Merge master into staging-next

     Type:

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

  */

  makeOverridable = f: lib.setFunctionArgs

    (origArgs: let

  makeOverridable = f:

    let

      # Creates a functor with the same arguments as f

      mirrorArgs = lib.mirrorFunctionArgs f;

    in

    mirrorArgs (origArgs:

    let

      result = f origArgs;

      # Creates a functor with the same arguments as f

      copyArgs = g: lib.setFunctionArgs g (lib.functionArgs f);

      # Changes the original arguments with (potentially a function that returns) a set of new attributes

      overrideWith = newArgs: origArgs // (if lib.isFunction newArgs then newArgs origArgs else newArgs);

      # Re-call the function but with different arguments

      overrideArgs = copyArgs (newArgs: makeOverridable f (overrideWith newArgs));

      overrideArgs = mirrorArgs (newArgs: makeOverridable f (overrideWith newArgs));

      # Change the result of the function call by applying g to it

      overrideResult = g: makeOverridable (copyArgs (args: g (f args))) origArgs;

      overrideResult = g: makeOverridable (mirrorArgs (args: g (f args))) origArgs;

    in

      if builtins.isAttrs result then

        result // {

        lib.setFunctionArgs result (lib.functionArgs result) // {

          override = overrideArgs;

        }

      else result)

    (lib.functionArgs f);

      else result);

  /* Call the package function in the file `fn` with the required

      importJSON importTOML warn warnIf warnIfNot throwIf throwIfNot checkListOfEnum

      info showWarnings nixpkgsVersion version isInOldestRelease

      mod compare splitByAndCompare

      functionArgs setFunctionArgs isFunction toFunction

      functionArgs setFunctionArgs isFunction toFunction mirrorFunctionArgs

      toHexString toBaseDigits inPureEvalMode;

    inherit (self.fixedPoints) fix fix' converge extends composeExtensions

      composeManyExtensions makeExtensible makeExtensibleWithCustomName;

## To update in the future

Here's a list of places in the library that need to be updated in the future:

- > The file set library is currently somewhat limited but is being expanded to include more functions over time.

  in [the manual](../../doc/functions/fileset.section.md)

- If/Once a function exists that can optionally include a path depending on whether it exists, the error message for the path not existing in `_coerce` should mention the new function

            - Set `root` to ${toString fileset._internalBase} or any directory higher up. This changes the layout of the resulting store path.

            - Set `fileset` to a file set that cannot contain files outside the `root` (${toString root}). This could change the files included in the result.''

    else

      builtins.seq sourceFilter

      seq sourceFilter

      cleanSourceWith {

        name = "source";

        src = root;

  isFunction = f: builtins.isFunction f ||

    (f ? __functor && isFunction (f.__functor f));

  /*

    `mirrorFunctionArgs f g` creates a new function `g'` with the same behavior as `g` (`g' x == g x`)

    but its function arguments mirroring `f` (`lib.functionArgs g' == lib.functionArgs f`).

    Type:

      mirrorFunctionArgs :: (a -> b) -> (a -> c) -> (a -> c)

    Example:

      addab = {a, b}: a + b

      addab { a = 2; b = 4; }

      => 6

      lib.functionArgs addab

      => { a = false; b = false; }

      addab1 = attrs: addab attrs + 1

      addab1 { a = 2; b = 4; }

      => 7

      lib.functionArgs addab1

      => { }

      addab1' = lib.mirrorFunctionArgs addab addab1

      addab1' { a = 2; b = 4; }

      => 7

      lib.functionArgs addab1'

      => { a = false; b = false; }

  */

  mirrorFunctionArgs =

    # Function to provide the argument metadata

    f:

    let

      fArgs = functionArgs f;

    in

    # Function to set the argument metadata to

    g:

    setFunctionArgs g fArgs;

  /*

    Turns any non-callable values into constant functions.

    Returns callable values as is.