Allow gnus-retrieve-headers to return headers directly

Previously, all Gnus backends returned header information by writing
nov lines into the nntp-server-buffer, which was later parsed.  This
commit allows the backends to return their header information as a
list of already-parsed headers, though so far none of the backends
actually do that.  The agent, cache, cloud etc. now operate on parsed
headers rather than nov text, ie. they use gnus-fetch-headers instead
of gnus-retrieve-headers.

* lisp/gnus/gnus-sum.el (gnus-fetch-headers): Handle the case in which
gnus-retrieve-headers returns headers directly.
* lisp/gnus/nnvirtual.el (nnvirtual-retrieve-headers): Use
gnus-fetch-headers rather than gnus-retrieve-headers to get headers,
meaning we're operating on already-parsed headers.
(nnvirtual-convert-headers): Remove now-unnecessary function.
(nnvirtual-update-xref-header): Rewrite to operate on parsed header.
* lisp/gnus/gnus-cloud.el (gnus-cloud-available-chunks): Use
gnus-fetch-headers instead of gnus-retrieve-headers.
* lisp/gnus/gnus-cache.el (gnus-cache-retrieve-headers): Use
gnus-fetch-headers.
(gnus-cache-braid-nov, gnus-cache-braid-heads): Delete unnecessary
functions -- we now do this work on a list of parsed headers.
* lisp/gnus/gnus-agent.el (gnus-agent-retrieve-headers): Use
gnus-fetch-headers.
(gnus-agent-braid-nov): Remove unnecessary function.
(gnus-agent-fetch-headers): Use gnus-fetch-headers.

1 files changed, 6 insertions, 10 deletions

diff --git a/lisp/gnus/gnus-cloud.el b/lisp/gnus/gnus-cloud.el
index f7c71f43ce8..00b85f546c2 100644
--- a/lisp/gnus/gnus-cloud.el
+++ b/lisp/gnus/gnus-cloud.el
@@ -30,6 +30,8 @@
 
 (require 'parse-time)
 (require 'nnimap)
+(declare-function gnus-fetch-headers "gnus-sum")
+(defvar gnus-alter-header-function)
 
 (eval-when-compile (require 'epg)) ;; setf-method for `epg-context-armor'
 (autoload 'epg-make-context "epg")
@@ -391,8 +393,6 @@ When FULL is t, upload everything, not just a difference from the last full."
             (gnus-group-refresh-group group))
         (gnus-error 2 "Failed to upload Gnus Cloud data to %s" group)))))
 
-(defvar gnus-alter-header-function)
-
 (defun gnus-cloud-add-timestamps (elems)
   (dolist (elem elems)
     (let* ((file-name (plist-get elem :file-name))
@@ -407,14 +407,10 @@ When FULL is t, upload everything, not just a difference from the last full."
   (gnus-activate-group gnus-cloud-group-name nil nil gnus-cloud-method)
   (let* ((group (gnus-group-full-name gnus-cloud-group-name gnus-cloud-method))
          (active (gnus-active group))
-         headers head)
-    (when (gnus-retrieve-headers (gnus-uncompress-range active) group)
-      (with-current-buffer nntp-server-buffer
-        (goto-char (point-min))
-	(while (setq head (nnheader-parse-head))
-          (when gnus-alter-header-function
-            (funcall gnus-alter-header-function head))
-          (push head headers))))
+	 (gnus-newsgroup-name group)
+         (headers (gnus-fetch-headers (gnus-uncompress-range active))))
+    (when gnus-alter-header-function
+      (mapc gnus-alter-header-function headers))
     (sort (nreverse headers)
           (lambda (h1 h2)
             (> (gnus-cloud-chunk-sequence (mail-header-subject h1))