Text filter should return a string, not a Markup object

It's working for me: Drupal 10.1.2, Collapse Text 2.0.0

Attached the .patch, thanks @bkosborne

Hi Brian (@bkosborne),

Thanks again very much for your great help on this, it's greatly appreciated.

Just a quick message to let you know the changes from related !MR3 have been committed manually at #7 with a slightly updated commit message (from the MR).

Otherwise, I have tested this locally and it worked as expected :
I created a node with the Collapse Text markup in Full HTML and moved the filter Collapsible text blocks right above the Lazy load images, as suggested in the issue summary.
After refreshing a node page with collapse text content, the following error appeared:

The website encountered an unexpected error. Try again later.

TypeError: stripos(): Argument #1 ($haystack) must be of type string, Drupal\Core\Render\Markup given in stripos() (line 31 of core/modules/filter/src/Plugin/Filter/FilterImageLazyLoad.php).
Drupal\filter\Plugin\Filter\FilterImageLazyLoad->process(Object, 'en') (Line: 118)
Drupal\filter\Element\ProcessedText::preRenderText(Array)
call_user_func_array(Array, Array) (Line: 111)
Drupal\Core\Render\Renderer->doTrustedCallback(Array, Array, 'Render #pre_render callbacks must be methods of a class that implements \Drupal\Core\Security\TrustedCallbackInterface or be an anonymous function. The callback was %s. See https://www.drupal.org/node/2966725', 'exception', 'Drupal\Core\Render\Element\RenderCallbackInterface') (Line: 858)
Drupal\Core\Render\Renderer->doCallback('#pre_render', Array, Array) (Line: 421)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 240)
Drupal\Core\Render\Renderer->render(Array) (Line: 475)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 88)
__TwigTemplate_3fe1a6925ac55df2dcc0b507a451e16c->doDisplay(Array, Array) (Line: 394)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 367)
Twig\Template->display(Array, Array) (Line: 46)
__TwigTemplate_f30e847664dc7313311f7b5f269e3cec->doDisplay(Array, Array) (Line: 394)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 367)
Twig\Template->display(Array, Array) (Line: 43)
__TwigTemplate_2b95f2567c5ed02a628d1f559a79016a->doDisplay(Array, Array) (Line: 394)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 367)
Twig\Template->display(Array) (Line: 379)
Twig\Template->render(Array) (Line: 38)
Twig\TemplateWrapper->render(Array) (Line: 39)
twig_render_template('core/themes/olivero/templates/field/field--text-with-summary.html.twig', Array) (Line: 348)
Drupal\Core\Theme\ThemeManager->render('field', Array) (Line: 480)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 493)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 240)
Drupal\Core\Render\Renderer->render(Array) (Line: 475)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 135)
__TwigTemplate_a9b34a8fde9573e53e43081bbf05e4ab->doDisplay(Array, Array) (Line: 394)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 367)
Twig\Template->display(Array) (Line: 379)
Twig\Template->render(Array) (Line: 38)
Twig\TemplateWrapper->render(Array) (Line: 39)
twig_render_template('core/themes/olivero/templates/content/node.html.twig', Array) (Line: 348)
Drupal\Core\Theme\ThemeManager->render('node', Array) (Line: 480)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 240)
Drupal\Core\Render\Renderer->render(Array, ) (Line: 238)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 627)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 239)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 128)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object)
call_user_func(Array, Object, 'kernel.view', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch(Object, 'kernel.view') (Line: 186)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 28)
Drupal\Core\StackMiddleware\ContentLength->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 36)
Drupal\Core\StackMiddleware\AjaxPageState->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object, 1, 1) (Line: 704)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

After applying the patch, the error disappeared and the page displayed fine.

Once again, thank you very much for keeping an eye on the module and fixing issues as they come.

Feel free to let us know at any time if you have any questions, concerns, suggestions or comments on any of the recent code changes, this ticket, or the module in general, we would be glad to help.
Thanks again to everyone for your contributions, testing and feedback.
Cheers !