afa6c51f27
Nix can perform static scope checking, but whenever code is inside a `with` expression, the analysis breaks down, because it can't know statically what's in the attribute set whose attributes were brought into scope. In those cases, Nix has to assume that everything works out. Except it doesnt. Removing `with` from lib/ revealed an undefined variable in an error message. If that doesn't convince you that we're better off without `with`, I can tell you that this PR results in a 3% evaluation performance improvement because Nix can look up local variables by index. This adds up with applications like the module system. Furthermore, removing `with` makes the binding site of each variable obvious, which helps with comprehension.
240 lines
8.9 KiB
Nix
240 lines
8.9 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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isAttrs isBool isDerivation isFunction isInt isList isString
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all collect concatMap concatLists elemAt filter foldl' head length mapAttrs optionals optional take
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;
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inherit (lib.attrsets) optionalAttrs;
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inherit (lib.strings) concatMapStrings concatStringsSep;
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inherit (lib.types) mkOptionType;
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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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