nixpkgs/pkgs/lib/options.nix
Eelco Dolstra 1ba3165b4e * Allow the default for option values displayed in the manual to be
overriden.  Some defaults should not be evaluated because they cause
  unnecessary evaluation or might cause evaluation errors
  (e.g. assertions).  For instance, the value of the
  `boot.kernelPackages' option is an attribute set.  Some packages in
  that set might not evaluate (e.g. AUFS2 on kernels that don't have
  the AUFS2 patch), and in any case it slows down nixos-rebuild to
  evaluate lots of packages that are not actually used in the
  configuration.

svn path=/nixpkgs/trunk/; revision=22043
2010-05-28 11:20:45 +00:00

292 lines
9.6 KiB
Nix

# 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;
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)
# extraConfigs (list of possible configurations)
};
mapSubOptions = f: opt:
if opt ? options then
opt // {
options = map f (toList opt.options);
}
else
opt;
# 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;
};
functionsFromType = opt:
if decl ? type && decl.type ? merge then
opt
// optionalAttrs (decl.type ? merge) { inherit (decl.type) merge; }
// optionalAttrs (decl.type ? check) { inherit (decl.type) check; }
else
opt;
addDeclaration = opt: opt // decl;
ensureMergeInputType = opt:
if opt ? check then
opt // {
merge = list:
if all opt.check list then
opt.merge list
else
throw "One of the definitions has a bad type.";
}
else opt;
ensureDefaultType = opt:
if opt ? check && opt ? default then
opt // {
default =
if opt.check opt.default then
opt.default
else
throw "The default value has a bad type.";
}
else opt;
handleOptionSets = opt:
if opt ? type && opt.type.hasOptions then
let
optionConfig = vals: args:
map (f: lib.applyIfFunction f args)
(opt.options ++ toList vals);
# Evaluate sub-modules.
subModuleMerge = path: vals:
lib.fix (args:
let result = recurseInto path (optionConfig vals args); in {
inherit (result) config options;
name = lib.removePrefix (opt.name + ".") path;
}
);
# Add _options in sub-modules to make it viewable from other
# modules.
subModuleMergeConfig = path: vals:
let result = subModuleMerge path vals; in
{ _args = result; } // result.config;
in
opt // {
merge = list:
opt.type.iter
subModuleMergeConfig
opt.name
(opt.merge list);
options =
let path = opt.type.docPath opt.name; in
(subModuleMerge path []).options;
}
else
opt;
in
foldl (opt: f: f opt) init [
# default settings
functionsFromType
# 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;
opt1 // opt2
// optionalAttrs (opt1 ? options || opt2 ? options) {
options =
(toList (attrByPath ["options"] [] opt1))
++ (toList (attrByPath ["options"] [] opt2));
}
// optionalAttrs (opt1 ? extraConfigs || opt2 ? extraConfigs) {
extraConfigs =
(attrByPath ["extraConfigs"] [] opt1)
++ (attrByPath ["extraConfigs"] [] 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 builtins.isBool list then fold lib.or false list
else if all builtins.isString list then lib.concatStrings list
else if all builtins.isInt list && all (x: x == head list) list
then head 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;
fixableMergeFun = merge: f: config:
merge (
# generate the list of option sets.
f config
);
fixableMergeModules = merge: initModules: {...}@args: config:
fixableMergeFun merge (config:
lib.moduleClosure initModules (args // { inherit config; })
) config;
fixableDefinitionsOf = initModules: {...}@args:
fixableMergeModules (modules: (lib.moduleMerge "" modules).config) initModules args;
fixableDeclarationsOf = initModules: {...}@args:
fixableMergeModules (modules: (lib.moduleMerge "" modules).options) initModules args;
definitionsOf = initModules: {...}@args:
(lib.fix (module:
fixableMergeModules (lib.moduleMerge "") initModules args module.config
)).config;
declarationsOf = initModules: {...}@args:
(lib.fix (module:
fixableMergeModules (lib.moduleMerge "") initModules args module.config
)).options;
# 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.";
declarations = map (x: toString x.source) opt.declarations;
definitions = map (x: toString x.source) opt.definitions;
}
// optionalAttrs (opt ? example) { example = scrubOptionValue opt.example; }
// optionalAttrs (opt ? default) { default = scrubOptionValue opt.default; }
// optionalAttrs (opt ? defaultText) { default = opt.defaultText; };
subOptions =
if opt ? options then
newOptionAttrSetToDocList opt.options
else
[];
in
[ docOption ] ++ subOptions ++ rest
) [] 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) x
else x;
}