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* Refactor mkIf to extract the concept of properties.

Browse source 
Properties can be delay on any attribute set and have
functions which are used to define the semantic of each
property.

* Introduce the mkOverride property.

svn path=/nixpkgs/trunk/; revision=14285
This commit is contained in:
Nicolas Pierron 2009-02-28 18:21:25 +00:00
parent 02b2540b15
commit e18a10d0ae
1 changed files with 362 additions and 46 deletions
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408
pkgs/lib/options.nix
View file

@ -3,7 +3,9 @@
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 {
@ -11,7 +13,8 @@ rec {
mkOption = attrs: attrs // {_type = "option";};
typeOf = x: if (__isAttrs x && x ? _type) then x._type else "";
hasType = x: __isAttrs x && x ? _type;
typeOf = x: if hasType x then x._type else "";
isOption = attrs: (typeOf attrs) == "option";
@ -97,11 +100,11 @@ rec {
} // (head decls);
# Return the list of option sets.
optAttrs = map delayIf defs;
optAttrs = map delayProperties defs;
# return the list of option values.
# Remove undefined values that are coming from evalIf.
optValues = filter (x: !isNotdef x) (map evalIf defs);
optValues = evalProperties defs;
in
if decls == [] then handleOptionSets optionHandler name optAttrs
else lib.addErrorContext "while evaluating the option ${name}:" (
@ -150,9 +153,9 @@ rec {
let
# remove possible mkIf to access the require attribute.
noImportConditions = cfgSet0:
let cfgSet1 = delayIf cfgSet0; in
let cfgSet1 = delayProperties cfgSet0; in
if cfgSet1 ? require then
cfgSet1 // { require = rmIf cfgSet1.require; }
cfgSet1 // { require = rmProperties cfgSet1.require; }
else
cfgSet1;
@ -176,12 +179,39 @@ rec {
cfg2 = noImportConditions cfg1;
in cfg2;
getRequire = x: toList (getAttr ["require"] [] (preprocess x));
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 (
lib.uniqFlatten getRequire [] [] (toList opts)
duplicateIncludeProperties (
lib.uniqFlatten getCleanRequire [] [] (toList opts)
)
)
);
@ -203,65 +233,351 @@ rec {
(l + (if l=="" then "" else ".") + s) (builtins.getAttr s attrs)))
(builtins.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. */
# !!! cleanup needed
# create "if" statement that can be dealyed 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: thenelse:
if isIf thenelse then
mkIf (condition && thenelse.condition) thenelse.thenelse
else {
mkIf = condition: content: mkProperty {
property = {
_type = "if";
inherit condition thenelse;
onGlobalDelay = onIfGlobalDelay;
onEval = onIfEval;
inherit condition;
};
inherit content;
};
isNotdef = attrs: (typeOf attrs) == "notdef";
mkNotdef = {_type = "notdef";};
# 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;
attrs // { _type = "then-else"; };
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: { inherit value; _type = "always"; };
mkAlways = value:
mkProperty {
property = {
_type = "always";
onEval = p@{content, ...}: content;
inherit value;
};
content = mkNotdef;
};
pushIf = f: attrs:
if isIf attrs then pushIf f (
let val = attrs.thenelse; in
# evaluate the condition.
if isThenElse val then
if attrs.condition then
val.thenPart
# 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
val.elsePart
# ignore the condition.
else if isAlways val then
val.value
# otherwise
else
f attrs.condition val)
let p = head list; in
# evaluate the condition.
if isThenElse p then
if condition then
foldProperty (a: p.thenPart) id content
else
foldProperty (a: p.elsePart) id content
# ignore the condition.
else if isAlways p then
foldProperty (a: p.value) id content
# 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
attrs;
mkNotdef;
# take care otherwise you will have to handle this by hand.
rmIf = pushIf (condition: val: val);
/* mkOverride */
evalIf = pushIf (condition: val:
if condition then val else mkNotdef
);
# 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;
};
delayIf = pushIf (condition: val:
# rewrite the condition on sub-attributes.
lib.mapAttrs (name: mkIf condition) val
);
# 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 builtins.isAttrs template && template != {} then
if builtins.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;
}