Save buffer before executing `markdown-open-command`

[saf-dmitry]

I would suggest some small improvements to the markdown-open command. The version below will first save the buffer content using (save-buffer (buffer-file-name)) and then run the markdown-open-command on the file.

(defun markdown-open ()
  "Open file for the current buffer with `markdown-open-command'."
  (interactive)
  (if (not markdown-open-command)
      (user-error "Variable `markdown-open-command' must be set")
    (if (not buffer-file-name)
        (user-error "Must be visiting a file")
      (save-buffer (buffer-file-name))
      (call-process markdown-open-command
                    nil nil nil buffer-file-name))))

For the time being you could advise the markdown-open function:

(defadvice markdown-open (before my-markdown-save-and-open activate)
  "Save buffer before open file for the current buffer."
  (unless (buffer-file-name) (user-error "Must be visiting a file"))
  (save-buffer (buffer-file-name)))

[jrblevin]

Nice idea, thanks. I'll add this.

[saf-dmitry]

Sorry for being obtrusive @jrblevin: Any news on implementing this, or did you change your mind?

[jrblevin]

I didn't change my mind, I'm just behind. Thanks for reminding me about this.

From my reading of the save-buffer docstring, it looks like we don't need the (buffer-file-name) argument. It only takes numerical arguments. I'll add (save-buffer) before the (call-process ... line.

[saf-dmitry]

By the way, why the markdown-open-command is called synchronously using call-process? Wouldn't it be more appropriate to use start-process-shell-command for an asynchronous call? This way we can open the current file in a viewer, e.g. Marked, and continue editing text in Emacs buffer while Marked (or other similar viewer) will run in parallel with Emacs updating every time the buffer is saved.

[jrblevin]

That's exactly how I use markdown-open-command, with Marked (see this post for details). After reading the call-process docstring carefully, when the third argument (destination) is nil it does seem as if it should wait, but when used with open command on macOS the script returns. I think we can safely change the third argument to 0 instead to make it asynchronous in all cases. Any thoughts?

[saf-dmitry]

Yes, this works when used with open command on macOS. Actually I ask because I'm now working on a cross-platform Markdown viewer, conceptually similar to the Marked app for macOS, and it does not work asynchronously on Linux with Markdown mode v2.3. Maybe changing the third argument of call-process to 0 will help (according to docstring it should), but if not, I would consider start-process-shell-command as truly asynchronous solution.

[jrblevin]

Modifying call-process as discussed above works for me in my testing. Good luck with your Markdown viewer, and let me know if for some reason this doesn't work for you.