bug#67287: 29.1; hs-set-up-overlay messes up indent-sexp

bug#67287: 29.1; hs-set-up-overlay messes up indent-sexp

[João Pedro]

Greetings!

When setting `hs-set-up-overlay' to a custom value, such as the one in
the docstring for the variable, it messes up the behaviour of
`indent-sexp' when it is called "before" the s-expression.

Steps to reproduce:

1. Go to any lisp buffer e.g. *scracth*
2. Paste the following piece of code

    (setq hs-set-up-overlay
          (lambda (ov)
            (when (eq 'code (overlay-get ov 'hs))
              (overlay-put ov 'display
                           (propertize
                            (format " ... <%d>"
                                    (count-lines (overlay-start ov)
                                                 (overlay-end ov)))
                            'face 'font-lock-type-face)))))

3. Evaluate it
4. Enable `hs-minor-mode'
5. Hide the block with `hs-hide-block' (need to be on the beginning line
   of the forms)
6. Move point either to the first opening parenthesis or the the empty
   line before the `setq' form

   (setq
   ^----

7. Call `indent-sexp'
8. Open the block with `hs-show-block'

You should see the following:

    (setq hs-set-up-overlay
          (lambda (ov)
            (when (eq 'code (overlay-get ov 'hs))
              (overlay-put ov 'display
                           (propertize
                            (format " ... <%d>"
                                    (count-lines (overlay-start ov)
                                                 (overlay-end ov)))
                            )

I tried to investigate why it does that, but couldn't really get to the
root cause. It seems that its only affected when we're setting the
`display' prop of the overlay, but I couldn't confirm it either.

Best regards,

-- 
João Pedro de A. Paula
IT bachelors at Universidade Federal do Rio Grande do Norte (UFRN)

bug#67287: 29.1; hs-set-up-overlay messes up indent-sexp

[Eli Zaretskii]

tags 67287 notabug wontfix
thanks

> From: João Pedro <jpedrodeamorim@gmail.com>
> Date: Sun, 19 Nov 2023 16:35:31 -0300
> 
> When setting `hs-set-up-overlay' to a custom value, such as the one in
> the docstring for the variable, it messes up the behaviour of
> `indent-sexp' when it is called "before" the s-expression.
> 
> Steps to reproduce:
> 
> 1. Go to any lisp buffer e.g. *scracth*
> 2. Paste the following piece of code
> 
>     (setq hs-set-up-overlay
>           (lambda (ov)
>             (when (eq 'code (overlay-get ov 'hs))
>               (overlay-put ov 'display
>                            (propertize
>                             (format " ... <%d>"
>                                     (count-lines (overlay-start ov)
>                                                  (overlay-end ov)))
>                             'face 'font-lock-type-face)))))
> 
> 3. Evaluate it
> 4. Enable `hs-minor-mode'
> 5. Hide the block with `hs-hide-block' (need to be on the beginning line
>    of the forms)
> 6. Move point either to the first opening parenthesis or the the empty
>    line before the `setq' form
> 
>    (setq
>    ^----
> 
> 7. Call `indent-sexp'
> 8. Open the block with `hs-show-block'
> 
> You should see the following:
> 
>     (setq hs-set-up-overlay
>           (lambda (ov)
>             (when (eq 'code (overlay-get ov 'hs))
>               (overlay-put ov 'display
>                            (propertize
>                             (format " ... <%d>"
>                                     (count-lines (overlay-start ov)
>                                                  (overlay-end ov)))
>                             )
> 
> I tried to investigate why it does that, but couldn't really get to the
> root cause. It seems that its only affected when we're setting the
> `display' prop of the overlay, but I couldn't confirm it either.

Indentation commands align text by columns, and 'display' properties
and invisible text affect those columns (starting from Emacs 29).  So
you shouldn't expect reasonable results from indenting a sexp which is
partially hidden and has a 'display' property that replaces it.  IOW,
always unhide the block before indenting it.

This is not a bug.

bug#67287: 29.1; hs-set-up-overlay messes up indent-sexp

[João Pedro]

Em domingo, 19/11/2023 às 22:18, Eli Zaretskii <eliz@gnu.org> escreveu:

Hey Eli, thanks for the quick reply.

> Indentation commands align text by columns, and 'display' properties
> and invisible text affect those columns (starting from Emacs 29).

Ah, that explains why I started seeing this behaviour recently...

> So you shouldn't expect reasonable results from indenting a sexp which
> is partially hidden and has a 'display' property that replaces it.
> IOW, always unhide the block before indenting it.

So you mean that whatever is going to indent or modify the hidden text
should be "unhiding" it before doing so? Can you point to a function
that does this so I could take as a reference?

> This is not a bug.

Yeah, but maybe it requires a bit more documenting? I couldn't find
where this new behaviour was documented in NEWS.29, all I could find was
that the implementation of overlays has changed, but no mention of how
it affects 'display' properties. Maybe I missed it?

Regards,

-- 
João Pedro de A. Paula
IT bachelors at Universidade Federal do Rio Grande do Norte (UFRN)

bug#67287: 29.1; hs-set-up-overlay messes up indent-sexp

[Eli Zaretskii]

> From: João Pedro <jpedrodeamorim@gmail.com>
> Cc: 67287@debbugs.gnu.org
> Date: Mon, 20 Nov 2023 10:42:24 -0300
> 
> > So you shouldn't expect reasonable results from indenting a sexp which
> > is partially hidden and has a 'display' property that replaces it.
> > IOW, always unhide the block before indenting it.
> 
> So you mean that whatever is going to indent or modify the hidden text
> should be "unhiding" it before doing so? Can you point to a function
> that does this so I could take as a reference?

Not sure what you want me to tell.  I meant hs-show-block and its
likes.

> > This is not a bug.
> 
> Yeah, but maybe it requires a bit more documenting? I couldn't find
> where this new behaviour was documented in NEWS.29, all I could find was
> that the implementation of overlays has changed, but no mention of how
> it affects 'display' properties. Maybe I missed it?

It was deemed to be a bug fix, since current-column would basically
ignore these features and behave as if display properties didn't
exist.  And we don't call out bug fixes in NEWS.

bug#67287: 29.1; hs-set-up-overlay messes up indent-sexp

[Stefan Kangas]

Eli Zaretskii <eliz@gnu.org> writes:

> This is not a bug.

I'm therefore closing this bug report.