Emacs: Reformat to Long Lines (unfill-paragraph) 🚀

unfill-paragraph, unfill-region

Emacs does not have a “unfill-paragraph” command to do the inverse of “fill”. Here's the solution:

(defun xah-unfill-paragraph ()
  "Replace newline chars in current paragraph by single spaces.
This command does the inverse of `fill-paragraph'.

URL `http://xahlee.info/emacs/emacs/emacs_unfill-paragraph.html'
Version 2016-07-13"
  (interactive)
  (let ((fill-column most-positive-fixnum))
    (fill-paragraph)))

(defun xah-unfill-region (start end)
  "Replace newline chars in region by single spaces.
This command does the inverse of `fill-region'.

URL `http://xahlee.info/emacs/emacs/emacs_unfill-paragraph.html'
Version 2016-07-13"
  (interactive "r")
  (let ((fill-column most-positive-fixnum))
    (fill-region start end)))

toggle “fill” or “unfill”

This command automatically toggle “fill” or “unfill” on the current paragraph. If there is a text selection, then the command automatically works on the region.

(defun xah-fill-or-unfill ()
  "Reformat current paragraph or region to `fill-column', like `fill-paragraph' or “unfill”.
When there is a text selection, act on the selection, else, act on a text block separated by blank lines.
URL `http://xahlee.info/emacs/emacs/modernization_fill-paragraph.html'
Version 2017-01-08"
  (interactive)
  ;; This command symbol has a property “'compact-p”, the possible values are t and nil. This property is used to easily determine whether to compact or uncompact, when this command is called again
  (let ( ($compact-p
          (if (eq last-command this-command)
              (get this-command 'compact-p)
            (> (- (line-end-position) (line-beginning-position)) fill-column)))
         (deactivate-mark nil)
         ($blanks-regex "\n[ \t]*\n")
         $p1 $p2
         )
    (if (use-region-p)
        (progn (setq $p1 (region-beginning))
               (setq $p2 (region-end)))
      (save-excursion
        (if (re-search-backward $blanks-regex nil "NOERROR")
            (progn (re-search-forward $blanks-regex)
                   (setq $p1 (point)))
          (setq $p1 (point)))
        (if (re-search-forward $blanks-regex nil "NOERROR")
            (progn (re-search-backward $blanks-regex)
                   (setq $p2 (point)))
          (setq $p2 (point)))))
    (if $compact-p
        (fill-region $p1 $p2)
      (let ((fill-column most-positive-fixnum ))
        (fill-region $p1 $p2)))
    (put this-command 'compact-p (not $compact-p))))

Note: an early implementation is named “compact-uncompact-block”.