[PATCH] emacs: View the output of pipe command when it fails

[Michal Sojka]

Previously, the user didn't know whether the pipe command succeeded or
not. It was only possible to find it out by manually inspecting
the work done (or not done) by the command or by manually switching to
*notmuch-pipe* buffer and determine it from command output. For this
the user had to first find the text corresponding to the last run of
pipe command as the buffer accumulated the output from all pipe commands.

This patch changes the following. The *notmuch-pipe* buffer is erased
before every pipe command so it contains only the output from the last
command. Additionally, when the command failed, the *notmuch-pipe* buffer
is shown and an error message is displayed.
with the output of pipe command.
---
 emacs/notmuch-show.el |   15 +++++++++++++--
 1 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index 3a60d43..f3150af 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -948,7 +948,7 @@ any effects from previous calls to
 
 The given command will be executed with the raw contents of the
 current email message as stdin. Anything printed by the command
-to stdout or stderr will appear in the *Messages* buffer.
+to stdout or stderr will appear in the *notmuch-pipe* buffer.
 
 When invoked with a prefix argument, the command will receive all
 open messages in the current thread (formatted as an mbox) rather
@@ -964,7 +964,18 @@ than only the current message."
       (setq shell-command
 	    (concat notmuch-command " show --format=raw "
 		    (shell-quote-argument (notmuch-show-get-message-id)) " | " command)))
-    (start-process-shell-command "notmuch-pipe-command" "*notmuch-pipe*" shell-command)))
+    (let ((buf (get-buffer-create (concat "*notmuch-pipe*"))))
+      (with-current-buffer buf
+	(setq buffer-read-only nil)
+	(erase-buffer)
+	(let ((exit-code (call-process-shell-command shell-command nil buf)))
+	  (goto-char (point-max))
+	  (set-buffer-modified-p nil)
+	  (setq buffer-read-only t)
+	  (unless (zerop exit-code)
+	    (switch-to-buffer-other-window buf)
+	    (message (format "Command '%s' exited abnormally with code %d"
+			     shell-command exit-code))))))))
 
 (defun notmuch-show-add-tags-worker (current-tags add-tags)
   "Add to `current-tags' with any tags from `add-tags' not
-- 
1.7.2.3