bug#81516: 31.0.91; delete-file-local-variable(-prop-line) should delete "Local Variables" block (prop-line)

Eli Zaretskii <[email protected]> writes:

>> Date: Wed, 29 Jul 2026 15:02:38 +0200
>> From: Daniel Mendler via "Bug reports for GNU Emacs,
>>  the Swiss army knife of text editors" <[email protected]>
>> 
>> When delete-file-local-variable is called for the last file-local
>> variable, the "Local Variables" block is not removed. Similarly for
>> delete-file-local-variable-prop-line, a remnant of the prop-line
>> remains: ;; -*- -*-
>> 
>> While the remnants are not highly problematic, one still gets an error
>> when the file is opened the next time:
>> 
>>   File mode specification error:
>>   (error "Invalid search bound (wrong side of point)")
>> 
>> This suggest that the empty prop line (or the "Local Variables" block)
>> should better be deleted.
>
> I cannot reproduce this error.  I created a file with file-local
> variables, then invoked delete-file-local-variable several times until
> all the variables were deleted and what was left was the empty block:
>
>   ;; Local Variables:
>   ;; End:
>
> Then I saved the buffer to its file, killed Emacs, and visited the
> file in a new session -- I saw no errors.
>
> If the recipe for reproducing the error is different, please describe
> it in enough detail for me to be able to reproduce it.

The error occurs only for delete-file-local-variable-prop-line. There
the header line ";; -*- -*-" remains which triggers the error the next
time the file is opened.

I suggest to handle both deletion commands the same, remove the faulty
prop line, and also the empty local variables block.

Daniel