REPL shell mode is incompatible with nushell

[MilesCranmer]

It seems that the nushell shell is incompatible with the Julia REPL at the moment. When I hit ; in the Julia REPL to open the shell, and write any command, I get this:

julia> ;
shell> echo "Hello World"
Error: nu::parser::shell_andand

  × The '&&' operator is not supported in Nushell
   ╭─[source:1:22]
 1 │ (echo 'Hello World') && true
   ·                      ─┬
   ·                       ╰── instead of '&&', use ';' or 'and'
   ╰────
  help: use ';' instead of the shell '&&', or 'and' instead of the boolean '&&'

I think the Julia REPL should either be made compatible with nushell, or it should run commands in a compatible shell like bash. Right now I can't seem to do anything in the shell mode because my default shell is nushell.

Context: Nushell is a new type of cross-platform shell written in pure rust: https://github.com/nushell/nushell/. Instead of "&&" they use "and" (among several other differences).

[jakobjpeters]

I also would like to use nushell. This Discourse post says that shell mode only supports POSIX shells and that one can set the JULIA_SHELL environment variable as a workaround.

[Seelengrab]

The shell> mode in the REPL doesn't actually spawn a shell, and instead evokes programs directly IIRC. How does this end up calling into nushell in the first place?

[MilesCranmer]

I’m not sure how it gets called. Maybe if JULIA_SHELL is unset it simply takes SHELL?

But where does the && come from? All that needs to be changed is that. Is that from run?

At the bottom of #23597 @xgdgsc and @stevengj were also discussing Nushell as a potential solution to having a shell mode on windows.

[KristofferC]

The shell> mode in the REPL doesn't actually spawn a shell, and instead evokes programs directly IIRC

I think the shell mode does spawn a shell. Perhaps you are thinking about run?

Anyway, a small tweak to

julia/base/client.jl

Lines 63 to 68 in 6023ad6

	if shell_name == "fish"
	shell_escape_cmd = "begin; $(shell_escape_posixly(cmd)); and true; end"
	else
	shell_escape_cmd = "($(shell_escape_posixly(cmd))) && true"
	end
	cmd = `$shell -c $shell_escape_cmd`

could probably fix this.