[Session] Added exception to save method

A RuntimeException is thrown if there is an attempt to save the session
without it being started, or if it has already been closed.

src/Symfony/Component/HttpFoundation/Session/Storage/MockArraySessionStorage.php

@@ -159,6 +159,9 @@ class MockArraySessionStorage implements SessionStorageInterface
      */
     public function save()
     {
+        if (!$this->started || $this->closed) {
+            throw new \RuntimeException("Trying to save a session that was not started yet or was already closed");
+        }
         // nothing to do since we don't persist the session data
         $this->closed = false;
     }

src/Symfony/Component/HttpFoundation/Session/Storage/MockFileSessionStorage.php

@@ -97,6 +97,10 @@ class MockFileSessionStorage extends MockArraySessionStorage
      */
     public function save()
     {
+        if (!$this->started) {
+            throw new \RuntimeException("Trying to save a session that was not started yet or was already closed");
+        }
+
         file_put_contents($this->getFilePath(), serialize($this->data));
 
         // this is needed for Silex, where the session object is re-used across requests

src/Symfony/Component/HttpFoundation/Session/Storage/SessionStorageInterface.php

@@ -110,6 +110,9 @@ interface SessionStorageInterface
      * used for a storage object design for unit or functional testing where
      * a real PHP session would interfere with testing, in which case it
      * it should actually persist the session data if required.
+     *
+     * @throws \RuntimeException If the session is saved without being started, or if the session
+     *                           is already closed.
      */
     public function save();
 

src/Symfony/Component/HttpFoundation/Tests/Session/SessionTest.php

@@ -151,6 +151,7 @@ class SessionTest extends \PHPUnit_Framework_TestCase
 
     public function testSave()
     {
+        $this->session->start();
         $this->session->save();
     }
 

src/Symfony/Component/HttpFoundation/Tests/Session/Storage/MockArraySessionStorageTest.php

@@ -95,4 +95,12 @@ class MockArraySessionStorageTest extends \PHPUnit_Framework_TestCase
         $this->storage->start();
         $this->assertNotEquals('', $this->storage->getId());
     }
+
+    /**
+     * @expectedException RuntimeException
+     */
+    public function testUnstartedSave()
+    {
+        $this->storage->save();
+    }
 }

src/Symfony/Component/HttpFoundation/Tests/Session/Storage/MockFileSessionStorageTest.php

@@ -106,6 +106,15 @@ class MockFileSessionStorageTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals('bar', $storage2->getBag('attributes')->get('foo'), 'values persist between instances');
     }
 
+    /**
+     * @expectedException RuntimeException
+     */
+    public function testSaveWithoutStart()
+    {
+        $storage1 = $this->getStorage();
+        $storage1->save();
+    }
+
     private function getStorage()
     {
         $storage = new MockFileSessionStorage($this->sessionDir);