Fix implementation to not render helper output

This ensures compatibility with the official Handlebars implementation.
See #26

ChangeLog.md

@@ -3,6 +3,12 @@ HandleBars change log
 
 ## ?.?.? / ????-??-??
 
+## 8.1.0 / 2023-04-07
+
+* Fixed implementation to not render helper output. This ensures
+  compatibility with the official Handlebars implementation. See
+  issue #26
+  (@thekid)
 * Merged PR #25: Migrate to new testing library - @thekid
 
 ## 8.0.0 / 2022-10-08

src/main/php/com/handlebarsjs/DefaultContext.class.php

@@ -36,6 +36,25 @@ public final function newInstance($result, Context $parent= null) {
     return new self($result, $parent ?: $this);
   }
 
+  /**
+   * Returns a rendering of a given helper closure
+   *
+   * @see    https://github.com/xp-forge/handlebars/issues/26
+   * @param  var $closure
+   * @param  com.github.mustache.Node $node
+   * @param  string[] $options
+   * @param  string $start
+   * @param  string $end
+   * @return string
+   */
+  public function asRendering($closure, $node, $options= [], $start= '{{', $end= '}}') {
+    $pass= [];
+    foreach ($options as $key => $option) {
+      $pass[$key]= $this->isCallable($option) ? $option($node, $this, []) : $option;
+    }
+    return $closure($node, $this, $pass);
+  }
+
   /**
    * Parse input into segments. Handles literal segments including quoted
    * strings, e.g. `input.["item-class"]`.

src/test/php/com/handlebarsjs/unittest/ExecutionTest.class.php

@@ -18,6 +18,7 @@ protected function evaluate($template, $variables, $templates= ['test' => 'Parti
       ->withTemplates(new InMemory($templates))
       ->withHelper('date', function($node, $context, $options) { return date('Y-m-d', $options[0] ?? time()); })
       ->withHelper('time', ['short' => ['24' => function($node, $context, $options) { return date('H:i', $options[0] ?? time()); }]])
+      ->withHelper('code', function($node, $context, $options) { return '<code>'.$options[0].'</code>'; })
       ->render($template, $variables)
     ;
   }
@@ -203,4 +204,14 @@ public function undefined_partial() {
   public function undefined_dynamic_partial() {
     $this->evaluate('{{> (template)}}', ['template' => 'undefined']);
   }
+
+  #[Test]
+  public function handlebars_in_replacement() {
+    Assert::equals('{{name}}', $this->evaluate('{{name}}', ['name' => '{{name}}']));
+  }
+
+  #[Test]
+  public function handlebars_returned_from_helper() {
+    Assert::equals('<code>{{name}}</code>', $this->evaluate('{{& code in}}', ['in' => '{{name}}']));
+  }
 }