messes up files when writing into multiple files at once with multiple formating lsp providers

[vitaly]

how to reproduce:

• install sumneko lua-language-server
• install stylua
• install null-ls and enable stylua formatter
• open about 50 lua files with, e.g. vim lua/**/*.lua
• run bufdo w

vim will start writing into all those files and lsp-format will endup with file contents mixed between the files. e.g.
file foo will have content of file bar, which, in turn will have content of file baz etc.

[lukas-reineke]

I found some issues when writing a buffer that is not the current one, I made a PR here #59
But none of those issues would write content from one buffer into another, and I also can't reproduce that 🤔

Can you check if the PR changes anything?

[lparry]

Is there a config option to not format anything except the focused buffer? I'm not sure if it's exactly the same thing as this issue, but I seem to get stuck in loops where if I save a file, every other buffer ends up with changes preventing :q, so I change buffer, :w and now every buffer is touched again. non-focused formatting just feels unhelpful

[lukas-reineke]

this is a different issue, and it should not happen.
Can you make a new ticket with steps to reproduce?