[stable28] fix(files): handle multidimensional arrays in scanner

lib/private/Files/Cache/Scanner.php

@@ -221,8 +221,9 @@ public function scanFile($file, $reuseExisting = 0, $parentId = -1, $cacheData =
 						}
 
 						// Only update metadata that has changed
-						$newData = array_diff_assoc($data, $cacheData->getData());
-
+						// i.e. get all the values in $data that are not present in the cache already
+						$newData = $this->array_diff_assoc_multi($data, $cacheData->getData());
+
 						// make it known to the caller that etag has been changed and needs propagation
 						if (isset($newData['etag'])) {
 							$data['etag_changed'] = true;
@@ -369,6 +370,50 @@ public function scan($path, $recursive = self::SCAN_RECURSIVE, $reuse = -1, $loc
 		return $data;
 	}
 
+	/**
+	 * Compares $array1 against $array2 and returns all the values in $array1 that are not in $array2
+	 * Note this is a one-way check - i.e. we don't care about things that are in $array2 that aren't in $array1
+	 *
+	 * Supports multi-dimensional arrays
+	 * Also checks keys/indexes
+	 * Comparisons are strict just like array_diff_assoc
+	 * Order of keys/values does not matter
+	 *
+	 * @param array $array1
+	 * @param array $array2
+	 * @return array with the differences between $array1 and $array1
+	 * @throws \InvalidArgumentException if $array1 isn't an actual array
+	 *
+	 */
+	protected function array_diff_assoc_multi(array $array1, array $array2) {
+
+		$result = [];
+
+		foreach ($array1 as $key => $value) {
+
+			// if $array2 doesn't have the same key, that's a result
+			if (!array_key_exists($key, $array2)) {
+				$result[$key] = $value;
+				continue;
+			}
+
+			// if $array2's value for the same key is different, that's a result
+			if ($array2[$key] !== $value && !is_array($value)) {
+				$result[$key] = $value;
+				continue;
+			}
+
+			if (is_array($value)) {
+				$nestedDiff = $this->array_diff_assoc_multi($value, $array2[$key]);
+				if (!empty($nestedDiff)) {
+					$result[$key] = $nestedDiff;
+					continue;
+				}
+			}
+		}
+		return $result;
+	}
+
 	/**
 	 * Get the children currently in the cache
 	 *