266 lines
9.0 KiB
Nix
266 lines
9.0 KiB
Nix
# Nixpkgs/NixOS option handling.
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{ lib }:
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let
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inherit (lib)
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all
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collect
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concatLists
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concatMap
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elemAt
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filter
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foldl'
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head
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isAttrs
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isBool
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isDerivation
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isFunction
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isInt
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isList
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isString
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length
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mapAttrs
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optional
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optionals
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take
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;
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inherit (lib.attrsets)
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optionalAttrs
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;
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inherit (lib.strings)
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concatMapStrings
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concatStringsSep
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;
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inherit (lib.types)
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mkOptionType
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;
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in
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rec {
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/* Returns true when the given argument is an option
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Type: isOption :: a -> bool
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Example:
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isOption 1 // => false
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isOption (mkOption {}) // => true
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*/
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isOption = lib.isType "option";
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/* Creates an Option attribute set. mkOption accepts an attribute set with the following keys:
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All keys default to `null` when not given.
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Example:
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mkOption { } // => { _type = "option"; }
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mkOption { defaultText = "foo"; } // => { _type = "option"; defaultText = "foo"; }
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*/
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mkOption =
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{
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# Default value used when no definition is given in the configuration.
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default ? null,
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# Textual representation of the default, for the manual.
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defaultText ? null,
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# Example value used in the manual.
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example ? null,
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# String describing the option.
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description ? null,
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# Related packages used in the manual (see `genRelatedPackages` in ../nixos/lib/make-options-doc/default.nix).
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relatedPackages ? null,
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# Option type, providing type-checking and value merging.
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type ? null,
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# Function that converts the option value to something else.
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apply ? null,
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# Whether the option is for NixOS developers only.
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internal ? null,
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# Whether the option shows up in the manual.
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visible ? null,
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# Whether the option can be set only once
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readOnly ? null,
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# Deprecated, used by types.optionSet.
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options ? null
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} @ attrs:
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attrs // { _type = "option"; };
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/* Creates an Option attribute set for a boolean value option i.e an
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option to be toggled on or off:
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Example:
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mkEnableOption "foo"
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=> { _type = "option"; default = false; description = "Whether to enable foo."; example = true; type = { ... }; }
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*/
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mkEnableOption =
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# Name for the created option
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name: mkOption {
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default = false;
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example = true;
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description = "Whether to enable ${name}.";
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type = lib.types.bool;
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};
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/* This option accepts anything, but it does not produce any result.
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This is useful for sharing a module across different module sets
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without having to implement similar features as long as the
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values of the options are not accessed. */
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mkSinkUndeclaredOptions = attrs: mkOption ({
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internal = true;
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visible = false;
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default = false;
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description = "Sink for option definitions.";
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type = mkOptionType {
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name = "sink";
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check = x: true;
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merge = loc: defs: false;
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};
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apply = x: throw "Option value is not readable because the option is not declared.";
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} // attrs);
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mergeDefaultOption = loc: defs:
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let list = getValues defs; in
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if length list == 1 then head list
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else if all isFunction list then x: mergeDefaultOption loc (map (f: f x) list)
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else if all isList list then concatLists list
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else if all isAttrs list then foldl' lib.mergeAttrs {} list
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else if all isBool list then foldl' lib.or false list
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else if all isString list then lib.concatStrings list
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else if all isInt list && all (x: x == head list) list then head list
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else throw "Cannot merge definitions of `${showOption loc}'. Definition values:${showDefs defs}";
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mergeOneOption = loc: defs:
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if defs == [] then abort "This case should never happen."
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else if length defs != 1 then
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throw "The unique option `${showOption loc}' is defined multiple times. Definition values:${showDefs defs}"
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else (head defs).value;
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/* "Merge" option definitions by checking that they all have the same value. */
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mergeEqualOption = loc: defs:
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if defs == [] then abort "This case should never happen."
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# Return early if we only have one element
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# This also makes it work for functions, because the foldl' below would try
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# to compare the first element with itself, which is false for functions
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else if length defs == 1 then (head defs).value
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else (foldl' (first: def:
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if def.value != first.value then
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throw "The option `${showOption loc}' has conflicting definition values:${showDefs [ first def ]}"
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else
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first) (head defs) defs).value;
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/* Extracts values of all "value" keys of the given list.
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Type: getValues :: [ { value :: a } ] -> [a]
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Example:
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getValues [ { value = 1; } { value = 2; } ] // => [ 1 2 ]
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getValues [ ] // => [ ]
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*/
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getValues = map (x: x.value);
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/* Extracts values of all "file" keys of the given list
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Type: getFiles :: [ { file :: a } ] -> [a]
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Example:
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getFiles [ { file = "file1"; } { file = "file2"; } ] // => [ "file1" "file2" ]
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getFiles [ ] // => [ ]
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*/
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getFiles = map (x: x.file);
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# Generate documentation template from the list of option declaration like
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# the set generated with filterOptionSets.
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optionAttrSetToDocList = optionAttrSetToDocList' [];
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optionAttrSetToDocList' = prefix: options:
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concatMap (opt:
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let
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docOption = rec {
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loc = opt.loc;
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name = showOption opt.loc;
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description = opt.description or (lib.warn "Option `${name}' has no description." "This option has no description.");
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declarations = filter (x: x != unknownModule) opt.declarations;
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internal = opt.internal or false;
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visible = opt.visible or true;
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readOnly = opt.readOnly or false;
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type = opt.type.description or null;
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}
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// optionalAttrs (opt ? example) { example = scrubOptionValue opt.example; }
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// optionalAttrs (opt ? default) { default = scrubOptionValue opt.default; }
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// optionalAttrs (opt ? defaultText) { default = opt.defaultText; }
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// optionalAttrs (opt ? relatedPackages && opt.relatedPackages != null) { inherit (opt) relatedPackages; };
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subOptions =
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let ss = opt.type.getSubOptions opt.loc;
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in if ss != {} then optionAttrSetToDocList' opt.loc ss else [];
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in
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[ docOption ] ++ optionals docOption.visible subOptions) (collect isOption options);
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/* This function recursively removes all derivation attributes from
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`x` except for the `name` attribute.
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This is to make the generation of `options.xml` much more
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efficient: the XML representation of derivations is very large
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(on the order of megabytes) and is not actually used by the
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manual generator.
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*/
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scrubOptionValue = x:
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if isDerivation x then
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{ type = "derivation"; drvPath = x.name; outPath = x.name; name = x.name; }
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else if isList x then map scrubOptionValue x
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else if isAttrs x then mapAttrs (n: v: scrubOptionValue v) (removeAttrs x ["_args"])
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else x;
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/* For use in the `example` option attribute. It causes the given
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text to be included verbatim in documentation. This is necessary
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for example values that are not simple values, e.g., functions.
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*/
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literalExample = text: { _type = "literalExample"; inherit text; };
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# Helper functions.
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/* Convert an option, described as a list of the option parts in to a
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safe, human readable version.
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Example:
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(showOption ["foo" "bar" "baz"]) == "foo.bar.baz"
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(showOption ["foo" "bar.baz" "tux"]) == "foo.bar.baz.tux"
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Placeholders will not be quoted as they are not actual values:
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(showOption ["foo" "*" "bar"]) == "foo.*.bar"
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(showOption ["foo" "<name>" "bar"]) == "foo.<name>.bar"
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Unlike attributes, options can also start with numbers:
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(showOption ["windowManager" "2bwm" "enable"]) == "windowManager.2bwm.enable"
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*/
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showOption = parts: let
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escapeOptionPart = part:
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let
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escaped = lib.strings.escapeNixString part;
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in if escaped == "\"${part}\""
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then part
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else escaped;
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in (concatStringsSep ".") (map escapeOptionPart parts);
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showFiles = files: concatStringsSep " and " (map (f: "`${f}'") files);
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showDefs = defs: concatMapStrings (def:
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let
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# Pretty print the value for display, if successful
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prettyEval = builtins.tryEval (lib.generators.toPretty {} def.value);
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# Split it into its lines
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lines = filter (v: ! isList v) (builtins.split "\n" prettyEval.value);
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# Only display the first 5 lines, and indent them for better visibility
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value = concatStringsSep "\n " (take 5 lines ++ optional (length lines > 5) "...");
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result =
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# Don't print any value if evaluating the value strictly fails
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if ! prettyEval.success then ""
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# Put it on a new line if it consists of multiple
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else if length lines > 1 then ":\n " + value
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else ": " + value;
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in "\n- In `${def.file}'${result}"
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) defs;
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unknownModule = "<unknown-file>";
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}
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