fetchurl: move curlOpts warnings down to its value

      "${lib.head mirrorList}${lib.elemAt mirrorSplit 1}";

in

assert

  (lib.isList curlOpts)

  -> lib.warn ''

    fetchurl for ${toString (builtins.head urls_)}: curlOpts is a list (${

      lib.generators.toPretty { multiline = false; } curlOpts

    }), which is not supported anymore.

    - If you wish to get the same effect as before, for elements with spaces (even if escaped) to expand to multiple curl arguments, use a string argument instead:

      curlOpts = ${lib.strings.escapeNixString (toString curlOpts)};

    - If you wish for each list element to be passed as a separate curl argument, allowing arguments to contain spaces, use curlOptsList instead:

      curlOptsList = [ ${lib.concatMapStringsSep " " lib.strings.escapeNixString curlOpts} ];'' true;

stdenvNoCC.mkDerivation (

  (

    if (pname != "" && version != "") then

    outputHashMode = if (recursiveHash || executable) then "recursive" else "flat";

    inherit curlOpts;

    curlOpts = lib.warnIf (lib.isList curlOpts) (

      let

        url = toString (builtins.head urls_);

        curlOptsRepresentation = lib.generators.toPretty { multiline = false; } curlOpts;

        curlOptsAsStringRepresentation = lib.strings.escapeNixString (toString curlOpts);

        curlOptsListElementsRepresentation =

          lib.concatMapStringsSep " " lib.strings.escapeNixString

            curlOpts;

      in

      ''

        fetchurl for ${url}: curlOpts is a list (${curlOptsRepresentation}), which is not supported anymore.

        - If you wish to get the same effect as before, for elements with spaces (even if escaped) to expand to multiple curl arguments, use a string argument instead:

          curlOpts = ${curlOptsAsStringRepresentation};

        - If you wish for each list element to be passed as a separate curl argument, allowing arguments to contain spaces, use curlOptsList instead:

          curlOptsList = [ ${curlOptsListElementsRepresentation} ];

      ''

    ) curlOpts;

    curlOptsList = lib.escapeShellArgs curlOptsList;

    inherit

      showURLs

      mirrorsFile