bug#21043: [PATCH] nnimap.el: make capability parsing more robust.

[Nikolaus Rath <Nikolaus@rath.org>]

Package: gnus
Tags: patch

Hello,

Currently Gnus relies on the server supplying the capabilities in its
response to the LOGIN command, e.g. like this:

  * CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE
  SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS THREAD=ORDEREDSUBJECT
  MULTIAPPEND URL-PARTIAL CATENATE UNSELECT CHILDREN NAMESPACE UIDPLUS
  LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES
  WITHIN CONTEXT=SEARCH LIST-STATUS SPECIAL-USE BINARY MOVE SEARCH=FUZZY
  QUOTA\r\n
  1 OK Logged in\r\n

However, this assumption breaks if the server doesn't return the
capabilities automatically, or if he returns them as part of the OK
response, e.g.:

   160 OK [CAPABILITY IMAP4rev1 LITERAL+ ID ENABLE ACL RIGHTS=kxten
   QUOTA MAILBOX-REFERRALS NAMESPACE UIDPLUS NO_ATOMIC_RENAME UNSELECT
   CHILDREN MULTIAPPEND BINARY CATENATE CONDSTORE ESEARCH SEARCH=FUZZY
   SORT SORT=MODSEQ SORT=DISPLAY SORT=UID THREAD=ORDEREDSUBJECT
   THREAD=REFERENCES ANNOTATEMORE ANNOTATE-EXPERIMENT-1 METADATA
   LIST-EXTENDED LIST-STATUS LIST-MYRIGHTS LIST-METADATA WITHIN QRESYNC
   SCAN XLIST XMOVE MOVE SPECIAL-USE CREATE-SPECIAL-USE DIGEST=SHA1
   X-REPLICATION LOGINDISABLED XCONVERSATIONS COMPRESS=DEFLATE
   X-QUOTA=STORAGE X-QUOTA=MESSAGE X-QUOTA=X-ANNOTATION-STORAGE
   X-QUOTA=X-NUM-FOLDERS IDLE] User logged in
   SESSIONID=<sloti32d1t18-237747-1436749914-1-18339819756817078727>\r\n


Currently, in this situation Gnus just keeps re-using the pre-LOGIN
capabilities (and thus does not take advantage of any additional
features).

The attached patch fixes this issue by explicitly asking the server for
its capabilities after login.


Thanks for considering,
-Nikolaus


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