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. */ evalModules = { modules, prefix ? [], args ? {}, check ? true }: let args' = args // { lib = import ./.; } // 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 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. 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 check && set ? _definedNames then fold (m: res: fold (name: res: if set ? ${name} then res else throw "The option `${showOption (prefix ++ [name])}' defined in `${m.file}' does not exist.") res m.names) res set._definedNames else res; result = { inherit options config; }; in result; /* Close a set of modules under the ‘imports’ relation. */ closeModules = modules: args: let toClosureList = file: parentKey: imap (n: x: if isAttrs x || isFunction x then unifyModuleSyntax file "${parentKey}:anon-${toString n}" (applyIfFunction x args) else unifyModuleSyntax (toString x) (toString x) (applyIfFunction (import x) args)); in builtins.genericClosure { startSet = toClosureList unknownModule "" modules; operator = m: toClosureList m.file m.key m.imports; }; /* Massage a module into canonical form, that is, a set consisting of ‘options’, ‘config’ and ‘imports’ attributes. */ unifyModuleSyntax = file: key: m: if m ? config || m ? options then let badAttrs = removeAttrs m ["imports" "options" "config" "key" "_file"]; in if badAttrs != {} then throw "Module `${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; key = toString m.key or key; imports = m.imports or []; options = m.options or {}; config = m.config or {}; } else { file = m._file or file; key = toString m.key or key; imports = m.require or [] ++ m.imports or []; options = {}; config = removeAttrs m ["key" "_file" "require" "imports"]; }; applyIfFunction = f: arg: if 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 = 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 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; # Process mkMerge and mkIf properties. defns' = concatMap (m: if m.config ? ${name} then map (m': { inherit (m) file; value = m'; }) (dischargeProperties m.config.${name}) 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 `${firstNonOption.file}'." else mergeModules' loc decls defns; }) (concatMap (m: attrNames m.options) options)) // { _definedNames = map (m: { inherit (m) file; names = attrNames m.config; }) configs; }; /* Merge multiple option declarations into a single declaration. In general, there should be only one declaration of each option. The exception is the ‘options’ attribute, which specifies sub-options. These can be specified multiple times to allow one module to add sub-options to an option declared somewhere else (e.g. multiple modules define sub-options for ‘fileSystems’). 'loc' is the list of attribute names where the option is located. 'opts' is a list of modules. Each module has an options attribute which correspond to the definition of 'loc' in 'opt.file'. */ mergeOptionDecls = loc: opts: fold (opt: res: if opt.options ? default && res ? default || opt.options ? example && res ? example || opt.options ? description && res ? description || opt.options ? apply && res ? apply || # Accept to merge options which have identical types. opt.options ? type && res ? type && opt.options.type.name != res.type.name then throw "The option `${showOption loc}' in `${opt.file}' is already declared in ${showFiles res.declarations}." else let /* Add the modules of the current option to the list of modules already collected. The options attribute except either a list of submodules or a submodule. For each submodule, we add the file of the current option declaration as the file use for the submodule. If the submodule defines any filename, then we ignore the enclosing option file. */ options' = toList opt.options.options; addModuleFile = m: if isFunction m then args: { _file = opt.file; } // (m args) else { _file = opt.file; } // m; coerceOption = file: opt: if isFunction opt then args: { _file = file; } // (opt args) else { _file = file; options = opt; }; getSubModules = opt.options.type.getSubModules or null; submodules = if getSubModules != null then map addModuleFile getSubModules ++ res.options else if opt.options ? options then map (coerceOption opt.file) options' ++ res.options else res.options; in opt.options // res // { declarations = [opt.file] ++ res.declarations; options = submodules; } ) { inherit loc; declarations = []; options = []; } opts; /* Merge all the definitions of an option to produce the final config value. */ evalOptionValue = loc: opt: defs: let # Process mkOverride properties, adding in the default # value specified in the option declaration (if any). defsFinal' = filterOverrides ((if opt ? default then [{ file = head opt.declarations; value = mkOptionDefault opt.default; }] else []) ++ defs); # Sort mkOrder properties. defsFinal = # Avoid sorting if we don't have to. if any (def: def.value._type or "" == "order") defsFinal' then sortProperties defsFinal' else defsFinal'; files = map (def: def.file) defsFinal; # Type-check the remaining definitions, and merge them if # possible. merged = if defsFinal == [] then throw "The option `${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 ${opt.type.name}.") (opt.type.merge loc defsFinal) defsFinal; # Finally, apply the ‘apply’ function to the merged # value. This allows options to yield a value computed # from the definitions. value = (opt.apply or id) merged; in opt // { value = addErrorContext "while evaluating the option `${showOption loc}':" value; definitions = map (def: def.value) defsFinal; isDefined = defsFinal != []; inherit files; }; /* Given a config set, expand mkMerge properties, and push down the 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) else if cfg._type or "" == "override" then map (mapAttrs (n: v: mkOverride cfg.priority v)) (pushDownProperties cfg.content) 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 ]; /* 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; /* 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 mkOrder = priority: content: { _type = "order"; inherit priority content; }; mkBefore = mkOrder 500; mkAfter = mkOrder 1500; /* Compatibility. */ fixMergeModules = modules: args: evalModules { inherit modules args; check = false; }; }