[PATCH 09/10] emacs: Improve error handling for notmuch-call-notmuch-json

[Austin Clements]

This checks for non-zero exit status and pops up an error buffer
giving the exit status, the stderr, and the stdout.  Schema version
mismatches are handled specially.
---
 emacs/notmuch-lib.el |   40 +++++++++++++++++++++++++++++++++-------
 1 file changed, 33 insertions(+), 7 deletions(-)

diff --git a/emacs/notmuch-lib.el b/emacs/notmuch-lib.el
index 31c69dc..9c6be13 100644
--- a/emacs/notmuch-lib.el
+++ b/emacs/notmuch-lib.el
@@ -361,15 +361,41 @@ You may need to restart Emacs or upgrade your notmuch package."))
   "Invoke `notmuch-command' with `args' and return the parsed JSON output.
 
 The returned output will represent objects using property lists
-and arrays as lists."
+and arrays as lists.  If notmuch exits with a non-zero status,
+this will pop up a buffer containing notmuch's output and signal
+an error."
 
   (with-temp-buffer
-    (apply #'call-process notmuch-command nil (list t nil) nil args)
-    (goto-char (point-min))
-    (let ((json-object-type 'plist)
-	  (json-array-type 'list)
-	  (json-false 'nil))
-      (json-read))))
+    (let ((err-file (make-temp-file "nmerr")))
+      (unwind-protect
+	  (let ((status (apply #'call-process
+			       notmuch-command nil (list t err-file) nil args)))
+	    (cond ((equal status 0)
+		   (goto-char (point-min))
+		   (let ((json-object-type 'plist)
+			 (json-array-type 'list)
+			 (json-false 'nil))
+		     (json-read)))
+		  ((or (equal status 20) (equal status 21))
+		   ;; Special handling of version mismatch errors
+		   (notmuch-version-mismatch-error status))
+		  (t
+		   (goto-char (point-min))
+		   (insert "Error:\n")
+		   (let ((pos (point)))
+		     (insert-file-contents err-file)
+		     (when (= (point) pos)
+		       (insert "(no error output)\n")))
+		   (unless (eobp)
+		     (insert "Output:\n"))
+		   (notmuch-pop-up-error
+		    (concat
+		     (format "CLI error.  %S exited with %s%s.\n"
+			     (cons notmuch-command args)
+			     (if (integerp status) "status " "")
+			     status)
+		     (buffer-string))))))
+	(delete-file err-file)))))
 
 ;; Compatibility functions for versions of emacs before emacs 23.
 ;;
-- 
1.7.10.4