nvim-config-local VS exrc.vim

it's been undeprecated recently, but if you would prefer to use a plugin, I use this one

The next version of neovim (and currently, nightly) re-enables support for exec, which sounds close to what you want. In the meantime check out https://github.com/klen/nvim-config-local. These both do a single file, but once you're running some code it's easy enough to get that file to source more.

I just use nvim-config-local, which is basically just souped up :h 'exrc'. And then from there I typically set makeprg and a custom "run" command if I want, along with any other settings I might want in the project. I tried using some custom runner type plugins in the past but I think this method has provided me with the most flexibility, and I don't have to learn anything new because it's just the same as what i do in my init.lua.

I took inspiration from nvim-config-local and added an integrity check, to force the user to review the settings file at least once. It's on by default, but is optional. The file can be safe to use if you don't expose any option that allows for arbitrary code execution.

nvim-config-local

exrc can enable untrusted arbitrary execution. See https://github.com/ii14/exrc.vim that tries to mitigate this.

'exrc' option or https://github.com/ii14/exrc.vim

Yeah, here's my plugin that does that: https://github.com/ii14/exrc.vim

:set exrc and and create .exrc file in your project directory with your project settings, or use a plugin like https://github.com/ii14/exrc.vim or https://github.com/jenterkin/vim-autosource

I did basically the same thing, but without recursive lookup: https://github.com/ii14/exrc.vim

https://github.com/ii14/exrc.vim for local vimrc. Basically a reimplementation of the 'exrc' option that keeps track of file hashes, so you don't evaluate anything malicious, without the limitations of 'secure' option.