function whitespace_from_nodelist()

in src/__Private/whitespace_from_nodelist.hack [27:67]

• 31 lines of code
• 11 McCabe index (conditional complexity)

function whitespace_from_nodelist(NodeList<Node> $list): NodeList<Trivia> {
  if ($list->isEmpty()) {
    // Nothing to analyze, single space should be a reasonable default.
    return NodeList::createMaybeEmptyList(vec[new WhiteSpace(' ')]);
  }

  // If there is an EndOfLine between the last and second-to-last item, we take
  // the last EndOfLine + any whitespace immediately after it (i.e. we exactly
  // preserve the current indentation). If there is no EndOfLine, we take
  // whitespace from immediately after the previous item. In both cases, we stop
  // when we hit the first non-whitespace trivium (e.g. a comment).
  $last_child = C\lastx($list->getChildren());
  $previous_child = $list->getCount() === 1
    ? $last_child // technically incorrect but should provide good enough result
    : $list->getChildren()[$list->getCount() - 2];
  $trivia = Vec\concat(
    $previous_child->getLastTokenx()->getTrailing()->getChildren(),
    $last_child->getFirstTokenx()->getLeading()->getChildren(),
  );
  if (!C\is_empty($trivia)) {
    for ($start_idx = C\count($trivia) - 1; $start_idx > 0; --$start_idx) {
      if ($trivia[$start_idx] is EndOfLine) {
        break;
      }
    }
    $trivia = Vec\drop($trivia, $start_idx);
  }
  for ($take_cnt = 0; $take_cnt < C\count($trivia); ++$take_cnt) {
    if (!$trivia[$take_cnt] is WhiteSpace && !$trivia[$take_cnt] is EndOfLine) {
      break;
    }
  }
  $ret = NodeList::createMaybeEmptyList(Vec\take($trivia, $take_cnt));

  // Special case for a single-line single-item list: If no other whitespace was
  // detected, we arbitrarily choose one space.
  if ($list->getCount() === 1 && $ret->isEmpty()) {
    $ret = NodeList::createMaybeEmptyList(vec[new WhiteSpace(' ')]);
  }
  return $ret;
}