Fix #154: Support for Twig 3.9

CHANGELOG.md

@@ -1,10 +1,14 @@
 Yii Framework 2 twig extension Change Log
 =========================================
 
-2.4.4 under development
+2.5.0 under development
 -----------------------
 
-- no changes in this release.
+- Bug #154: Support for Twig 3.9  
+  In twig 3.9 there were many internal changes that might affect and break codebases using twig:
+  - Internal functions (including twig_get_attribute) has been moved and renamed.
+  - The internal working of twig does not store template state in the output buffer anymore.  
+    This means if a custom twig function reads and modifies the output buffer, it might not work as expected.
 
 
 2.4.3 April 29, 2024

composer.json

@@ -20,10 +20,7 @@
     "require": {
         "php": "^7.2.5|^8.0|^8.1",
         "yiisoft/yii2": "~2.0.4",
-        "twig/twig": "~3.0"
-    },
-    "conflict": {
-        "twig/twig": ">=3.9"
+        "twig/twig": "~3.9"
     },
     "require-dev": {
         "cweagans/composer-patches": "^1.7",

src/Extension.php

@@ -37,6 +37,18 @@ class Extension extends AbstractExtension
      */
     protected $widgets = [];
 
+    /**
+     * Little hack to work with twig 3.9
+     * see explanation at the end of yii\twig\ViewRenderer::render function
+     *
+     * @var bool
+     */
+    protected $viewEndPage = false;
+
+    public function withViewEndPage(): bool
+    {
+        return $this->viewEndPage;
+    }
 
     /**
      * Creates new instance
@@ -194,7 +206,11 @@ public function widget($widget, $config = [])
     public function viewHelper($context, $name = null)
     {
         if ($name !== null && isset($context['this'])) {
-            $this->call($context['this'], Inflector::variablize($name));
+            if ($name === 'end_page') {
+                $this->viewEndPage = true;
+            } else {
+                $this->call($context['this'], Inflector::variablize($name));
+            }
         }
     }
 

src/Template.php

@@ -12,6 +12,7 @@
 use Twig\Error\RuntimeError;
 use Twig\Template as TwigTemplate;
 use Twig\Markup;
+use Twig\Extension\CoreExtension;
 
 /**
  * Template helper
@@ -51,6 +52,7 @@ public static function attribute(Environment $env, Source $source, $object, $ite
                 $arguments[$key] = (string)$value;
             }
         }
-        return \twig_get_attribute($env, $source, $object, $item, $arguments, $type, $isDefinedTest, $ignoreStrictCheck);
+
+        return CoreExtension::getAttribute($env, $source, $object, $item, $arguments, $type, $isDefinedTest, $ignoreStrictCheck);
     }
 }

src/ViewRenderer.php

@@ -113,6 +113,14 @@ class ViewRenderer extends BaseViewRenderer
      */
     public $twigFallbackPaths = [];
 
+    /**
+     * Custom Extension for twig
+     * Need this in the render function for twig3.9 fix.
+     *
+     * @var Extension
+     */
+    protected $extension;
+
 
     public function init()
     {
@@ -121,6 +129,7 @@ public function init()
         $this->twig = new Environment($loader, array_merge([
             'cache' => Yii::getAlias($this->cachePath),
             'charset' => Yii::$app->charset,
+            'use_yield' => false
         ], $this->options));
 
         // Adding custom globals (objects or static classes)
@@ -138,7 +147,8 @@ public function init()
             $this->addFilters($this->filters);
         }
 
-        $this->addExtensions([new Extension($this->uses)]);
+        $this->extension = new Extension($this->uses);
+        $this->addExtensions([$this->extension]);
 
         // Adding custom extensions
         if (!empty($this->extensions)) {
@@ -176,7 +186,30 @@ public function render($view, $file, $params)
             $this->setLexerOptions($this->lexerOptions);
         }
 
-        return $this->twig->render(pathinfo($file, PATHINFO_BASENAME), $params);
+        $content = $this->twig->render(pathinfo($file, PATHINFO_BASENAME), $params);
+        /**
+         * Hack to work with twig3.9.
+         * Explanation:
+         * Twig 3.9 does not hold the contents of the template in the output buffer anymore,
+         * but it still reads the contents from it (if we stick to use `use_yield` false)
+         * (it was an internal implementation and this package relied on this fact)
+         * This means that when the endPage method in the yii2 View class wants to read the output buffer
+         * to replace the placeholders it will be empty, because twig has already emptied it (and does not hold its state anymore).
+         *
+         * By not doing anything in the twig function call yet (see yii\twig\Extension::viewHelper), we can work around this limitation
+         * by calling the endPage function with the twig render results in the buffer after twig has already done its work.
+         */
+        if ($this->extension->withViewEndPage()) {
+            // $view->endPage will end the current buffer when calling ob_get_clean and echo the modified(replaced placeholders) contents.
+            // this means that we need 2 levels deep output buffer.
+            ob_start();
+            ob_start();
+            echo $content;
+            $view->endPage();
+            $content = ob_get_clean();
+        }
+
+        return $content;
     }
 
     /**