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;
rec {
mkOption = attrs: attrs // {_type = "option";};
hasType = x: isAttrs x && x ? _type;
typeOf = x: if hasType x then x._type else "";
isOption = attrs: (typeOf attrs) == "option";
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
# 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 isOption opts;
decls = test.right; defs = test.wrong;
# Return the option declaration and add missing default
# attributes.
opt = {
inherit name;
merge = mergeDefaultOption;
apply = lib.id;
} // (head 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 handleOptionSets optionHandler name optAttrs
else lib.addErrorContext "while evaluating the option ${name}:" (
if tail decls != [] then throw "Multiple options."
else 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: {};
};
# Evaluate a list of option sets that would be merged with the
# function "merge" which expects two arguments. The attribute named
# "require" is used to imports option declarations and bindings.
#
# * cfg[0-9]: configuration
# * cfgSet[0-9]: configuration set
#
# merge: the function used to merge options sets.
# pkgs: is the set of packages available. (nixpkgs)
# opts: list of option sets or option set functions.
# config: result of this evaluation.
fixOptionSetsFun = merge: pkgs: opts: config:
let
# remove possible mkIf to access the require attribute.
noImportConditions = cfgSet0:
let cfgSet1 = delayProperties cfgSet0; in
if cfgSet1 ? require then
cfgSet1 // { require = rmProperties cfgSet1.require; }
else
cfgSet1;
# call configuration "files" with one of the existing convention.
argumentHandler = cfg:
let
# {..}
cfg0 = cfg;
# {pkgs, config, ...}: {..}
cfg1 = cfg { inherit pkgs config merge; };
# pkgs: config: {..}
cfg2 = cfg {} {};
in
if builtins.isFunction cfg0 then
if isAttrs cfg1 then cfg1
else builtins.trace "Use '{pkgs, config, ...}:'." cfg2
else cfg0;
preprocess = cfg0:
let cfg1 = argumentHandler cfg0;
cfg2 = noImportConditions cfg1;
in cfg2;
getRequire = x:
toList (getAttr ["require"] [] (preprocess x));
getCleanRequire = x: map rmProperties (getRequire x);
rmRequire = x: removeAttrs (preprocess x) ["require"];
duplicateIncludeProperties = list:
# iterate on all configurations
fold (cfg: l:
# iterate on all imported configuration from cfg
fold (include: l:
# clean up the included cfg to get the same result
let includedCfg = rmProperties include; in
# if the include has properties
if include != includedCfg then
# iterate on all configurations
map (cfg:
# if the imported configuration is seen
if (rmProperties cfg) == includedCfg then
# copy the properties from the import to the configuration.
delayProperties (copyProperties include cfg)
else
cfg
) l
else
l
) l (getRequire cfg)
) list list;
in
merge "" (
map rmRequire (
duplicateIncludeProperties (
lib.uniqFlatten getCleanRequire [] [] (toList opts)
)
)
);
fixOptionSets = merge: pkgs: opts:
lib.fix (fixOptionSetsFun merge pkgs opts);
optionAttrSetToDocList = l: attrs:
if (getAttr ["_type"] "" attrs) == "option" then
[({
#inherit (attrs) description;
description = if attrs ? description then attrs.description else
throw ("No description ${toString l} : ${lib.whatis attrs}");
}
// (if attrs ? example then {inherit(attrs) example;} else {} )
// (if attrs ? default then {inherit(attrs) default;} else {} )
// {name = l;}
)]
else (concatLists (map (s: (optionAttrSetToDocList
(l + (if l=="" then "" else ".") + s) (builtins.getAttr s attrs)))
(attrNames attrs)));
/* Option Properties */
# Generalize the problem of delayable properties. Any property can be created
# Tell that nothing is defined. When properties are evaluated, this type
# is used to remove an entry. Thus if your property evaluation semantic
# implies that you have to mute the content of an attribute, then your
# property should produce this value.
isNotdef = attrs: (typeOf attrs) == "notdef";
mkNotdef = {_type = "notdef";};
# General property type, it has a property attribute and a content
# attribute. The property attribute refer to an attribute set which
# contains a _type attribute and a list of functions which are used to
# evaluate this property. The content attribute is used to stack property
# on top of each other.
#
# The optional functions which may be contained in the property attribute
# are:
# - onDelay: run on a copied property.
# - onGlobalDelay: run on all copied properties.
# - onEval: run on an evaluated property.
# - onGlobalEval: run on a list of property stack on top of their values.
isProperty = attrs: (typeOf attrs) == "property";
mkProperty = p@{property, content, ...}: p // {
_type = "property";
};
# Go throw the stack of properties and apply the function `op' on all
# property and call the function `nul' on the final value which is not a
# property. The stack is traversed in reversed order. The `op' function
# should expect a property with a content which have been modified.
#
# Warning: The `op' function expects only one argument in order to avoid
# calls to mkProperties as the argument is already a valid property which
# contains the result of the folding inside the content attribute.
foldProperty = op: nul: attrs:
if isProperty attrs then
op (attrs // {
content = foldProperty op nul attrs.content;
})
else
nul attrs;
# Simple function which can be used as the `op' argument of the
# foldProperty function. Properties that you don't want to handle can be
# ignored with the `id' function. `isSearched' is a function which should
# check the type of a property and return a boolean value. `thenFun' and
# `elseFun' are functions which behave as the `op' argument of the
# foldProperty function.
foldFilter = isSearched: thenFun: elseFun: attrs:
if isSearched attrs.property then
thenFun attrs
else
elseFun attrs;
# Move properties from the current attribute set to the attribute
# contained in this attribute set. This trigger property handlers called
# `onDelay' and `onGlobalDelay'.
delayProperties = attrs:
let cleanAttrs = rmProperties attrs; in
if cleanAttrs != attrs then
lib.mapAttrs (a: v:
lib.addErrorContext "while moving properties on the attribute `${a}'." (
triggerPropertiesGlobalDelay a (
triggerPropertiesDelay a (
copyProperties attrs v
)))) cleanAttrs
else
attrs;
# Call onDelay functions.
triggerPropertiesDelay = name: attrs:
let
callOnDelay = p@{property, ...}:
lib.addErrorContext "while calling a onDelay function." (
if property ? onDelay then
property.onDelay name p
else
p
);
in
foldProperty callOnDelay id attrs;
# Call onGlobalDelay functions.
triggerPropertiesGlobalDelay = name: attrs:
let
globalDelayFuns = uniqListExt {
getter = property: property._type;
inputList = foldProperty (p@{property, content, ...}:
if property ? onGlobalDelay then
[ property ] ++ content
else
content
) (a: []) attrs;
};
callOnGlobalDelay = property: content:
lib.addErrorContext "while calling a onGlobalDelay function." (
property.onGlobalDelay name content
);
in
fold callOnGlobalDelay attrs globalDelayFuns;
# Expect a list of values which may have properties and return the same
# list of values where all properties have been evaluated and where all
# ignored values are removed. This trigger property handlers called
# `onEval' and `onGlobalEval'.
evalProperties = valList:
if valList != [] then
filter (x: !isNotdef x) (
lib.addErrorContext "while evaluating properties an attribute." (
triggerPropertiesGlobalEval (
map triggerPropertiesEval valList
)))
else
valList;
# Call onEval function
triggerPropertiesEval = val:
foldProperty (p@{property, ...}:
lib.addErrorContext "while calling a onEval function." (
if property ? onEval then
property.onEval p
else
p
)
) id val;
# Call onGlobalEval function
triggerPropertiesGlobalEval = valList:
let
globalEvalFuns = uniqListExt {
getter = property: property._type;
inputList =
fold (attrs: list:
foldProperty (p@{property, content, ...}:
if property ? onGlobalEval then
[ property ] ++ content
else
content
) (a: list) attrs
) [] valList;
};
callOnGlobalEval = property: valList:
lib.addErrorContext "while calling a onGlobalEval function." (
property.onGlobalEval valList
);
in
fold callOnGlobalEval valList globalEvalFuns;
# Remove all properties on top of a value and return the value.
rmProperties =
foldProperty (p@{content, ...}: content) id;
# Copy properties defined on a value on another value.
copyProperties = attrs: newAttrs:
foldProperty id (x: newAttrs) attrs;
/* If. ThenElse. Always. */
# create "if" statement that can be delayed on sets until a "then-else" or
# "always" set is reached. When an always set is reached the condition
# is ignore.
# Create a "If" property which only contains a condition.
isIf = attrs: (typeOf attrs) == "if";
mkIf = condition: content: mkProperty {
property = {
_type = "if";
onGlobalDelay = onIfGlobalDelay;
onEval = onIfEval;
inherit condition;
};
inherit content;
};
# Create a "ThenElse" property which contains choices which can choosed by
# the evaluation of an "If" statement.
isThenElse = attrs: (typeOf attrs) == "then-else";
mkThenElse = attrs:
assert attrs ? thenPart && attrs ? elsePart;
mkProperty {
property = {
_type = "then-else";
onEval = val: throw "Missing mkIf statement.";
inherit (attrs) thenPart elsePart;
};
content = mkNotdef;
};
# Create an "Always" property remove ignore all "If" statement.
isAlways = attrs: (typeOf attrs) == "always";
mkAlways = value:
mkProperty {
property = {
_type = "always";
onEval = p@{content, ...}: content;
inherit value;
};
content = mkNotdef;
};
# Remove all "If" statement defined on a value.
rmIf = foldProperty (
foldFilter isIf
({content, ...}: content)
id
) id;
# Evaluate the "If" statements when either "ThenElse" or "Always"
# statement is encounter. Otherwise it remove multiple If statement and
# replace them by one "If" staement where the condition is the list of all
# conditions joined with a "and" operation.
onIfGlobalDelay = name: content:
let
# extract if statements and non-if statements and repectively put them
# in the attribute list and attrs.
ifProps =
foldProperty
(foldFilter (p: isIf p || isThenElse p || isAlways p)
# then, push the codition inside the list list
(p@{property, content, ...}:
{ inherit (content) attrs;
list = [property] ++ content.list;
}
)
# otherwise, add the propertie.
(p@{property, content, ...}:
{ inherit (content) list;
attrs = p // { content = content.attrs; };
}
)
)
(attrs: { list = []; inherit attrs; })
content;
# compute the list of if statements.
evalIf = content: condition: list:
if list == [] then
mkIf condition content
else
let p = head list; in
# evaluate the condition.
if isThenElse p then
if condition then
copyProperties content p.thenPart
else
copyProperties content p.elsePart
# ignore the condition.
else if isAlways p then
copyProperties content p.value
# otherwise (isIf)
else
evalIf content (condition && p.condition) (tail list);
in
evalIf ifProps.attrs true ifProps.list;
# Evaluate the condition of the "If" statement to either get the value or
# to ignore the value.
onIfEval = p@{property, content, ...}:
if property.condition then
content
else
mkNotdef;
/* mkOverride */
# Create an "Override" statement which allow the user to define
# prioprities between values. The default priority is 100 and the lowest
# priorities are kept. The template argument must reproduce the same
# attribute set hierachy to override leaves of the hierarchy.
isOverride = attrs: (typeOf attrs) == "override";
mkOverride = priority: template: content: mkProperty {
property = {
_type = "override";
onDelay = onOverrideDelay;
onGlobalEval = onOverrideGlobalEval;
inherit priority template;
};
inherit content;
};
# Make the template traversal in function of the property traversal. If
# the template define a non-empty attribute set, then the property is
# copied only on all mentionned attributes inside the template.
# Otherwise, the property is kept on all sub-attribute definitions.
onOverrideDelay = name: p@{property, content, ...}:
let inherit (property) template; in
if isAttrs template && template != {} then
if hasAttr name template then
p // {
property = p.property // {
template = builtins.getAttr name template;
};
}
# Do not override the attribute \name\
else
content
# Override values defined inside the attribute \name\.
else
p;
# Ignore all values which have a higher value of the priority number.
onOverrideGlobalEval = valList:
let
defaultPrio = 100;
inherit (builtins) lessThan;
getPrioVal =
foldProperty
(foldFilter isOverride
(p@{property, content, ...}:
if lessThan content.priority property.priority then
content
else
content // {
inherit (property) priority;
}
)
(p@{property, content, ...}:
content // {
value = p // { content = content.value; };
}
)
) (value: { priority = defaultPrio; inherit value; });
prioValList = map getPrioVal valList;
higherPrio = fold (x: y:
if lessThan x.priority y then
x.priority
else
y
) defaultPrio prioValList;
in
map (x:
if x.priority == higherPrio then
x.value
else
mkNotdef
) prioValList;
}