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Detect some API violations in combine-change-calls (bug#80877)

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Quickly verify that the number of unchanged characters before and
after the region that changes are supposed to be limited to doesn't
change.

Suggested by Stefan Monnier.

* lisp/subr.el (combine-change-calls-1): Copy BEG into a marker, and
count the characters after the changed region.  After the changes,
ensure the character counts still match.
* test/lisp/subr-tests.el (subr-test-combine-change-calls-error): New.
This commit is contained in:
Pip Cet 2026-05-17 15:27:03 +00:00
parent a8b9fad897
commit 0b5ead9923
2 changed files with 32 additions and 2 deletions
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15
lisp/subr.el
View file

@ -5664,10 +5664,17 @@ the function `undo--wrap-and-run-primitive-undo'."
(if (markerp beg) (setq beg (marker-position beg)))
(if (markerp end) (setq end (marker-position end)))
(let ((old-bul buffer-undo-list)
(beg-marker (copy-marker beg))
(unchanged-after (- (point-max) end))
(end-marker (copy-marker end t))
result)
(if undo--combining-change-calls
(setq result (funcall body))
(progn
(setq result (funcall body))
(unless (and (= beg-marker beg)
(= unchanged-after (- (point-max) end-marker)))
(error "Modifications outside the announced region"))
(set-marker beg-marker nil))
(let ((undo--combining-change-calls t))
(if (not inhibit-modification-hooks)
(run-hook-with-args 'before-change-functions beg end))
@ -5686,7 +5693,11 @@ the function `undo--wrap-and-run-primitive-undo'."
(if (memq #'syntax-ppss-flush-cache bcf)
'(syntax-ppss-flush-cache)))
(setq-local after-change-functions nil)
(setq result (funcall body)))
(setq result (funcall body))
(unless (and (= beg-marker beg)
(= unchanged-after (- (point-max) end-marker)))
(error "Modifications outside the announced region"))
(set-marker beg-marker nil))
(if local-bcf (setq before-change-functions bcf)
(kill-local-variable 'before-change-functions))
(if local-acf (setq after-change-functions acf)

19
test/lisp/subr-tests.el
View file

@ -1773,5 +1773,24 @@ The argument names are important."
'("foo" "bar" "bazzzzzz"))
'(("foo" "bar") ("bazzzzzz"))))))
(ert-deftest subr-test-combine-change-calls-error ()
"Test detection of unexpected changes in `combine-change-calls'."
(with-temp-buffer
(insert "a\nb\nc\n")
(combine-change-calls 3 5
(goto-char (point-min))
(search-forward "b")
(replace-match "bbb"))
(should-error
(combine-change-calls 3 7
(goto-char (point-min))
(search-forward "a")
(replace-match "aaa")))
(should-error
(combine-change-calls 5 9
(goto-char (point-min))
(search-forward "c")
(replace-match "ccc")))))
(provide 'subr-tests)
;;; subr-tests.el ends here