testers.invalidateFetcherByDrvHash: take fixed-point arguments args

  invalidateFetcherByDrvHash =

    f: args:

    let

      optionalFix = if lib.isFunction args then lib.id else lib.fix;

      unsalted = f args;

      drvPath = unsalted.drvPath;

      # It's safe to discard the context, because we don't access the path.

        else

          { name = saltName args.name or "source"; };

      # New derivation incorporating the original drv hash in the name

      saltedByArgs = f (args // getSaltedNames args);

      saltedByArgs = f (optionalFix (lib.extends (lib.toExtension getSaltedNames) (lib.toFunction args)));

      saltedByOverrideAttrs = unsalted.overrideAttrs (previousAttrs: getSaltedNames previousAttrs);

      saltedByOverrideAttrsForced = unsalted.overrideAttrs (previousAttrs: {

        name = saltName unsalted.name;