NOTE: I have noticed some strage bugs (in indent and smart mode at least), and currently I do not have the time to hunt them down - the problem may be in the Lua library itself - , so consider this as WIP for the moment (or use it at your own risk).
Fast and light parinfer plugin for Neovim.
The two maintained parinfer plugins currently available for (Neo)Vim both have certain drawbacks: The good old VimL plugin uses the library ported by oakmac, which implements an older version of Parinfer, and - unfortunately - is terribly slow, often on the verge of being unusable. The more recent Rust port, on the other hand, while super-fast and very polished, requires building dynamic libraries and a Rust toolchain for that, which makes it inconvenient for less involved users, not to say that it takes up a considerable amount of disk space too. (If you're fine with these, just go ahead and use it of course!)
With a Lua library available (thanks to Chris Oakman, again!), we can have the best of both worlds now, a lightweight yet fast plugin in the native scripting language of the editor, with hassle-free installation and the latest features (smart mode) provided.
All credit goes to the aforementioned authors, I just took the Vim plugin and the doc file from the parinfer-rust repo, and made trivial modifications to stitch it together with the Lua lib.
Use your favourite package manager, e.g. vim-plug:
Plug 'ggandor/nvim-parinfer'