[templates] add shuffle filter

doc/filters/shuffle.rst

@@ -1,5 +1,5 @@
 ``shuffle``
-========
+===========
 
 The ``shuffle`` filter shuffles an array:
 
@@ -11,9 +11,9 @@ The ``shuffle`` filter shuffles an array:
 
 .. caution::
 
-    Internally, Twig uses the PHP `shuffle`_ function.
-    This function assigns new keys to the elements in array. It will remove
-    any existing keys that may have been assigned, rather than just reordering the keys.
+    The shuffled array does not preserve keys. So if the input had not sequential keys
+    but indexed keys (using the user id for instance),
+    it is not the case anymore after shuffling it.
 
 Example 1:
 
@@ -72,5 +72,3 @@ The above example will be rendered as:
 
 Note, results can also be :
 "d, e, f" or "e, d, f" or "e, f, d" or "f, d, e" or "f, e, d".
-
-.. _`shuffle`: https://www.php.net/shuffle

src/Extension/CoreExtension.php

@@ -953,18 +953,10 @@ public static function sortFilter(Environment $env, $array, $arrow = null)
      * Shuffle an array.
      * The function does not preserve keys.
      *
-     * @param array|\Traversable $array
-     *
-     * @return array
-     *
      * @internal
      */
-    public function shuffle($array)
+    public function shuffle(iterable $array): array
     {
-        if (!is_iterable($array)) {
-            throw new RuntimeError(sprintf('The shuffle filter only works with array or "Traversable", got "%s" as argument.', \gettype($array)));
-        }
-
         $array = self::toArray($array, false);
         shuffle($array);