* mu4e: some better escaping for queries with backslashes

mu4e/mu4e-headers.el

@@ -444,7 +444,7 @@ after the end of the search results."
     (let ((map (make-sparse-keymap)))
 
       (define-key map  (kbd "C-S-u") 'mu4e-update-mail-and-index)
-      
+
       (define-key map "s" 'mu4e-headers-search)
       (define-key map "S" 'mu4e-headers-search-edit)
 
@@ -805,7 +805,6 @@ non-nill, don't raise an error when the docid is not found."
       (unless ignore-missing
 	(mu4e-error "Cannot find message with docid %S" docid)))))
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
-
 (defun mu4e~headers-search-execute (expr ignore-history)
   "Search in the mu database for EXPR, and switch to the output
 buffer for the results. If IGNORE-HISTORY is true, do *not* update
@@ -829,7 +828,7 @@ the query history stack."
 			     'face 'mu4e-title-face)))
     (switch-to-buffer buf)
     (mu4e~proc-find
-      (replace-regexp-in-string "\"" "\\\\\"" expr) ;; escape "\"
+      expr
       mu4e-headers-show-threads
       mu4e-headers-sortfield
       mu4e-headers-sort-revert

mu4e/mu4e-proc.el

@@ -312,6 +312,12 @@ The results are reporter through either (:update ... ) or (:error)
 sexp, which are handled my `mu4e-error-func', respectively."
   (mu4e~proc-send-command "remove docid:%d" docid))
 
+(defun mu4e~proc-escape-query (query)
+  "Escape the query QUERY for transport, in particular, backslashes
+and double-quotes."
+  (let ((esc (replace-regexp-in-string "\\\\" "\\\\\\\\" query)))
+    (replace-regexp-in-string "\"" "\\\\\"" esc)))
+
 (defun mu4e~proc-find (query threads sortfield revert maxnum)
   "Start a database query for QUERY. If THREADS is non-nil, show
 results in threaded fasion, SORTFIELD is a symbol describing the
@@ -323,7 +329,7 @@ result. The variables `mu4e-error-func' contain the function that
 will be called for, resp., a message (header row) or an error."
   (mu4e~proc-send-command
     "find query:\"%s\" threads:%s sortfield:%s reverse:%s maxnum:%d"
-    query
+    (mu4e~proc-escape-query query)
     (if threads "true" "false")
     ;; sortfield is e.g. ':subject'; this removes the ':'
     (if (null sortfield) "nil" (substring (symbol-name sortfield) 1))