CacheableMetadata::merge

public CacheableMetadata::merge(CacheableMetadata $other)

public function merge(CacheableMetadata $other) {
  $result = clone $this;

  // This is called many times per request, so avoid merging unless absolutely
  // necessary.
  if (empty($this->cacheContexts)) {
    $result->cacheContexts = $other->cacheContexts;
  }
  elseif (empty($other->cacheContexts)) {
    $result->cacheContexts = $this->cacheContexts;
  }
  else {
    $result->cacheContexts = Cache::mergeContexts($this->cacheContexts, $other->cacheContexts);
  }

  if (empty($this->cacheTags)) {
    $result->cacheTags = $other->cacheTags;
  }
  elseif (empty($other->cacheTags)) {
    $result->cacheTags = $this->cacheTags;
  }
  else {
    $result->cacheTags = Cache::mergeTags($this->cacheTags, $other->cacheTags);
  }

  if ($this->cacheMaxAge === Cache::PERMANENT) {
    $result->cacheMaxAge = $other->cacheMaxAge;
  }
  elseif ($other->cacheMaxAge === Cache::PERMANENT) {
    $result->cacheMaxAge = $this->cacheMaxAge;
  }
  else {
    $result->cacheMaxAge = Cache::mergeMaxAges($this->cacheMaxAge, $other->cacheMaxAge);
  }
  return $result;
}