Issue #2981584 by Wim Leers, JvE, ndobromirov: BigPipe breaks on large amounts of placeholders (e.g. Flag module on view displaying ~1000 entities)

core/modules/big_pipe/src/Render/BigPipe.php

@@ -389,14 +389,11 @@ class BigPipe {
    */
   protected function sendNoJsPlaceholders($html, $no_js_placeholders, AttachedAssetsInterface $cumulative_assets) {
     // Split the HTML on every no-JS placeholder string.
-    $prepare_for_preg_split = function ($placeholder_string) {
+    $placeholder_strings = array_keys($no_js_placeholders);
-      return '(' . preg_quote($placeholder_string, '/') . ')';
+    $fragments = static::splitHtmlOnPlaceholders($html, $placeholder_strings);
-    };
-    $preg_placeholder_strings = array_map($prepare_for_preg_split, array_keys($no_js_placeholders));
-    $fragments = preg_split('/' . implode('|', $preg_placeholder_strings) . '/', $html, NULL, PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE);
 
     // Determine how many occurrences there are of each no-JS placeholder.
-    $placeholder_occurrences = array_count_values(array_intersect($fragments, array_keys($no_js_placeholders)));
+    $placeholder_occurrences = array_count_values(array_intersect($fragments, $placeholder_strings));
 
     // Set up a variable to store the content of placeholders that have multiple
     // occurrences.
@@ -754,4 +751,39 @@ EOF;
     return $ordered_placeholder_ids;
   }
 
+  /**
+   * Splits a HTML string into fragments.
+   *
+   * Creates an array of HTML fragments, separated by placeholders. The result
+   * includes the placeholders themselves. The original order is respected.
+   *
+   * @param string $html_string
+   *   The HTML to split.
+   * @param string[] $html_placeholders
+   *   The HTML placeholders to split on.
+   *
+   * @return string[]
+   *   The resulting HTML fragments.
+   */
+  private static function splitHtmlOnPlaceholders($html_string, array $html_placeholders) {
+    $prepare_for_preg_split = function ($placeholder_string) {
+      return '(' . preg_quote($placeholder_string, '/') . ')';
+    };
+    $preg_placeholder_strings = array_map($prepare_for_preg_split, $html_placeholders);
+    $pattern = '/' . implode('|', $preg_placeholder_strings) . '/';
+    if (strlen($pattern) < 31000) {
+      // Only small (<31K characters) patterns can be handled by preg_split().
+      $flags = PREG_SPLIT_NO_EMPTY | PREG_SPLIT_DELIM_CAPTURE;
+      $result = preg_split($pattern, $html_string, NULL, $flags);
+    }
+    else {
+      // For large amounts of placeholders we use a simpler but slower approach.
+      foreach ($html_placeholders as $placeholder) {
+        $html_string = str_replace($placeholder, "\x1F" . $placeholder . "\x1F", $html_string);
+      }
+      $result = array_filter(explode("\x1F", $html_string));
+    }
+    return $result;
+  }
+
 }

core/modules/big_pipe/tests/src/Unit/Render/ManyPlaceholderTest.php

@@ -0,0 +1,59 @@
+<?php
+
+namespace Drupal\Tests\big_pipe\Unit\Render;
+
+use Drupal\big_pipe\Render\BigPipe;
+use Drupal\big_pipe\Render\BigPipeResponse;
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\Render\HtmlResponse;
+use Drupal\Core\Render\RendererInterface;
+use Drupal\Tests\UnitTestCase;
+use Symfony\Component\EventDispatcher\EventDispatcherInterface;
+use Symfony\Component\HttpFoundation\RequestStack;
+use Symfony\Component\HttpFoundation\Session\SessionInterface;
+use Symfony\Component\HttpKernel\HttpKernelInterface;
+
+/**
+ * @coversDefaultClass \Drupal\big_pipe\Render\BigPipe
+ * @group big_pipe
+ */
+class ManyPlaceholderTest extends UnitTestCase {
+
+  /**
+   * @covers \Drupal\big_pipe\Render\BigPipe::sendNoJsPlaceholders
+   */
+  public function testManyNoJsPlaceHolders() {
+    $bigpipe = new BigPipe(
+      $this->prophesize(RendererInterface::class)->reveal(),
+      $this->prophesize(SessionInterface::class)->reveal(),
+      $this->prophesize(RequestStack::class)->reveal(),
+      $this->prophesize(HttpKernelInterface::class)->reveal(),
+      $this->prophesize(EventDispatcherInterface::class)->reveal(),
+      $this->prophesize(ConfigFactoryInterface::class)->reveal()
+    );
+    $response = new BigPipeResponse(HtmlResponse::create());
+
+    // Add many placeholders.
+    $many_placeholders = [];
+    for ($i = 0; $i < 400; $i++) {
+      $many_placeholders[$this->randomMachineName(80)] = $this->randomMachineName(80);
+    }
+    $attachments = [
+      'library' => [],
+      'big_pipe_nojs_placeholders' => $many_placeholders,
+    ];
+    $response->setAttachments($attachments);
+
+    // Construct minimal HTML response.
+    $content = '<html><body>content<drupal-big-pipe-scripts-bottom-marker>script-bottom<drupal-big-pipe-scripts-bottom-marker></body></html>';
+    $response->setContent($content);
+
+    // Capture the result to avoid PHPUnit complaining.
+    ob_start();
+    $bigpipe->sendContent($response);
+    $result = ob_get_clean();
+
+    $this->assertNotEmpty($result);
+  }
+
+}