merged branch fabpot/twig-engine-exists (PR #8547)

This PR was merged into the 2.2 branch.

Discussion
----------

[Twig] fixed TwigEngine::exists() method when a template contains a syntax error (closes #8546)

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #8546
| License       | MIT
| Doc PR        | n/a

Commits
-------

ae7fa11 [Twig] fixed TwigEngine::exists() method when a template contains a syntax error (closes #88546)

src/Symfony/Bridge/Twig/Tests/TwigEngineTest.php

@@ -0,0 +1,56 @@
+<?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\Bridge\Twig\Tests;
+
+use Symfony\Bridge\Twig\TwigEngine;
+
+class TwigEngineTest extends TestCase
+{
+    public function testExistsWithTemplateInstances()
+    {
+        $engine = $this->getTwig();
+
+        $this->assertTrue($engine->exists($this->getMockForAbstractClass('Twig_Template', array(), '', false)));
+    }
+
+    public function testExistsWithNonExistentTemplates()
+    {
+        $engine = $this->getTwig();
+
+        $this->assertFalse($engine->exists('foobar'));
+    }
+
+    public function testExistsWithTemplateWithSyntaxErrors()
+    {
+        $engine = $this->getTwig();
+
+        $this->assertTrue($engine->exists('error'));
+    }
+
+    public function testExists()
+    {
+        $engine = $this->getTwig();
+
+        $this->assertTrue($engine->exists('index'));
+    }
+
+    protected function getTwig()
+    {
+        $twig = new \Twig_Environment(new \Twig_Loader_Array(array(
+            'index' => 'foo',
+            'error' => '{{ foo }',
+        )));
+        $parser = $this->getMock('Symfony\Component\Templating\TemplateNameParserInterface');
+
+        return new TwigEngine($twig, $parser);
+    }
+}

src/Symfony/Bridge/Twig/TwigEngine.php

@@ -75,9 +75,19 @@ class TwigEngine implements EngineInterface, StreamingEngineInterface
      */
     public function exists($name)
     {
+        if ($name instanceof \Twig_Template) {
+            return true;
+        }
+
+        $loader = $this->environment->getLoader();
+
+        if ($loader instanceof \Twig_ExistsLoaderInterface) {
+            return $loader->exists($name);
+        }
+
         try {
-            $this->load($name);
-        } catch (\InvalidArgumentException $e) {
+            $loader->getSource($name);
+        } catch (\Twig_Error_Loader $e) {
             return false;
         }