; broken when using Fish shell

[malmaud]

With fish as my default shell, I get the below error. Presumably that is because in Fish, (x) is like $x in bash and not a grouping operator.

julia> ;ls
fish: Illegal command name '(ls)'
Standard input: (ls) && true
^
ERROR: failed process: Process(/usr/local/bin/fish -i -c '(ls) && true', ProcessExited(127)) [127]
in pipeline_error at process.jl:476
in run at process.jl:453
in repl_cmd at client.jl:62

[staticfloat]

What is the grouping operator in fish? (Actually, I think this is called the "subshell syntax")

[StefanKarpinski]

We can special-case this base on the SHELL environment variable (see base/client.jl), but in the meantime you can also export JULIA_SHELL=/bin/bash to get this to work now.

[malmaud]

I'm not sure Fish actually has subshell support. I think the canonical way to translate
(ls) && true
into fish is
ls; true

But I'm no expert on shells.

[StefanKarpinski]

Well, in that case I would have to recommend setting JULIA_SHELL. What kind of shell doesn't have subshell support?

[malmaud]

I went ahead and set JULIA_SHELL. I dont' really know anything about this, but the fish wikipedia page http://en.wikipedia.org/wiki/Friendly_interactive_shell seems to advertise the lack of subshells as a feature.

"One important difference between fish and other shells is the lack of subshells. Many tasks like pipelines, functions and loops are implemented using so called subshells in other languages. Subshells are simply child programs that run a few commands for the shell and then exit. Unfortunately, changes made inside a subshell do not have any effect in the main shell, meaning that actions such as variable assignments and the use of many builtin functions do not work as expected. Fish never forks off so-called subshells; all builtins are always fully functional."

[StefanKarpinski]

Uh, ok. Well, in that case we're not going to be able to support fish. I'm declaring setting JULIA_SHELL to be the official solution to this problem.

[iamed2]

May I ask why the subshells are necessary for Julia's shell integration?

[StefanKarpinski]

Relevant code is here:

julia/base/client.jl

Lines 91 to 126 in cfac61d

	function repl_cmd(cmd, out)
	shell = shell_split(get(ENV,"JULIA_SHELL",get(ENV,"SHELL","/bin/sh")))
	# Note that we can't support the fish shell due to its lack of subshells
	# See this for details: https://github.com/JuliaLang/julia/issues/4918
	if Base.basename(shell[1]) == "fish"
	warn_once("cannot use the fish shell, defaulting to /bin/sh\
	set the JULIA_SHELL environment variable to silence this warning")
	shell = "/bin/sh"
	end
	if isempty(cmd.exec)
	throw(ArgumentError("no cmd to execute"))
	elseif cmd.exec[1] == "cd"
	new_oldpwd = pwd()
	if length(cmd.exec) > 2
	throw(ArgumentError("cd method only takes one argument"))
	elseif length(cmd.exec) == 2
	dir = cmd.exec[2]
	if dir == "-"
	if !haskey(ENV, "OLDPWD")
	error("cd: OLDPWD not set")
	end
	cd(ENV["OLDPWD"])
	else
	cd(@static is_windows() ? dir : readchomp(`$shell -c "echo $(shell_escape(dir))"`))
	end
	else
	cd()
	end
	ENV["OLDPWD"] = new_oldpwd
	println(out, pwd())
	else
	run(ignorestatus(@static is_windows() ? cmd : (isa(STDIN, TTY) ? `$shell -i -c "($(shell_escape(cmd))) && true"` : `$shell -c "($(shell_escape(cmd))) && true"`)))
	end
	nothing
	end

. It seems like it's so that we can do (...) && true to suppress failures, but we're also ignoring the status of the shell command, so maybe we don't need that anymore.

[iamed2]

In fish you could also use begin; ...; true; end to get an unconditional true status.

[StefanKarpinski]

Good to know. If anyone's using fish shell and wants to make a PR for this, that would be great 👍