Issue #3463038 by longwave: Add helper method to generate HTML placeholders

core/lib/Drupal/Core/Render/PlaceholderGenerator.php

@@ -111,16 +111,13 @@ public function createPlaceholder(array $element) {
 
     // Generate placeholder markup. Note that the only requirement is that this
     // is unique markup that isn't easily guessable. The #lazy_builder callback
-    // and its arguments are put in the placeholder markup solely to simplify<<<
+    // and its arguments are put in the placeholder markup solely to simplify
     // debugging.
-    $callback = $placeholder_render_array['#lazy_builder'][0];
-    $arguments = UrlHelper::buildQuery($placeholder_render_array['#lazy_builder'][1]);
-    $token = Crypt::hashBase64(serialize($placeholder_render_array));
-    $placeholder_markup = '<drupal-render-placeholder callback="' . Html::escape($callback) . '"';
-    if ($arguments !== '') {
-      $placeholder_markup .= ' arguments="' . Html::escape($arguments) . '"';
-    }
-    $placeholder_markup .= ' token="' . Html::escape($token) . '"></drupal-render-placeholder>';
+    $placeholder_markup = static::createPlaceholderTag('drupal-render-placeholder', [
+      'callback' => $placeholder_render_array['#lazy_builder'][0],
+      'arguments' => UrlHelper::buildQuery($placeholder_render_array['#lazy_builder'][1]),
+      'token' => Crypt::hashBase64(serialize($placeholder_render_array)),
+    ]);
 
     // Build the placeholder element to return.
     $placeholder_element = [];
@@ -129,4 +126,18 @@ public function createPlaceholder(array $element) {
     return $placeholder_element;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public static function createPlaceholderTag(string $tag, array $attributes): string {
+    $markup = "<$tag";
+    foreach ($attributes as $key => $value) {
+      if ($value !== '') {
+        $markup .= ' ' . $key . '="' . Html::escape($value) . '"';
+      }
+    }
+    $markup .= "></$tag>";
+    return $markup;
+  }
+
 }

core/lib/Drupal/Core/Render/PlaceholderGeneratorInterface.php

@@ -62,4 +62,17 @@ public function shouldAutomaticallyPlaceholder(array $element);
    */
   public function createPlaceholder(array $element);
 
+  /**
+   * Generates a placeholder HTML tag.
+   *
+   * @param string $tag
+   *   The placeholder tag.
+   * @param array $attributes
+   *   An array of key-value pairs to use as tag attributes.
+   *
+   * @return string
+   *   The HTML placeholder.
+   */
+  public static function createPlaceholderTag(string $tag, array $attributes): string;
+
 }

core/modules/filter/src/FilterProcessResult.php

@@ -3,9 +3,9 @@
 namespace Drupal\filter;
 
 use Drupal\Component\Utility\Crypt;
-use Drupal\Component\Utility\Html;
 use Drupal\Component\Utility\UrlHelper;
 use Drupal\Core\Render\BubbleableMetadata;
+use Drupal\Core\Render\PlaceholderGenerator;
 
 /**
  * Used to return values from a text filter plugin's processing method.
@@ -133,14 +133,11 @@ public function setProcessedText($processed_text) {
    */
   public function createPlaceholder($callback, array $args) {
     // Generate placeholder markup.
-    // @see \Drupal\Core\Render\PlaceholderGenerator::createPlaceholder()
-    $arguments = UrlHelper::buildQuery($args);
-    $token = Crypt::hashBase64(serialize([$callback, $args]));
-    $placeholder_markup = '<drupal-filter-placeholder callback="' . Html::escape($callback) . '"';
-    if ($arguments !== '') {
-      $placeholder_markup .= ' arguments="' . Html::escape($arguments) . '"';
-    }
-    $placeholder_markup .= ' token="' . Html::escape($token) . '"></drupal-filter-placeholder>';
+    $placeholder_markup = PlaceholderGenerator::createPlaceholderTag('drupal-filter-placeholder', [
+      'callback' => $callback,
+      'arguments' => UrlHelper::buildQuery($args),
+      'token' => Crypt::hashBase64(serialize([$callback, $args])),
+    ]);
 
     // Add the placeholder attachment.
     $this->addAttachments([