Deleting a choice should delete the votes over it in the database

1. +++ b/src/Entity/Poll.php
   @@ -439,6 +439,15 @@ class Poll extends ContentEntityBase implements PollInterface {
   +        foreach ($removed_choices as $removed_choice) {
   +          $votes = \Drupal::entityTypeManager()->getStorage('poll')->getVotes($this);
   +          foreach ($votes as $key => $vote) {
   +            if ($key == $removed_choice && $vote != 0) {
   +              \Drupal::service('poll_vote.storage')->deleteChoiceVotes(PollChoice::load($removed_choice));
   +            }
   

   Do we need this complexity? What about making deleteChoiceVotes() a list of choice ID's? It can write a super-simple, single db delete query to delete them all in one go.

2. +++ b/src/PollVoteStorageInterface.php
   @@ -0,0 +1,28 @@
   +   *
   +   * @return int
   +   *   The number of rows affected by the delete query.
   

   not sure if we need that.

Once this is in, lets do a follow-up to move all vote related methods from PollStorage to this new service.

Thanks, committed.

Reopening the issue and renaming the title.
I was about to start working on the followup #2648836: Alert the user that deleting a choice will delete the votes on it and after a discussion with @berdir what is missing here is to check that the vote has been actually deleted from the database. I've added this check on the new patch.

+++ b/src/Tests/PollDeleteChoiceTest.php
@@ -73,9 +73,15 @@ class PollDeleteChoiceTest extends PollTestBase {
+
+    // Assert that the existing vote has been deleted from the database.
+    $ids = \Drupal::entityQuery('poll_choice')
+      ->condition('choice', $this->poll->choice[1]->entity->label())
+      ->execute();
+    $this->assertEqual(count($ids), 0, 'Choice 2 has been deleted in the database');

This verifies that the poll *choice* got deleted. That's fine.

But what we're actually after here is that the *vote* for the poll choice got deleted. You need to look at the poll_vote table, with a normal select query, as that's not an entity.

Oops, was trying to do something and then forgot to re-fix it...
Now should be the right one.

Thanks, committed.

Forgot to created follow-up as prompted at comment #6 (?) #2682423: Move all vote related methods from PollStorage to the new poll_vote.storage service