[PATCH] emacs: Use the minibuffer for CLI error reporting

[Austin Clements <amdragon@MIT.EDU>]

We recently switched to popping up a buffer to report CLI errors, but
this was too intrusive, especially for transient errors and especially
since we made fewer things ignore errors.  This patch changes this to
display a basic error message in the minibuffer (using Emacs' usual
error handling path) and, if there are additional details, to log
these to a separate error buffer and reference the error buffer from
the minibuffer message.  This is more in line with how Emacs typically
handles errors, but makes the details available to the user without
flooding them with the details.

Given this split, we pare down the basic message and make it more
user-friendly, and also make the verbose message even more detailed
(and more debugging-oriented).
---
 emacs/notmuch-lib.el |   92 ++++++++++++++++++++++++++++----------------------
 emacs/notmuch.el     |    9 +++--
 test/emacs           |   11 +++---
 test/emacs-show      |    6 ++--
 4 files changed, 67 insertions(+), 51 deletions(-)

diff --git a/emacs/notmuch-lib.el b/emacs/notmuch-lib.el
index 77a591d..3baab97 100644
--- a/emacs/notmuch-lib.el
+++ b/emacs/notmuch-lib.el
@@ -316,23 +316,28 @@ string), a property list of face attributes, or a list of these."
 	(put-text-property pos next 'face (cons face cur))
 	(setq pos next)))))
 
-(defun notmuch-pop-up-error (msg)
-  "Pop up an error buffer displaying MSG.
-
-This will accumulate error messages in the errors buffer until
-the user dismisses it."
-
-  (let ((buf (get-buffer-create "*Notmuch errors*")))
-    (with-current-buffer buf
-      (view-mode-enter nil #'kill-buffer)
-      (let ((inhibit-read-only t))
-	(goto-char (point-max))
-	(unless (bobp)
-	  (insert "\n"))
-	(insert msg)
+(defun notmuch-logged-error (msg &optional extra)
+  "Log MSG and EXTRA to *Notmuch errors* and signal MSG.
+
+This logs MSG and EXTRA to the *Notmuch errors* buffer and
+signals MSG as an error.  If EXTRA is non-nil, text referring the
+user to the *Notmuch errors* buffer will be appended to the
+signaled error."
+
+  (with-current-buffer (get-buffer-create "*Notmuch errors*")
+    (goto-char (point-max))
+    (unless (bobp)
+      (newline))
+    (save-excursion
+      (insert "[" (current-time-string) "]\n" msg)
+      (unless (bolp)
+	(newline))
+      (when extra
+	(insert extra)
 	(unless (bolp)
-	  (insert "\n"))))
-    (pop-to-buffer buf)))
+	  (newline)))))
+  (error "%s" (concat msg (when extra
+			    " (see *Notmuch errors* for more details)"))))
 
 (defun notmuch-check-async-exit-status (proc msg)
   "If PROC exited abnormally, pop up an error buffer and signal an error.
@@ -363,35 +368,40 @@ contents of ERR-FILE will be included in the error message."
   (cond
    ((eq exit-status 0) t)
    ((eq exit-status 20)
-    (notmuch-pop-up-error "Error: Version mismatch.
+    (notmuch-logged-error "notmuch CLI version mismatch
 Emacs requested an older output format than supported by the notmuch CLI.
-You may need to restart Emacs or upgrade your notmuch Emacs package.")
-    (error "notmuch CLI version mismatch"))
+You may need to restart Emacs or upgrade your notmuch Emacs package."))
    ((eq exit-status 21)
-    (notmuch-pop-up-error "Error: Version mismatch.
+    (notmuch-logged-error "notmuch CLI version mismatch
 Emacs requested a newer output format than supported by the notmuch CLI.
-You may need to restart Emacs or upgrade your notmuch package.")
-    (error "notmuch CLI version mismatch"))
+You may need to restart Emacs or upgrade your notmuch package."))
    (t
-    (notmuch-pop-up-error
-     (concat
-      (format "Error invoking notmuch.  %s exited with %s%s.\n"
-	      (mapconcat #'identity command " ")
-	      ;; Signal strings look like "Terminated", hence the
-	      ;; colon.
-	      (if (integerp exit-status) "status " "signal: ")
-	      exit-status)
-      (when err-file
-	(concat "Error:\n"
-		(with-temp-buffer
-		  (insert-file-contents err-file)
-		  (if (eobp)
-		      "(no error output)\n"
-		    (buffer-string)))))
-      (when (and output (not (equal output "")))
-	(format "Output:\n%s" output))))
-    ;; Mimic `process-lines'
-    (error "%s exited with status %s" (car command) exit-status))))
+    (let ((err (when err-file
+		 (with-temp-buffer
+		   (insert-file-contents err-file)
+		   (unless (eobp)
+		     (buffer-string)))))
+	  (basic-msg (format "%s exited with status %s"
+			     (car command) exit-status)))
+      (when (and (null err) (or (null output) (equal output "")))
+	;; We have no details to speak of.  Mimic `process-lines'.
+	(notmuch-logged-error basic-msg))
+      (let ((extra
+	     (concat
+	      "Command: " (mapconcat #'shell-quote-argument command " ") "\n"
+	      (if (integerp exit-status)
+		  (format "Exit status: %s\n" exit-status)
+		(format "Exit signal: %s\n" exit-status))
+	      "Output:\n"
+	      (if (and output (not (equal output "")))
+		  output
+		"(none)"))))
+	(if err
+	    ;; We have an error message straight from the CLI.
+	    (notmuch-logged-error err extra)
+	  ;; We only have combined output from the CLI; don't inundate
+	  ;; the user with it.
+	  (notmuch-logged-error basic-msg extra)))))))
 
 (defun notmuch-call-notmuch-json (&rest args)
   "Invoke `notmuch-command' with `args' and return the parsed JSON output.
diff --git a/emacs/notmuch.el b/emacs/notmuch.el
index 63387a2..c98a4fe 100644
--- a/emacs/notmuch.el
+++ b/emacs/notmuch.el
@@ -654,11 +654,14 @@ of the result."
 		    ;; showing the search buffer
 		    (when (or (= exit-status 20) (= exit-status 21))
 		      (kill-buffer))
-		    (condition-case nil
+		    (condition-case err
 			(notmuch-check-async-exit-status proc msg)
 		      ;; Suppress the error signal since strange
-		      ;; things happen if a sentinel signals.
-		      (error (throw 'return nil)))
+		      ;; things happen if a sentinel signals.  Mimic
+		      ;; the top-level's handling of error messages.
+		      (error
+		       (message "%s" (second err))
+		       (throw 'return nil)))
 		    (if (and atbob
 			     (not (string= notmuch-search-target-thread "found")))
 			(set 'never-found-target-thread t)))))
diff --git a/test/emacs b/test/emacs
index 6b18968..8e0a4fd 100755
--- a/test/emacs
+++ b/test/emacs
@@ -862,18 +862,19 @@ exit 1
 EOF
 chmod a+x notmuch_fail
 test_emacs "(let ((notmuch-command \"$PWD/notmuch_fail\"))
+	       (with-current-buffer \"*Messages*\" (erase-buffer))
 	       (notmuch-search \"tag:inbox\")
 	       (notmuch-test-wait)
-	       (test-output)
-	       (with-current-buffer \"*Notmuch errors*\"
-		  (test-output \"ERROR\")))"
-test_expect_equal "$(cat OUTPUT ERROR)" "\
+	       (with-current-buffer \"*Messages*\"
+		  (test-output \"MESSAGES\"))
+	       (test-output))"
+test_expect_equal "$(cat OUTPUT MESSAGES)" "\
 Error: Unexpected output from notmuch search:
 This is output
 Error: Unexpected output from notmuch search:
 This is an error
 End of search results.
-Error invoking notmuch.  $PWD/notmuch_fail search --format=json --format-version=1 --sort=newest-first tag:inbox exited with status 1."
+$PWD/notmuch_fail exited with status 1"
 
 
 test_done
diff --git a/test/emacs-show b/test/emacs-show
index ebf530b..ae9459d 100755
--- a/test/emacs-show
+++ b/test/emacs-show
@@ -177,10 +177,12 @@ test_emacs "(let ((notmuch-command \"$PWD/notmuch_fail\"))
 	       (test-output)
 	       (with-current-buffer \"*Notmuch errors*\"
 		  (test-output \"ERROR\")))"
+sed -i -e 's/^\[.*\]$/[XXX]/' ERROR
 test_expect_equal "$(cat OUTPUT ERROR)" "\
-Error invoking notmuch.  $PWD/notmuch_fail show --format=json --format-version=1 --exclude=false ' * ' exited with status 1.
-Error:
+[XXX]
 This is an error
+Command: $PWD/notmuch_fail show --format\\=json --format-version\\=1 --exclude\\=false \\' \\* \\'
+Exit status: 1
 Output:
 This is output"
 
-- 
1.7.10.4