Add test to check if a block exists

doc/tests/block_name.rst

@@ -0,0 +1,13 @@
+``block name``
+==============
+
+.. versionadded:: 1.28
+    The ``block name`` test was added in Twig 1.28.
+
+``block name`` checks if a block is defined in the current context of the template.
+
+.. code-block:: jinja
+
+    {% if 'title' is block name %}
+        <title>{{ block('title') }}<title>
+    {% endif %}

doc/tests/index.rst

@@ -4,6 +4,7 @@ Tests
 .. toctree::
     :maxdepth: 1
 
+    block_name
     constant
     defined
     divisibleby

lib/Twig/Extension/Core.php

@@ -222,6 +222,7 @@ class Twig_Extension_Core extends Twig_Extension
             new Twig_SimpleTest('constant', null, array('node_class' => 'Twig_Node_Expression_Test_Constant')),
             new Twig_SimpleTest('empty', 'twig_test_empty'),
             new Twig_SimpleTest('iterable', 'twig_test_iterable'),
+            new Twig_SimpleTest('block name', null, array('node_class' => 'Twig_Node_Expression_Test_BlockName')),
         );
     }
 

lib/Twig/Node/Expression/Test/BlockName.php

@@ -0,0 +1,33 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) 2016 Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ * Checks whether a block is defined.
+ *
+ * <pre>
+ *  {% if 'title' is block name %}
+ *    <title>{{ block('title') }}</title>
+ *  {% endif %}
+ * </pre>
+ *
+ * @author Martin Hasoň <martin.hason@gmail.com>
+ */
+class Twig_Node_Expression_Test_BlockName extends Twig_Node_Expression_Test
+{
+    public function compile(Twig_Compiler $compiler)
+    {
+        $compiler
+            ->raw('$this->blockExists(')
+            ->subcompile($this->getNode('node'))
+            ->raw(', $context, $blocks)')
+        ;
+    }
+}

lib/Twig/Template.php

@@ -286,6 +286,8 @@ abstract class Twig_Template implements Twig_TemplateInterface
      *
      * @return bool true if the block exists, false otherwise
      *
+     * @see blockExists
+     *
      * @internal
      */
     public function hasBlock($name)
@@ -653,4 +655,37 @@ abstract class Twig_Template implements Twig_TemplateInterface
 
         return $ret;
     }
+
+    /**
+     * Returns whether a block exists or not in the current context of the template.
+     *
+     * This method checks blocks defined in the current template
+     * or defined in "used" traits or defined in parent templates.
+     *
+     * @param string $name    The block name
+     * @param array  $context The context
+     * @param array  $blocks  The current set of blocks
+     *
+     * @return bool true if the block exists, false otherwise
+     *
+     * @see hasBlock
+     *
+     * @internal
+     */
+    protected function blockExists($name, array $context, array $blocks = array())
+    {
+        if (isset($blocks[$name])) {
+            return $blocks[$name][0] instanceof self;
+        }
+
+        if (isset($this->blocks[$name])) {
+            return true;
+        }
+
+        if (false !== $parent = $this->getParent($context)) {
+            return $parent->blockExists($name, $context);
+        }
+
+        return false;
+    }
 }

test/Twig/Tests/Fixtures/tests/block_name.test

@@ -0,0 +1,38 @@
+--TEST--
+"block name" test
+--TEMPLATE--
+{% extends 'parent' %}
+{% block icon %}icon{% endblock %}
+{% block body %}
+    {{ parent() }}
+    {{ 'foo' is block name ? 'ok' : 'ko' }}
+    {{ 'footer' is block name ? 'ok' : 'ko' }}
+    {{ 'icon' is block name ? 'ok' : 'ko' }}
+    {{ 'block1' is block name ? 'ok' : 'ko' }}
+    {%- embed 'embed' %}
+        {% block content %}content{% endblock %}
+    {% endembed %}
+{% endblock %}
+{% use 'blocks' %}
+--TEMPLATE(parent)--
+{% block body %}
+  {{ 'icon' is block name ? 'ok' : 'ko' -}}
+{% endblock %}
+{% block footer %}{% endblock %}
+--TEMPLATE(embed)--
+{{ 'icon' is block name ? 'ok' : 'ko' }}
+{{ 'content' is block name ? 'ok' : 'ko' }}
+{{ 'block1' is block name ? 'ok' : 'ko' }}
+--TEMPLATE(blocks)--
+{% block block1 %}{%endblock %}
+--DATA--
+return array()
+--EXPECT--
+ok
+    ko
+    ok
+    ok
+    ok
+ko
+ok
+ko