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Big cleanup of the NixOS module system

Browse Source 
The major changes are:

* The evaluation is now driven by the declared options.  In
  particular, this fixes the long-standing problem with lack of
  laziness of disabled option definitions.  Thus, a configuration like

    config = mkIf false {
      environment.systemPackages = throw "bla";
    };

  will now evaluate without throwing an error.  This also improves
  performance since we're not evaluating unused option definitions.

* The implementation of properties is greatly simplified.

* There is a new type constructor "submodule" that replaces
  "optionSet".  Unlike "optionSet", "submodule" gets its option
  declarations as an argument, making it more like "listOf" and other
  type constructors.  A typical use is:

    foo = mkOption {
      type = type.attrsOf (type.submodule (
        { config, ... }:
        { bar = mkOption { ... };
          xyzzy = mkOption { ... };
        }));
    };

  Existing uses of "optionSet" are automatically mapped to
  "submodule".

* Modules are now checked for unsupported attributes: you get an error
  if a module contains an attribute other than "config", "options" or
  "imports".

* The new implementation is faster and uses much less memory.
This commit is contained in:
Eelco Dolstra
2013-10-28 22:45:55 +01:00
parent f4dadc5df8
commit 0e333688ce
9 changed files with 294 additions and 974 deletions
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lib/modules.nix
+223 -357
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@@ -1,379 +1,245 @@
# NixOS module handling.
let lib = import ./default.nix; in
with { inherit (builtins) head; };
with import ./trivial.nix;
with import ./lists.nix;
with import ./misc.nix;
with import ./attrsets.nix;
with import ./options.nix;
with import ./properties.nix;
with import ./.. {};
with lib;
rec {
# Unfortunately this can also be a string.
isPath = x: !(
builtins.isFunction x
|| builtins.isAttrs x
|| builtins.isInt x
|| builtins.isBool x
|| builtins.isList x
);
importIfPath = path:
if isPath path then
import path
else
path;
applyIfFunction = f: arg:
if builtins.isFunction f then
f arg
else
f;
isModule = m:
(m ? config && isAttrs m.config && ! isOption m.config)
|| (m ? options && isAttrs m.options && ! isOption m.options);
# Convert module to a set which has imports / options and config
# attributes.
unifyModuleSyntax = m:
/* 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
delayedModule = delayProperties m;
getImports =
toList (rmProperties (delayedModule.require or []));
getImportedPaths = filter isPath getImports;
getImportedSets = filter (x: !isPath x) getImports;
getConfig =
removeAttrs delayedModule ["require" "key" "imports"];
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-${toString n}" (applyIfFunction x args)
else
unifyModuleSyntax (toString x) (applyIfFunction (import x) args);
toClosureList = imap (path: coerceToModule path);
in
if isModule m then
{ key = "<unknown location>"; } // m
builtins.genericClosure {
startSet = toClosureList modules;
operator = m: toClosureList m.imports;
};
/* Massage a module into canonical form, that is, a set consisting
of ‘options’, ‘config’ and ‘imports’ attributes. */
unifyModuleSyntax = key: m:
if m ? config || m ? options || m ? imports then
let badAttrs = removeAttrs m ["imports" "options" "config"]; in
if badAttrs != {} then
throw "Module `${key}' has an unsupported attribute `${head (attrNames badAttrs)}'. ${builtins.toXML m} "
else
{ key = "<unknown location>";
imports = (m.imports or []) ++ getImportedPaths;
config = getConfig;
} // (
if getImportedSets != [] then
assert length getImportedSets == 1;
{ options = head getImportedSets; }
{ inherit key;
imports = m.imports or [];
options = m.options or {};
config = m.config or {};
}
else
{ inherit key;
imports = m.require or [];
options = {};
config = m;
};
applyIfFunction = f: arg: if builtins.isFunction f then f arg else f;
/* Merge a list of modules. This will recurse over the option
declarations in all modules, combining them into a single set.
At the same time, for each option declaration, it will merge the
corresponding option definitions in all machines, returning them
in the ‘value’ attribute of each option. */
mergeModules = modules:
mergeModules' [] (map (m: m.options) modules) (concatMap (m: pushDownProperties m.config) modules);
mergeModules' = loc: options: configs:
zipAttrsWith (name: vals:
let loc' = loc ++ [name]; in
if all isOption vals then
let opt = fixupOptionType loc' (mergeOptionDecls loc' vals);
in evalOptionValue loc' opt (catAttrs name configs)
else if any isOption vals then
throw "There are options with the prefix `${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 `${showOption loc}' has multiple values (with no way to merge them)."
else
{}
);
unifyOptionModule = {key ? "<unknown location>"}: name: index: m: (args:
let
module = lib.applyIfFunction m args;
key_ = rec {
file = key;
option = name;
number = index;
outPath = key;
};
in if lib.isModule module then
{ key = key_; } // module
else
{ key = key_; options = module; }
);
moduleClosure = initModules: args:
let
moduleImport = origin: index: m:
let m' = applyIfFunction (importIfPath m) args;
in (unifyModuleSyntax m') // {
# used by generic closure to avoid duplicated imports.
key =
if isPath m then m
else m'.key or (newModuleName origin index);
};
getImports = m: m.imports or [];
newModuleName = origin: index:
"${origin.key}:<import-${toString index}>";
topLevel = {
key = "<top-level>";
throw "A value of the option `${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 != [];
};
in
(lazyGenericClosure {
startSet = imap (moduleImport topLevel) initModules;
operator = m: imap (moduleImport m) (getImports m);
});
/* 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; }) ]
moduleApply = funs: module:
lib.mapAttrs (name: value:
if builtins.hasAttr name funs then
let fun = lib.getAttr name funs; in
fun value
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
value
) module;
# Handle mkMerge function left behind after a delay property.
moduleFlattenMerge = module:
if module ? config &&
isProperty module.config &&
isMerge module.config.property
then
(map (cfg: { key = module.key; config = cfg; }) module.config.content)
++ [ (module // { config = {}; }) ]
[ ]
else
[ module ];
[ 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,
# Handle mkMerge attributes which are left behind by previous delay
# properties and convert them into a list of modules. Delay properties
# inside the config attribute of a module and create a second module if a
# mkMerge attribute was left behind.
#
# Module -> [ Module ]
delayModule = module:
map (moduleApply { config = delayProperties; }) (moduleFlattenMerge module);
[ (mkOverride 10 "a") (mkOverride 20 "b") "z" (mkOverride 10 "d") ]
evalDefinitions = opt: values:
if opt.type.delayOnGlobalEval or false then
map (delayPropertiesWithIter opt.type.iter opt.name)
(evalLocalProperties values)
else
evalProperties values;
selectModule = name: m:
{ inherit (m) key;
} // (
if m ? options && builtins.hasAttr name m.options then
{ options = lib.getAttr name m.options; }
else {}
) // (
if m ? config && builtins.hasAttr name m.config then
{ config = lib.getAttr name m.config; }
else {}
);
filterModules = name: modules:
filter (m: m ? config || m ? options) (
map (selectModule name) modules
);
modulesNames = modules:
lib.concatMap (m: []
++ optionals (m ? options) (lib.attrNames m.options)
++ optionals (m ? config) (lib.attrNames m.config)
) modules;
moduleZip = funs: modules:
lib.mapAttrs (name: fun:
fun (catAttrs name modules)
) funs;
moduleMerge = path: modules_:
yields ‘[ "a" "d" ]’. Note that "z" has the default priority 100.
*/
filterOverrides = defs:
let
addName = name:
if path == "" then name else path + "." + name;
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;
modules = concatLists (map delayModule modules_);
modulesOf = name: filterModules name modules;
declarationsOf = name: filter (m: m ? options) (modulesOf name);
definitionsOf = name: filter (m: m ? config ) (modulesOf name);
recurseInto = name:
moduleMerge (addName name) (modulesOf name);
recurseForOption = name: modules: args:
moduleMerge name (
moduleClosure modules args
);
errorSource = modules:
"The error may come from the following files:\n" + (
lib.concatStringsSep "\n" (
map (m:
if m ? key then toString m.key else "<unknown location>"
) modules
)
);
eol = "\n";
allNames = modulesNames modules;
getResults = m:
let fetchResult = s: mapAttrs (n: v: v.result) s; in {
options = fetchResult m.options;
config = fetchResult m.config;
};
endRecursion = { options = {}; config = {}; };
in if modules == [] then endRecursion else
getResults (fix (crossResults: moduleZip {
options = lib.zipWithNames allNames (name: values: rec {
config = lib.getAttr name crossResults.config;
declarations = declarationsOf name;
declarationSources =
map (m: {
source = m.key;
}) declarations;
hasOptions = values != [];
isOption = any lib.isOption values;
decls = # add location to sub-module options.
map (m:
mapSubOptions
(unifyOptionModule {inherit (m) key;} name)
m.options
) declarations;
decl =
lib.addErrorContext "${eol
}while enhancing option `${addName name}':${eol
}${errorSource declarations}${eol
}" (
addOptionMakeUp
{ name = addName name; recurseInto = recurseForOption; }
(mergeOptionDecls decls)
);
value = decl // (with config; {
inherit (config) isNotDefined;
isDefined = ! isNotDefined;
declarations = declarationSources;
definitions = definitionSources;
config = strictResult;
});
recurse = (recurseInto name).options;
result =
if isOption then value
else if !hasOptions then {}
else if all isAttrs values then recurse
else
throw "${eol
}Unexpected type where option declarations are expected.${eol
}${errorSource declarations}${eol
}";
});
config = lib.zipWithNames allNames (name: values_: rec {
option = lib.getAttr name crossResults.options;
definitions = definitionsOf name;
definitionSources =
map (m: {
source = m.key;
value = m.config;
}) definitions;
values = values_ ++
optionals (option.isOption && option.decl ? extraConfigs)
option.decl.extraConfigs;
defs = evalDefinitions option.decl values;
isNotDefined = defs == [];
value =
lib.addErrorContext "${eol
}while evaluating the option `${addName name}':${eol
}${errorSource (modulesOf name)}${eol
}" (
let opt = option.decl; in
opt.apply (
if isNotDefined then
opt.default or (throw "Option `${addName name}' not defined and does not have a default value.")
else opt.merge defs
)
);
strictResult = builtins.tryEval (builtins.toXML value);
recurse = (recurseInto name).config;
configIsAnOption = v: isOption (rmProperties v);
errConfigIsAnOption =
let badModules = filter (m: configIsAnOption m.config) definitions; in
"${eol
}Option ${addName name} is defined in the configuration section.${eol
}${errorSource badModules}${eol
}";
errDefinedWithoutDeclaration =
let badModules = definitions; in
"${eol
}Option '${addName name}' defined without option declaration.${eol
}${errorSource badModules}${eol
}";
result =
if option.isOption then value
else if !option.hasOptions then throw errDefinedWithoutDeclaration
else if any configIsAnOption values then throw errConfigIsAnOption
else if all isAttrs values then recurse
# plain value during the traversal
else throw errDefinedWithoutDeclaration;
});
} modules));
fixMergeModules = initModules: {...}@args:
lib.fix (result:
# This trick avoids an infinite loop because names of attribute
# are know and it is not required to evaluate the result of
# moduleMerge to know which attributes are present as arguments.
let module = { inherit (result) options config; }; in
moduleMerge "" (
moduleClosure initModules (module // args)
)
);
# Visit all definitions to raise errors related to undeclared options.
checkModule = path: {config, options, ...}@m:
/* Hack for backward compatibility: convert options of type
optionSet to configOf. FIXME: remove eventually. */
fixupOptionType = loc: opt:
let
eol = "\n";
addName = name:
if path == "" then name else path + "." + name;
in
if lib.isOption options then
if options ? options then
options.type.fold
(cfg: res: res && checkModule (options.type.docPath path) cfg._args)
true config
else
true
else if isAttrs options && lib.attrNames m.options != [] then
all (name:
lib.addErrorContext "${eol
}while checking the attribute `${addName name}':${eol
}" (checkModule (addName name) (selectModule name m))
) (lib.attrNames m.config)
else
builtins.trace "try to evaluate config ${lib.showVal config}."
false;
options' = opt.options or
(throw "Option `${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.
}