[Cache] Create NullAdapter to disable cache if needed

src/Symfony/Component/Cache/Adapter/NullAdapter.php

@@ -0,0 +1,121 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Cache\Adapter;
+
+use Psr\Cache\CacheItemInterface;
+use Symfony\Component\Cache\CacheItem;
+
+/**
+ * @author Titouan Galopin <galopintitouan@gmail.com>
+ */
+class NullAdapter implements AdapterInterface
+{
+    private $createCacheItem;
+
+    public function __construct()
+    {
+        $this->createCacheItem = \Closure::bind(
+            function ($key) {
+                $item = new CacheItem();
+                $item->key = $key;
+                $item->isHit = false;
+
+                return $item;
+            },
+            $this,
+            CacheItem::class
+        );
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getItem($key)
+    {
+        $f = $this->createCacheItem;
+
+        return $f($key);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getItems(array $keys = array())
+    {
+        return $this->generateItems($keys);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function hasItem($key)
+    {
+        return false;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function clear()
+    {
+        return true;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function deleteItem($key)
+    {
+        return true;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function deleteItems(array $keys)
+    {
+        return true;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function save(CacheItemInterface $item)
+    {
+        return false;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function saveDeferred(CacheItemInterface $item)
+    {
+        return false;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function commit()
+    {
+        return false;
+    }
+
+    private function generateItems(array $keys)
+    {
+        $f = $this->createCacheItem;
+
+        foreach ($keys as $key) {
+            yield $key => $f($key);
+        }
+    }
+}

src/Symfony/Component/Cache/Tests/Adapter/NullAdapterTest.php

@@ -0,0 +1,124 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Cache\Tests\Adapter;
+
+use Psr\Cache\CacheItemInterface;
+use Symfony\Component\Cache\Adapter\NullAdapter;
+
+class NullAdapterTest extends \PHPUnit_Framework_TestCase
+{
+    public function createCachePool()
+    {
+        return new NullAdapter();
+    }
+
+    public function testGetItem()
+    {
+        $adapter = $this->createCachePool();
+
+        $item = $adapter->getItem('key');
+        $this->assertFalse($item->isHit());
+        $this->assertNull($item->get(), "Item's value must be null when isHit is false.");
+    }
+
+    public function testHasItem()
+    {
+        $this->assertFalse($this->createCachePool()->hasItem('key'));
+    }
+
+    public function testGetItems()
+    {
+        $adapter = $this->createCachePool();
+
+        $keys = array('foo', 'bar', 'baz', 'biz');
+
+        /** @var CacheItemInterface[] $items */
+        $items = $adapter->getItems($keys);
+        $count = 0;
+
+        foreach ($items as $key => $item) {
+            $itemKey = $item->getKey();
+
+            $this->assertEquals($itemKey, $key, 'Keys must be preserved when fetching multiple items');
+            $this->assertTrue(in_array($key, $keys), 'Cache key can not change.');
+            $this->assertFalse($item->isHit());
+
+            // Remove $key for $keys
+            foreach ($keys as $k => $v) {
+                if ($v === $key) {
+                    unset($keys[$k]);
+                }
+            }
+
+            ++$count;
+        }
+
+        $this->assertSame(4, $count);
+    }
+
+    public function testIsHit()
+    {
+        $adapter = $this->createCachePool();
+
+        $item = $adapter->getItem('key');
+        $this->assertFalse($item->isHit());
+    }
+
+    public function testClear()
+    {
+        $this->assertTrue($this->createCachePool()->clear());
+    }
+
+    public function testDeleteItem()
+    {
+        $this->assertTrue($this->createCachePool()->deleteItem('key'));
+    }
+
+    public function testDeleteItems()
+    {
+        $this->assertTrue($this->createCachePool()->deleteItems(array('key', 'foo', 'bar')));
+    }
+
+    public function testSave()
+    {
+        $adapter = $this->createCachePool();
+
+        $item = $adapter->getItem('key');
+        $this->assertFalse($item->isHit());
+        $this->assertNull($item->get(), "Item's value must be null when isHit is false.");
+
+        $this->assertFalse($adapter->save($item));
+    }
+
+    public function testDeferredSave()
+    {
+        $adapter = $this->createCachePool();
+
+        $item = $adapter->getItem('key');
+        $this->assertFalse($item->isHit());
+        $this->assertNull($item->get(), "Item's value must be null when isHit is false.");
+
+        $this->assertFalse($adapter->saveDeferred($item));
+    }
+
+    public function testCommit()
+    {
+        $adapter = $this->createCachePool();
+
+        $item = $adapter->getItem('key');
+        $this->assertFalse($item->isHit());
+        $this->assertNull($item->get(), "Item's value must be null when isHit is false.");
+
+        $this->assertFalse($adapter->saveDeferred($item));
+        $this->assertFalse($this->createCachePool()->commit());
+    }
+}