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

[Mark Walters]

On Fri, 28 Dec 2012, Austin Clements <amdragon at MIT.EDU> wrote:
> 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).

I like this approach but have some queries below.

> ---
>  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."

It might be worth commenting that since this signals an error it does
not "return"; I found the code in notmuch-check-exit-status rather
confusing until I realised that.

> +
> +  (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'.

This means that if err and output are null we give a minimal error message and we
don't log the command line that fails. Perhaps the `when' clause could
be omitted so we get the extra information from below?

> +	(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)))))))

Also, depending how the above gets changed, would it be worth pulling the let
clause before the cond clause, and subsuming some of the when/if/else
logic into the cond? This has the nice side effect that the reader
expects cond clauses to stop after the first match so the fact that
notmuch-check-exit-status signals an error would not matter when reading
this code.

I think a command line would be useful in almost all cases (in the error
buffer). If you decide to always supply that then your error message
might want tweaking as it would always have extra information in the
error buffer.

Finally, and this is only a thought, I wonder if the mechanism can be
tweaked to provide debug information along these lines for all notmuch
commands whether or not they succeed: something like if
notmuch-debug-commands is set or there is an error? 

Incidentally do you have good ways to test this code (ie see what it
does in each case)? My hackish experiments suggested the async errors
were less useful than the sync ones but maybe that is just an inherent
limitation of the emacs async mechanisms.


Best wishes

Mark






>  
>  (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