bug#71727: Deleting TAGS buffer will cause `etags-regen--update-file` doesn't work

[Dmitry Gutov <dmitry@gutov.dev>]

Hi!

Thanks for the report.

On 23/06/2024 02:55, Siyuan Chen wrote:
> 5. M-x kill-buffer TAGS
> 
> 6. Add `#define APPLICATION_WINDOW_HEIGHT 320` to test.c and M-x save-buffer
> 
> 7. Move the cursor to APPLICATION_WINDOW_HEIGHT and M-x 
> xref-find-definitions.

What happens here, is etags-regen--update-file (added to 
after-save-hook) fails the check

   (get-file-buffer etags-regen--tags-file)

and so the buffer and the file are not updated.

Note that if after step 7 you make an edit to the same file and then try 
navigating again it will work because at step 7 the tags file is visited 
again. So this doesn't seem an urgent problem, but it would be nice to 
fix nevertheless.

I think we couldn't re-visit the tags file inside after-save-hook (it 
might not be fast enough, for one thing), but the second alternative 
mentioned inside the TODO at the top of etags-regen--update-file should 
be fix this as well.

Is there are particular reason you killed the TAGS buffer? Perhaps a 
quicker fix would be to visit the tags file in a hidden buffer, rather 
than use the name that's so easy to find and kill or do something else 
by accident.