List all folder recursively instead using the * wildcard when issuing an imap LIST command

[egallego]

Doing a LIST "" "*" is discouraged as it could return millions of folders. Instead, IMAP implementations are expected to issue a LIST "" "%" to list the first level of the hierarchy and then proceed recursively when the user request more folder.

This is difficult to achieve in roundcube without using AJAX in the folder view and switching it to a tree.

See:

• ​http://www.imapwiki.org/ClientImplementation/MailboxList
• ​http://dovecot.org/client-commandments.txt (commandment 10)
• ​http://dovecot.org/imap-client-coding-howto.html

[egallego]

A sketch of the implementation would be:

• [PHP] Define a _get_subfolders(folder) that returns the subfolders of folder and whether they have children.
• [PHP] Format that as a tree (list) and mark expansible nodes folders with children.
• [jquery folderview]: Setup click of expansible items to call _get_subfolders and replace innerHtml with it.

[egallego]

IMHO, I'd target this to RC 1.0 release. My reasoning is that for instance RC may not work with UW-IMAP, which reponds to LIST "" "*" with all the files in $HOME by default.

I think fully supporting this IMAP server may be a 1.0 release goal.

[egallego]

Places affected:

• trunk/roundcubemail/program/include/rcube_imap.php#L1908

[thomasb]

The LIST "" "*" command is only used to list folders in the folder manager. Otherwise subscribed folders are listed. Loading a big list of folders in that step seems OK to me since it's not a common action. However, maybe only listing the advertised NAMESPACES as suggested in #1486796 would help here.

[alec]

Why we should care about outdated and unmaintained UW-IMAP server? We by default display all levels of hierarchy which means implementing this will not really help here.