"Hide" action hides field on node edit form even if "Apply action on edit" is unchecked

Yeah, I'm working on it, but I'm actually struggling to understand some of the logic in the code.

Specifically, in this snippet:

<?php
if ($id && empty($entity->is_new)) {
  return $settings['action'] == 'hide' ? FALSE : NULL;
}

if ($settings['action'] == 'hide') {
  // If entity is already saved and not just inserted, deny access, otherwise
  // ignore.
  return $id && empty($entity->is_new) ? FALSE : NULL;
}
?>

It seems to me that the second if condition is only evaluated if the first one evaluates to FALSE, and if the first one does evaluate to FALSE, then return $id && empty($entity->is_new) ? FALSE : NULL; must also evaluate to FALSE and can only ever return NULL. If I'm following it correctly, that's just redundant code...

Also, I don't get why the following snippet is evaluated last in the function:

<?php
if (!$ids && $settings['fallback'] == 'hide') {
  return FALSE;
}
?>

Surely if there are no prepopulate values passed to the form and we're checking the fallback behaviour, then there is no reason to have carried out the previous checks as though prepopulate values had been passed?

I'll post a patch later if I manage to figure it all out.

Ok, I *think* I've got it all figured out, so here's a patch.

It seems to work correctly for all combinations of action and fallback settings, but I haven't tested extensively.