switched to namespace first, PSR-0 as a fallback

src/Loader/ChainLoader.php

@@ -1,11 +1,164 @@
 <?php
 
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
 namespace Twig\Loader;
 
-class_exists('Twig_Loader_Chain');
+use Twig\Error\LoaderError;
+use Twig\Source;
 
-if (\false) {
-    class ChainLoader extends \Twig_Loader_Chain
+/**
+ * Loads templates from other loaders.
+ *
+ * @final
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class ChainLoader implements LoaderInterface, ExistsLoaderInterface, SourceContextLoaderInterface
+{
+    private $hasSourceCache = [];
+    protected $loaders = [];
+
+    /**
+     * @param LoaderInterface[] $loaders
+     */
+    public function __construct(array $loaders = [])
     {
+        foreach ($loaders as $loader) {
+            $this->addLoader($loader);
+        }
+    }
+
+    public function addLoader(LoaderInterface $loader)
+    {
+        $this->loaders[] = $loader;
+        $this->hasSourceCache = [];
+    }
+
+    /**
+     * @return LoaderInterface[]
+     */
+    public function getLoaders()
+    {
+        return $this->loaders;
+    }
+
+    public function getSource($name)
+    {
+        @trigger_error(sprintf('Calling "getSource" on "%s" is deprecated since 1.27. Use getSourceContext() instead.', \get_class($this)), E_USER_DEPRECATED);
+
+        $exceptions = [];
+        foreach ($this->loaders as $loader) {
+            if ($loader instanceof ExistsLoaderInterface && !$loader->exists($name)) {
+                continue;
+            }
+
+            try {
+                return $loader->getSource($name);
+            } catch (LoaderError $e) {
+                $exceptions[] = $e->getMessage();
+            }
+        }
+
+        throw new LoaderError(sprintf('Template "%s" is not defined%s.', $name, $exceptions ? ' ('.implode(', ', $exceptions).')' : ''));
+    }
+
+    public function getSourceContext($name)
+    {
+        $exceptions = [];
+        foreach ($this->loaders as $loader) {
+            if ($loader instanceof ExistsLoaderInterface && !$loader->exists($name)) {
+                continue;
+            }
+
+            try {
+                if ($loader instanceof SourceContextLoaderInterface) {
+                    return $loader->getSourceContext($name);
+                }
+
+                return new Source($loader->getSource($name), $name);
+            } catch (LoaderError $e) {
+                $exceptions[] = $e->getMessage();
+            }
+        }
+
+        throw new LoaderError(sprintf('Template "%s" is not defined%s.', $name, $exceptions ? ' ('.implode(', ', $exceptions).')' : ''));
+    }
+
+    public function exists($name)
+    {
+        $name = (string) $name;
+
+        if (isset($this->hasSourceCache[$name])) {
+            return $this->hasSourceCache[$name];
+        }
+
+        foreach ($this->loaders as $loader) {
+            if ($loader instanceof ExistsLoaderInterface) {
+                if ($loader->exists($name)) {
+                    return $this->hasSourceCache[$name] = true;
+                }
+
+                continue;
+            }
+
+            try {
+                if ($loader instanceof SourceContextLoaderInterface) {
+                    $loader->getSourceContext($name);
+                } else {
+                    $loader->getSource($name);
+                }
+
+                return $this->hasSourceCache[$name] = true;
+            } catch (LoaderError $e) {
+            }
+        }
+
+        return $this->hasSourceCache[$name] = false;
+    }
+
+    public function getCacheKey($name)
+    {
+        $exceptions = [];
+        foreach ($this->loaders as $loader) {
+            if ($loader instanceof ExistsLoaderInterface && !$loader->exists($name)) {
+                continue;
+            }
+
+            try {
+                return $loader->getCacheKey($name);
+            } catch (LoaderError $e) {
+                $exceptions[] = \get_class($loader).': '.$e->getMessage();
+            }
+        }
+
+        throw new LoaderError(sprintf('Template "%s" is not defined%s.', $name, $exceptions ? ' ('.implode(', ', $exceptions).')' : ''));
+    }
+
+    public function isFresh($name, $time)
+    {
+        $exceptions = [];
+        foreach ($this->loaders as $loader) {
+            if ($loader instanceof ExistsLoaderInterface && !$loader->exists($name)) {
+                continue;
+            }
+
+            try {
+                return $loader->isFresh($name, $time);
+            } catch (LoaderError $e) {
+                $exceptions[] = \get_class($loader).': '.$e->getMessage();
+            }
+        }
+
+        throw new LoaderError(sprintf('Template "%s" is not defined%s.', $name, $exceptions ? ' ('.implode(', ', $exceptions).')' : ''));
     }
 }
+
+class_alias('Twig\Loader\ChainLoader', 'Twig_Loader_Chain');