emacs: Use the minibuffer for CLI error reporting

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

@@ -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.
+(defun notmuch-logged-error (msg &optional extra)
+  "Log MSG and EXTRA to *Notmuch errors* and signal MSG.
 
-This will accumulate error messages in the errors buffer until
-the user dismisses it."
+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.  This function does not return."
 
-  (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)
+  (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)))))
+	   (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))
+	     (when err
+	       (concat "stderr:\n" err))
+	     (when output
+	       (concat "stdout:\n" output)))))
+	(if err
+	    ;; We have an error message straight from the CLI.
+	    (notmuch-logged-error
+	     (replace-regexp-in-string "\\s $" "" err) extra)
+	  ;; We only have combined output from the CLI; don't inundate
+	  ;; the user with it.  Mimic `process-lines'.
+	  (notmuch-logged-error (format "%s exited with status %s"
+					(car command) exit-status)
+				extra))
+	;; `notmuch-logged-error' does not return.
+	))))
 
 (defun notmuch-call-notmuch-json (&rest args)
   "Invoke `notmuch-command' with `args' and return the parsed JSON output.

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)))))

test/emacs

@@ -862,18 +862,27 @@ exit 1
 EOF
 chmod a+x notmuch_fail
 test_emacs "(let ((notmuch-command \"$PWD/notmuch_fail\"))
+	       (with-current-buffer \"*Messages*\" (erase-buffer))
 	       (notmuch-search \"tag:inbox\")
 	       (notmuch-test-wait)
-	       (test-output)
+	       (with-current-buffer \"*Messages*\"
+		  (test-output \"MESSAGES\"))
 	       (with-current-buffer \"*Notmuch errors*\"
-		  (test-output \"ERROR\")))"
-test_expect_equal "$(cat OUTPUT ERROR)" "\
+		  (test-output \"ERROR\"))
+	       (test-output))"
+sed -i -e 's/^\[.*\]$/[XXX]/' ERROR
+test_expect_equal "$(cat OUTPUT; echo ---; cat MESSAGES; echo ---; cat ERROR)" "\
 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 (see *Notmuch errors* for more details)
+---
+[XXX]
+$PWD/notmuch_fail exited with status 1
+command: $PWD/notmuch_fail search --format\=json --format-version\=1 --sort\=newest-first tag\:inbox
+exit status: 1"
 
 test_done

test/emacs-show

@@ -172,16 +172,28 @@ exit 1
 EOF
 chmod a+x notmuch_fail
 test_emacs "(let ((notmuch-command \"$PWD/notmuch_fail\"))
-	       (ignore-errors (notmuch-show \"*\"))
+	       (with-current-buffer \"*Messages*\" (erase-buffer))
+	       (condition-case err
+		   (notmuch-show \"*\")
+		 (error (message \"%s\" (second err))))
 	       (notmuch-test-wait)
-	       (test-output)
+	       (with-current-buffer \"*Messages*\"
+		  (test-output \"MESSAGES\"))
 	       (with-current-buffer \"*Notmuch errors*\"
-		  (test-output \"ERROR\")))"
-test_expect_equal "$(cat OUTPUT ERROR)" "\
-Error invoking notmuch.  $PWD/notmuch_fail show --format=json --format-version=1 --exclude=false ' * ' exited with status 1.
-Error:
+		  (test-output \"ERROR\"))
+	       (test-output))"
+sed -i -e 's/^\[.*\]$/[XXX]/' ERROR
+test_expect_equal "$(cat OUTPUT; echo ---; cat MESSAGES; echo ---; cat ERROR)" "\
+---
+This is an error (see *Notmuch errors* for more details)
+---
+[XXX]
 This is an error
-Output:
+command: $PWD/notmuch_fail show --format\\=json --format-version\\=1 --exclude\\=false \\' \\* \\'
+exit status: 1
+stderr:
+This is an error
+stdout:
 This is output"