Simple toggle doesn't work

[enoryw]

I reduced my toggle script the simplest form where it doesn't work--when the script starts, it shows 1 item personal. Ctrl-R to toggle once results in the error:

[Command failed: evail printf "%s" non_personal]

Toggle once more to return to original state results in the error:

[Command failed: evail printf "%s" personal]

Below, I define personal variable which will be exported to fzf child process shell spawned by reload. It gets evaled for fzf and on reload it gets evaled again.

I don't understand why eval $personal | fzf for the initial state works, but on reloads that does the same eval $personal it doesn't.

If I replace the variables that use printf with the echo variant (it's not equiavlant, I know), then toggling works as you would expect.

Any ideas? I tried escaping stuff from the printf command but to no success.

#!/usr/bin/zsh

personal='printf "%s\0" personal'
non_personal='printf "%s\0" non_personal'

# personal='echo -n personal'
# non_personal='echo -n non-personal'

# Make available to fzf child shell processes
export personal non_personal

file=$(
    eval $personal |
    SHELL=/usr/bin/zsh fzf --read0  \
      --prompt="Files (personal) > " \
      --bind 'ctrl-r:transform:[[ ! $FZF_PROMPT == "Files (personal) > " ]] &&
      echo "change-prompt(Files (personal) > )+reload(eval $personal)" ||
      echo "change-prompt(Files (non-personal) > )+reload(eval $non_personal)"'
) || exit

[junegunn]

Try escaping $ so that the variables are not immediately expanded. i.e. eval \$personal and eval \$non_personal

[enoryw]

This works! But to be honest I still don't understand why escaping is necessary in reload(), e.g. isn't eval on the string that gets expanded what's needed?

[junegunn]

I looked into it and found that the null byte is causing the problem. \0 evaluates to a real null byte which zsh treats as the end of a string argument.

% zsh -c $'eval printf "%s\0" foo'
zsh:1: unmatched "

This is the go code that shows it:

package main

import (
	"fmt"
	"os"
	"os/exec"
)

func main() {
	cmd := exec.Command("zsh", "-c", "eval printf \"%s\x00\" hello")
	cmd.Stdout = os.Stdout
	fmt.Println(cmd.Run())
}

go run main.go
fork/exec /opt/homebrew/bin/zsh: invalid argument