When adding patrons in the staff client it checks for duplicates, but when doing self registration it does not. Self registration should warn of duplication.
Hm, couldn't that be a privacy problem? If I want to figure out if someone is registered as a user at a library, I could try and register as them and Koha would tell me "yes, that person is already registered here".
I agree with Magnuse - we can't show anything to the OPAC user about a duplicate. Maybe what we can do is add a duplicate warning in staff somewhere?
What about "Something has gone wrong, please visit the library for more details" and cite an error code?
(a non-descriptive to-the-user error code that the library would know what it means.)
*** This bug has been marked as a duplicate of bug 12566 ***