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lib: Add composeManyExtensions

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This commit is contained in:
Joe Hermaszewski 2020-11-11 10:36:19 +08:00 committed by Peter Simons
parent bacdeffd80
commit c3b35f21f7
3 changed files with 32 additions and 3 deletions
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4
lib/default.nix
View File

@ -5,7 +5,7 @@
*/ */
let let
inherit (import ./fixed-points.nix {}) makeExtensible; inherit (import ./fixed-points.nix { inherit lib; }) makeExtensible;
lib = makeExtensible (self: let lib = makeExtensible (self: let
callLibs = file: import file { lib = self; }; callLibs = file: import file { lib = self; };
@ -69,7 +69,7 @@ let
importJSON importTOML warn info showWarnings nixpkgsVersion version mod compare importJSON importTOML warn info showWarnings nixpkgsVersion version mod compare
splitByAndCompare functionArgs setFunctionArgs isFunction toHexString toBaseDigits; splitByAndCompare functionArgs setFunctionArgs isFunction toHexString toBaseDigits;
inherit (self.fixedPoints) fix fix' converge extends composeExtensions inherit (self.fixedPoints) fix fix' converge extends composeExtensions
makeExtensible makeExtensibleWithCustomName; composeManyExtensions makeExtensible makeExtensibleWithCustomName;
inherit (self.attrsets) attrByPath hasAttrByPath setAttrByPath inherit (self.attrsets) attrByPath hasAttrByPath setAttrByPath
getAttrFromPath attrVals attrValues getAttrs catAttrs filterAttrs getAttrFromPath attrVals attrValues getAttrs catAttrs filterAttrs
filterAttrsRecursive foldAttrs collect nameValuePair mapAttrs filterAttrsRecursive foldAttrs collect nameValuePair mapAttrs

11
lib/fixed-points.nix
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@ -1,4 +1,4 @@
{ ... }: { lib, ... }:
rec { rec {
# Compute the fixed point of the given function `f`, which is usually an # Compute the fixed point of the given function `f`, which is usually an
# attribute set that expects its final, non-recursive representation as an # attribute set that expects its final, non-recursive representation as an
@ -77,6 +77,15 @@ rec {
super' = super // fApplied; super' = super // fApplied;
in fApplied // g self super'; in fApplied // g self super';
# Compose several extending functions of the type expected by 'extends' into
# one where changes made in preceding functions are made available to
# subsequent ones.
#
# composeManyExtensions : [packageSet -> packageSet -> packageSet] -> packageSet -> packageSet -> packageSet
# ^final ^prev ^overrides ^final ^prev ^overrides
composeManyExtensions =
lib.foldr (x: y: composeExtensions x y) (self: super: {});
# Create an overridable, recursive attribute set. For example: # Create an overridable, recursive attribute set. For example:
# #
# nix-repl> obj = makeExtensible (self: { }) # nix-repl> obj = makeExtensible (self: { })

20
lib/tests/misc.nix
View File

@ -87,6 +87,26 @@ runTests {
expected = true; expected = true;
}; };
testComposeManyExtensions0 = {
expr = let obj = makeExtensible (self: { foo = true; });
emptyComposition = composeManyExtensions [];
composed = obj.extend emptyComposition;
in composed.foo;
expected = true;
};
testComposeManyExtensions =
let f = self: super: { bar = false; baz = true; };
g = self: super: { bar = super.baz or false; };
h = self: super: { qux = super.bar or false; };
obj = makeExtensible (self: { foo = self.qux; });
in {
expr = let composition = composeManyExtensions [f g h];
composed = obj.extend composition;
in composed.foo;
expected = (obj.extend (composeExtensions f (composeExtensions g h))).foo;
};
testBitAnd = { testBitAnd = {
expr = (bitAnd 3 10); expr = (bitAnd 3 10);
expected = 2; expected = 2;