The Definitive Neovim Unity Setup of 2023

If you use neovim to write code for Unity, it's likely that you want (or have wanted) a language server to be set up in your configuration, giving you access to autocomplete, references, definition jumping, diagnostics, and much more.

However, setting up a Unity-compatible C# LSP is not the easiest task. Personally, I struggled for hours trying to get it to work, scouring the internet for any source even remotely related to the issues I was facing. Many of the blog posts for setting it up were quite outdated and failed to work with recent changes in Mono and other systems

This post assumes you already have a neovim configuration set up, and you are using nvim-lspconfig for your server configurations.

Installing Dependencies

The first system-wide dependency you'll need is mono. The one vendored by the lsp does not work. I used Homebrew for installation, with brew install mono. I got version v6.12.0.182, but theoretically this should work for any mono version 6.

Next, you'll need OmniSharp, which is the actual LSP. You will not need to install this globally on your system, you just need an accessible path to the binary. This is where things are a bit tricky: the latest version of OmniSharp will not work. You need an old version of the LSP that is compatible with the mono you just installed.

The most recent working release I found was v1.38.2. To install, first follow that link. Then, find the asset that works with your system and download the non-http version of the server. Put the download in a path you'll remember!

The last dependency you need is Visual Studio Code (VSCode). Yes, I know this is a strange requirement, but it's a necessary step for Unity to generate project files (credits to this post for the trick). Don't worry: the download is actually only needed for a short amount of time; after the first time you set it up, Unity doesn't care if VSCode exists anymore (a bug which hopefully is never fixed).

Setting Up

After you've finished installing dependencies, you can actually start setting it up! The hard part is over! This step requires a tiny bit of work on both the Neovim and Unity ends, but nothing too complicated or error-prone.

Neovim Setup

First, start by going into your nvim-lspconfig setup, and enter the following code:

-- Change this to your actual download path.
local path_to_download = '/Users/dzfrias/.dotfiles/downloads/omnisharp-osx'
require('lspconfig').omnisharp.setup {
  cmd = {
    'mono',
    '--assembly-loader=strict',
    path_to_download .. '/omnisharp/OmniSharp.exe',
  },
  -- Assuming you have an on_attach function. Delete this line if you don't.
  on_attach = on_attach,
  use_mono = true,
}

Of course, change the path_to_download variable to the actual path of the OmniSharp you downloaded. After that, everything from the Neovim side should be set up!

Unity Setup

Now, for the Unity part. Open up any Unity project, and go to Unity > Settings in the menu bar. This should take you to a page that looks like this:

As seen in the picture, go to External Tools section and select VSCode as your external editor. Once that's done, check all the boxes and click the Regenerate project files button. Unfortunately, this means you can't set Neovim to external editor for Unity, but I think the trade-off is worth it. As promised earlier in the post, you can delete/uninstall VSCode now!

Wrapping Up

If you've followed these steps, you should have a working LSP for Unity! OmniSharp takes a while to start up (for me, about 10 seconds), so stick around for at least a minute or two to see if it actually works or not.

I'm using macOS Ventura with an aarch64 CPU. I don't think this should matter, but in the event this doesn't work, that's one possible avenue worth looking into.

Here are some other reasons this guide might not work for people reading this in the future:

• Mono changed again. To solve this, try installing v6.12.0.182 (which was the latest release at the time of this article)
• Unity changed project file generation
• nvim-lspconfig changed their OmniSharp setup

Thanks for reading this article! I hope you found it helpful, and good luck with your future Neovim/Unity ventures!