bug#71750: 29.4; hs-hide-all can't handle unmatched pairs in Org-mode

bug#71750: 29.4; hs-hide-all can't handle unmatched pairs in Org-mode

[Forty Five]

If an Org entry contains an unmatched pairing character (as defined by
the syntax table), `hs-hide-all' will fail to fold anything, with an
error as demonstrated by the recipe below:

;;; recipe.el
(scratch-buffer)
(insert "* heading\n(")
(org-mode)
(hs-minor-mode)
(hs-hide-all)
;;;recipe.el ends here

$ emacs -Q --batch -l recipe.el
Hiding all blocks...

Error: scan-error ("Unbalanced parentheses" 11 12)
  mapbacktrace(#f(compiled-function (evald func args flags) #<bytecode -0x13a4d4fc50517829>))
  debug-early-backtrace()
  debug-early(error (scan-error "Unbalanced parentheses" 11 12))
  scan-sexps(11 1)
  forward-sexp(1)
  hs-forward-sexp((11 12 #<buffer *scratch*>) 1)
  hs-hide-block-at-point(t)
  hs-hide-all()
  load-with-code-conversion("/home/user/recipe.el" "/home/user/recipe.el" nil t)
  command-line-1(("-l" "recipe.el"))
  command-line()
  normal-top-level()
Scan error: "Unbalanced parentheses", 11, 12


In GNU Emacs 29.4 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.42,
cairo version 1.18.0)
System Description: Arch Linux

Configured using:
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JSON LCMS2 LIBOTF LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY
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Major mode: Fundamental

Minor modes in effect:
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bug#71750: 29.4; hs-hide-all can't handle unmatched pairs in Org-mode

[Eli Zaretskii]

> From: Forty Five <mathewegeorge@gmail.com>
> Date: Mon, 24 Jun 2024 21:25:31 +0530
> 
> If an Org entry contains an unmatched pairing character (as defined by
> the syntax table), `hs-hide-all' will fail to fold anything, with an
> error as demonstrated by the recipe below:
> 
> ;;; recipe.el
> (scratch-buffer)
> (insert "* heading\n(")
> (org-mode)
> (hs-minor-mode)
> (hs-hide-all)
> ;;;recipe.el ends here
> 
> $ emacs -Q --batch -l recipe.el
> Hiding all blocks...
> 
> Error: scan-error ("Unbalanced parentheses" 11 12)
>   mapbacktrace(#f(compiled-function (evald func args flags) #<bytecode -0x13a4d4fc50517829>))
>   debug-early-backtrace()
>   debug-early(error (scan-error "Unbalanced parentheses" 11 12))
>   scan-sexps(11 1)
>   forward-sexp(1)
>   hs-forward-sexp((11 12 #<buffer *scratch*>) 1)
>   hs-hide-block-at-point(t)
>   hs-hide-all()
>   load-with-code-conversion("/home/user/recipe.el" "/home/user/recipe.el" nil t)
>   command-line-1(("-l" "recipe.el"))
>   command-line()
>   normal-top-level()
> Scan error: "Unbalanced parentheses", 11, 12

What do we expect hs-hide-all to do in this case?

bug#71750: 29.4; hs-hide-all can't handle unmatched pairs in Org-mode

[Mathew George]

> What do we expect hs-hide-all to do in this case?

So, it looks like I got confused here. I thought I was invoking `hs-hide-all` to fold all
Org headings; I was actually invoking a different function of my own, which calls
`hs-hide-all` followed by `outline-show-only-headings`, and it was
aborting with the scan-error from `hs-hide-all`. `hs-hide-all` does not fold Org
headings, which is what I thought it was doing.

With that said, the scan-error is still kind of odd. So I think I have the same question as
you - what is `hs-hide-all`, and hs-minor-mode in general, able to do in
Org-mode? If it doesn't do anything, shouldn't `hs-grok-mode-type` produce an
error like 'Org Mode doesn't support Hideshow Minor Mode'? I can just
`condition-case` the scan-error in my function, but maybe we want Hideshow to 
fail in a more intelligible way...