Language Server

Language Server (scaf-lsp)

scaf-lsp is the language server for scaf, providing diagnostics, hover information, and other IDE features.

Installation

go install github.com/rlch/scaf/cmd/scaf-lsp@latest

Verify installation:

scaf-lsp --version

Features

Diagnostics

Real-time error detection:

• Syntax errors — Invalid scaf syntax
• Undefined queries — Test scopes referencing undefined queries
• Duplicate definitions — Queries or tests with same name
• Type mismatches — Invalid value types in statements

Hover Information

Hover over elements to see:

• Query definitions and their bodies
• Test descriptions and paths
• Parameter documentation

Go to Definition

Jump from:

• Test scope → Query definition
• Named setup → Imported setup
• Import → File

Document Symbols

Outline view showing:

• Queries
• Test scopes
• Groups
• Tests

Editor Setup

Neovim (scaf.nvim)

scaf.nvim starts the LSP automatically:

require("scaf").setup({
  lsp = {
    enabled = true,  -- default
    cmd = { "scaf-lsp" },
  },
})

Neovim (manual)

vim.api.nvim_create_autocmd("FileType", {
  pattern = "scaf",
  callback = function()
    vim.lsp.start({
      name = "scaf-lsp",
      cmd = { "scaf-lsp" },
      root_dir = vim.fs.dirname(
        vim.fs.find({ ".scaf.yaml", ".git" }, { upward = true })[1]
      ),
    })
  end,
})

nvim-lspconfig

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

if not configs.scaf then
  configs.scaf = {
    default_config = {
      cmd = { "scaf-lsp" },
      filetypes = { "scaf" },
      root_dir = lspconfig.util.root_pattern(".scaf.yaml", ".git"),
      single_file_support = true,
    },
  }
end

lspconfig.scaf.setup({})

VS Code

Note

VS Code extension is planned. For now, use a generic LSP client extension.

LSP Capabilities

Supported

Capability	Description
textDocument/publishDiagnostics	Error/warning diagnostics
textDocument/hover	Hover information
textDocument/definition	Go to definition
textDocument/documentSymbol	Document outline

Planned

Capability	Description
textDocument/completion	Auto-completion
textDocument/rename	Rename symbol
textDocument/formatting	Format document
textDocument/references	Find references

Configuration

Command Line Options

# Verbose logging
scaf-lsp --verbose

# Custom log file
scaf-lsp --log-file=/tmp/scaf-lsp.log

# TCP mode (for debugging)
scaf-lsp --tcp --port=9999

Environment Variables

Variable	Description
SCAF_LSP_LOG	Log level (debug, info, warn, error)
SCAF_LSP_LOG_FILE	Log file path

Diagnostics

Error Types

Syntax Error

users.scaf:5:1: error: unexpected token 'test', expected '}'

Undefined Query

users.scaf:10:1: error: undefined query 'GetUsr' (did you mean 'GetUser'?)

Duplicate Definition

users.scaf:15:1: warning: duplicate query definition 'GetUser'

Import Error

users.scaf:1:8: error: cannot find module './shared/fixtures'

Diagnostic Severity

Severity	Description
Error	Parse errors, undefined references
Warning	Duplicate definitions, unused queries
Information	Style suggestions
Hint	Best practice recommendations

Troubleshooting

LSP Not Starting

1. Verify installation:

   which scaf-lsp
   scaf-lsp --version

2. Check PATH in your shell:

   echo $PATH

3. Try running manually:

   echo '{"jsonrpc":"2.0","method":"initialize","id":1,"params":{"capabilities":{}}}' | scaf-lsp

No Diagnostics

1. Check filetype: :set ft? should show scaf
2. Check LSP is attached: :LspInfo
3. Enable verbose logging and check output

Performance Issues

1. Large files may cause lag
2. Try disabling real-time diagnostics
3. File an issue with reproduction steps

Development

Building from Source

git clone https://github.com/rlch/scaf
cd scaf
go build ./cmd/scaf-lsp

Running Tests

go test ./lsp/...

Debug Mode

Run with TCP for easier debugging:

# Terminal 1
scaf-lsp --tcp --port=9999

# Terminal 2 (connect with netcat)
nc localhost 9999