[Cache] allow to skip saving the computed value when using CacheInterface::get()

Author: nicolas-grekas

Cache/CacheInterface.php

@@ -29,13 +29,13 @@ interface CacheInterface
      * requested key, that could be used e.g. for expiration control. It could also
      * be an ItemInterface instance when its additional features are needed.
      *
-     * @param string                             $key      The key of the item to retrieve from the cache
-     * @param callable(CacheItemInterface):mixed $callback Should return the computed value for the given key/item
-     * @param float|null                         $beta     A float that, as it grows, controls the likeliness of triggering
-     *                                                     early expiration. 0 disables it, INF forces immediate expiration.
-     *                                                     The default (or providing null) is implementation dependent but should
-     *                                                     typically be 1.0, which should provide optimal stampede protection.
-     *                                                     See https://en.wikipedia.org/wiki/Cache_stampede#Probabilistic_early_expiration
+     * @param string                     $key      The key of the item to retrieve from the cache
+     * @param callable|CallbackInterface $callback Should return the computed value for the given key/item
+     * @param float|null                 $beta     A float that, as it grows, controls the likeliness of triggering
+     *                                             early expiration. 0 disables it, INF forces immediate expiration.
+     *                                             The default (or providing null) is implementation dependent but should
+     *                                             typically be 1.0, which should provide optimal stampede protection.
+     *                                             See https://en.wikipedia.org/wiki/Cache_stampede#Probabilistic_early_expiration
      *
      * @return mixed The value corresponding to the provided key
      *

Cache/CacheTrait.php

@@ -59,7 +59,11 @@ private function doGet(CacheItemPoolInterface $pool, string $key, callable $call
         }
 
         if ($recompute) {
-            $pool->save($item->set($callback($item)));
+            $save = true;
+            $item->set($callback($item, $save));
+            if ($save) {
+                $pool->save($item);
+            }
         }
 
         return $item->get();

Cache/CallbackInterface.php

@@ -0,0 +1,30 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Contracts\Cache;
+
+use Psr\Cache\CacheItemInterface;
+
+/**
+ * Computes and returns the cached value of an item.
+ *
+ * @author Nicolas Grekas <[email protected]>
+ */
+interface CallbackInterface
+{
+    /**
+     * @param CacheItemInterface|ItemInterface $item  The item to compute the value for
+     * @param bool                             &$save Should be set to false when the value should not be saved in the pool
+     *
+     * @return mixed The computed value for the passed item
+     */
+    public function __invoke(CacheItemInterface $item, bool &$save);
+}

Cache/TagAwareCacheInterface.php

@@ -22,8 +22,6 @@ interface TagAwareCacheInterface extends CacheInterface
 {
     /**
      * {@inheritdoc}
-     *
-     * @param callable(ItemInterface):mixed $callback Should return the computed value for the given key/item
      */
     public function get(string $key, callable $callback, float $beta = null);