with import ./.. {};
with lib;
rec {
/* Evaluate a set of modules. The result is a set of two
attributes: ‘options’: the nested set of all option declarations,
and ‘config’: the nested set of all option values. */
evalModules = modules: args:
let
args' = args // result;
closed = closeModules modules args';
# Note: the list of modules is reversed to maintain backward
# compatibility with the old module system. Not sure if this is
# the most sensible policy.
options = mergeModules (reverseList closed);
config = yieldConfig options;
yieldConfig = mapAttrs (n: v: if isOption v then v.value else yieldConfig v);
result = { inherit options config; };
in result;
/* Close a set of modules under the ‘imports’ relation. */
closeModules = modules: args:
let
coerceToModule = n: x:
if isAttrs x || builtins.isFunction x then
unifyModuleSyntax "anon-${toString n}" (applyIfFunction x args)
else
unifyModuleSyntax (toString x) (applyIfFunction (import x) args);
toClosureList = imap (path: coerceToModule path);
in
builtins.genericClosure {
startSet = toClosureList modules;
operator = m: toClosureList m.imports;
};
/* Massage a module into canonical form, that is, a set consisting
of ‘options’, ‘config’ and ‘imports’ attributes. */
unifyModuleSyntax = key: m:
if m ? config || m ? options || m ? imports then
let badAttrs = removeAttrs m ["imports" "options" "config"]; in
if badAttrs != {} then
throw "Module `${key}' has an unsupported attribute `${head (attrNames badAttrs)}'. ${builtins.toXML m} "
else
{ inherit key;
imports = m.imports or [];
options = m.options or {};
config = m.config or {};
}
else
{ inherit key;
imports = m.require or [];
options = {};
config = m;
};
applyIfFunction = f: arg: if builtins.isFunction f then f arg else f;
/* Merge a list of modules. This will recurse over the option
declarations in all modules, combining them into a single set.
At the same time, for each option declaration, it will merge the
corresponding option definitions in all machines, returning them
in the ‘value’ attribute of each option. */
mergeModules = modules:
mergeModules' [] (map (m: m.options) modules) (concatMap (m: pushDownProperties m.config) modules);
mergeModules' = loc: options: configs:
zipAttrsWith (name: vals:
let loc' = loc ++ [name]; in
if all isOption vals then
let opt = fixupOptionType loc' (mergeOptionDecls loc' vals);
in evalOptionValue loc' opt (catAttrs name configs)
else if any isOption vals then
throw "There are options with the prefix `${showOption loc'}', which is itself an option."
else
mergeModules' loc' vals (concatMap pushDownProperties (catAttrs name configs))
) options;
/* Merge multiple option declarations into a single declaration. In
general, there should be only one declaration of each option.
The exception is the ‘options’ attribute, which specifies
sub-options. These can be specified multiple times to allow one
module to add sub-options to an option declared somewhere else
(e.g. multiple modules define sub-options for ‘fileSystems’). */
mergeOptionDecls = loc: opts:
fold (opt1: opt2:
if opt1 ? default && opt2 ? default ||
opt1 ? example && opt2 ? example ||
opt1 ? description && opt2 ? description ||
opt1 ? merge && opt2 ? merge ||
opt1 ? apply && opt2 ? apply ||
opt1 ? type && opt2 ? type
then
throw "Conflicting declarations of the option `${showOption loc}'."
else
opt1 // opt2
// optionalAttrs (opt1 ? options && opt2 ? options)
{ options = [ opt1.options opt2.options ]; }
) {} opts;
/* Merge all the definitions of an option to produce the final
config value. */
evalOptionValue = loc: opt: defs:
let
# Process mkMerge and mkIf properties.
defs' = concatMap dischargeProperties defs;
# Process mkOverride properties, adding in the default
# value specified in the option declaration (if any).
defsFinal = filterOverrides (optional (opt ? default) (mkOptionDefault opt.default) ++ defs');
# Type-check the remaining definitions, and merge them
# if possible.
merged =
if defsFinal == [] then
throw "The option `${showOption loc}' is used but not defined."
else
if all opt.type.check defsFinal then
opt.type.merge defsFinal
#throw "The option `${showOption loc}' has multiple values (with no way to merge them)."
else
throw "A value of the option `${showOption loc}' has a bad type.";
# Finally, apply the ‘apply’ function to the merged
# value. This allows options to yield a value computed
# from the definitions.
value = (opt.apply or id) merged;
in opt //
{ inherit value;
definitions = defsFinal;
isDefined = defsFinal != [];
};
/* Given a config set, expand mkMerge properties, and push down the
mkIf properties into the children. The result is a list of
config sets that do not have properties at top-level. For
example,
mkMerge [ { boot = set1; } (mkIf cond { boot = set2; services = set3; }) ]
is transformed into
[ { boot = set1; } { boot = mkIf cond set2; services mkIf cond set3; } ].
This transform is the critical step that allows mkIf conditions
to refer to the full configuration without creating an infinite
recursion.
*/
pushDownProperties = cfg:
if cfg._type or "" == "merge" then
concatMap pushDownProperties cfg.contents
else if cfg._type or "" == "if" then
map (mapAttrs (n: v: mkIf cfg.condition v)) (pushDownProperties cfg.content)
else
# FIXME: handle mkOverride?
[ cfg ];
/* Given a config value, expand mkMerge properties, and discharge
any mkIf conditions. That is, this is the place where mkIf
conditions are actually evaluated. The result is a list of
config values. For example, ‘mkIf false x’ yields ‘[]’,
‘mkIf true x’ yields ‘[x]’, and
mkMerge [ 1 (mkIf true 2) (mkIf true (mkIf false 3)) ]
yields ‘[ 1 2 ]’.
*/
dischargeProperties = def:
if def._type or "" == "merge" then
concatMap dischargeProperties def.contents
else if def._type or "" == "if" then
if def.condition then
dischargeProperties def.content
else
[ ]
else
[ def ];
/* Given a list of config value, process the mkOverride properties,
that is, return the values that have the highest (that
is,. numerically lowest) priority, and strip the mkOverride
properties. For example,
[ (mkOverride 10 "a") (mkOverride 20 "b") "z" (mkOverride 10 "d") ]
yields ‘[ "a" "d" ]’. Note that "z" has the default priority 100.
*/
filterOverrides = defs:
let
defaultPrio = 100;
getPrio = def: if def._type or "" == "override" then def.priority else defaultPrio;
min = x: y: if x < y then x else y;
highestPrio = fold (def: prio: min (getPrio def) prio) 9999 defs;
strip = def: if def._type or "" == "override" then def.content else def;
in concatMap (def: if getPrio def == highestPrio then [(strip def)] else []) defs;
/* Hack for backward compatibility: convert options of type
optionSet to configOf. FIXME: remove eventually. */
fixupOptionType = loc: opt:
let
options' = opt.options or
(throw "Option `${showOption loc'}' has type optionSet but has no option attribute.");
coerce = x:
if builtins.isFunction x then x
else { config, ... }: { options = x; };
options = map coerce (flatten options');
f = tp:
if tp.name == "option set" then types.submodule options
else if tp.name == "attribute set of option sets" then types.attrsOf (types.submodule options)
else if tp.name == "list or attribute set of option sets" then types.loaOf (types.submodule options)
else if tp.name == "list of option sets" then types.listOf (types.submodule options)
else if tp.name == "null or option set" then types.nullOr (types.submodule options)
else tp;
in opt // { type = f (opt.type or types.unspecified); };
/* Properties. */
mkIf = condition: content:
{ _type = "if";
inherit condition content;
};
mkAssert = assertion: message: content:
mkIf
(if assertion then true else throw "\nFailed assertion: ${message}")
content;
mkMerge = contents:
{ _type = "merge";
inherit contents;
};
mkOverride = priority: content:
{ _type = "override";
inherit priority content;
};
mkOptionDefault = mkOverride 1001;
mkDefault = mkOverride 1000;
mkForce = mkOverride 50;
mkFixStrictness = id; # obsolete, no-op
# FIXME: Add mkOrder back in. It's not currently used anywhere in
# NixOS, but it should be useful.
}