mu4e: get maildirs from server

We were determining the list of maildirs using, but his is rather *slow*.
So instead, get it from the server, through a "data" call.

mu4e/mu4e-folders.el

@@ -244,47 +244,8 @@ to create it; otherwise return nil."
       (setq mu4e-maildir-list nil) ;; clear cache
       t)))
 
-(defun mu4e--get-maildirs-1 (path mdir)
-  "Get maildirs for MDIR under PATH.
-Do so recursively and produce a list of relative paths."
-  (let ((dirs)
-        (dentries
-         (ignore-errors
-           (directory-files-and-attributes
-            (mu4e-join-paths path mdir) nil
-            "^[^.]\\|\\.[^.][^.]" t))))
-    (dolist (dentry dentries)
-      (when (or (and (booleanp (cadr dentry)) (cadr dentry))
-                (file-directory-p (mu4e-join-paths path (car dentry))))
-        (if (file-accessible-directory-p
-             (mu4e-join-paths (mu4e-root-maildir) mdir (car dentry) "cur"))
-            (setq dirs
-                  (cons (mu4e-join-paths mdir (car dentry)) dirs)))
-        (unless (member (car dentry) '("cur" "new" "tmp"))
-          (setq dirs
-                (append dirs
-                        (mu4e--get-maildirs-1
-                         path (mu4e-join-paths mdir (car dentry))))))))
-    dirs))
-
 (defun mu4e-get-maildirs ()
-  "Get maildirs under `mu4e-maildir'.
-Do so recursively, and produce a list of relative paths (ie.,
-/archive, /sent etc.). Most of the work is done in
-`mu4e--get-maildirs-1'. Note, these results are /cached/ if
-`mu4e-cache-maildir-list' is customized to non-nil. In that case,
-the list of maildirs will not change until you restart mu4e."
-  (unless (and mu4e-maildir-list mu4e-cache-maildir-list)
-    (setq mu4e-maildir-list
-          (sort
-           (append
-            (when (file-accessible-directory-p
-                   (mu4e-join-paths
-                    (mu4e-root-maildir) "cur"))
-              '("/"))
-            (mu4e--get-maildirs-1 (mu4e-root-maildir) "/"))
-           (lambda (s1 s2)
-             (string< (downcase s1) (downcase s2))))))
+  "Get maildirs under `mu4e-maildir'."
   mu4e-maildir-list)
 
 (defun mu4e-ask-maildir (prompt)

mu4e/mu4e-search.el

@@ -226,9 +226,9 @@ the search."
 
 
 (defun mu4e-search-maildir (maildir &optional edit)
-  "Search the messages in maildir.
-The user is prompted to ask what maildir. If prefix arg EDIT is
-given, offer to edit the search query before executing it."
+  "Search the messages in MAILDIR.
+The user is prompted to ask what maildir. If prefix-argument EDIT
+is given, offer to edit the search query before executing it."
   (interactive
    (let ((maildir (mu4e-ask-maildir "Jump to maildir: ")))
      (list maildir current-prefix-arg)))

mu4e/mu4e-server.el

@@ -88,6 +88,10 @@ to take effect, you need to stop/start mu4e."
   :group 'mu4e
   :safe  'booleanp)
 
+
+;; Cached data
+(defvar mu4e-maildir-list)
+
 
 ;; Handlers are not strictly internal, but are not meant
 ;; for overriding outside mu4e. The are mainly for breaking
@@ -398,6 +402,12 @@ The server output is as follows:
          ((plist-get sexp :info)
           (funcall mu4e-info-func sexp))
 
+         ;; get some data
+         ((plist-get sexp :data)
+          (pcase (plist-get sexp :data)
+            ('maildirs (setq mu4e-maildir-list (plist-get sexp :value)))
+            (_ (mu4e-warn "unknown data kind"))))
+
          ;; receive an error
          ((plist-get sexp :error)
           (funcall mu4e-error-func
@@ -577,6 +587,12 @@ get at most MAX contacts."
      :tstamp   ,(or tstamp nil)
      :maxnum   ,(or maxnum nil))))
 
+(defun mu4e--server-data (kind)
+  "Request data of some KIND.
+KIND is a symbol. Currently supported kinds: maildirs."
+  (mu4e--server-call-mu
+   `(data :kind ,kind)))
+
 (defun mu4e--server-find (query threads sortfield sortdir maxnum skip-dups
                                 include-related)
   "Run QUERY with THREADS SORTFIELD SORTDIR MAXNUM SKIP-DUPS INCLUDE-RELATED.

mu4e/mu4e.el

@@ -148,8 +148,10 @@ Otherwise, check requirements, then start mu4e. When successful, invoke
   (add-hook 'mu4e-query-items-updated-hook #'mu4e--main-redraw)
   (mu4e--query-items-refresh 'reset-baseline)
   (mu4e--server-ping)
+  ;; ask for the maildir-list
+  (mu4e--server-data 'maildirs)
   ;; maybe request the list of contacts, automatically refreshed after
-  ;; reindexing
+  ;; re-indexing
   (unless mu4e--contacts-set
     (mu4e--request-contacts-maybe)))