revision_timestamp is not set to current time when quick editing (it stays unchanged)

Thanks for all your help! Much appreciated :)

See

  /**
   * Initialize the form state and the entity before the first form build.
   */
  protected function init(FormStateInterface $form_state, EntityInterface $entity, $field_name) {
    // @todo Rather than special-casing $node->revision, invoke prepareEdit()
    //   once https://www.drupal.org/node/1863258 lands.
    if ($entity->getEntityTypeId() == 'node') {
      $node_type = $this->nodeTypeStorage->load($entity->bundle());
      $entity->setNewRevision($node_type->isNewRevision());
      $entity->revision_log = NULL;
    }
    …
  }

  …

  protected function buildEntity(array $form, FormStateInterface $form_state) {
    /** @var $entity \Drupal\Core\Entity\EntityInterface */
    $entity = clone $form_state->get('entity');
    $field_name = $form_state->get('field_name');

    $form_state->get('form_display')->extractFormValues($entity, $form, $form_state);

    // @todo Refine automated log messages and abstract them to all entity
    //   types: https://www.drupal.org/node/1678002.
    if ($entity->getEntityTypeId() == 'node' && $entity->isNewRevision() && $entity->revision_log->isEmpty()) {
      $entity->revision_log = t('Updated the %field-name field through in-place editing.', array('%field-name' => $entity->get($field_name)->getFieldDefinition()->getLabel()));
    }

    return $entity;
  }

i.e. that's all the revision handling we have today. We simply respect the entity type's "autocreate revisions or not" setting.

But I understand that the problem is that the revision timestamp is not being updated accordingly. I'd expect the Entity API to handle this for us. Where is revision_timestamp being set for regular node edits? (I couldn't find it in a quick search.)

Clarifying issue title further.

I'd expect the Entity API to handle this for us.

I think we all would. Unfortunately none of us live in that beatiful world you depict.

See \Drupal\node\NodeForm::submitForm(). There the setNewRevision() flag is being set and the revision author and timestamp, as well. (The revision log field comes from the form values.)

Thanks, @tstoeckler! That's helpful.

In other words, we want Node-specific logic to be removed from NodeForm. For that, we need #1863258: Move entity preparation from form controller to entity class: "last changed" timestamp not updated and "create new revision" setting not respected when updating entities via Entity API + #2248983: Define the revision metadata base fields in the entity annotation in order for the storage to create them only in the revision table. Is that accurate?

I wasn't aware #1863258: Move entity preparation from form controller to entity class: "last changed" timestamp not updated and "create new revision" setting not respected when updating entities via Entity API existed, and that seems like super, super non-trivial to get done at this point, but yes, I think that is correct.

We can now actually do this! See #2925846-3: Quick Edit only creates revision for Node entities, should do it for all content entity types that support it.

We're still adding logic to Quick Edit that should not exist. We still have #1863258: Move entity preparation from form controller to entity class: "last changed" timestamp not updated and "create new revision" setting not respected when updating entities via Entity API to fix that. But in the mean time, we can at least make it work generically for all (content) entity types. That's what #2925846: Quick Edit only creates revision for Node entities, should do it for all content entity types that support it is about.