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LSP Server

The Newt LSP server (newter-lsp) implements the Language Server Protocol to provide IDE features for Newt files in any compatible editor.

Installation​

Via Cargo​

cargo install newter-lsp

This builds and installs the newter-lsp binary to your Cargo bin directory.

Via the VS Code extension​

If you use VS Code, the Newt extension bundles the LSP server. No separate installation is needed.

Capabilities​

The Newt LSP server supports the following LSP methods:

textDocument/completion​

Provides context-aware completions for:

  • Built-in element names (all 73 elements)
  • Prop names within element declarations
  • Variable names (let and state)
  • Component names
  • Keywords (screen, component, state, let, theme, use, import, if, else, for)

textDocument/hover​

Returns documentation on hover for:

  • Elements: description and list of accepted props
  • Props: type, default value, and description
  • Variables: declared type and value
  • Components: name and parameter list

textDocument/definition​

Jumps to the definition of:

  • Variables (navigates to the let or state declaration)
  • Components (navigates to the component definition)
  • Imported files (opens the referenced .newt file)

textDocument/publishDiagnostics​

Publishes real-time diagnostics as you edit. The server re-parses the file on every change and reports:

  • Syntax errors with line and column positions
  • Undefined variable references
  • Unknown element names
  • Type mismatches in prop values
  • Circular import detection

Editor configuration​

Neovim (nvim-lspconfig)​

Add the following to your Neovim LSP configuration:

local lspconfig = require('lspconfig')
local configs = require('lspconfig.configs')

configs.newt = {
  default_config = {
    cmd = { 'newter-lsp' },
    filetypes = { 'newt' },
    root_dir = lspconfig.util.find_git_ancestor,
  },
}

lspconfig.newt.setup({})

You also need to associate the .newt file extension with the newt filetype:

vim.filetype.add({
  extension = {
    newt = 'newt',
  },
})

Helix​

Add to your ~/.config/helix/languages.toml:

[[language]]
name = "newt"
scope = "source.newt"
file-types = ["newt"]
language-servers = ["newter-lsp"]
comment-token = "//"

[language-server.newter-lsp]
command = "newter-lsp"

Emacs (lsp-mode)​

Add to your Emacs configuration:

(with-eval-after-load 'lsp-mode
  (add-to-list 'lsp-language-id-configuration '(newt-mode . "newt"))
  (lsp-register-client
   (make-lsp-client
    :new-connection (lsp-stdio-connection '("newter-lsp"))
    :activation-fn (lsp-activate-on "newt")
    :server-id 'newter-lsp)))

Other editors​

Any editor that supports LSP can use the Newt language server. Point the editor's LSP client to the newter-lsp binary and associate it with the .newt file extension.

Troubleshooting​

The LSP server is not starting​

Verify that newter-lsp is on your PATH:

which newter-lsp
newter-lsp --help

If not found, check that ~/.cargo/bin is in your PATH.

Diagnostics are not appearing​

The LSP server only activates for files with the .newt extension. Make sure your file is saved with the correct extension and that your editor associates .newt files with the Newt language.

Completions are slow​

The LSP server re-parses the entire file on each keystroke. For very large files (thousands of lines), consider splitting the code into smaller files using imports.

Next steps​