312 lines
12 KiB
Nix
312 lines
12 KiB
Nix
with import ./lists.nix;
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with import ./trivial.nix;
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with import ./attrsets.nix;
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with import ./options.nix;
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with import ./debug.nix;
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with import ./types.nix;
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rec {
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/* Evaluate a set of modules. The result is a set of two
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attributes: ‘options’: the nested set of all option declarations,
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and ‘config’: the nested set of all option values. */
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evalModules = { modules, prefix ? [], args ? {}, check ? true }:
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let
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args' = args // result;
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closed = closeModules modules args';
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# Note: the list of modules is reversed to maintain backward
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# compatibility with the old module system. Not sure if this is
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# the most sensible policy.
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options = mergeModules prefix (reverseList closed);
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# Traverse options and extract the option values into the final
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# config set. At the same time, check whether all option
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# definitions have matching declarations.
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config = yieldConfig prefix options;
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yieldConfig = prefix: set:
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let res = removeAttrs (mapAttrs (n: v:
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if isOption v then v.value
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else yieldConfig (prefix ++ [n]) v) set) ["_definedNames"];
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in
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if check && set ? _definedNames then
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fold (m: res:
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fold (name: res:
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if hasAttr name set then res else throw "The option `${showOption (prefix ++ [name])}' defined in `${m.file}' does not exist.")
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res m.names)
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res set._definedNames
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else
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res;
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result = { inherit options config; };
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in result;
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/* Close a set of modules under the ‘imports’ relation. */
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closeModules = modules: args:
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let
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toClosureList = file: parentKey: imap (n: x:
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if isAttrs x || isFunction x then
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unifyModuleSyntax file "${parentKey}:anon-${toString n}" (applyIfFunction x args)
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else
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unifyModuleSyntax (toString x) (toString x) (applyIfFunction (import x) args));
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in
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builtins.genericClosure {
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startSet = toClosureList unknownModule "" modules;
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operator = m: toClosureList m.file m.key m.imports;
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};
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/* Massage a module into canonical form, that is, a set consisting
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of ‘options’, ‘config’ and ‘imports’ attributes. */
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unifyModuleSyntax = file: key: m:
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if m ? config || m ? options then
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let badAttrs = removeAttrs m ["imports" "options" "config" "key" "_file"]; in
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if badAttrs != {} then
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throw "Module `${key}' has an unsupported attribute `${head (attrNames badAttrs)}'."
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else
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{ file = m._file or file;
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key = toString m.key or key;
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imports = m.imports or [];
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options = m.options or {};
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config = m.config or {};
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}
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else
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{ 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 [];
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options = {};
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config = removeAttrs m ["key" "_file" "require" "imports"];
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};
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applyIfFunction = f: arg: if isFunction f then f arg else f;
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/* Merge a list of modules. This will recurse over the option
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declarations in all modules, combining them into a single set.
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At the same time, for each option declaration, it will merge the
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corresponding option definitions in all machines, returning them
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in the ‘value’ attribute of each option. */
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mergeModules = prefix: modules:
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mergeModules' prefix modules
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(concatMap (m: map (config: { inherit (m) file; inherit config; }) (pushDownProperties m.config)) modules);
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mergeModules' = prefix: options: configs:
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listToAttrs (map (name: {
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# We're descending into attribute ‘name’.
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inherit name;
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value =
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let
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loc = prefix ++ [name];
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# Get all submodules that declare ‘name’.
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decls = concatLists (map (m:
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if hasAttr name m.options
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then [ { inherit (m) file; options = getAttr name m.options; } ]
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else []
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) options);
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# Get all submodules that define ‘name’.
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defns = concatLists (map (m:
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if hasAttr name m.config
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then map (config: { inherit (m) file; inherit config; })
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(pushDownProperties (getAttr name m.config))
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else []
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) configs);
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nrOptions = count (m: isOption m.options) decls;
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# Process mkMerge and mkIf properties.
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defns' = concatMap (m:
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if hasAttr name m.config
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then map (m': { inherit (m) file; value = m'; }) (dischargeProperties (getAttr name m.config))
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else []
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) configs;
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in
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if nrOptions == length decls then
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let opt = fixupOptionType loc (mergeOptionDecls loc decls);
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in evalOptionValue loc opt defns'
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else if nrOptions != 0 then
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let
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firstOption = findFirst (m: isOption m.options) "" decls;
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firstNonOption = findFirst (m: !isOption m.options) "" decls;
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in
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throw "The option `${showOption loc}' in `${firstOption.file}' is a prefix of options in `${firstNonOption.file}'."
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else
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mergeModules' loc decls defns;
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}) (concatMap (m: attrNames m.options) options))
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// { _definedNames = map (m: { inherit (m) file; names = attrNames m.config; }) configs; };
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/* Merge multiple option declarations into a single declaration. In
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general, there should be only one declaration of each option.
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The exception is the ‘options’ attribute, which specifies
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sub-options. These can be specified multiple times to allow one
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module to add sub-options to an option declared somewhere else
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(e.g. multiple modules define sub-options for ‘fileSystems’). */
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mergeOptionDecls = loc: opts:
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fold (opt: res:
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if opt.options ? default && res ? default ||
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opt.options ? example && res ? example ||
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opt.options ? description && res ? description ||
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opt.options ? apply && res ? apply ||
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opt.options ? type && res ? type
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then
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throw "The option `${showOption loc}' in `${opt.file}' is already declared in ${showFiles res.declarations}."
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else
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opt.options // res //
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{ declarations = [opt.file] ++ res.declarations;
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options = if opt.options ? options then [(toList opt.options.options ++ res.options)] else [];
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}
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) { inherit loc; declarations = []; options = []; } opts;
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/* Merge all the definitions of an option to produce the final
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config value. */
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evalOptionValue = loc: opt: defs:
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let
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# Process mkOverride properties, adding in the default
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# value specified in the option declaration (if any).
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defsFinal = filterOverrides
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((if opt ? default then [{ file = head opt.declarations; value = mkOptionDefault opt.default; }] else []) ++ defs);
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files = map (def: def.file) defsFinal;
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# Type-check the remaining definitions, and merge them if
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# possible.
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merged =
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if defsFinal == [] then
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throw "The option `${showOption loc}' is used but not defined."
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else
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fold (def: res:
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if opt.type.check def.value then res
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else throw "The option value `${showOption loc}' in `${def.file}' is not a ${opt.type.name}.")
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(opt.type.merge loc defsFinal) defsFinal;
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# Finally, apply the ‘apply’ function to the merged
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# value. This allows options to yield a value computed
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# from the definitions.
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value = (opt.apply or id) merged;
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in opt //
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{ value = addErrorContext "while evaluating the option `${showOption loc}':" value;
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definitions = map (def: def.value) defsFinal;
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isDefined = defsFinal != [];
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inherit files;
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};
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/* Given a config set, expand mkMerge properties, and push down the
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mkIf properties into the children. The result is a list of
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config sets that do not have properties at top-level. For
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example,
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mkMerge [ { boot = set1; } (mkIf cond { boot = set2; services = set3; }) ]
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is transformed into
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[ { boot = set1; } { boot = mkIf cond set2; services mkIf cond set3; } ].
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This transform is the critical step that allows mkIf conditions
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to refer to the full configuration without creating an infinite
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recursion.
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*/
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pushDownProperties = cfg:
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if cfg._type or "" == "merge" then
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concatMap pushDownProperties cfg.contents
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else if cfg._type or "" == "if" then
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map (mapAttrs (n: v: mkIf cfg.condition v)) (pushDownProperties cfg.content)
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else if cfg._type or "" == "override" then
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map (mapAttrs (n: v: mkOverride cfg.priority v)) (pushDownProperties cfg.content)
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else
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[ cfg ];
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/* Given a config value, expand mkMerge properties, and discharge
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any mkIf conditions. That is, this is the place where mkIf
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conditions are actually evaluated. The result is a list of
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config values. For example, ‘mkIf false x’ yields ‘[]’,
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‘mkIf true x’ yields ‘[x]’, and
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mkMerge [ 1 (mkIf true 2) (mkIf true (mkIf false 3)) ]
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yields ‘[ 1 2 ]’.
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*/
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dischargeProperties = def:
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if def._type or "" == "merge" then
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concatMap dischargeProperties def.contents
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else if def._type or "" == "if" then
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if def.condition then
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dischargeProperties def.content
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else
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[ ]
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else
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[ def ];
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/* Given a list of config values, process the mkOverride properties,
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that is, return the values that have the highest (that is,
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numerically lowest) priority, and strip the mkOverride
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properties. For example,
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[ { file = "/1"; value = mkOverride 10 "a"; }
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{ file = "/2"; value = mkOverride 20 "b"; }
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{ file = "/3"; value = "z"; }
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{ file = "/4"; value = mkOverride 10 "d"; }
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]
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yields
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[ { file = "/1"; value = "a"; }
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{ file = "/4"; value = "d"; }
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]
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Note that "z" has the default priority 100.
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*/
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filterOverrides = defs:
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let
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defaultPrio = 100;
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getPrio = def: if def.value._type or "" == "override" then def.value.priority else defaultPrio;
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min = x: y: if builtins.lessThan x y then x else y;
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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;
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in concatMap (def: if getPrio def == highestPrio then [(strip def)] else []) defs;
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/* Hack for backward compatibility: convert options of type
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optionSet to configOf. FIXME: remove eventually. */
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fixupOptionType = loc: opt:
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let
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options' = opt.options or
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(throw "Option `${showOption loc'}' has type optionSet but has no option attribute.");
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coerce = x:
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if isFunction x then x
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else { config, ... }: { options = x; };
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options = map coerce (flatten options');
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f = tp:
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if tp.name == "option set" then types.submodule options
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else if tp.name == "attribute set of option sets" then types.attrsOf (types.submodule options)
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else if tp.name == "list or attribute set of option sets" then types.loaOf (types.submodule options)
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else if tp.name == "list of option sets" then types.listOf (types.submodule options)
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else if tp.name == "null or option set" then types.nullOr (types.submodule options)
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else tp;
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in opt // { type = f (opt.type or types.unspecified); };
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/* Properties. */
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mkIf = condition: content:
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{ _type = "if";
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inherit condition content;
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};
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mkAssert = assertion: message: content:
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mkIf
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(if assertion then true else throw "\nFailed assertion: ${message}")
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content;
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mkMerge = contents:
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{ _type = "merge";
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inherit contents;
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};
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mkOverride = priority: content:
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{ _type = "override";
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inherit priority content;
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};
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mkOptionDefault = mkOverride 1001; # priority of option defaults
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mkDefault = mkOverride 1000; # used in config sections of non-user modules to set a default
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mkForce = mkOverride 50;
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mkVMOverride = mkOverride 10; # used by ‘nixos-rebuild build-vm’
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mkFixStrictness = id; # obsolete, no-op
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# FIXME: Add mkOrder back in. It's not currently used anywhere in
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# NixOS, but it should be useful.
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/* Compatibility. */
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fixMergeModules = modules: args: evalModules { inherit modules args; check = false; };
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}
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