Fix the code in \Drupal\render_example\Controller\RenderExampleController::preRender()

Drupal 11.x uses the following code, for example.

$class = static::class;
return [
  '#input' => TRUE,
  '#theme' => 'input__date',
  '#process' => [
    [$class, 'processAjaxForm'],
  ],
  '#pre_render' => [[$class, 'preRenderDate']],
  '#theme_wrappers' => ['form_element'],
  '#attributes' => ['type' => 'date'],
  '#date_date_format' => 'Y-m-d',
];

The correct code to use in the RenderExampleController class would be the following one.

    // Properties that contain callbacks can also reference methods on a class
    // in addition to functions. See
    // \Drupal\render_example\Controller\RenderExampleController::preRender()
    $build['#pre_render'] = [[static::class, 'preRender']];

[static::class . '::postRenderAddPrefix'] used by that class works because it is an array with a singe string. [static::class, 'preRender'] contains two strings and Drupal would use '\Drupal\render_example\Controller\RenderExampleController' (the class name) as callback, which would work only if the class has a __invoke() method.

somehow 17 tests failed but only 13 in other issues

The only failing tests this module implements are the following ones.

• Drupal\Tests\render_example\Functional\RenderExampleTest::testRenderExample()
Behat\Mink\Exception\ResponseTextException: The text "Hello ug26w3ez, welcome to the #cache example." was not found anywhere in the text of the current page.
• Drupal\Tests\render_example\Functional\RenderExampleMenuTest::testRenderExampleLinksExist
Behat\Mink\Exception\ExpectationException: Current response status code is 500, but 200 expected.

I updated the issue summary to make clearer what needs to be fixed.

apaderno → changed the visibility of the branch 2986435-without-prerender-test to hidden.

MR !42 can be used as start to fix this issue.

IMO, the code in \Drupal\render_example\Controller\RenderExampleController::preRender()is too complex to show what a pre-render callback can do, and it duplicates the code already used from \Drupal\render_example\Controller\RenderExampleController::arrays().

$output = [];
// We are going to create a new output render array that pairs each
// example with a set of helper render arrays. These are used to display
// the description as a title and the unrendered content alongside the
// examples.
foreach (Element::children($build) as $key) {
  if (isset($build[$key])) {
    $output[$key] = [
      '#theme' => 'render_array',
      'description' => [
        '#type' => 'markup',
        '#markup' => $build[$key]['#description'] ?? '',
      ],
      'rendered' => $build[$key],
      'unrendered' => [
        '#type' => 'markup',
        '#markup' => htmlentities(Variable::export($build[$key])), 
      ],
    ];
  }
}

foreach (Element::properties($build) as $key) {
  $output[$key] = $build[$key];
}

I would rather keep it simple like \Drupal\render_example\Controller\RenderExampleController::postRenderAddPrefix().

public static function postRenderAddPrefix($markup, array $element) {
  $markup .= '<div style="color:blue">This markup was added after rendering by a #post_render callback.</div>';
  return $markup;
}

apaderno → changed the visibility of the branch 2986435-fix-RenderExampleController to hidden.

The failing tests after the last commit in the fork are the following ones.

Drupal\Tests\render_example\Functional\RenderExampleTest::testRenderExample()
Behat\Mink\Exception\ResponseTextException: The text "This element has been altered by the #pre_render callback." was not found anywhere in the text of the current page.
Drupal\Tests\hooks_example\Functional\HooksExampleTest::testHooksExample()
Behat\Mink\Exception\ExpectationException: Current response status code is 403, but 200 expected.

From the first failing test, I gather that either the #pre_render callback is not invoked, or the render array has a structure that is different from what that callback expects. Since the last commit commented out (just for testing) the code that builds a new render array from $build, the issue is not how the new render array is built.
🐛 var_export() does not handle circular references Needs review , which does not use the #pre_render callback, but changes how the build array items are shown in the page (using json_export() instead of Variables::export()), does not cause any failure in the tests defined by the Render Example module. It means the tests failing for this MR are not caused by what reported in the other issue.

As for the second failing test, the status code is now 403 instead of 500.

apaderno → credited jmohino → .

apaderno → credited optlai → .

I am crediting jmohino, who created the related issue, which gave me a confirm of what should have been fixed for RenderExampleController::preRender() to work without tests failures, and optlai, who confirmed the bug described in the related issue was still present.