Prevent locked-file errors in Rmail

* lisp/mail/rmail.el (rmail-get-new-mail-1): Lock file before
calling 'rmail-insert-inbox-text'.  Unlock if
'rmail-insert-inbox-text' doesn't modify buffer.
(rmail-insert-inbox-text): Remove lock-checking code.  (Bug#17706)

1 files changed, 15 insertions, 8 deletions

diff --git a/lisp/mail/rmail.el b/lisp/mail/rmail.el
index 734155e217d..e9882253c70 100644
--- a/lisp/mail/rmail.el
+++ b/lisp/mail/rmail.el
@@ -1818,9 +1818,21 @@ not be a new one).  It returns non-nil if it got any new messages."
         ;; Read in the contents of the inbox files, renaming them as
         ;; necessary, and adding to the list of files to delete
         ;; eventually.
-        (if file-name
-            (rmail-insert-inbox-text files nil)
-          (setq delete-files (rmail-insert-inbox-text files t)))
+        (unwind-protect
+            (progn
+              ;; Set modified now to lock the file, so that we don't
+              ;; encounter locking problems later in the middle of
+              ;; reading the mail.
+              (set-buffer-modified-p t)
+              (if file-name
+                  (rmail-insert-inbox-text files nil)
+                (setq delete-files (rmail-insert-inbox-text files t))))
+          ;; If there was no new mail, or we aborted before actually
+          ;; trying to get any, mark buffer unmodified.  Otherwise the
+          ;; buffer is correctly marked modified and the file locked
+          ;; until we save out the new mail.
+          (if (= (point-min) (point-max))
+              (set-buffer-modified-p nil)))
         ;; Scan the new text and convert each message to
         ;; Rmail/mbox format.
         (goto-char (point-min))
@@ -1969,11 +1981,6 @@ Value is the size of the newly read mail after conversion."
     size))
 
 (defun rmail-insert-inbox-text (files renamep)
-  ;; Detect a locked file now, so that we avoid moving mail
-  ;; out of the real inbox file.  (That could scare people.)
-  (or (memq (file-locked-p buffer-file-name) '(nil t))
-      (error "RMAIL file %s is locked"
-             (file-name-nondirectory buffer-file-name)))
   (let (file tofile delete-files popmail got-password password)
     (while files
       ;; Handle remote mailbox names specially; don't expand as filenames