bug#42424: 27.0.90; replace-match: point is NOT left at the end of replacement

[Ren Victor]

I attach an ert case to show the recipe.

This issue happens when modification hooks modify the text before the
end of replacement text.

`replace-match' calls `replace_range' to do the actual replacement,
which can trigger modification hooks.  Before calling `replace_range',
the position of the end of replacement is saved. After `replace_range',
the point is moved to the saved position.

But the end of replacement might be changed inside of
`replace_range'.  So the final movement of point may end up to a wrong
place.

Other types of modification (insert or delete) do not have this issue.
`point' is adjusted before running modification hooks.

In `replace_range', the point is also relocated.  I am not sure why it has
to be moved again just before returning from `replace-match'.

This is not a new issue.  It is in Emacs24 at least.


In GNU Emacs 27.0.90 (build 1, x86_64-pc-cygwin)
 of 2020-03-04 built on moufang2
Repository revision: afff43a72e96fcccabe77ff63226cddd540e068d
Repository branch: master
Windowing system distributor 'Microsoft Corp.', version 10.0.19041
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Quit
ert
next-line: End of buffer [3 times]
test-replace-match
Ran 1 tests, 0 results were as expected, 1 unexpected
next-line: End of buffer
previous-line: Beginning of buffer [13 times]
previous-line: Beginning of buffer
Configured using:
 'configure
 
--srcdir=/home/kbrown/src/cygpackages/emacs/emacs-27.0.90-1.x86_64/src/emacs-27.0.90
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Important settings:
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Major mode: Emacs-Lisp

Minor modes in effect:
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Load-path shadows:
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Memory information:
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 (string-bytes 1 668356)
 (vectors 16 12971)
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test_replace_match.el
Description: Binary data