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Re: Bug Re: Greater than, less than bug in emacs-lisp source block


From: Tim Cross
Subject: Re: Bug Re: Greater than, less than bug in emacs-lisp source block
Date: Sun, 05 Sep 2021 07:05:43 +1000
User-agent: mu4e 1.7.0; emacs 27.2.50

John Kitchin <jkitchin@andrew.cmu.edu> writes:

> My previous solution seems like it stopped working for some reason. Here is a 
> new version that "should" only change syntax
> inside src-blocks, but not inside strings.
>
> It looks like this does not impact html blocks, or xml blocks.
>
> It is probably possible to make it mode specific if needed.
>
> (defun scimax-org-mode-<>-syntax-fix (start end)
>   "Change syntax of characters ?< and ?> to symbol within source code blocks."
>   ;; I think this gets run in a special edit buffer for src-blocks. For now I
>   ;; only run this in the src blocks, so that outside the src-blocks these 
> still
>   ;; act like b=open/close brackets.
>   (when (org-src-edit-buffer-p)
>     (let ((case-fold-search t))
>       (goto-char start)
>       ;; this "fixes" <>, {} and [] that fixes some issues in src blocks, but
>       ;; makes some new issues, which is now you cannot use them as brackets.
>       ;; this tries to be fancy and not change the syntax in strings.
>       (while (re-search-forward "[[<{]\\|[]>}]" end t)
> (unless (ppss-string-terminator (syntax-ppss (point)))
>  (put-text-property (point) (1- (point))
>                              'syntax-table (string-to-syntax "_")))))))
>
> (defun scimax-fix-<>-syntax ()
>   "Fix syntax of <> in code blocks.
> This function should be added to `org-mode-hook' to make it work."
>   (setq syntax-propertize-function 'scimax-org-mode-<>-syntax-fix)
>   (syntax-propertize (point-max)))
>
> (add-hook 'org-mode-hook
>  #'scimax-fix-<>-syntax)
>
> John
>
> -----------------------------------
> Professor John Kitchin (he/him/his)
> Doherty Hall A207F
> Department of Chemical Engineering
> Carnegie Mellon University
> Pittsburgh, PA 15213
> 412-268-7803
> @johnkitchin
> http://kitchingroup.cheme.cmu.edu
>
> On Fri, Sep 3, 2021 at 9:47 AM Tim Cross <theophilusx@gmail.com> wrote:
>
>  I think what is happening here is that org is bumping up against
>  fundamental design limitations of Emacs. In basic terms, much of Emacs'
>  underlying design is based on an assumption that a file only has a
>  single major mode. Org works hard to get around this limitation, but it
>  comes with cost - usually either performance or complexity.
>
>  I think this could probably be characterised as a bug without a workable
>  solution. While there are things youc an do, they all seem to have
>  unwanted side effects. To what extent those side effect impact you
>  depends on your use case (as John points out, if you have blocks of HTML
>  or XML or JSX etc, changing the syntax table to make < and > 'normal'
>  characters would fix the elisp issue, but break things in those source
>  blocks.
>
>  So really, what we have is an issue without a clean solution. Best
>  anyone can do is select one of the proposed work-arounds which has
>  minimal impact on the user. Personally, I never edit source blocks
>  except in the special edit mode, so don't really notice the problem with
>  mismatched parens.
>

If this does work without unwanted side effects or negative performance
impact, then it probably should be considered for inclusion in org as it
seem pretty clean and straight-forward. I have to wonder why it hasn't
given how long this issue has been known about?



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