bug#38867: 27.0.60; fileloop-initialize-replace misses occurrences to be replaced

[Noam Postavsky]

Eric Michael Timmons <etimmons@mit.edu> writes:

> Fix by telling `perform-replace' to operate over the entire
> buffer. Could potentially be further be optimized by saving the point
> in the scan-function and using it as the start point in the
> operate-function.

Since the current code is trying to save the point in the scan function,
it's better to keep that optimization.  See patch below.  Should this go
to emacs-27 or master?  The assumption that point would be preserved
seems to be long-standing, but I guess the change in the default of
switch-to-buffer-preserve-window-point is what surfaces the bug and
makes it more recent...

>From 033564127065e213868f034f08b32d14ad3d1c74 Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Tue, 24 Mar 2020 05:39:03 -0400
Subject: [PATCH] Don't lose point during fileloop replace (Bug#38867)

Suggested by Eric Michael Timmons <etimmons@mit.edu>.
* lisp/fileloop.el (fileloop-initialize-replace): Save the
match-beginning position in a variable instead of the buffer's point.
The point may be changed by the time perform-replace is called, e.g.,
due to switch-to-buffer-preserve-window-point.
---
 lisp/fileloop.el | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/lisp/fileloop.el b/lisp/fileloop.el
index 543963feaf..8f4911638e 100644
--- a/lisp/fileloop.el
+++ b/lisp/fileloop.el
@@ -200,18 +200,22 @@ fileloop-initialize-replace
 DELIMITED if non-nil means replace only word-delimited matches."
   ;; FIXME: Not sure how the delimited-flag interacts with the regexp-flag in
   ;; `perform-replace', so I just try to mimic the old code.
-  (fileloop-initialize
-   files
-   (lambda ()
-     (let ((case-fold-search
-            (if (memql case-fold '(nil t)) case-fold case-fold-search)))
-       (if (re-search-forward from nil t)
-          ;; When we find a match, move back
-          ;; to the beginning of it so perform-replace
-          ;; will see it.
-          (goto-char (match-beginning 0)))))
-   (lambda ()
-     (perform-replace from to t t delimited nil multi-query-replace-map))))
+  (let ((mstart (make-hash-table :test 'eq)))
+    (fileloop-initialize
+     files
+     (lambda ()
+       (let ((case-fold-search
+              (if (memql case-fold '(nil t)) case-fold case-fold-search)))
+         (when (re-search-forward from nil t)
+           ;; When we find a match, save its beginning for
+           ;; `perform-replace' (we used to just set point, but this
+           ;; is unreliable in the face of
+           ;; `switch-to-buffer-preserve-window-point').
+           (puthash (current-buffer) (match-beginning 0) mstart))))
+     (lambda ()
+       (perform-replace from to t t delimited nil multi-query-replace-map
+                        (gethash (current-buffer) mstart (point-min))
+                        (point-max))))))
 
 (provide 'fileloop)
 ;;; fileloop.el ends here
-- 
2.11.0