bug#24073: 24.5; outline-on-heading-p sees any invisible text property as outline invisible

[Paul Rankin <hello@paulwrankin.com>]

npostavs@users.sourceforge.net on Mon, 01 Aug 2016 10:16 -0400:
> I don't think it's necessarily a misuse of defsubst, that just happens
> to be one of the limitations.

Jks ;)

> Well, as you saw, re`eval'uating outline-on-heading-p (so that it
> becomes uncompiled) seems to work, you could try doing that from lisp:
> 
>     (pcase (find-function-noselect 'outline-on-heading-p)
>       (`(,buffer . ,position)
>        (with-current-buffer buffer
>          (goto-char position)
>          (eval (read (current-buffer)))))
>       (_ (error "Couldn't find `outline-on-heading-p'")))

Whoa this is terrifying...

Would something like the following work? Maybe with a
(condition-case ...) ?

    (let ((source (find-function-noselect 'outline-on-heading-p)))
      (with-current-buffer (car source)
        (goto-char (cdr source))
        (eval-defun nil)))
 
> Or advise :override outline-on-heading-p instead of outline-invisible-p.

But I want to act with a light touch...

> By the way, shouldn't that be
> 
>                   (lambda (return) (or (eq return 'outline) return))

I think this will fail when outline-invisible-p returns foo in the
initial example. We want to only return t when outline-invisible-p
returns outline, not foo or otherwise.