User sync writes twice to account table

[PVince81]

Steps

1. Setup LDAP and specify a user with an email address
2. Set a breakpoint in SyncService::run()
3. Run occ user:sync 'OCA\User_LDAP\User_LDAP'
4. Track it down into processAttributes

Expected

processAttributes doesn't retrieve the account table's IUser entry.
It must return its own IUser instance that stores email, quota, etc.
It's the SyncService that uses these values then to populate the account table

Actual

processAttributes calls UserManager->get($uid) and $user->setEMailAddress() which internally stores the email already into the account table.
Then later on the sync service does the same again. Or it skips it because the email didn't change.

Versions

ownCloud 10.0 beta2+ master

While the end result might look the same, this makes problems with duplicate email addresses not solvable, see owncloud/core#27652

[PVince81]

It's here https://github.com/owncloud/user_ldap/blob/v10.0.0beta2/lib/User/User.php#L451

This is all old behavior which is obsoleted by the account table.
A user backend shouldn't do such gymnastics to set email addresses or other values.

[PVince81]

@jvillafanez @DeepDiver1975 do we agree that any user backend should return its own implementation of IUser containing the necessary attributes ?

It should be possible here to make LDAP's User class actually implement IUser and have the getter/setters store into local attributes.

[PVince81]

Instead of implementing IUser, the backend should implement IProvidesEmailBackend and IProvidesQuotaBackend

[butonic]

fixed with #125