[PATCH] Support hiding deleted IMAP messages (v3)

[Nikolaus Rath <Nikolaus@rath.org>]

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Hello,

This patch introduces a new server variable, nnimap-hide-deleted. If
non-nil, articles with the IMAP \Deleted flag will not be included in
Summary buffers.

This is intended to increase operability with other IMAP mailreaders and
the new 'never value for nnimap-expunge (see patch in bug 20670).

Changes in v2:

  * Take into account that server may send the UID, FLAGS and RFC822.SIZE
    response data items in arbitrary order

Changes in v3:

  * Made first line of docstring a complete sentence.

Thanks for considering,
-Nikolaus

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diff --git a/nnimap.el b/nnimap.el
--- a/nnimap.el
+++ b/nnimap.el
@@ -135,6 +135,11 @@
 likely value would be \"text/\" to automatically fetch all
 textual parts.")
 
+(defvoo nnimap-hide-deleted nil
+  "Whether to hide deletes messages in summary buffer.
+If non-nil, articles flagged as deleted (using the IMAP
+\\Delete flag) will not be shown in the Summary buffer.")
+
 (defgroup nnimap nil
   "IMAP for Gnus."
   :group 'gnus)
@@ -181,7 +186,7 @@
   (nnimap-find-process-buffer nntp-server-buffer))
 
 (defun nnimap-header-parameters ()
-  (format "(UID RFC822.SIZE BODYSTRUCTURE %s)"
+  (format "(UID FLAGS RFC822.SIZE BODYSTRUCTURE %s)"
 	  (format
 	   (if (nnimap-ver4-p)
 	       "BODY.PEEK[HEADER.FIELDS %s]"
@@ -240,12 +245,19 @@
 	      (and (re-search-forward "UID \\([0-9]+\\)" (line-end-position)
 				      t)
 		   (match-string 1)))
-	(setq lines nil)
+	(beginning-of-line)
+	(setq flags
+	      (and (re-search-forward "FLAGS (\\([^)]+\\))"
+				      (line-end-position)
+				      t)
+		   (split-string (match-string 1))))
+	(beginning-of-line)
 	(setq size
 	      (and (re-search-forward "RFC822.SIZE \\([0-9]+\\)"
 				      (line-end-position)
 				      t)
 		   (match-string 1)))
+	(setq lines nil)
 	(beginning-of-line)
 	(when (search-forward "BODYSTRUCTURE" (line-end-position) t)
 	  (let ((structure (ignore-errors
@@ -259,20 +271,25 @@
 			     (equal (upcase (nth 1 structure)) "RFC822"))
 			    (nth 9 structure)
 			  (nth 7 structure)))))
-	(delete-region (line-beginning-position) (line-end-position))
-	(insert (format "211 %s Article retrieved." article))
-	(forward-line 1)
-	(when size
-	  (insert (format "Chars: %s\n" size)))
-	(when lines
-	  (insert (format "Lines: %s\n" lines)))
-	;; Most servers have a blank line after the headers, but
-	;; Davmail doesn't.
-	(unless (re-search-forward "^\r$\\|^)\r?$" nil t)
-	  (goto-char (point-max)))
-	(delete-region (line-beginning-position) (line-end-position))
-	(insert ".")
-	(forward-line 1)))))
+        (if (and nnimap-hide-deleted
+                 (member "\\Deleted" flags))
+            (delete-region (line-beginning-position)
+                           (or (re-search-forward "^\r$\\|^)\r?$" nil t)
+                               (point-max)))
+          (delete-region (line-beginning-position) (line-end-position))
+          (insert (format "211 %s Article retrieved." article))
+          (forward-line 1)
+          (when size
+            (insert (format "Chars: %s\n" size)))
+          (when lines
+            (insert (format "Lines: %s\n" lines)))
+          ;; Most servers have a blank line after the headers, but
+          ;; Davmail doesn't.
+          (unless (re-search-forward "^\r$\\|^)\r?$" nil t)
+            (goto-char (point-max)))
+          (delete-region (line-beginning-position) (line-end-position))
+          (insert ".")
+          (forward-line 1))))))
 
 (defun nnimap-unfold-quoted-lines ()
   ;; Unfold quoted {number} strings.