mount -o<TAB> exception

[edgesider]

~ » fish --version
fish, version 3.0.2
~ » echo $version
3.0.2
~ » uname -a
Linux kai-acer 5.0.2-arch1-1-ARCH #1 SMP PREEMPT Thu Mar 14 18:47:49 UTC 2019 x86_64 GNU/Linux
~ » echo $TERM
xterm-256color

I got followed exception while I type mount -o<TAB> in fish shell.

~ » mount -o/usr/share/fish/functions/__fish_complete_mount_opts.fish (line 147): switch: Expected exactly one argument, got 0                                                       14:51:40
        switch (string replace -r '=.*' '=' -- $last_arg)
               ^
        in function “__fish_complete_mount_opts”
            called on standard input
        in command substitution
            called on standard input

I checked the file, I guess because the last_args parameter is empty, causing a switch error.

But I tested the same situation under version 2.7.1 and found that there is no such problem. In this version, although the last_args parameter is also empty, there is no such problem.