Subject: [PATCH] Make whitespace.el cleanup add missing final newline

From: Björn Lindström <[email-masked]>
Date: Tue, 11 Jun 2024 20:16:03 +0200

Hello,

attaching patch to make the whitespace-cleanup and whitespace-cleanup-region functions add a final newline to a file if whitespace-style contains `missing-newline-at-eof

I'm aware this somewhat replicates what setting `require-final-newline would do, but I think since whitespace.el with this configuration highlights this as an error, it should also clean it up when asked.

Best wishes,
Björn

From 73e20b34c1669a9d52cbc70f4c02cc26fa23cf5b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Lindstr=C3=B6m?= <[email-masked]>
Date: Tue, 11 Jun 2024 19:49:55 +0200
Subject: [PATCH] Make whitespace.el cleanup add missing final newline

* lisp/whitespace.el (whitespace-cleanup-region): if cleaning up at end
of file, add missing newline if indicated by whitespace-style.
---
 lisp/whitespace.el | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/lisp/whitespace.el b/lisp/whitespace.el
index bc23a8794eb..a41a7520915 100644
--- a/lisp/whitespace.el
+++ b/lisp/whitespace.el
@@ -1465,6 +1465,11 @@ defun whitespace-cleanup-region
    If `whitespace-style' includes the value
    `space-after-tab::space', replace TABs by SPACEs.
 
+5. missing newline at end of file.
+   If `whitespace-style' includes the value `missing-newline-at-eof',
+   and the cleanup region includes the end of file, add a final newline
+   if it is not there already.
+
 See `whitespace-style', `indent-tabs-mode' and `tab-width' for
 documentation."
   (interactive "@r")
@@ -1545,7 +1550,13 @@ defun whitespace-cleanup-region
          ((memq 'space-before-tab::space whitespace-style)
           (whitespace-replace-action
            'untabify rstart rend
-           whitespace-space-before-tab-regexp 2))))
+           whitespace-space-before-tab-regexp 2)))
+        ;; PROBLEM 5: missing newline at end of file
+        (when (and (memq 'missing-newline-at-eof)
+                   (= (point-max) (without-restriction (point-max))))
+          (goto-char (point-max))
+          (when (re-search-backward ".\\'" nil t)
+            (insert "\n")))
       (set-marker rend nil))))		; point marker to nowhere

-- 
2.45.2