@function recursive-map-merge($map1, $map2, $config:() ) {
  @if (type-of($map1) == map or (type-of($map1) == list and length($map1) == 0)) and (type-of($map2) == map or (type-of($map2) == list and length($map2) == 0)) {
    $result: $map1;
    @each $key, $value in $map2 {
      @if (type-of(map-get($result, $key)) == map and type-of($value) == map) {
        $result: map-merge($result, ($key: recursive-map-merge(map-get($result, $key), $value)));
      } @else if (map-get($config, "merge-lists") and type-of(map-get($result, $key)) == list and type-of($value) == list) {
        $result: map-merge($result, ($key: join(map-get($result, $key), $value)));
      } @else {
        $result: map-merge($result, ($key: $value));
      }
    }
    @return $result;
  } @else {
    @warn "recursive-map-merge() expects it\'s parameters to be map types!";
    @return null;
  }
}

// thanks for https://gist.github.com/morewry/9522776
@function debug-map($map, $result: '') {
  @each $k, $v in $map {
    @if (type-of($v) == map) {
      $result: '#{$result}#{$k}: (#{debug-map($v)}), ';
    } @else {
      $result: '#{$result}#{$k}: #{$v}, ';
    }
  }
  @return $result;
}