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emacs: Use make-process when available

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make-process is a new function introduced in Emacs 25, which provides
greater control over process creation. Crucially, it allows
separately redirecting stderr directly to a buffer, which allows us to
avoid needing to use the shell to redirect to a temporary file in
order to correctly distinguish stdout and stderr.

* notmuch-lib.el: Use make-process when it is available; fall back to
  the previous method when not.
This commit is contained in:
Vladimir Panteleev 2017-08-17 17:57:12 +00:00 committed by David Bremner
parent 69946c47c9
commit fdf2b3007a
1 changed files with 44 additions and 22 deletions
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56
emacs/notmuch-lib.el
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@ -909,21 +909,42 @@ invoke `set-process-sentinel' directly on the returned process,
as that will interfere with the handling of stderr and the exit
status."
;; There is no way (as of Emacs 24.3) to capture stdout and stderr
;; separately for asynchronous processes, or even to redirect stderr
;; to a file, so we use a trivial shell wrapper to send stderr to a
;; temporary file and clean things up in the sentinel.
(let* ((err-file (make-temp-file "nmerr"))
;; Use a pipe
(process-connection-type nil)
(let (err-file err-buffer proc
;; Find notmuch using Emacs' `exec-path'
(command (or (executable-find notmuch-command)
(error "command not found: %s" notmuch-command)))
(proc (apply #'start-process name buffer
(error "Command not found: %s" notmuch-command))))
(if (fboundp 'make-process)
(progn
(setq err-buffer (generate-new-buffer " *notmuch-stderr*"))
;; Emacs 25 and newer has `make-process', which allows
;; redirecting stderr independently from stdout to a
;; separate buffer. As this allows us to avoid using a
;; temporary file and shell invocation, use it when
;; available.
(setq proc (make-process
:name name
:buffer buffer
:command (cons command args)
:connection-type 'pipe
:stderr err-buffer))
(process-put proc 'err-buffer err-buffer)
;; Silence "Process NAME stderr finished" in stderr by adding a
;; no-op sentinel to the fake stderr process object
(set-process-sentinel (get-buffer-process err-buffer) #'ignore))
;; On Emacs versions before 25, there is no way to capture
;; stdout and stderr separately for asynchronous processes, or
;; even to redirect stderr to a file, so we use a trivial shell
;; wrapper to send stderr to a temporary file and clean things
;; up in the sentinel.
(setq err-file (make-temp-file "nmerr"))
(let ((process-connection-type nil)) ;; Use a pipe
(setq proc (apply #'start-process name buffer
"/bin/sh" "-c"
"exec 2>\"$1\"; shift; exec \"$0\" \"$@\""
command err-file args)))
(process-put proc 'err-file err-file)
(process-put proc 'err-file err-file))
(process-put proc 'sub-sentinel sentinel)
(process-put proc 'real-command (cons notmuch-command args))
(set-process-sentinel proc #'notmuch-start-notmuch-sentinel)
@ -932,10 +953,10 @@ status."
(defun notmuch-start-notmuch-sentinel (proc event)
"Process sentinel function used by `notmuch-start-notmuch'."
(let* ((err-file (process-get proc 'err-file))
(err (with-temp-buffer
(insert-file-contents err-file)
(unless (eobp)
(buffer-string))))
(err-buffer (or (process-get proc 'err-buffer)
(find-file-noselect err-file)))
(err (when (not (zerop (buffer-size err-buffer)))
(with-current-buffer err-buffer (buffer-string))))
(sub-sentinel (process-get proc 'sub-sentinel))
(real-command (process-get proc 'real-command)))
(condition-case err
@ -953,8 +974,8 @@ status."
;; If that didn't signal an error, then any error output was
;; really warning output. Show warnings, if any.
(let ((warnings
(with-temp-buffer
(unless (= (second (insert-file-contents err-file)) 0)
(when err
(with-current-buffer err-buffer
(goto-char (point-min))
(end-of-line)
;; Show first line; stuff remaining lines in the
@ -969,7 +990,8 @@ status."
;; Emacs behaves strangely if an error escapes from a sentinel,
;; so turn errors into messages.
(message "%s" (error-message-string err))))
(ignore-errors (delete-file err-file))))
(when err-buffer (kill-buffer err-buffer))
(when err-file (ignore-errors (delete-file err-file)))))
;; This variable is used only buffer local, but it needs to be
;; declared globally first to avoid compiler warnings.