diff --git a/lib/attrsets.nix b/lib/attrsets.nix index 5c4f735b63da..83f8d0f34186 100644 --- a/lib/attrsets.nix +++ b/lib/attrsets.nix @@ -913,6 +913,40 @@ rec { ) [{}] (attrNames attrsOfLists); + /** + Return the result of function f applied to the cartesian product of attribute set value combinations. + Equivalent to using cartesianProduct followed by map. + + # Inputs + + `f` + + : A function, given an attribute set, it returns a new value. + + `attrsOfLists` + + : Attribute set with attributes that are lists of values + + # Type + + ``` + mapCartesianProduct :: (AttrSet -> a) -> AttrSet -> [a] + ``` + + # Examples + :::{.example} + ## `lib.attrsets.mapCartesianProduct` usage example + + ```nix + mapCartesianProduct ({a, b}: "${a}-${b}") { a = [ "1" "2" ]; b = [ "3" "4" ]; } + => [ "1-3" "1-4" "2-3" "2-4" ] + ``` + + ::: + + */ + mapCartesianProduct = f: attrsOfLists: map f (cartesianProduct attrsOfLists); + /** Utility function that creates a `{name, value}` pair as expected by `builtins.listToAttrs`. diff --git a/lib/default.nix b/lib/default.nix index 97a81d4763bf..44a2a5216ec7 100644 --- a/lib/default.nix +++ b/lib/default.nix @@ -87,7 +87,7 @@ let recursiveUpdate matchAttrs mergeAttrsList overrideExisting showAttrPath getOutput getBin getLib getDev getMan chooseDevOutputs zipWithNames zip recurseIntoAttrs dontRecurseIntoAttrs cartesianProduct cartesianProductOfSets - updateManyAttrsByPath; + mapCartesianProduct updateManyAttrsByPath; inherit (self.lists) singleton forEach foldr fold foldl foldl' imap0 imap1 concatMap flatten remove findSingle findFirst any all count optional optionals toList range replicate partition zipListsWith zipLists diff --git a/lib/tests/misc.nix b/lib/tests/misc.nix index b66f335c74f5..e15e110682fb 100644 --- a/lib/tests/misc.nix +++ b/lib/tests/misc.nix @@ -71,6 +71,7 @@ let makeIncludePath makeOverridable mapAttrs + mapCartesianProduct matchAttrs mergeAttrs meta @@ -1753,6 +1754,30 @@ runTests { ]; }; + testMapCartesianProductOfOneSet = { + expr = mapCartesianProduct ({a}: a * 2) { a = [ 1 2 3 ]; }; + expected = [ 2 4 6 ]; + }; + + testMapCartesianProductOfTwoSets = { + expr = mapCartesianProduct ({a,b}: a + b) { a = [ 1 ]; b = [ 10 20 ]; }; + expected = [ 11 21 ]; + }; + + testMapCartesianProcutOfTwoSetsWithOneEmpty = { + expr = mapCartesianProduct (x: x.a + x.b) { a = [ ]; b = [ 10 20 ]; }; + expected = [ ]; + }; + + testMapCartesianProductOfThreeSets = { + expr = mapCartesianProduct ({a,b,c}: a + b + c) { + a = [ 1 2 3 ]; + b = [ 10 20 30 ]; + c = [ 100 200 300 ]; + }; + expected = [ 111 211 311 121 221 321 131 231 331 112 212 312 122 222 322 132 232 332 113 213 313 123 223 323 133 233 333 ]; + }; + # The example from the showAttrPath documentation testShowAttrPathExample = { expr = showAttrPath [ "foo" "10" "bar" ];