bug#54025: 27.2; dired-do-find-regexp skips occurences

[Dmitry Gutov <dgutov@yandex.ru>]

On 23.02.2022 09:01, Петров Андрей wrote:
> It seems that processing unmodified (or not open) files with grep and modified ones with searching in buffers would be a well-balanced approach saving both memory and possible network traffic (or SSD rewrite cycles) but this is rather feature to make in the future then a hot fix )).

This, together with the previous discussion, gave me an idea.

Do you personally want to be prompted to save the buffers? If not, we 
could just do the "with appropriate logging" part. More than that, when 
the buffer is unsaved, we can just process the text returned by grep in 
a temp buffer (which is what we do for all non-visited files anyway).

So, how about just the change below? Or should we add the prompting to 
save as well?

diff --git a/lisp/progmodes/xref.el b/lisp/progmodes/xref.el
index aa98aa89f1..96fb835d0f 100644
--- a/lisp/progmodes/xref.el
+++ b/lisp/progmodes/xref.el
@@ -2010,10 +2010,16 @@ xref--collect-matches-1

  (defun xref--find-file-buffer (file)
    (unless (equal (car xref--last-file-buffer) file)
-    (setq xref--last-file-buffer
-          ;; `find-buffer-visiting' is considerably slower,
-          ;; especially on remote files.
-          (cons file (get-file-buffer file))))
+    ;; `find-buffer-visiting' is considerably slower,
+    ;; especially on remote files.
+    (let ((buf (get-file-buffer file)))
+      (when (and buf
+                 (or
+                  (buffer-modified-p buf)
+                  (not (verify-visited-file-modtime (current-buffer)))))
+        ;; We can't use buffers whose contents diverge from disk 
(bug#54025).
+        (setq buf nil))
+      (setq xref--last-file-buffer (cons file buf))))
    (cdr xref--last-file-buffer))

  (provide 'xref)