Re: Remove "shell" as a supported Babel language within ob-shell.el (was Re: [SUGGESTION] ob-shell async result output should not contains shell prompt)

[Ihor Radchenko]

Matt <matt@excalamus.com> writes:

> What benefit does "shell" provide?
>
> - The "shell" language allows an arbitrary executable to be run.  This means 
> that shells other than those given in `org-babel-shell-names' can be run.  
> People using a non-supported shell could still benefit from ob-shell.
>
> What downsides does "shell" bring?
>
> - "shell" falls back to `shell-file-name' which can be an arbitrary 
> executable.  Whenever I hear "runs an arbitrary executable", my ears perk up 
> and I start to sweat.  There may be security considerations.  
> - If that executable is a shell, then the prompt gets set independently from 
> Emacs.  For the prompt to be filtered from the output, users would need to 
> provide Emacs with the correct regexp.  A recent thread discussed creating a 
> header arg to address this: https://list.orgmode.org/87ttzgeg3w.fsf@localhost/
> - We would get bug reports about non-supported shells which kind of work, but 
> have issues because they're not supported
> - Maintence associated with supporting arbitrary (shell) executables
>
> As the current maintainer of ob-shell, I'm in favor of removing "shell" as a 
> Babel language.  The cons appear to far outweigh the pros.  However, I'm 
> aware others may have good use for it.  It's been a part of Org for nearly a 
> decade.  I'm sure it's part of people's workflow, especially since it's been 
> in the manual for 6 years.  Are there any pros, cons, use-cases, or 
> considerations I've overlooked?

I would not see arbitrary executable to be such a big deal. At the end,
if SHELL is set to something fishy, the user is likely in serious
trouble anyway. SHELL is a part POSIX standard at the end.

Yet, the problem with unsupported shells is indeed real.
Moreover, "shell" code blocks are currently not portable to different
environments.

I suggest the following:
1. Introduce a new customization `org-babel-default-shell', defaulting
   to (or (executable-find "sh") (executable-find "cmd.exe")).
2. Use the value as default shell in "shell" code blocks.
3. Document and announce the change.
4. Create org-lint checker that will mark "shell" code blocks as not
   desired.

The above steps will ensure minimal breakage for existing uses of
"shell" blocks. Only users who wrote shell blocks for non-standard shell
will have to adapt.

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at <https://orgmode.org/>.
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