makeOverridable

lib.makeOverridable

Docs pulled from | This Revision | about 1 hour ago

makeOverridable takes a function from attribute set to attribute set and injects override attribute which can be used to override arguments of the function.

Please refer to documentation on <pkg>.overrideDerivation to learn about overrideDerivation and caveats related to its use.

Inputs

f: 1. Function argument

Type

makeOverridable :: (AttrSet -> a) -> AttrSet -> a

Examples

`lib.customisation.makeOverridable` usage example

nix-repl> x = {a, b}: { result = a + b; }

nix-repl> y = lib.makeOverridable x { a = 1; b = 2; }

nix-repl> y
{ override = «lambda»; overrideDerivation = «lambda»; result = 3; }

nix-repl> y.override { a = 10; }
{ override = «lambda»; overrideDerivation = «lambda»; result = 12; }

(lib.customisation.makeOverridable)

Noogle detected

Aliases

Implementation

The following is the current implementation of this function.

makeOverridable =
    f:
    let
      # Creates a functor with the same arguments as f
      mirrorArgs = mirrorFunctionArgs f;
    in
    mirrorArgs (
      origArgs:
      let
        result = f origArgs;

        # Changes the original arguments with (potentially a function that returns) a set of new attributes
        overrideWith = newArgs: origArgs // (if isFunction newArgs then newArgs origArgs else newArgs);

        # Re-call the function but with different arguments
        overrideArgs = mirrorArgs (newArgs: makeOverridable f (overrideWith newArgs));
        # Change the result of the function call by applying g to it
        overrideResult = g: makeOverridable (mirrorArgs (args: g (f args))) origArgs;
      in
      if isAttrs result then
        result
        // {
          override = overrideArgs;
          overrideDerivation = fdrv: overrideResult (x: overrideDerivation x fdrv);
          ${if result ? overrideAttrs then "overrideAttrs" else null} =
            fdrv: overrideResult (x: x.overrideAttrs fdrv);
        }
      else if isFunction result then
        # Transform the result into a functor while propagating its arguments
        setFunctionArgs result (functionArgs result)
        // {
          override = overrideArgs;
        }
      else
        result
    );