TypeError: Illegal offset type in isset or empty

Thanks for the report. We require the steps to reproduce for bugs to understand if there is missing test coverage.

• Why specifically is $input not a string in this case?
• Can we get a stack trace too please?

I am running into this error on a site after upgrading from drupal/core 9.3.22 to 9.5.8. The page where this error happens is a view page, pretty straightforward setup, view based on content, with a taxonomy filter:

Configure filter criterion: Content: Has taxonomy term -> Is none of -> [term_name]

Patch #6 fixes the issue for me on this view page.

Here is error with backtrace:

The website encountered an unexpected error. Please try again later.
TypeError: Illegal offset type in isset or empty in Drupal\taxonomy\Plugin\views\filter\TaxonomyIndexTid->validateExposed() (line 353 of core/modules/taxonomy/src/Plugin/views/filter/TaxonomyIndexTid.php).

Drupal\taxonomy\Plugin\views\filter\TaxonomyIndexTid->validateExposed(Array, Object) (Line: 169)
Drupal\views\Form\ViewsExposedForm->validateForm(Array, Object)
call_user_func_array(Array, Array) (Line: 82)
Drupal\Core\Form\FormValidator->executeValidateHandlers(Array, Object) (Line: 275)
Drupal\Core\Form\FormValidator->doValidateForm(Array, Object, 'views_exposed_form') (Line: 118)
Drupal\Core\Form\FormValidator->validateForm('views_exposed_form', Array, Object) (Line: 69)
Drupal\autosave_form\Form\AutosaveFormValidator->validateForm('views_exposed_form', Array, Object) (Line: 591)
Drupal\Core\Form\FormBuilder->processForm('views_exposed_form', Array, Object) (Line: 144)
Drupal\autosave_form\Form\AutosaveFormBuilder->processForm('views_exposed_form', Array, Object) (Line: 323)
Drupal\Core\Form\FormBuilder->buildForm('\Drupal\views\Form\ViewsExposedForm', Object) (Line: 97)
Drupal\autosave_form\Form\AutosaveFormBuilder->buildForm('\Drupal\views\Form\ViewsExposedForm', Object) (Line: 134)
Drupal\views\Plugin\views\exposed_form\ExposedFormPluginBase->renderExposedForm() (Line: 1243)
Drupal\views\ViewExecutable->build() (Line: 392)
Drupal\views\Plugin\views\display\PathPluginBase->execute() (Line: 196)
Drupal\views\Plugin\views\display\Page->execute() (Line: 1635)
Drupal\views\ViewExecutable->executeDisplay('page_1', Array) (Line: 81)
Drupal\views\Element\View::preRenderViewElement(Array)
call_user_func_array(Array, Array) (Line: 101)
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: 788)
Drupal\Core\Render\Renderer->doCallback('#pre_render', Array, Array) (Line: 374)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 204)
Drupal\Core\Render\Renderer->render(Array, ) (Line: 242)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 580)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 243)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 132)
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: 142)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch(Object, 'kernel.view') (Line: 174)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
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: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 718)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Was previously tagged for steps to reproduce, see that's missing in the issue summary.

Typically for issues like this we need to discover why it's empty at this location. Putting just a check may be covering a bigger problem.

Regardless will need test coverage.

I'm running into a similar problem after upgrading the site from 8 to 9 ,
I'm using grouped filter exposed with 'any' checked, allowing multiple values is disabled and the operation is "is one of".
the value inside $selected_group when broke is

array:1 [▼
  1 => "1"
]

The website encountered an unexpected error. Please try again later.
TypeError: Illegal offset type in isset or empty in Drupal\views\Plugin\views\filter\FilterPluginBase->convertExposedInput() (line 1407 of core/modules/views/src/Plugin/views/filter/FilterPluginBase.php).
Drupal\views\Plugin\views\filter\FilterPluginBase->convertExposedInput(Array, NULL) (Line: 1365)
Drupal\views\ViewExecutable->_build('filter') (Line: 1267)
Drupal\views\ViewExecutable->build(NULL) (Line: 1396)
Drupal\views\ViewExecutable->execute(NULL) (Line: 1459)
Drupal\views\ViewExecutable->render() (Line: 131)
Drupal\views\Plugin\views\display\Block->execute() (Line: 1635)
Drupal\views\ViewExecutable->executeDisplay('professionals_pager', Array) (Line: 81)
Drupal\views\Element\View::preRenderViewElement(Array) (Line: 59)
Drupal\views\Plugin\Block\ViewsBlock->build() (Line: 90)
Drupal\ds\Plugin\DsField\BlockBase->build() (Line: 364)
ds_entity_view_alter(Array, Object, Object) (Line: 562)
Drupal\Core\Extension\ModuleHandler->alter('user_view', Array, Object, Object) (Line: 305)
Drupal\Core\Entity\EntityViewBuilder->buildMultiple(Array) (Line: 239)
Drupal\Core\Entity\EntityViewBuilder->build(Array)
call_user_func_array(Array, Array) (Line: 101)
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: 788)
Drupal\Core\Render\Renderer->doCallback('#pre_render', Array, Array) (Line: 374)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 204)
Drupal\Core\Render\Renderer->render(Array, ) (Line: 242)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 580)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 243)
Drupal\Core\Render\MainContent\HtmlRenderer->prepare(Array, Object, Object) (Line: 132)
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: 142)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch(Object, 'kernel.view') (Line: 174)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
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: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 718)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Hi,
I was facing that issue, the patch solves it, but it break with the patch for this issue: https://www.drupal.org/project/drupal/issues/3357973
This issue: https://www.drupal.org/project/drupal/issues/3357973 solves both cases, I would say with more testing we can close the issue https://www.drupal.org/project/drupal/issues/3336222

Drupal 9 is no longer supported. There will be no further releases.

Based on comments from last year, this is a duplicate.

Patch that applies to 10.4.x

The above patch applies cleanly to Drupal 11.2.x, 11.1.x, 11.0.x, 10.*, etc. I've opened up a MR for this over at:
https://git.drupalcode.org/project/drupal/-/merge_requests/12750

This was marked as a duplicate to check the parent issue

Patch #15 worked and message issue disappear from logs but Filter still does not work - it won't show any result. So this patch fixed just "message" it seems.

It isn't clear to me why a duplicate issue was re-opened. As a duplicate, work continues in the other issue, which is #3357973: Grouped exposed filters do not work when input from user is an array.

I am restoring the duplicate status, and other meta data, of this issue and closing the MR.