[Feature Request] functional, blocking version of `fzf#run` for neovim about fzf.vim

[junegunn]

See junegunn/fzf#2916 (comment)

fzf#run returning values on regular Vim is a happy coincidence, and you shouldn't rely on this behavior because it's not guaranteed if you open fzf in different layouts. And there's no way to implement blocking fzf#run on Neovim unless you set up fzf to open using fzf-tmux. It's a shame we don't have better options.

[Jasha10]

After using the minimal setup using vim -Nu <(curl https://gist.githubusercontent.com/junegunn/6936bf79fedd3a079aeb1dd2f3c81ef5/raw) I realized that fzf#run already returns the selected line(s). I must have a problem somewhere in my .vimrc that's making fzf#run not return the selected lines.

[Jasha10]

Ok I'm reopening because :echo fzf#run() works with the minimal vim setup but it doesn't work with a minimal Neovim setup!
Steps to reproduce:

1. Open a minimal neovim setup:

$ nvim --version
NVIM v0.9.1
...
nvim -Nu <(curl https://gist.githubusercontent.com/junegunn/6936bf79fedd3a079aeb1dd2f3c81ef5/raw)

2. Run :echo fzf#run(). Nothing is echo'd.

[Jasha10]

Thanks for your reply, @junegunn. If my understanding is correct, the fundamental issue is that vim/neovim have a single-threaded event loop. This makes it difficult to escape from the callback paradigm without using green threads.

Thanks also for the tip about fzf-tmux. I'll give that a try.