black.vim integration with native 'formatprg' option possible?

[craigmac]

Hi, I was wondering if black.vim is able to integrate with vim's 'formatprg' option (:h 'formatprg'), which is supposed to be set to an external command to run when using 'gq' operator. I'm not sure if it's possible or at-odds with how black is supposed to be run, can anyone clarify? Docs say the external program must take the input on stdin and produce output on stdout.

[craigmac]

Best effort so far:

in my personal ~/.vim/after/ftplugin/python.vim:

setlocal formatprg=black\ --quiet\ -
augroup black-fmt
    autocmd!
    autocmd BufWritePre <buffer> normal gggqG``
augroup END

This will set a local autocommand to run black on the current buffer file each time it is about to
save, but only if :set ft? value is 'python'. 'gq' operator works with stdin and stdout, not stderr so we tell black to be --quiet (else you get messages from black pasted into your file) and we pass it the '-' argument to tell black to use stdin.

I'm sure there are improvements that can be made, open to suggestions.

[mooreniemi]

Above has one disadvantage: loses cursor position (sends you to top of file).

[EgZvor]

@mooreniemi This kinda works, but since the file is changed outside of Vim it cannot track the changes to a mark (cannot remember "current" position).

    autocmd BufWritePre <buffer> keepjumps normal m'gggqG``