nixpkgs/lib/modules.nix

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with import ./lists.nix;
with import ./trivial.nix;
with import ./attrsets.nix;
with import ./options.nix;
with import ./debug.nix;
with import ./types.nix;
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.
!!! Please think twice before adding to this argument list! The more
that is specified here instead of in the modules themselves the harder
it is to transparently move a set of modules to be a submodule of another
config (as the proper arguments need to be replicated at each call to
evalModules) and the less declarative the module set is. */
evalModules = { modules
, prefix ? []
, # This would be remove in the future, Prefer _module.args option instead.
args ? {}
, # This would be remove in the future, Prefer _module.check option instead.
check ? true
}:
let
# This internal module declare internal options under the `_module'
# attribute. These options are fragile, as they are used by the
# module system to change the interpretation of modules.
internalModule = rec {
_file = ./modules.nix;
key = _file;
options = {
_module.args = mkOption {
type = types.attrsOf types.unspecified;
internal = true;
description = "Arguments passed to each module.";
};
_module.check = mkOption {
type = types.uniq types.bool;
internal = true;
default = check;
description = "Whether to check whether all option definitions have matching declarations.";
};
};
config = {
_module.args = args;
};
};
closed = closeModules (modules ++ [ internalModule ]) { inherit config options; lib = import ./.; };
# 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 prefix (reverseList closed);
# Traverse options and extract the option values into the final
# config set. At the same time, check whether all option
# definitions have matching declarations.
# !!! _module.check's value can't depend on any other config values
# without an infinite recursion. One way around this is to make the
# 'config' passed around to the modules be unconditionally unchecked,
# and only do the check in 'result'.
config = yieldConfig prefix options;
yieldConfig = prefix: set:
let res = removeAttrs (mapAttrs (n: v:
if isOption v then v.value
else yieldConfig (prefix ++ [n]) v) set) ["_definedNames"];
in
if options._module.check.value && set ? _definedNames then
fold (m: res:
fold (name: res:
if set ? ${name} then res else throw "The option `${showOption (prefix ++ [name])}' defined in `${m.file}' does not exist.")
res m.names)
res set._definedNames
else
res;
result = { inherit options config; };
in result;
/* Close a set of modules under the imports relation. */
closeModules = modules: args:
let
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toClosureList = file: parentKey: imap (n: x:
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if isAttrs x || isFunction x then
unifyModuleSyntax file "${parentKey}:anon-${toString n}" (unpackSubmodule applyIfFunction x args)
else
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unifyModuleSyntax (toString x) (toString x) (applyIfFunction (import x) args));
in
builtins.genericClosure {
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startSet = toClosureList unknownModule "" modules;
operator = m: toClosureList m.file m.key m.imports;
};
/* Massage a module into canonical form, that is, a set consisting
of options, config and imports attributes. */
unifyModuleSyntax = file: key: m:
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if m ? config || m ? options then
let badAttrs = removeAttrs m ["imports" "options" "config" "key" "_file"]; in
if badAttrs != {} then
throw "Module `${key}' has an unsupported attribute `${head (attrNames badAttrs)}'. This is caused by assignments to the top-level attributes `config' or `options'."
else
{ file = m._file or file;
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key = toString m.key or key;
imports = m.imports or [];
options = m.options or {};
config = m.config or {};
}
else
{ file = m._file or file;
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key = toString m.key or key;
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imports = m.require or [] ++ m.imports or [];
options = {};
config = removeAttrs m ["key" "_file" "require" "imports"];
};
applyIfFunction = f: arg@{ config, options, lib }: if isFunction f then
let
# Module arguments are resolved in a strict manner when attribute set
# deconstruction is used. As the arguments are now defined with the
# config._module.args option, the strictness used on the attribute
# set argument would cause an infinite loop, if the result of the
# option is given as argument.
#
# To work-around the strictness issue on the deconstruction of the
# attributes set argument, we create a new attribute set which is
# constructed to satisfy the expected set of attributes. Thus calling
# a module will resolve strictly the attributes used as argument but
# not their values. The values are forwarding the result of the
# evaluation of the option.
requiredArgs = builtins.attrNames (builtins.functionArgs f);
extraArgs = builtins.listToAttrs (map (name: {
inherit name;
value = config._module.args.${name};
}) requiredArgs);
in f (extraArgs // arg)
else
f;
/* We have to pack and unpack submodules. We cannot wrap the expected
result of the function as we would no longer be able to list the arguments
of the submodule. (see applyIfFunction) */
unpackSubmodule = unpack: m: args:
if isType "submodule" m then
{ _file = m.file; } // (unpack m.submodule args)
else unpack m args;
packSubmodule = file: m:
{ _type = "submodule"; file = file; submodule = m; };
/* 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 = prefix: modules:
mergeModules' prefix modules
(concatMap (m: map (config: { inherit (m) file; inherit config; }) (pushDownProperties m.config)) modules);
mergeModules' = prefix: options: configs:
listToAttrs (map (name: {
# We're descending into attribute name.
inherit name;
value =
let
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loc = prefix ++ [name];
# Get all submodules that declare name.
decls = concatLists (map (m:
if m.options ? ${name}
then [ { inherit (m) file; options = m.options.${name}; } ]
else []
) options);
# Get all submodules that define name.
defns = concatLists (map (m:
if m.config ? ${name}
then map (config: { inherit (m) file; inherit config; })
(pushDownProperties m.config.${name})
else []
) configs);
nrOptions = count (m: isOption m.options) decls;
# Extract the definitions for this loc
defns' = map (m: { inherit (m) file; value = m.config.${name}; })
(filter (m: m.config ? ${name}) configs);
in
if nrOptions == length decls then
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let opt = fixupOptionType loc (mergeOptionDecls loc decls);
in evalOptionValue loc opt defns'
else if nrOptions != 0 then
let
firstOption = findFirst (m: isOption m.options) "" decls;
firstNonOption = findFirst (m: !isOption m.options) "" decls;
in
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throw "The option `${showOption loc}' in `${firstOption.file}' is a prefix of options in `${firstNonOption.file}'."
else
mergeModules' loc decls defns;
}) (concatMap (m: attrNames m.options) options))
// { _definedNames = map (m: { inherit (m) file; names = attrNames m.config; }) configs; };
/* 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).
'loc' is the list of attribute names where the option is located.
'opts' is a list of modules. Each module has an options attribute which
correspond to the definition of 'loc' in 'opt.file'. */
mergeOptionDecls = loc: opts:
fold (opt: res:
if opt.options ? default && res ? default ||
opt.options ? example && res ? example ||
opt.options ? description && res ? description ||
opt.options ? apply && res ? apply ||
# Accept to merge options which have identical types.
opt.options ? type && res ? type && opt.options.type.name != res.type.name
then
throw "The option `${showOption loc}' in `${opt.file}' is already declared in ${showFiles res.declarations}."
else
let
/* Add the modules of the current option to the list of modules
already collected. The options attribute except either a list of
submodules or a submodule. For each submodule, we add the file of the
current option declaration as the file use for the submodule. If the
submodule defines any filename, then we ignore the enclosing option file. */
options' = toList opt.options.options;
coerceOption = file: opt:
if isFunction opt then packSubmodule file opt
else packSubmodule file { options = opt; };
getSubModules = opt.options.type.getSubModules or null;
submodules =
if getSubModules != null then map (packSubmodule opt.file) getSubModules ++ res.options
else if opt.options ? options then map (coerceOption opt.file) options' ++ res.options
else res.options;
in opt.options // res //
{ declarations = [opt.file] ++ res.declarations;
options = submodules;
}
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) { inherit loc; declarations = []; options = []; } opts;
/* Merge all the definitions of an option to produce the final
config value. */
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evalOptionValue = loc: opt: defs:
let
# Add in the default value for this option, if any.
defs' = (optional (opt ? default)
{ file = head opt.declarations; value = mkOptionDefault opt.default; }) ++ defs;
# Handle properties, check types, and merge everything together
inherit (mergeDefinitions loc opt.type defs') isDefined defsFinal mergedValue;
files = map (def: def.file) defsFinal;
merged =
if isDefined then mergedValue
else throw "The option `${showOption loc}' is used but not defined.";
# 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 //
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{ value = addErrorContext "while evaluating the option `${showOption loc}':" value;
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definitions = map (def: def.value) defsFinal;
inherit isDefined files;
};
# Merge definitions of a value of a given type
mergeDefinitions = loc: type: defs: rec {
defsFinal =
let
# Process mkMerge and mkIf properties
processIfAndMerge = defs: concatMap (m:
map (value: { inherit (m) file; inherit value; }) (dischargeProperties m.value)
) defs;
# Process mkOverride properties
processOverride = defs: filterOverrides defs;
# Sort mkOrder properties
processOrder = defs:
# Avoid sorting if we don't have to.
if any (def: def.value._type or "" == "order") defs
then sortProperties defs
else defs;
in
processOrder (processOverride (processIfAndMerge defs));
# Type-check the remaining definitions, and merge them
mergedValue = fold (def: res:
if type.check def.value then res
else throw "The option value `${showOption loc}' in `${def.file}' is not a ${type.name}.")
(type.merge loc defsFinal) defsFinal;
isDefined = defsFinal != [];
optionalValue =
if isDefined then { value = mergedValue; }
else {};
};
/* Given a config set, expand mkMerge properties, and push down the
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other 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)
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else if cfg._type or "" == "override" then
map (mapAttrs (n: v: mkOverride cfg.priority v)) (pushDownProperties cfg.content)
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else # FIXME: handle mkOrder?
[ 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 ];
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/* Given a list of config values, 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,
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[ { file = "/1"; value = mkOverride 10 "a"; }
{ file = "/2"; value = mkOverride 20 "b"; }
{ file = "/3"; value = "z"; }
{ file = "/4"; value = mkOverride 10 "d"; }
]
yields
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[ { file = "/1"; value = "a"; }
{ file = "/4"; value = "d"; }
]
Note that "z" has the default priority 100.
*/
filterOverrides = defs:
let
defaultPrio = 100;
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getPrio = def: if def.value._type or "" == "override" then def.value.priority else defaultPrio;
min = x: y: if x < y then x else y;
highestPrio = fold (def: prio: min (getPrio def) prio) 9999 defs;
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strip = def: if def.value._type or "" == "override" then def // { value = def.value.content; } else def;
in concatMap (def: if getPrio def == highestPrio then [(strip def)] else []) defs;
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/* Sort a list of properties. The sort priority of a property is
1000 by default, but can be overriden by wrapping the property
using mkOrder. */
sortProperties = defs:
let
strip = def:
if def.value._type or "" == "order"
then def // { value = def.value.content; inherit (def.value) priority; }
else def;
defs' = map strip defs;
compare = a: b: (a.priority or 1000) < (b.priority or 1000);
in sort compare defs';
/* Hack for backward compatibility: convert options of type
optionSet to options of type submodule. FIXME: remove
eventually. */
fixupOptionType = loc: opt:
let
options = opt.options or
(throw "Option `${showOption loc'}' has type optionSet but has no option attribute, in ${showFiles opt.declarations}.");
f = tp:
if tp.name == "option set" || tp.name == "submodule" then
throw "The option ${showOption loc} uses submodules without a wrapping type, in ${showFiles opt.declarations}."
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
if opt.type.getSubModules or null == null
then opt // { type = f (opt.type or types.unspecified); }
else opt // { type = opt.type.substSubModules opt.options; options = []; };
/* 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; # priority of option defaults
mkDefault = mkOverride 1000; # used in config sections of non-user modules to set a default
mkForce = mkOverride 50;
mkVMOverride = mkOverride 10; # used by nixos-rebuild build-vm
mkStrict = builtins.trace "`mkStrict' is obsolete; use `mkOverride 0' instead." (mkOverride 0);
mkFixStrictness = id; # obsolete, no-op
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mkOrder = priority: content:
{ _type = "order";
inherit priority content;
};
mkBefore = mkOrder 500;
mkAfter = mkOrder 1500;
# Convenient property used to transfer all definitions and their
# properties from one option to another. This property is useful for
# renaming options, and also for including properties from another module
# system, including sub-modules.
#
# { config, options, ... }:
#
# {
# # 'bar' might not always be defined in the current module-set.
# config.foo.enable = mkAliasDefinitions (options.bar.enable or {});
#
# # 'barbaz' has to be defined in the current module-set.
# config.foobar.paths = mkAliasDefinitions options.barbaz.paths;
# }
#
# Note, this is different than taking the value of the option and using it
# as a definition, as the new definition will not keep the mkOverride /
# mkDefault properties of the previous option.
#
mkAliasDefinitions = mkAliasAndWrapDefinitions id;
mkAliasAndWrapDefinitions = wrap: option:
mkMerge
(optional (isOption option && option.isDefined)
(wrap (mkMerge option.definitions)));
/* Compatibility. */
fixMergeModules = modules: args: evalModules { inherit modules args; check = false; };
}