If the user denies the email permission, authentication then fails with the "This site requires permission to get your email address."
However, if you try again, you do not get to set your preferences the next time round but instead come straight back to the same page.
Store the fact that we don't have their email permission in the session, and if they attempt to re-use facebook, pass the auth_type=rerequest parameter along with the redirect (see docs) so the user gets presented the option again.
Implement it
None
I don't believe any
Possibly storing some session data
Needs work
4.0
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
I stumbled here as I am trying to upgrade/migrate a D7 site I made many moons ago which has facebook connect as the only option to login.
It seems back in the day I wrote my own action for the D7 only fboauth module that would set the user email to {facebook_ID}@facebook.com if the email was not authorised.
Site has been running for over 10 years without a hitch... so just thought I would suggest it.