Pipe appears in select value, key is blank

Thanks, that looks like a good and easy fix, though we should probably make it so that a key of 0 is supported by default too. I haven't checked what happens if you manually create the keys, i.e.

0|zero
1|one

But I'm guessing that this problem only exhibits itself when there aren't any keys at all? In any case it's a good fix, as this problem arose because of the change we made to Form Builder that used the same pattern of starting at 1 instead of 0. See #1404988: Set default option keys to numbers and increment intellegently for backstory.

This bit of code is responsible for the improper numbering:

    if (is_int($item['key'] * 1)) {
      $new_key = max($item['key'], $new_key);
    }

So $item['key'] is NULL, which results in the calculation of max(NULL, 0) == NULL, which I would not have expected. While this is the cause of the improper numbering and we can fix it by making sure that the starting number is 0, I agree with you that we should make the starting number 1 nonetheless. Let's do both changes so we don't accidentally run into this problem again. How does this patch look to you?

Committed. Thanks Liam, let me know if you discover any other issues.