trait XmlNormalizationQuirksTrait

trait XmlNormalizationQuirksTrait {
    
    /**
     * Applies the XML encoding quirks that remain after decoding.
     *
     * The XML encoding:
     * - maps empty arrays to the empty string
     * - maps single-item arrays to just that single item
     * - restructures multiple-item arrays that lives in a single-item array
     *
     * @param array $normalization
     *   A normalization.
     *
     * @return array
     *   The updated normalization.
     *
     * @see \Symfony\Component\Serializer\Encoder\XmlEncoder
     */
    protected function applyXmlDecodingQuirks(array $normalization) {
        foreach ($normalization as $key => $value) {
            if ($value === [] || $value === NULL) {
                $normalization[$key] = '';
            }
            elseif (is_array($value)) {
                // Collapse single-item numeric arrays to just the single item.
                if (count($value) === 1 && is_numeric(array_keys($value)[0]) && is_scalar($value[0])) {
                    $value = $value[0];
                }
                elseif (count($value) === 1 && is_numeric(array_keys($value)[0]) && is_array(reset($value))) {
                    $rewritten_value = [];
                    foreach ($value[0] as $child_key => $child_value) {
                        if (is_numeric(array_keys(reset($value))[0])) {
                            $rewritten_value[$child_key] = [
                                '@key' => $child_key,
                            ] + $child_value;
                        }
                        else {
                            $rewritten_value[$child_key] = $child_value;
                        }
                    }
                    $value = $rewritten_value;
                }
                // If the post-quirk value is still an array after the above, recurse.
                if (is_array($value)) {
                    $value = $this->applyXmlDecodingQuirks($value);
                }
                // Store post-quirk value.
                $normalization[$key] = $value;
            }
        }
        return $normalization;
    }

}