[PATCH] emacs: Leave blank subjects alone by default.

[David Edmondson]

Add `notmuch-blank-subject' to control how empty or whitespace only
subjects are treated. The default behaviour is to leave them
alone. The user can choose a string to use as a replacement.

Modify code that cannot handle blank subjects to use a fixed string.
---
 emacs/notmuch-lib.el   |   20 +++++++++++++++++---
 emacs/notmuch-print.el |    4 ++--
 emacs/notmuch-show.el  |    2 +-
 emacs/notmuch.el       |    4 ++--
 4 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/emacs/notmuch-lib.el b/emacs/notmuch-lib.el
index d315f76..2edc868 100644
--- a/emacs/notmuch-lib.el
+++ b/emacs/notmuch-lib.el
@@ -67,6 +67,13 @@
   :type 'boolean
   :group 'notmuch-search)
 
+(defcustom notmuch-blank-subject nil
+  "How should subjects that are empty or whitespace only be
+treated?"
+  :type '(choice (const :tag "Leave them alone" nil)
+		 (string :tag "Replacement string" "[No Subject]"))
+  :group 'notmuch)
+
 ;;
 
 (defvar notmuch-search-history nil
@@ -133,13 +140,20 @@ the user hasn't set this variable with the old or new value."
   (interactive)
   (kill-buffer (current-buffer)))
 
-(defun notmuch-prettify-subject (subject)
+(defun notmuch-pretty-non-empty-subject (subject)
+  (let ((subject (notmuch-pretty-subject subject)))
+    (if (string-match "^[ \t]*$" subject)
+	"no subject"
+      subject)))
+
+(defun notmuch-pretty-subject (subject)
   ;; This function is used by `notmuch-search-process-filter' which
   ;; requires that we not disrupt its' matching state.
   (save-match-data
-    (if (and subject
+    (if (and (stringp notmuch-blank-subject)
+	     subject
 	     (string-match "^[ \t]*$" subject))
-	"[No Subject]"
+	notmuch-blank-subject
       subject)))
 
 ;;
diff --git a/emacs/notmuch-print.el b/emacs/notmuch-print.el
index 6653d97..dda082a 100644
--- a/emacs/notmuch-print.el
+++ b/emacs/notmuch-print.el
@@ -60,7 +60,7 @@ Optional OUTPUT allows passing a list of flags to muttprint."
 
 (defun notmuch-print-ps-print (msg)
   "Print a message buffer using the ps-print package."
-  (let ((subject (notmuch-prettify-subject
+  (let ((subject (notmuch-pretty-non-empty-subject
 		  (plist-get (notmuch-show-get-prop :headers msg) :Subject))))
     (rename-buffer subject t)
     (ps-print-buffer)))
@@ -68,7 +68,7 @@ Optional OUTPUT allows passing a list of flags to muttprint."
 (defun notmuch-print-ps-print/evince (msg)
   "Preview a message buffer using ps-print and evince."
   (let ((ps-file (make-temp-file "notmuch"))
-	(subject (notmuch-prettify-subject
+	(subject (notmuch-pretty-non-empty-subject
 		  (plist-get (notmuch-show-get-prop :headers msg) :Subject))))
     (rename-buffer subject t)
     (ps-print-buffer ps-file)
diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index 7469e2e..4a23cc2 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -1261,7 +1261,7 @@ Some useful entries are:
   (notmuch-show-get-prop :depth))
 
 (defun notmuch-show-get-pretty-subject ()
-  (notmuch-prettify-subject (notmuch-show-get-subject)))
+  (notmuch-pretty-subject (notmuch-show-get-subject)))
 
 (defun notmuch-show-set-tags (tags)
   "Set the tags of the current message."
diff --git a/emacs/notmuch.el b/emacs/notmuch.el
index cd04ffd..aab6946 100644
--- a/emacs/notmuch.el
+++ b/emacs/notmuch.el
@@ -467,7 +467,7 @@ Complete list of currently available key bindings:
   "Display the currently selected thread."
   (interactive "P")
   (let ((thread-id (notmuch-search-find-thread-id))
-	(subject (notmuch-prettify-subject (notmuch-search-find-subject))))
+	(subject (notmuch-pretty-non-empty-subject (notmuch-search-find-subject))))
     (if (> (length thread-id) 0)
 	(notmuch-show thread-id
 		      (current-buffer)
@@ -850,7 +850,7 @@ non-authors is found, assume that all of the authors match."
 			  (insert (concat "Error: Unexpected output from notmuch search:\n" (substring string line (match-beginning 1)) "\n")))
 		      (let ((beg (point)))
 			(notmuch-search-show-result date count authors
-						    (notmuch-prettify-subject subject) tags)
+						    (notmuch-pretty-subject subject) tags)
 			(notmuch-search-color-line beg (point) tag-list)
 			(put-text-property beg (point) 'notmuch-search-thread-id thread-id)
 			(put-text-property beg (point) 'notmuch-search-authors authors)
-- 
1.7.8.3