bug #9923 [DoctrineBridge] Fixed an issue with DoctrineParserCache (florianv)

This PR was merged into the 2.4 branch.

Discussion
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[DoctrineBridge] Fixed an issue with DoctrineParserCache

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

The `DoctrineParserCache` returns `false` when there is no entry (https://github.com/doctrine/cache/blob/master/lib/Doctrine/Common/Cache/Cache.php#L52).
But the `ExpressionLanguage` class expects `null` to be returned by the `ParserCacheInterface`, which causes the expressions to not be parsed when using a `DoctrineParserCache`.

Commits
-------

16728f7 [DoctrineBridge] Fixed an issue with DoctrineParserCache

src/Symfony/Bridge/Doctrine/ExpressionLanguage/DoctrineParserCache.php

@@ -35,7 +35,11 @@ class DoctrineParserCache implements ParserCacheInterface
      */
     public function fetch($key)
     {
-        return $this->cache->fetch($key);
+        if (false === $value = $this->cache->fetch($key)) {
+            return null;
+        }
+
+        return $value;
     }
 
     /**

src/Symfony/Bridge/Doctrine/Tests/ExpressionLanguage/DoctrineParserCacheTest.php

@@ -29,6 +29,19 @@ class DoctrineParserCacheTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals('bar', $result);
     }
 
+    public function testFetchUnexisting()
+    {
+        $doctrineCacheMock = $this->getMock('Doctrine\Common\Cache\Cache');
+        $parserCache = new DoctrineParserCache($doctrineCacheMock);
+
+        $doctrineCacheMock
+            ->expects($this->once())
+            ->method('fetch')
+            ->will($this->returnValue(false));
+
+        $this->assertNull($parserCache->fetch(''));
+    }
+
     public function testSave()
     {
         $doctrineCacheMock = $this->getMock('Doctrine\Common\Cache\Cache');