master b5db5a6443: with-buffer-unmodified-if-unchanged: Tweak the implementation

[Stefan Monnier]

branch: master
commit b5db5a64435b86de6e5277d1d173c57784783e5e
Author: Stefan Monnier <monnier@iro.umontreal.ca>
Commit: Stefan Monnier <monnier@iro.umontreal.ca>

    with-buffer-unmodified-if-unchanged: Tweak the implementation
    
    * lisp/emacs-lisp/subr-x.el (with-buffer-unmodified-if-unchanged):
    Skip the hash if the buffer was not modified at all.
    Use `restore-buffer-modified-p`.
    Also mention that it's imperative that the current buffer is preserved.
---
 lisp/emacs-lisp/subr-x.el | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/lisp/emacs-lisp/subr-x.el b/lisp/emacs-lisp/subr-x.el
index afa0423d90..8e763b613e 100644
--- a/lisp/emacs-lisp/subr-x.el
+++ b/lisp/emacs-lisp/subr-x.el
@@ -426,7 +426,9 @@ modification status:
 
   (with-buffer-unmodified-if-unchanged
     (insert \"a\")
-    (delete-char -1))"
+    (delete-char -1))
+
+BODY must preserve the current buffer."
   (declare (debug t) (indent 0))
   (let ((hash (gensym)))
     `(let ((,hash (and (not (buffer-modified-p))
@@ -437,9 +439,9 @@ modification status:
          ;; If we didn't change anything in the buffer (and the buffer
          ;; was previously unmodified), then flip the modification status
          ;; back to "unchanged".
-         (when (and ,hash
+         (when (and ,hash (buffer-modified-p)
                     (equal ,hash (buffer-hash)))
-           (set-buffer-modified-p nil))))))
+           (restore-buffer-modified-p nil))))))
 
 (provide 'subr-x)