Is there a way to recognize `-- vim: et:sw=4:ts=8:sts=4:tw=80` in emacs?

Question

I'm working on a project with all source files appended with this vim formating rule -- vim: et:sw=4:ts=8:sts=4:tw=80. Is there a way to make Emacs setup the correct indentation for me automatically?

The indentation options of vim are described at http://vimdoc.sourceforge.net/htmldoc/options.html. There follows a rough description of the used options:

• et / expandtabs means to insert whitespaces instead of tabs. It should at least be similar to (setq indent-tabs-mode nil)

• sw / shiftwidth is the number of spaces to use for each indent

• sts / softtabstop Number of spaces that a counts for while performing editing operations, like inserting a or using . It "feels" like s are being inserted, while in fact a mix of spaces and s is used. This is useful to keep the ~ts~ setting at its standard value of 8, while being able to edit like it is set to ~sts~.

• tw / textwidth corresponds to fill-column in emacs

Answer 1

I wouldn't be surprised if there's already a package out there that does it, but I couldn't find one. You should be able to cover most of it with something along the lines of the untested code below:

(advice-add 'hack-local-variables-prop-line
            :after-until
            #'my-hack-local-vim-props)
(defun my-hack-local-vim-props (&optional handle-mode)
  (unless (eq handle-mode t)
    (save-excursion
      (goto-char (point-max))
      (when (re-search-backward 
             "-- vim:[ \t]*"
             (max (point-min) (- (point) 1000)) t)
        (let ((opts ()))
          (while (looking-at "\\([[:alpha:]]+\\)\\(?:=\\([^:\n]+\\)[:\n]")
            (let ((var (match-string 1))
                  (val (match-string 2)))
              (pcase var
                ((or "et" "expandtabs")
                 (push '(indent-tabs-mode . t) opts))
                ((or "ts" "tabstop")
                 (push `(tab-width . ,(string-to-number val))
                       opts))
                ((or "tw" "textwidth")
                 (push '(fill-column . ,(string-to-number val))
                       opts))
                ((or "sts" "softtabstop")
                 (push `(tab-stop-list 0 ,(string-to-number val))
                       opts))
                (_ (message "Unhandled Vim option %s=%s"
                            var val)))))
          opts)))))

Notice:

• I did not try to handle sw because which variable to set for that depends on the major mode. It could be c-basic-offset or sh-basic-offset, or octave-block-offset, or sml-indent-level, or smie-indent-basic, ...
• the sts setting is "more or less equivalent", except that tab-stop-list is very rarely used.