LSP Setup

Carina includes a Language Server Protocol (LSP) implementation that provides a rich editing experience for .crn files. This guide covers how to set it up and what features are available.

Features

The Carina LSP (carina-lsp) provides:

Autocompletion — resource types, attributes, attribute values, keywords, and built-in function names
Diagnostics — parse errors, type validation, unknown resource types, and module validation
Hover information — documentation for resource attributes and types on hover
Semantic tokens — syntax highlighting for keywords, resource types, regions, and identifiers
Document formatting — automatic formatting of .crn files

Installation

If you installed Carina via Homebrew or GitHub Releases, carina-lsp is already included — no additional installation is needed.

To build from source instead:

cargo install --git https://github.com/carina-rs/carina.git carina-lsp

Make sure the carina-lsp binary is in your PATH.

VS Code setup

Install the Carina extension from the VS Code marketplace, or configure a generic LSP client extension (such as vscode-languageclient).
If using a generic LSP client, add to your VS Code settings.json:

{
  "carina.lsp.path": "carina-lsp"
}

Open a .crn file. The LSP server starts automatically.

Neovim setup

With nvim-lspconfig

Add a custom server configuration:

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

if not configs.carina then
  configs.carina = {
    default_config = {
      cmd = { 'carina-lsp' },
      filetypes = { 'crn' },
      root_dir = lspconfig.util.root_pattern('.git', 'main.crn'),
    },
  }
end

lspconfig.carina.setup {}

File type detection

Add to your Neovim configuration:

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

Autocompletion

The LSP provides context-aware completions:

Top-level keywords: provider, backend, let, import, fn, for, if, arguments, attributes, moved, removed, require, read
Resource types: Type awscc. to see available services, then awscc.ec2. to see resource types
Attributes: Inside a resource block, get completions for all valid attributes
Attribute values: For enum-typed attributes, get valid value completions
Built-in functions: Function names with signature information

Completions are triggered by ., =, and space characters.

Diagnostics

The LSP reports errors and warnings as you type:

Parse errors: Syntax mistakes detected by the Carina parser
Unknown resource types: Using a resource type that does not exist in the provider schema
Type validation: Attribute values that do not match the expected type
Missing required attributes: Required attributes that are not set
Module validation: Errors in imported modules, missing module files

Hover

Hover over a resource attribute to see its documentation, including the expected type and description from the provider schema.

Semantic tokens

The LSP provides semantic token information for enhanced syntax highlighting:

Keywords: provider, backend, let, fn, for, if, else, import, arguments, attributes, moved, removed, require, read
Types: Resource types and region identifiers
Functions: Built-in and user-defined function names

Document formatting

The LSP supports formatting .crn files. In VS Code, use Format Document (Shift+Alt+F). The formatter aligns attributes and applies consistent indentation.

You can also format from the CLI:

# Format a single file
carina fmt main.crn

# Format all .crn files in a directory recursively
carina fmt --recursive .

# Check formatting without modifying files
carina fmt --check main.crn

# Show diff of formatting changes
carina fmt --diff main.crn

Troubleshooting

If the LSP is not working:

Check the binary: Run carina-lsp --version to verify it is installed
Check your PATH: The LSP client must be able to find carina-lsp
Check logs: Set the RUST_LOG=debug environment variable and check the LSP output in your editor’s log panel
File type: Ensure your editor recognizes .crn files and routes them to the Carina LSP