nixpkgs/lib/modules.nix
2013-10-28 22:45:57 +01:00

296 lines
12 KiB
Nix
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

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, prefix ? [], args ? {}, check ? true }:
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 check prefix (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
toClosureList = file: parentKey: imap (n: x:
if isAttrs x || builtins.isFunction x then
unifyModuleSyntax file "${parentKey}:anon-${toString n}" (applyIfFunction x args)
else
unifyModuleSyntax (toString x) (toString x) (applyIfFunction (import x) args));
in
builtins.genericClosure {
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:
if m ? config || m ? options then
let badAttrs = removeAttrs m ["imports" "options" "config" "key"]; in
if badAttrs != {} then
throw "Module `${key}' has an unsupported attribute `${head (attrNames badAttrs)}'."
else
{ inherit file;
key = m.key or key;
imports = m.imports or [];
options = m.options or {};
config = m.config or {};
}
else
{ inherit file;
key = m.key or key;
imports = m.require or [] ++ m.imports or [];
options = {};
config = removeAttrs m ["key" "require" "imports"];
};
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 = check: prefix: modules:
mergeModules' check prefix modules
(concatMap (m: map (config: { inherit (m) file; inherit config; }) (pushDownProperties m.config)) modules);
mergeModules' = check: prefix: options: configs:
let
declaredNames = concatMap (m: attrNames m.options) options;
declaredNames' = listToAttrs (map (n: { name = n; value = 1; }) declaredNames);
checkDefinedNames = res: fold (m: res: fold (n: res:
if hasAttr n declaredNames' then res else
throw "The option `${showOption (prefix ++ [n])}' defined in `${m.file}' does not exist."
) res (attrNames m.config)) res configs;
in (if check then checkDefinedNames else id) (listToAttrs (map (name: {
# We're descending into attribute name.
inherit name;
value =
let
loc = prefix ++ [name];
# Get all submodules that declare name.
decls = concatLists (map (m:
if hasAttr name m.options
then [ { inherit (m) file; options = getAttr name m.options; } ]
else []
) options);
# Get all submodules that define name.
defns = concatLists (map (m:
if hasAttr name m.config
then map (config: { inherit (m) file; inherit config; })
(pushDownProperties (getAttr name m.config))
else []
) configs);
nrOptions = count (m: isOption m.options) decls;
# Process mkMerge and mkIf properties.
defns' = concatMap (m:
if hasAttr name m.config
then map (m': { inherit (m) file; value = m'; }) (dischargeProperties (getAttr name m.config))
else []
) configs;
in
if nrOptions == length decls then
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
throw "The option `${showOption loc}' in `${firstOption.file}' is a prefix of options in `${firstNonOption.file}'."
else
mergeModules' check loc decls defns;
}) declaredNames));
/* Merge multiple option declarations into a single declaration. In
general, there should be only one declaration of each option.
The exception is the options attribute, which specifies
sub-options. These can be specified multiple times to allow one
module to add sub-options to an option declared somewhere else
(e.g. multiple modules define sub-options for fileSystems). */
mergeOptionDecls = loc: opts:
fold (opt: res:
if opt.options ? default && res ? default ||
opt.options ? example && res ? example ||
opt.options ? description && res ? description ||
opt.options ? merge && res ? merge || # FIXME: remove merge
opt.options ? apply && res ? apply ||
opt.options ? type && res ? type
then
throw "The option `${showOption loc}' in `${opt.file}' is already declared in ${concatStringsSep " and " (map (d: "`${d}'") res.declarations)}."
else
opt.options // res //
{ declarations = [opt.file] ++ res.declarations;
options = if opt.options ? options then [(toList opt.options.options ++ res.options)] else [];
}
) { inherit loc; declarations = []; options = []; } opts;
/* Merge all the definitions of an option to produce the final
config value. */
evalOptionValue = loc: opt: defs:
let
# Process mkOverride properties, adding in the default
# value specified in the option declaration (if any).
defsFinal = filterOverrides'
((if opt ? default then [{ file = head opt.declarations; value = mkOptionDefault opt.default; }] else []) ++ defs);
# Type-check the remaining definitions, and merge them if
# possible.
merged =
if defsFinal == [] then
throw "The option `${showOption loc}' is used but not defined."
else
fold (def: res:
if opt.type.check def.value then res
else throw "The option value `${showOption loc}' in `${def.file}' is not a ${opt.type.name}.")
(opt.type.merge' { prefix = loc; } (map (m: m.value) defsFinal)) defsFinal;
# Finally, apply the apply function to the merged
# value. This allows options to yield a value computed
# from the definitions.
value = (opt.apply or id) merged;
in opt //
{ value = addErrorContext "while evaluating the option `${showOption loc}':" value;
definitions = map (def: def.value) 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 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,
[ { file = "/1"; value = mkOverride 10 "a"; }
{ file = "/2"; value = mkOverride 20 "b"; }
{ file = "/3"; value = "z"; }
{ file = "/4"; value = mkOverride 10 "d"; }
]
yields
[ { file = "/1"; value = "a"; }
{ file = "/4"; value = "d"; }
]
Note that "z" has the default priority 100.
*/
filterOverrides' = defs:
let
defaultPrio = 100;
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;
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;
/* For use in options like environment.variables. */
filterOverrides = defs: map (def: def.value) (filterOverrides' (map (def: { value = def; }) 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.
}