handleOptionSets {
export = opt: values:
opt.apply (
if values == [] then
if opt ? default then opt.default
else throw "Not defined."
else opt.merge values
);
notHandle = opts: throw "Used without option declaration.";
};
# Keep all option declarations.
filterOptionSets =
handleOptionSets {
export = opt: values: opt;
notHandle = opts: {};
};
fixableMergeFun = merge: f: config:
merge (
# remove require because this is not an option.
map (m: removeAttrs m ["require"]) (
# Delay top-level properties like mkIf
map delayProperties (
# generate the list of option sets.
f config
)
)
);
fixableMergeModules = merge: initModules: {...}@args: config:
fixableMergeFun merge (config:
# filter the list of option sets.
selectDeclsAndDefs (
# generate the list of modules from a closure of imports/require
# attribtues.
moduleClosure initModules (args // { inherit config; })
)
) config;
fixableDefinitionsOf = initModules: {...}@args:
fixableMergeModules (mergeOptionSets "") initModules args;
fixableDeclarationsOf = initModules: {...}@args:
fixableMergeModules (filterOptionSets "") initModules args;
definitionsOf = initModules: {...}@args:
lib.fix (fixableDefinitionsOf initModules args);
declarationsOf = initModules: {...}@args:
lib.fix (fixableDeclarationsOf initModules args);
fixMergeModules = merge: initModules: {...}@args:
lib.fix (fixableMergeModules merge initModules args);
# old interface.
fixOptionSetsFun = merge: {...}@args: initModules: config:
fixableMergeModules (merge "") initModules args config;
fixOptionSets = merge: args: initModules:
fixMergeModules (merge "") initModules args;
# Generate documentation template from the list of option declaration like
# the set generated with filterOptionSets.
optionAttrSetToDocList = ignore: newOptionAttrSetToDocList;
newOptionAttrSetToDocList = attrs:
let options = collect isOption attrs; in
fold (opt: rest:
let
docOption = {
inherit (opt) name;
description = if opt ? description then opt.description else
throw "Option ${opt.name}: No description.";
}
// (if opt ? example then {inherit(opt) example;} else {})
// (if opt ? default then {inherit(opt) default;} else {});
subOptions =
if opt ? options then
newOptionAttrSetToDocList opt.options
else
[];
in
[ docOption ] ++ subOptions ++ rest
) [] options;
}