my logins duplicates login id, why?

Question

The "my logins" section of my user profile shows the same email twice. I have "remove" option for both. When I removed one, both were removed and I had to resign up I guess to get back to SO.

Is that bug or so?

Answer 1

This is something of a 30 edge-case pileup.

When we display the login popup we do our best to associate an email with OpenIDs, and display the email instead of the URL when we have it. We do this because, most of the time anyway, you're going to login to a service with your email and knowing the URL doesn't do you a lot of immediate good.

Now the edge cases start. Google gives us per-domain URLs, so what we actually do is consider emails & OpenIDs as credentials and then try and pair them off with each other based on historical usage. We typically de-duplicate these pairings, but there's another edge case when we don't have a history of an email being used with an OpenID (there have been many changes to this system, so history doesn't go back terribly far).

End result, you end up with a paired email & OpenID and an unpaired email. In the case where the email's are the same, this bug manifests (the "same" credential twice, but there's actually a suppressed OpenID associated with one of those rows).

I've deployed a fix. Basically what I'm doing is suppressing an email (on all but one credential) if it would be rendered twice within a single group (ie. Google, Facebook, Yahoo, or Stack Exchange; other groups can't have emails). The winning credential pair will always be the most recently used one, which if deleted will reveal the suppressed row.

This seemed like the simplest (I use that term very very loosely) solution that wouldn't have us displaying URLs instead of emails.