Newsletter subscription (opt-in) as guest not working correctly

[Quinten]

I have the following settings in my backend under Stores > Configuration > Customers > Newsletter > Subscription Options:
Need to Confirm: Yes
Allow Guest Subscription: Yes

When i subscribe as guest with the form in the footer 2 things go wrong:

1. There is no check wether the email address is already subscribed. Which means i can keep sending emails with confirmation links to the same address.
   2 . When i click the confirmation link in the email: i return to the homepage and there is no feedback message. But then only when i fill out the form in the footer again, i'll get 2 messages: "Your subscription has been confirmed." and "Thank you for your subscription."

[whizkid79]

Same issue here, but I can't get anyone activated, even by filling out the form again, like described above it is still not working.
I wouldn't call that an improvement, that is a bug to be fixed!

[homecoded]

Here is the problem and the solution to this bug:

When we enter an new email address (one that is not connected to an extisting subscriber), the subscriber object ($this) has no id ($this->getId(); // null) yet in Magento\Newsletter\Model\Subscriber::subscribe. The verification email is sent out before the subscriber is saved, thus the subscriber id is missing from the verification link. The link does not do anything when you click on it because the verification method in Magento\Newsletter\Controller\Subscriber\Confirm::execute rejects the link because of the missing id.

You can easily mend the problem by calling $this->save() before calling $this->sendConfirmationRequestEmail();

[mazhalai]

@homecoded would you like to submit a PR with this fix?