Re: [PATCH] before emit an error message, try to load the babel language

[Ruijie Yu via "General discussions about Org-mode." <emacs-orgmode@gnu.org>]

lin Sun <sunlin7@yahoo.com> writes:

> Hi,
> The function `org-babel-execute-src-block' will emit an error message
> if the language is not loaded.
>
> Before the error message, the patch will give a try to load the
> associated babel language.
>
> Why does the language exist in the `lang org-babel-load-languages' but
> not be loaded?
> Because the `org-babel-load-languages' are defined as a customer
> variable with  :set 'org-babel-do-load-languages,  the ":set" function
> can only be triggered with function `custom-set-variables`.
> While setq/cl-pushnew `org-babel-load-languages' won't trigger the
> `:set' function, then the error message will be displayed if I run the
> code in the org file.
>
> Please help review that patch. Thanks. Regards
>
> [2. text/x-patch; 0001-lisp-ob-core.el-load-lang-in-org-babel-execute-src-b.patch]...

I think this patch slightly modifies the logic of the error.

--8<---------------cut here---------------start------------->8---
 	    (unless (fboundp cmd)
-	      (error "No org-babel-execute function for %s!" lang))
+              (if (alist-get lang org-babel-load-languages)
+                  (require (intern (concat "ob-" lang)))
+                (error "No org-babel-execute function for %s!" lang)))
--8<---------------cut here---------------end--------------->8---

You are saying, that when (fboundp cmd) returns nil, and when (alist-get
...) returns non-nil, then perform the `require', and assume this
function is now available.

Instead of that, I think you should have some sort of conditional in the
`unless' condition.  Something like:

--8<---------------cut here---------------start------------->8---
(unless (or (fboundp cmd)
            (ignore (and (alist-get lang org-babel-load-languages)
                         (require (intern (concat "ob-" lang)))))
            (fboundp cmd))
  (error "... %s" lang))
--8<---------------cut here---------------end--------------->8---

This preserves the logic of the message: when we cannot get
"org-babel-execute" immediately, we then try to require the module and
try again.  Then, we check the function again and conclude that the
org-babel-execute function is not found for this language.

Thoughts?

-- 
Best,


RY

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