How can I automatically close buffers when the underlying file is deleted?

Question

I leave Emacs running all day, and will often will do a lot of file system manipulation on files that are open in Emacs buffers. For example, I might switch to a different branch in Git that has a very different directory structure.

Unfortunately this leaves me with a bunch of open buffers that Emacs now registers as "modified" buffers referring to "new" files. Unless I'm careful to manually close them each time I do this, it's easy to reflexively save those buffers which then results in spurious, probably duplicate files in my project. I can't even close emacs without answering the "save this buffer" question for each one.

Is there a way to automatically close unmodified buffers when the underlying file disappears? Similar in spirit to a global-auto-revert-mode that also handles when a file is removed entirely?

Answer 1

I think something along these lines could work:

(defun buffer-backed-by-file-p (buffer)
  (let ((backing-file (buffer-file-name buffer)))
    (if (buffer-modified-p buffer)
        t
      (if backing-file
          (file-exists-p (buffer-file-name buffer))
        t))))

(mapc 'kill-buffer (-remove 'buffer-backed-by-file-p (buffer-list)))

The buffer-backed-by-file-p function checks if the file is backed by a file - if not, returns true, otherwise returns if the backing file exists. We then take the list of buffers, filtering out anything but those that should have a backing file, but the file doesn't exist, and then kill them.

Requires dash.el for -remove, because I was too lazy to find a built-in to achieve the same thing.

Hope this helps!