Upgrade to 8.4.3 breaks Create Content links

It'd be awesome to see a test replicating the issue.

Is it possible to replicate on a clean install of 8.4.3? or only after upgrading from 8.4.2?
How about a clean install of 8.4.2, then upgrade to 8.4.3?

I've run into this problem when updating from 8.3.7 to 8.4.5 also. I haven't found a solution yet.

This is usually a custom module/template that calls toUrl() on an unsaved entity, which is not allowed.

Enable verbose error logging which should print a backtrace, post that here.

I updated my site from 8.3.7 to 8.4.2 without an issue. Updated to 8.5.0 when it was released. Got the same error but pointing to a different line number. Enabled verbose logging with backtrace information as described here

Here's what came back.

The website encountered an unexpected error. Please try again later.Drupal\Core\Entity\EntityMalformedException: The "node" entity cannot have a URI as it does not have an ID in Drupal\Core\Entity\Entity->toUrl() (line 189 of core\lib\Drupal\Core\Entity\Entity.php).

Drupal\pathauto\PathautoState->getValue() (Line: 140)
Drupal\Core\Field\FieldItemBase->__get('pathauto') (Line: 116)
Drupal\Core\Field\FieldItemList->__get('pathauto') (Line: 54)
Drupal\pathauto\PathautoWidget->formElement(Object, 0, Array, Array, Object) (Line: 335)
Drupal\Core\Field\WidgetBase->formSingleElement(Object, 0, Array, Array, Object) (Line: 202)
Drupal\Core\Field\WidgetBase->formMultipleElements(Object, Array, Object) (Line: 104)
Drupal\Core\Field\WidgetBase->form(Object, Array, Object) (Line: 171)
Drupal\Core\Entity\Entity\EntityFormDisplay->buildForm(Object, Array, Object) (Line: 122)
Drupal\Core\Entity\ContentEntityForm->form(Array, Object) (Line: 115)
Drupal\node\NodeForm->form(Array, Object) (Line: 117)
Drupal\Core\Entity\EntityForm->buildForm(Array, Object)
call_user_func_array(Array, Array) (Line: 514)
Drupal\Core\Form\FormBuilder->retrieveForm('node_article_form', Object) (Line: 271)
Drupal\Core\Form\FormBuilder->buildForm('node_article_form', Object) (Line: 48)
Drupal\Core\Entity\EntityFormBuilder->getForm(Object) (Line: 113)
Drupal\node\Controller\NodeController->add(Object)
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 582)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 151)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 68)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 57)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 99)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 78)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 47)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 50)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 657)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

That's coming from pathauto, strange.

Make sure that you are using an up to date version of pathauto, there has not been a toUrl() call in PathautoState in a *very* long time. Not since 29.11.2015 to be exact. You need to keep your contrib modules up to date, not just drupal core, because minor versions tend to introduce changes that can break contrib modules in subtle (and sometimes not so subtle ways..)

I usually update the contributed modules first, take a backup, and then update the core. Pathauto wasn't listed as an available update when I updated to 8.4.2. Browsing the pathauto files, I see a reference that it's for 8.x and that should be the latest version available.

Can you post the content of the pathauto.info.yml file?

I downloaded the latest pathauto zip file from Drupal and compared them to what I have and they aren't the same. Not sure why it wasn't listed as an available update. I attached a screenshot comparing the differences of the pathauto.info.yml files and the list of available updates as displayed from my Drupal site.

Because the version you had wasn't from drupal.org, you probably installed it years ago from github, Drupal didn't know how to update that as it didn't have the required information in the info.yml file.

Marking this as fixed.

I inherited this site so it's quite possible the original developers might have gotten it from there when it was developed in Drupal 6. I'll replace it with the latest version from Drupal. Thanks for your help.