ER's label formatter needs to take into account that $entity->urlInfo() might throw an exception

This doesn't seem like a critical/release-blocking bug to me. What is your use case to reference an action?

See https://www.drupal.org/node/45111 on how the priority is defined, it is only critical if it renders the whole system unusable. One broken feature that I think is not very frequently used does IMHO not qualify as breaking the whole system.

This should fix it. Tests will need to be added after #2370703: ER's "autocreate" feature is mostly broken (and untested) gets in.

+++ b/core/modules/entity_reference/src/Plugin/Field/FieldFormatter/EntityReferenceLabelFormatter.php
@@ -61,12 +62,26 @@ public function settingsSummary() {
+      if ($output_as_link) {
+        try {
+          $uri = $entity->urlInfo();
+        }
+        catch (UndefinedLinkTemplateException $e) {
+          // This exception is thrown by \Drupal\Core\Entity\Entity::urlInfo()
+          // and it means that the entity type doesn't have a link template nor
+          // a valid "uri_callback", so don't bother trying to output a link for
+          // the rest of the referenced entities.
+          $output_as_link = FALSE;
+        }
+      }

I find it very annoying that config entities overide urlInfo() and set the default to edit-form.

If it would not, then instead of checking against the exception, we could simply check for the existence of 'canonical' directly.

@Berdir, I see your point but the fact is that most config entities don't have a 'canonical' link so 'edit-form' is the next best thing.

@iantresman, well, the default formatter for entity reference fields is entity_reference_label so I'm not sure why someone would expect anything else than the label :)

Here's the test I promised earlier.

@Berdir, thinking about it more, even if ConfigEntityBase wouldn't override urlInfo(), any other (custom) entity class could do that so checking against the exception is still the right thing to do :)

Not sure what happened there, let's try again.

Who wants to press the RTBC button? :)

@Berdir, thinking about it more, even if ConfigEntityBase wouldn't override urlInfo(), any other (custom) entity class could do that so checking against the exception is still the right thing to do :)

Right.

Let's just fix it like this then.

Committed 7c6a23f and pushed to 8.0.x. Thanks!