[PATCH v2] emacs: show: stop stderr appearing in buffer

[Mark Walters]

In emacs 24.3+ the stdout/stderr from externally displaying an
attachment gets inserted into the show buffer. This is caused by
changes in mm-display-external in mm-decode.el.

Ideally, we would put this output in the notmuch errors buffer but the
handler is called asynchronously so we don't know when the output will
appear. Thus if we put it straight into the errors buffer it could get
interleaved with other errors. Also we can't easily tell when we
have got all the error output so can't wait until the process is complete.

One solution would be to create a new buffer for the stderr of each
attachment viewed. Again, since we can't tell when the process has
finished, we can't close these buffers automatically so this will
leave lots of buffers around.

Thus we add a debug variable notmuch-show-attachment-debug: it this is
non-nil we create a new buffer for each viewer; if this variable is
nil we just use a temp buffer which means all error output is
discarded (this is the same behaviour as with emacs pre 24.3).
---

This version just adds a docstring to the debug variable describing
what it does and where the debug data is stored (ie what the buffer
name is).

Best wishes

Mark

 emacs/notmuch-show.el |   19 ++++++++++++++++++-
 1 files changed, 18 insertions(+), 1 deletions(-)

diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index f00273a..784644c 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -159,6 +159,15 @@ indentation."
 (make-variable-buffer-local 'notmuch-show-indent-content)
 (put 'notmuch-show-indent-content 'permanent-local t)
 
+(defvar notmuch-show-attachment-debug nil
+  "If t log stdout and stderr from attachment handlers
+
+When set to nil (the default) stdout and stderr from attachment
+handlers is discarded. When set to t the stdout and stderr from
+each attachment handler is logged in buffers with names beginning
+\" *notmuch-part*\". This option requires emacs version at least
+24.3 to work.")
+
 (defcustom notmuch-show-stash-mlarchive-link-alist
   '(("Gmane" . "http://mid.gmane.org/")
     ("MARC" . "http://marc.info/?i=")
@@ -2089,8 +2098,16 @@ caller is responsible for killing this buffer as appropriate."
 This ensures that the temporary buffer created for the mm-handle
 is destroyed when FN returns."
   (let ((handle (notmuch-show-current-part-handle)))
+    ;; emacs 24.3+ puts stdout/stderr into the calling buffer so we
+    ;; call it from a temp-buffer, unless
+    ;; notmuch-show-attachment-debug is non-nil in which case we put
+    ;; it in " *notmuch-part*".
     (unwind-protect
-	(funcall fn handle)
+	(if notmuch-show-attachment-debug
+	    (with-current-buffer (generate-new-buffer " *notmuch-part*")
+	      (funcall fn handle))
+	  (with-temp-buffer
+	    (funcall fn handle)))
       (kill-buffer (mm-handle-buffer handle)))))
 
 (defun notmuch-show-part-button-default (&optional button)
-- 
1.7.9.1