Ediff: compare two files Word-by-word

Question

I use Emacs 26.1 and would like to compare two files word-by-word. Clicking "Tools -> Compare (Ediff) -> Windows Word-by-word..." allows only to compare the visible parts of two buffers, not the whole buffers. This seems to be intended behavior as per my other question. The response there contains a working solution for comparing two complete buffers. There seem to be no issues with performance.

How can this be used to compare two files? It would be nice if a menu option could be added as well: "Tools -> Compare (Ediff) -> Files Word-by-word...".

Answer 1

You can copy the following Elisp snippet into your init file.

Disclaimer: The code comes without any guaranty. It references internal functions of ediff. So use it with caution.

The newly defined command ediff-files-wordwise just runs ediff-files with two main modifications:

• (ediff-word-mode . word-mode) is added to the SETUP-PARAMETERS of ediff-setup.

• The buffer contents of buf-A and buf-B is wordified and saved in temporary files that are used for the diff-program.

  (eval-after-load "ediff"
    (progn
      (eval
       `(defun ediff-files-wordwise (file-A file-B &optional startup-hooks)
          ,(concat (documentation 'ediff-files)
                   "\nComparison is done wordwise.")
          ,(interactive-form 'ediff-files)
          (cl-letf* ((oldfun (symbol-function 'ediff-setup))
                     ((symbol-function 'ediff-setup)
                      (lambda (buffer-A file-A buffer-B file-B buffer-C file-C startup-hooks setup-parameters &optional merge-buffer-file)
                        (let* ((tmp-buffer (get-buffer-create ediff-tmp-buffer)))
                          (with-current-buffer buffer-A
                            (ediff-wordify (point-min) (point-max) buffer-A tmp-buffer))
                          (setq file-A (ediff-make-temp-file tmp-buffer "regA"))
                          (with-current-buffer buffer-B
                            (ediff-wordify (point-min) (point-max) buffer-B tmp-buffer))
                          (setq file-B (ediff-make-temp-file tmp-buffer "regB"))
                          (setq overl-A (with-current-buffer buffer-A
                                          (ediff-make-bullet-proof-overlay (point-min) (point-max) buffer-A))
                                overl-B (with-current-buffer buffer-B
                                          (ediff-make-bullet-proof-overlay (point-min) (point-max) buffer-B)))
                          (funcall oldfun
                                   buffer-A file-A buffer-B file-B buffer-C file-C startup-hooks
                                   (append
                                    (list (cons 'ediff-word-mode 'word-mode)
                                          (cons 'ediff-narrow-bounds (list overl-A overl-B)))
                                    setup-parameters)
                                   merge-buffer-file)))))
            (ediff-files file-A file-B startup-hooks))))
      (require 'easymenu)
      (easy-menu-add-item
       menu-bar-tools-menu
       '("Compare (Ediff)")
       ["Two Files Word-by-word..." ediff-files-wordwise t]
       "Two Buffers...")))