slow midnight commander and broken fish subshell in fish 3.2.0

[chrysos349]

mc 4.8.25 (or 4.8.26)
fish 3.2.0

With fish 3.2.0 set as a default shell, upon launch midnight commander hangs for about 10 seconds and has a broken subshell.
If launched with --nosubshell (or -u), the problem disappears in mc.
However, the fish subshell worked fine in fish 3.1.2, and mc launched immediately.

[olfway]

Have the same issue on mac os catalina with mc and fish from homebrew

mc 4.8.26

[ridiculousfish]

Thank you for filing this bug. Please do share the information requested in the issue template. The OS and terminal are crucial information.

When I try Midnight Commander 4.8.26 on macOS 11.2.1 with iTerm2 3.4.0, I see reproducible hangs on startup with fish 3.2.0, 3.1.2, and 3.0.2, and also bash 5.1, and zsh 5.8.0.2. I do not see any hangs on Linux. Scratch that, what matters is your $SHELL env value, not what shell is actually running...bleh.

My guess is that this is mc injecting weird commands into fish. mc attempts to detect your shell, and if it's fish, tries to echo to weird file descriptors; this is now an error in fish; maybe we have to try to support that somehow.

[olfway]

I see this issue with fish 3.2.0 and it works fine in fish 3.1.2 (both from homebrew)

mc 4.8.26 (homebrew)
Mac OS 10.15.7
iTerm2 3.4.4

[chrysos349]

I forgot to say in my case this bug happens on Linux with fish 3.2.0 ONLY if fish shell is set as a default shell.
fish 3.1.2 worked fine.

I tried these configurations:

1. Void Linux with xfce4-terminal 0.8.10,
2. Void Linux with Konsole 20.12.2,
3. Kubuntu 20.10 with Konsole 20.08.2

[faho]

I would imagine just reverting 11a373f should work for the time being? I think mc opens those fds so they should be safe to use (and not some of our internal fds)?

Maybe just error out when the fd is a fish internal one?

[ridiculousfish]

Yeah I think we should just revert 11a373f. I thought redirecting to internal fds was useless, but I didn't consider fds that were inherited; on reflection I think mc's usage here makes sense.

[faho]

Alright, reverted.