Re-subscription confirmation glitch

[javierarce]

Version:

• listmonk: 2.5.1
• OS: Ubuntu 20.04.6 LTS

Steps to Reproduce This Issue:

1. Create a public double opt-in list and subscribe to it.
2. Confirm the subscription from the opt-in email.
3. Send a campaign.
4. Unsubscribe from the list through the campaign email.

At this point, the user is unsubscribed but still exists in the listmonk db without subscriptions.

6. Subscribe again to the same list.

Expected Result:

• The user sees a screen indicating that they need to confirm the subscription.
• The user receives an opt-in message to confirm the subscription.

Actual Result:

• The user sees a screen indicating that they were successfully subscribed to the list.
• In the admin panel, the user is not subscribed.

This error is similar to this issue. The difference in this case is that if a user is unsubscribed from a list and tries to subscribe again, they'll see a message indicating that the subscription was successful, but they won't be subscribed. Adding to the confusion, they'll get a message to opt-in. If they confirm the subscription, they'll get correctly subscribed, but obviously the previous message is confusing.

[javierarce]

I suspect the problem lies in this line of the processSubForm method. If the subscriber already exists, the method returns false no matter what. I think the method should check the subscription status to return true or false accordingly.