Tests that the debug markup does not significantly alter the DOM.

This is done by comparing the textContent property of the document body with and without the debug output. Since textContent is the concatenation of all child nodes, including whitespace and text nodes, it will significantly differ if new whitespace is added by the HTML comments. The comments themselves will not be part of the textContent.

See also

https://developer.mozilla.org/en-US/docs/Web/API/Node/textContent

File

core/modules/system/tests/src/Functional/Theme/TwigDebugMarkupTest.php, line 115

Class

TwigDebugMarkupTest

Tests for Twig debug markup.

Namespace

Drupal\Tests\system\Functional\Theme

Code

public function testTwigDebugMarkupDomParity() : void {
  $node = $this->drupalCreateNode();
  
  /**
   * @return array{textContent: string, innerHTML: string}
   */
  $get_text_and_html = function () use ($node) : array {
    $html = $this->drupalGet(Url::fromRoute('entity.node.canonical', [
      'node' => $node->id(),
    ]));
    $dom = HTMLDocument::createFromString($html);
    $element = $dom->querySelector('body');
    return [
      'textContent' => trim($element->textContent),
      'innerHTML' => $element->innerHTML,
    ];
  };
  $twig_debug_output_needle = "<!--\n\nTHEME DEBUG -->";
  $text_and_html = $get_text_and_html();
  $this->assertStringNotContainsString($twig_debug_output_needle, $text_and_html['innerHTML']);
  $this->enableTwigDebug();
  $text_and_html_debug = $get_text_and_html();
  $this->assertStringContainsString($twig_debug_output_needle, $text_and_html_debug['innerHTML']);
  $this->assertEquals($text_and_html['textContent'], $text_and_html_debug['textContent']);
}

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