mirror of
https://github.com/NixOS/nixpkgs.git
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631 lines
20 KiB
Nix
631 lines
20 KiB
Nix
{ lib }:
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# Operations on attribute sets.
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let
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inherit (builtins) head tail length;
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inherit (lib.trivial) id;
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inherit (lib.strings) concatStringsSep concatMapStringsSep escapeNixIdentifier sanitizeDerivationName;
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inherit (lib.lists) foldr foldl' concatMap concatLists elemAt all partition groupBy take foldl;
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in
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rec {
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inherit (builtins) attrNames listToAttrs hasAttr isAttrs getAttr;
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/* Return an attribute from nested attribute sets.
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Example:
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x = { a = { b = 3; }; }
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attrByPath ["a" "b"] 6 x
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=> 3
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attrByPath ["z" "z"] 6 x
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=> 6
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*/
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attrByPath = attrPath: default: e:
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let attr = head attrPath;
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in
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if attrPath == [] then e
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else if e ? ${attr}
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then attrByPath (tail attrPath) default e.${attr}
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else default;
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/* Return if an attribute from nested attribute set exists.
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Example:
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x = { a = { b = 3; }; }
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hasAttrByPath ["a" "b"] x
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=> true
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hasAttrByPath ["z" "z"] x
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=> false
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*/
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hasAttrByPath = attrPath: e:
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let attr = head attrPath;
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in
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if attrPath == [] then true
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else if e ? ${attr}
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then hasAttrByPath (tail attrPath) e.${attr}
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else false;
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/* Return nested attribute set in which an attribute is set.
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Example:
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setAttrByPath ["a" "b"] 3
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=> { a = { b = 3; }; }
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*/
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setAttrByPath = attrPath: value:
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let
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len = length attrPath;
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atDepth = n:
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if n == len
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then value
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else { ${elemAt attrPath n} = atDepth (n + 1); };
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in atDepth 0;
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/* Like `attrByPath' without a default value. If it doesn't find the
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path it will throw.
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Example:
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x = { a = { b = 3; }; }
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getAttrFromPath ["a" "b"] x
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=> 3
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getAttrFromPath ["z" "z"] x
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=> error: cannot find attribute `z.z'
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*/
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getAttrFromPath = attrPath:
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let errorMsg = "cannot find attribute `" + concatStringsSep "." attrPath + "'";
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in attrByPath attrPath (abort errorMsg);
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/* Update or set specific paths of an attribute set.
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Takes a list of updates to apply and an attribute set to apply them to,
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and returns the attribute set with the updates applied. Updates are
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represented as { path = ...; update = ...; } values, where `path` is a
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list of strings representing the attribute path that should be updated,
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and `update` is a function that takes the old value at that attribute path
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as an argument and returns the new
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value it should be.
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Properties:
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- Updates to deeper attribute paths are applied before updates to more
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shallow attribute paths
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- Multiple updates to the same attribute path are applied in the order
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they appear in the update list
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- If any but the last `path` element leads into a value that is not an
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attribute set, an error is thrown
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- If there is an update for an attribute path that doesn't exist,
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accessing the argument in the update function causes an error, but
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intermediate attribute sets are implicitly created as needed
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Example:
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updateManyAttrsByPath [
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{
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path = [ "a" "b" ];
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update = old: { d = old.c; };
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}
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{
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path = [ "a" "b" "c" ];
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update = old: old + 1;
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}
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{
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path = [ "x" "y" ];
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update = old: "xy";
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}
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] { a.b.c = 0; }
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=> { a = { b = { d = 1; }; }; x = { y = "xy"; }; }
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*/
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updateManyAttrsByPath = let
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# When recursing into attributes, instead of updating the `path` of each
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# update using `tail`, which needs to allocate an entirely new list,
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# we just pass a prefix length to use and make sure to only look at the
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# path without the prefix length, so that we can reuse the original list
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# entries.
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go = prefixLength: hasValue: value: updates:
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let
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# Splits updates into ones on this level (split.right)
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# And ones on levels further down (split.wrong)
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split = partition (el: length el.path == prefixLength) updates;
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# Groups updates on further down levels into the attributes they modify
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nested = groupBy (el: elemAt el.path prefixLength) split.wrong;
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# Applies only nested modification to the input value
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withNestedMods =
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# Return the value directly if we don't have any nested modifications
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if split.wrong == [] then
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if hasValue then value
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else
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# Throw an error if there is no value. This `head` call here is
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# safe, but only in this branch since `go` could only be called
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# with `hasValue == false` for nested updates, in which case
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# it's also always called with at least one update
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let updatePath = (head split.right).path; in
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throw
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( "updateManyAttrsByPath: Path '${showAttrPath updatePath}' does "
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+ "not exist in the given value, but the first update to this "
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+ "path tries to access the existing value.")
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else
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# If there are nested modifications, try to apply them to the value
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if ! hasValue then
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# But if we don't have a value, just use an empty attribute set
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# as the value, but simplify the code a bit
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mapAttrs (name: go (prefixLength + 1) false null) nested
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else if isAttrs value then
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# If we do have a value and it's an attribute set, override it
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# with the nested modifications
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value //
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mapAttrs (name: go (prefixLength + 1) (value ? ${name}) value.${name}) nested
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else
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# However if it's not an attribute set, we can't apply the nested
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# modifications, throw an error
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let updatePath = (head split.wrong).path; in
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throw
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( "updateManyAttrsByPath: Path '${showAttrPath updatePath}' needs to "
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+ "be updated, but path '${showAttrPath (take prefixLength updatePath)}' "
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+ "of the given value is not an attribute set, so we can't "
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+ "update an attribute inside of it.");
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# We get the final result by applying all the updates on this level
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# after having applied all the nested updates
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# We use foldl instead of foldl' so that in case of multiple updates,
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# intermediate values aren't evaluated if not needed
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in foldl (acc: el: el.update acc) withNestedMods split.right;
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in updates: value: go 0 true value updates;
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/* Return the specified attributes from a set.
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Example:
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attrVals ["a" "b" "c"] as
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=> [as.a as.b as.c]
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*/
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attrVals = nameList: set: map (x: set.${x}) nameList;
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/* Return the values of all attributes in the given set, sorted by
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attribute name.
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Example:
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attrValues {c = 3; a = 1; b = 2;}
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=> [1 2 3]
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*/
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attrValues = builtins.attrValues or (attrs: attrVals (attrNames attrs) attrs);
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/* Given a set of attribute names, return the set of the corresponding
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attributes from the given set.
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Example:
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getAttrs [ "a" "b" ] { a = 1; b = 2; c = 3; }
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=> { a = 1; b = 2; }
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*/
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getAttrs = names: attrs: genAttrs names (name: attrs.${name});
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/* Collect each attribute named `attr' from a list of attribute
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sets. Sets that don't contain the named attribute are ignored.
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Example:
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catAttrs "a" [{a = 1;} {b = 0;} {a = 2;}]
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=> [1 2]
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*/
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catAttrs = builtins.catAttrs or
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(attr: l: concatLists (map (s: if s ? ${attr} then [s.${attr}] else []) l));
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/* Filter an attribute set by removing all attributes for which the
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given predicate return false.
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Example:
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filterAttrs (n: v: n == "foo") { foo = 1; bar = 2; }
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=> { foo = 1; }
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*/
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filterAttrs = pred: set:
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listToAttrs (concatMap (name: let v = set.${name}; in if pred name v then [(nameValuePair name v)] else []) (attrNames set));
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/* Filter an attribute set recursively by removing all attributes for
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which the given predicate return false.
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Example:
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filterAttrsRecursive (n: v: v != null) { foo = { bar = null; }; }
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=> { foo = {}; }
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*/
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filterAttrsRecursive = pred: set:
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listToAttrs (
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concatMap (name:
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let v = set.${name}; in
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if pred name v then [
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(nameValuePair name (
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if isAttrs v then filterAttrsRecursive pred v
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else v
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))
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] else []
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) (attrNames set)
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);
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/* Apply fold functions to values grouped by key.
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Example:
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foldAttrs (n: a: [n] ++ a) [] [{ a = 2; } { a = 3; }]
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=> { a = [ 2 3 ]; }
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*/
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foldAttrs = op: nul:
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foldr (n: a:
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foldr (name: o:
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o // { ${name} = op n.${name} (a.${name} or nul); }
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) a (attrNames n)
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) {};
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/* Recursively collect sets that verify a given predicate named `pred'
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from the set `attrs'. The recursion is stopped when the predicate is
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verified.
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Type:
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collect ::
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(AttrSet -> Bool) -> AttrSet -> [x]
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Example:
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collect isList { a = { b = ["b"]; }; c = [1]; }
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=> [["b"] [1]]
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collect (x: x ? outPath)
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{ a = { outPath = "a/"; }; b = { outPath = "b/"; }; }
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=> [{ outPath = "a/"; } { outPath = "b/"; }]
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*/
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collect = pred: attrs:
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if pred attrs then
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[ attrs ]
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else if isAttrs attrs then
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concatMap (collect pred) (attrValues attrs)
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else
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[];
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/* Return the cartesian product of attribute set value combinations.
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Example:
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cartesianProductOfSets { a = [ 1 2 ]; b = [ 10 20 ]; }
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=> [
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{ a = 1; b = 10; }
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{ a = 1; b = 20; }
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{ a = 2; b = 10; }
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{ a = 2; b = 20; }
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]
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*/
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cartesianProductOfSets = attrsOfLists:
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foldl' (listOfAttrs: attrName:
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concatMap (attrs:
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map (listValue: attrs // { ${attrName} = listValue; }) attrsOfLists.${attrName}
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) listOfAttrs
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) [{}] (attrNames attrsOfLists);
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/* Utility function that creates a {name, value} pair as expected by
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builtins.listToAttrs.
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Example:
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nameValuePair "some" 6
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=> { name = "some"; value = 6; }
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*/
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nameValuePair = name: value: { inherit name value; };
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/* Apply a function to each element in an attribute set. The
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function takes two arguments --- the attribute name and its value
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--- and returns the new value for the attribute. The result is a
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new attribute set.
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Example:
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mapAttrs (name: value: name + "-" + value)
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{ x = "foo"; y = "bar"; }
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=> { x = "x-foo"; y = "y-bar"; }
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*/
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mapAttrs = builtins.mapAttrs or
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(f: set:
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listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set)));
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/* Like `mapAttrs', but allows the name of each attribute to be
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changed in addition to the value. The applied function should
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return both the new name and value as a `nameValuePair'.
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Example:
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mapAttrs' (name: value: nameValuePair ("foo_" + name) ("bar-" + value))
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{ x = "a"; y = "b"; }
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=> { foo_x = "bar-a"; foo_y = "bar-b"; }
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*/
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mapAttrs' = f: set:
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listToAttrs (map (attr: f attr set.${attr}) (attrNames set));
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/* Call a function for each attribute in the given set and return
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the result in a list.
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Type:
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mapAttrsToList ::
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(String -> a -> b) -> AttrSet -> [b]
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Example:
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mapAttrsToList (name: value: name + value)
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{ x = "a"; y = "b"; }
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=> [ "xa" "yb" ]
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*/
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mapAttrsToList = f: attrs:
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map (name: f name attrs.${name}) (attrNames attrs);
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/* Like `mapAttrs', except that it recursively applies itself to
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attribute sets. Also, the first argument of the argument
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function is a *list* of the names of the containing attributes.
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Type:
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mapAttrsRecursive ::
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([String] -> a -> b) -> AttrSet -> AttrSet
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Example:
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mapAttrsRecursive (path: value: concatStringsSep "-" (path ++ [value]))
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{ n = { a = "A"; m = { b = "B"; c = "C"; }; }; d = "D"; }
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=> { n = { a = "n-a-A"; m = { b = "n-m-b-B"; c = "n-m-c-C"; }; }; d = "d-D"; }
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*/
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mapAttrsRecursive = mapAttrsRecursiveCond (as: true);
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/* Like `mapAttrsRecursive', but it takes an additional predicate
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function that tells it whether to recurse into an attribute
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set. If it returns false, `mapAttrsRecursiveCond' does not
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recurse, but does apply the map function. If it returns true, it
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does recurse, and does not apply the map function.
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Type:
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mapAttrsRecursiveCond ::
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(AttrSet -> Bool) -> ([String] -> a -> b) -> AttrSet -> AttrSet
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Example:
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# To prevent recursing into derivations (which are attribute
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# sets with the attribute "type" equal to "derivation"):
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mapAttrsRecursiveCond
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(as: !(as ? "type" && as.type == "derivation"))
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(x: ... do something ...)
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attrs
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*/
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mapAttrsRecursiveCond = cond: f: set:
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let
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recurse = path:
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let
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g =
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name: value:
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if isAttrs value && cond value
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then recurse (path ++ [name]) value
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else f (path ++ [name]) value;
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in mapAttrs g;
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in recurse [] set;
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/* Generate an attribute set by mapping a function over a list of
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attribute names.
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Example:
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genAttrs [ "foo" "bar" ] (name: "x_" + name)
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=> { foo = "x_foo"; bar = "x_bar"; }
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*/
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genAttrs = names: f:
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listToAttrs (map (n: nameValuePair n (f n)) names);
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|
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/* Check whether the argument is a derivation. Any set with
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{ type = "derivation"; } counts as a derivation.
|
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|
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Example:
|
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nixpkgs = import <nixpkgs> {}
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isDerivation nixpkgs.ruby
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=> true
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isDerivation "foobar"
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=> false
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*/
|
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isDerivation = x: x.type or null == "derivation";
|
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|
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/* Converts a store path to a fake derivation. */
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toDerivation = path:
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let
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path' = builtins.storePath path;
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res =
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{ type = "derivation";
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name = sanitizeDerivationName (builtins.substring 33 (-1) (baseNameOf path'));
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outPath = path';
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outputs = [ "out" ];
|
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out = res;
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outputName = "out";
|
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};
|
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in res;
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|
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|
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/* If `cond' is true, return the attribute set `as',
|
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otherwise an empty attribute set.
|
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|
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Example:
|
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optionalAttrs (true) { my = "set"; }
|
||
=> { my = "set"; }
|
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optionalAttrs (false) { my = "set"; }
|
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=> { }
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*/
|
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optionalAttrs = cond: as: if cond then as else {};
|
||
|
||
|
||
/* Merge sets of attributes and use the function f to merge attributes
|
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values.
|
||
|
||
Example:
|
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zipAttrsWithNames ["a"] (name: vs: vs) [{a = "x";} {a = "y"; b = "z";}]
|
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=> { a = ["x" "y"]; }
|
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*/
|
||
zipAttrsWithNames = names: f: sets:
|
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listToAttrs (map (name: {
|
||
inherit name;
|
||
value = f name (catAttrs name sets);
|
||
}) names);
|
||
|
||
/* Implementation note: Common names appear multiple times in the list of
|
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names, hopefully this does not affect the system because the maximal
|
||
laziness avoid computing twice the same expression and listToAttrs does
|
||
not care about duplicated attribute names.
|
||
|
||
Example:
|
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zipAttrsWith (name: values: values) [{a = "x";} {a = "y"; b = "z";}]
|
||
=> { a = ["x" "y"]; b = ["z"] }
|
||
*/
|
||
zipAttrsWith =
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||
builtins.zipAttrsWith or (f: sets: zipAttrsWithNames (concatMap attrNames sets) f sets);
|
||
/* Like `zipAttrsWith' with `(name: values: values)' as the function.
|
||
|
||
Example:
|
||
zipAttrs [{a = "x";} {a = "y"; b = "z";}]
|
||
=> { a = ["x" "y"]; b = ["z"] }
|
||
*/
|
||
zipAttrs = zipAttrsWith (name: values: values);
|
||
|
||
/* Does the same as the update operator '//' except that attributes are
|
||
merged until the given predicate is verified. The predicate should
|
||
accept 3 arguments which are the path to reach the attribute, a part of
|
||
the first attribute set and a part of the second attribute set. When
|
||
the predicate is verified, the value of the first attribute set is
|
||
replaced by the value of the second attribute set.
|
||
|
||
Example:
|
||
recursiveUpdateUntil (path: l: r: path == ["foo"]) {
|
||
# first attribute set
|
||
foo.bar = 1;
|
||
foo.baz = 2;
|
||
bar = 3;
|
||
} {
|
||
#second attribute set
|
||
foo.bar = 1;
|
||
foo.quz = 2;
|
||
baz = 4;
|
||
}
|
||
|
||
returns: {
|
||
foo.bar = 1; # 'foo.*' from the second set
|
||
foo.quz = 2; #
|
||
bar = 3; # 'bar' from the first set
|
||
baz = 4; # 'baz' from the second set
|
||
}
|
||
|
||
*/
|
||
recursiveUpdateUntil = pred: lhs: rhs:
|
||
let f = attrPath:
|
||
zipAttrsWith (n: values:
|
||
let here = attrPath ++ [n]; in
|
||
if length values == 1
|
||
|| pred here (elemAt values 1) (head values) then
|
||
head values
|
||
else
|
||
f here values
|
||
);
|
||
in f [] [rhs lhs];
|
||
|
||
/* A recursive variant of the update operator ‘//’. The recursion
|
||
stops when one of the attribute values is not an attribute set,
|
||
in which case the right hand side value takes precedence over the
|
||
left hand side value.
|
||
|
||
Example:
|
||
recursiveUpdate {
|
||
boot.loader.grub.enable = true;
|
||
boot.loader.grub.device = "/dev/hda";
|
||
} {
|
||
boot.loader.grub.device = "";
|
||
}
|
||
|
||
returns: {
|
||
boot.loader.grub.enable = true;
|
||
boot.loader.grub.device = "";
|
||
}
|
||
|
||
*/
|
||
recursiveUpdate = recursiveUpdateUntil (path: lhs: rhs: !(isAttrs lhs && isAttrs rhs));
|
||
|
||
/* Returns true if the pattern is contained in the set. False otherwise.
|
||
|
||
Example:
|
||
matchAttrs { cpu = {}; } { cpu = { bits = 64; }; }
|
||
=> true
|
||
*/
|
||
matchAttrs = pattern: attrs: assert isAttrs pattern;
|
||
all id (attrValues (zipAttrsWithNames (attrNames pattern) (n: values:
|
||
let pat = head values; val = elemAt values 1; in
|
||
if length values == 1 then false
|
||
else if isAttrs pat then isAttrs val && matchAttrs pat val
|
||
else pat == val
|
||
) [pattern attrs]));
|
||
|
||
/* Override only the attributes that are already present in the old set
|
||
useful for deep-overriding.
|
||
|
||
Example:
|
||
overrideExisting {} { a = 1; }
|
||
=> {}
|
||
overrideExisting { b = 2; } { a = 1; }
|
||
=> { b = 2; }
|
||
overrideExisting { a = 3; b = 2; } { a = 1; }
|
||
=> { a = 1; b = 2; }
|
||
*/
|
||
overrideExisting = old: new:
|
||
mapAttrs (name: value: new.${name} or value) old;
|
||
|
||
/* Turns a list of strings into a human-readable description of those
|
||
strings represented as an attribute path. The result of this function is
|
||
not intended to be machine-readable.
|
||
|
||
Example:
|
||
showAttrPath [ "foo" "10" "bar" ]
|
||
=> "foo.\"10\".bar"
|
||
showAttrPath []
|
||
=> "<root attribute path>"
|
||
*/
|
||
showAttrPath = path:
|
||
if path == [] then "<root attribute path>"
|
||
else concatMapStringsSep "." escapeNixIdentifier path;
|
||
|
||
/* Get a package output.
|
||
If no output is found, fallback to `.out` and then to the default.
|
||
|
||
Example:
|
||
getOutput "dev" pkgs.openssl
|
||
=> "/nix/store/9rz8gxhzf8sw4kf2j2f1grr49w8zx5vj-openssl-1.0.1r-dev"
|
||
*/
|
||
getOutput = output: pkg:
|
||
if ! pkg ? outputSpecified || ! pkg.outputSpecified
|
||
then pkg.${output} or pkg.out or pkg
|
||
else pkg;
|
||
|
||
getBin = getOutput "bin";
|
||
getLib = getOutput "lib";
|
||
getDev = getOutput "dev";
|
||
getMan = getOutput "man";
|
||
|
||
/* Pick the outputs of packages to place in buildInputs */
|
||
chooseDevOutputs = drvs: builtins.map getDev drvs;
|
||
|
||
/* Make various Nix tools consider the contents of the resulting
|
||
attribute set when looking for what to build, find, etc.
|
||
|
||
This function only affects a single attribute set; it does not
|
||
apply itself recursively for nested attribute sets.
|
||
*/
|
||
recurseIntoAttrs =
|
||
attrs: attrs // { recurseForDerivations = true; };
|
||
|
||
/* Undo the effect of recurseIntoAttrs.
|
||
*/
|
||
dontRecurseIntoAttrs =
|
||
attrs: attrs // { recurseForDerivations = false; };
|
||
|
||
/*** deprecated stuff ***/
|
||
|
||
zipWithNames = zipAttrsWithNames;
|
||
zip = builtins.trace
|
||
"lib.zip is deprecated, use lib.zipAttrsWith instead" zipAttrsWith;
|
||
}
|