public function assertIsSorted()

in src/Assert.hack [607:650]

• 29 lines of code
• 6 McCabe index (conditional complexity)

  public function assertIsSorted<Tv>(
    Traversable<Tv> $collection,
    (function(Tv, Tv): bool) $comparator,
    string $message = '',
  ): void {
    // Note: the way we maintain the pair of values to be compared may seem
    // weird and convoluted. However, there is a reason for this weirdness.
    // Because $collection is a Traversable (we're trying to be general here),
    // we can't index directly into it, so at some point we'd have to do a
    // comparison like $comparator($prev_item, $current_item). Unfortunately
    // there seems to be no way to initialize $prev_item so as to satisfy the
    // Hack type checker. If we init it to null, Hack complains that we are
    // passing a nullable into $comparator(Tv,Tv). If we omit it, Hack complains
    // of an undefined variable. And we can't init it to the first item of the
    // collection either, because we can only foreach into it and by then it's
    // too late.
    $pair = Vector {};

    $index = 0;
    foreach ($collection as $item) {
      if ($pair->count() < 2) {
        $pair->add($item);
      } else {
        $pair[0] = $pair[1];
        $pair[1] = $item;
      }

      if (($pair->count() === 2) && !$comparator($pair[0], $pair[1])) {
        $main_message = $message === '' ? 'Collection is not sorted' : $message;
        $failure_detail = \sprintf(
          'at pos %d, %s and %s are in the wrong order',
          $index,
          \var_export($pair[0], true),
          \var_export($pair[1], true),
        );

        throw new ExpectationFailedException(
          $main_message.': '.$failure_detail,
        );
      }

      $index++;
    }
  }