Node preview shows and defaults to "Default" instead of "Full" view mode

Hm, at least for me now looks more confusing having both "Full" and "Default" in the dropdown list. I have to confess that it took me a while in the past to familiarize with the difference between Default and Full.

Makes sense to me.

Looks good. Just a very minor nit

+++ b/core/modules/node/src/Form/NodePreviewForm.php
@@ -85,9 +85,11 @@ public function buildForm(array $form, FormStateInterface $form_state, EntityInt
+    $view_mode_options = ['full' => t('Full')] + $this->entityManager->getViewModeOptionsByBundle('node', $node->bundle());

FormBase is already using the StringTranslationTrait, so $this->t() is available. s/t()/$this->t()

What happens when the full mode is deleted? I tried this locally and everything works - it just falls back to default but I'm not sure that adding full makes sense if it doesn't exist.

Committed and pushed 959df8d to 8.3.x and 333a973 to 8.2.x. Thanks!

Discussed with @Berdir in IRC and we decided that this makes things better since as @Berdir wrote:

it is all very weird. and even our own API is completely wrong about default/full, which of course doesn't help with actually understand what view modes/view displays are and results in all our UI's being wrong :)

based on discussions with slashrsm and others, I'm thinking about just making "Full" the fallback or maybe drop the fallback concept completely (no view display enabled => no pre-configured fields), but those are 9.x changes..

yeah. I can live with entity reference formatters and views being wrong about default/full, but you almost never use either default or full in those cases, so easy to ignore. node preview is different though because is the default selection and what you actually want to see in most cases