LSP.md

yag-template-lsp for Neovim

Note

Initially I wrote this guide for one user on the YAGPDB support server, but I figured others might find it useful as well. The idea is to go into some detail why we need to do certain things. If you're already familiar with Neovim, please feel free to ignore those :-)

An implementation of the Language Server Protocol for YAGPDB custom commands can be found at https://github.com/jo3-l/yag-template-lsp.

Installing yag-template-lsp for Neovim is a little more involved than for VSCode, as you'll have to install the binary yourself and also install some syntax definition for YAGPDB's custom command language.

Prerequisites

Obviously, you need to have Neovim installed, as usual the latest stable release is recommended.

If you wish to compile yag-template-lsp from source, you'll need to have Git and the Rust toolchain installed as well.

Because yag-template-lsp itself does not provide a syntax definition that is understood by Neovim, you'll also need a plugin that adds that functionality, if you want syntax highlighting. We'll use l-zeuch/yagpdb.vim for that.

Installing the Server

You can either download a precompiled yag-template-lsp binary from the releases, or compile it from source. Either way you'll need to place it in your $PATH, so that Neovim's LSP client can find it.

To install from source, clone the repository, change into crates/yag-template-lsp and build the binary.

git clone github.com/jo3-l/yag-template-lsp
cd yag-template-lsp/crates/yag-template-lsp
cargo install --path .

This will place the binary in your cargo bin directory, which should be in your $PATH already.

Configuring Neovim

Filetype Detection

To get basic filetype detection working, we need to tell Neovim which file extensions correspond to the filetype we defined in the LSP config. Without any plugins, we can just do this by adding an autocommand to our init.lua:

vim.api.nvim_create_autocmd("BufRead,BufNewFile", {
    pattern = {"*.yag", "*.yagcc"},
    command = "set filetype=yagpdbcc",
})

Optional: Syntax Highlighting

If you wish to have syntax highlighting for YAGPDB command files as well, you can install https://github.com/l-zeuch/yagpdb.vim using your favorite plugin manager. Because yagpdb.vim provides its own filetype detection as well, you can omit the suggested autocommand above if you install the plugin.

Alternatively, if you prefer no highlighting, read on. (but keep the autocommand for filetype detection!)

LSP Client Configuration

In your init.lua, let the LSP client know about the binary, the associated filetype and some basic configuration. If you prefer using a plugin like nvim-lspconfig, you can adapt the configuration accordingly, in this example we'll just use the built-in LSP client configuration functions.

For Windows, be aware that the binary will be named yag-template-lsp-x86_64-pc-windows-msvc.exe or similar, depending on your toolchain, so you'll need to use that name for cmd instead.

-- baseline lsp configuration. make sure the cmd string matches the filename of the LSP binary!
vim.lsp.config('YAGPDB CC', {
    cmd = { 'yag-template-lsp' },
    filetypes = { 'yagpdbcc' },
    on_attach = function(client, bufnr)
        vim.lsp.inlay_hint.enable(true, { bufnr = bufnr })
        vim.lsp.completion.enable(true, client.id, bufnr, {})
    end,
})
vim.lsp.enable('YAGPDB CC')

Because yag-template-lsp provides inlay hints for functions with three or more parameters, we'll enable severity.HINT diagnostics for virtual text display as well. It is a good idea to let the client update in insert mode, but if you're struggling with performance, you can disable that.

-- enumerate all severities for virtual text display. we want the inlay type hints too!
severities = {
    vim.diagnostic.severity.ERROR,
    vim.diagnostic.severity.WARN,
    vim.diagnostic.severity.INFO,
    vim.diagnostic.severity.HINT,
}

-- enable diagnostics for inlay hints and stuff
vim.diagnostic.config({
    virtual_text = {
        source = true,
        severity = severities,
    },
    update_in_insert = true, })

Testing the Configuration

To verify that everything is working correctly, open a .yag or .yagcc file in Neovim, preferably one that already contains some code. You should see syntax highlighting (if you installed the plugin) and inlay hints for functions with three or more parameters, as well as diagnostics for any issues in the code.

We provided a sample of YAGPDB command code below that you can use to test your setup.

{{ sendMessage nil "hi" }}
{{ $x := parseArgs 1 "pain" (carg "int" "how much pain?") }}
{{}}
{{ $y := }}

You should see inlay hints for the parseArgs function parameters and diagnostics for the incomplete command at the end, errors for the empty {{}} and the incomplete assignment to $y.