Re: Proposal: diff-remove-trailing-blanks

[Vinicius Jose Latorre <viniciusjl@ig.com.br>]

>>> Hummm, I'm confused, the original mail said:
>>>
>>>  "When on a buffer that contains a diff, inspects the
>>> differences and removes trailing whitespace (spaces, tabs) from
>>> the lines modified or introduced by this diff. Shows a message
>>> with the name of the altered buffers, which are unsaved.  If a
>>> file referenced on the diff has no buffer and needs to be fixed,
>>> a buffer visiting that file is created."
>>>
>>>
>>> So, I thought it was to remove trailing whitespaces from a diff buffer.
>>
>> The "removing" part is accomplished by my function. We are discussing
>> the "displaying" part, which shows to the user that there is trailing
>> whitespace to be removed.
>>
>> But I'm afraid I confused things out relating `show-trailing-whitespace'
>> to whitespace-mode'.
>
> Well, both parts, the "removing" part and the "displaying" part, 
> related with trailing whitespaces can be done by whitespace-mode.
>
> Does the following function do the job?
>
> (defun diff-remove-trailing-blanks ()
>  "When on a buffer that contains a diff, inspects the
> differences and removes trailing whitespace (spaces, tabs).
> Shows a message with the name of the altered buffers, which are
> unsaved.  If a file referenced on the diff has no buffer and
> needs to be fixed, a buffer visiting that file is created."
>  (interactive)
>  (goto-char (point-min))
>  ;; We assume that the diff header has no trailing whitespace.
>  (let (modified-buffers)
>    (while (re-search-forward "^[+!>].*[ \t]+$" (point-max) t)
>      (save-excursion
>    (destructuring-bind (buf line-offset pos src dst &optional switched)
>            (diff-find-source-location t t)
>          (unless (member buf modified-buffers)
>            (when line-offset
>              (set-buffer buf)
>              (when (re-search-forward "\\([ \t]+\\)$" (point-max) t)
>                (push buf modified-buffers)
>                (let ((whitespace-style '(trailing)))
>                  (whitespace-cleanup)))))))) ; cleanup trailing blanks 
> in buf
>    (if modified-buffers
>        (let ((bufs (mapconcat #(lambda (buf)
>                                  (format "`%s'" (buffer-name buf)))
>                               modified-buffers
>                               " "))
>              (whitespace-style '(trailing)))
>          (whitespace-mode)           ; display trailing blanks in diff 
> buffer
>          (message "Deleted trailing whitespace from: %s" bufs))
>      (message "No fixes needed."))))


A better implementation of function above:

(defun diff-remove-trailing-blanks ()
  "When on a buffer that contains a diff, inspects the
differences and removes trailing whitespace (spaces, tabs).
Shows a message with the name of the altered buffers, which are
unsaved.  If a file referenced on the diff has no buffer and
needs to be fixed, a buffer visiting that file is created."
  (interactive)
  (save-excursion
    ;; We assume that the diff header has no trailing whitespace.
    (let ((whitespace-style '(trailing))
          modified-buffers)
      (goto-char (point-min))
      (while (re-search-forward "^[-+!>] .*[ \t]+$" (point-max) t)
        (save-excursion
          (destructuring-bind (buf line-offset pos src dst &optional 
switched)
              (diff-find-source-location t t)
            (when (and line-offset
                       (not (member buf modified-buffers)))
              (set-buffer buf)
              (when (re-search-forward "\\([ \t]+\\)$" (point-max) t)
                (push buf modified-buffers)
                (whitespace-cleanup)))))) ; cleanup trailing blanks in buf
      (if modified-buffers
          (progn
            (whitespace-mode) ; display trailing blanks in diff buffer
            (message "Deleted trailing whitespace from: %s"
                     (mapconcat
                      #'(lambda (buf)
                          (format "`%s'" (buffer-name buf)))
                      modified-buffers
                      " ")))
        (message "No fixes needed.")))))