Dummy LSP Server

This project contains a dummy implementation of a custom Language Server Protocol (LSP) server, exploring different types of I/O happening between the client and the server.
You can find the examples in the lsp/ folder.

Some of the interactions covered:

• Initialization & Synchronization
  When a client connects, it sends an initialize request, and the server attaches to the workspace/buffer. The server and client then synchronize document state (textDocument/didOpen, didChange, didSave).

• Document Events
  Every time we edit or save a file, the client notifies the server (e.g., textDocument/didChange, textDocument/didSave).

• Hover Information
  When hovering over a symbol, the client sends a textDocument/hover request, and the server responds with documentation or type info.

• Go to Definition / References
  Clicking on a function, variable, or method triggers requests like textDocument/definition or textDocument/references, allowing navigation across files.

• Completions
  As we type, the client sends a textDocument/completion request, and the server suggests completions (functions, variables, snippets, etc.).

• Diagnostics
  On each edit or save, the server can publish diagnostics (textDocument/publishDiagnostics), which the client shows as errors, warnings, or hints.

This dummy server demonstrates how these requests and notifications are exchanged between an LSP client (e.g., VSCode, Neovim) and the server.

Architecture

┌─────────────┐    JSON-RPC     ┌─────────────┐    JSON-RPC     ┌─────────────┐
│             │ ──────────────→ │             │ ←────────────── │             │
│   VSCode    │                 │ GLSP Server │                 │   Neovim    │
│ Extension   │ ←────────────── │   Binary    │ ──────────────→ │ Lua Client  │
└─────────────┘                 └─────────────┘                 └─────────────┘

Lua-Client setup

To attach the custom glsp server to Markdown files in Neovim, add the following configuration in:

and add the following code:

-- lua/after/plugin/glsp-client.lua
-- Example: attach custom GLSP server to Markdown files

-- Find project root (search upward for .git or go.mod, fallback to cwd)
-- it will prvent starting new lsp server for diff file in same project
local root = vim.fs.dirname(vim.fs.find({ ".git", "go.mod" }, { upward = true })[1]) or vim.loop.cwd()

-- Attach custom keymaps when LSP starts
local on_attach = require("shekhar.lsp_keymaps")

-- Start GLSP client
local client = vim.lsp.start_client({
  name = "glsp",
  cmd = { "/home/shekhar/Personal/glsp/glsp" }, -- path to your server binary
  root_dir = root,
  on_attach = on_attach,
})

if not client then
  vim.notify("Error while starting GLSP client!", vim.log.levels.ERROR)
end

-- Attach GLSP only for Markdown files
vim.api.nvim_create_autocmd("FileType", {
  pattern = "markdown",
  callback = function(args)
    vim.lsp.buf_attach_client(args.buf, client)
  end,
})

Example logs

[ glsp ]2025/09/08 23:55:38 main.go:15: glsp is started
[ glsp ]2025/09/08 23:55:38 handler.go:11: A request of initialize type came...
[ glsp ]2025/09/08 23:55:38 handler.go:19: Connected to: Neovim~0.11.3+v0.11.3
[ glsp ]2025/09/08 23:55:38 handler.go:11: A request of initialized type came...
[ glsp ]2025/09/09 00:07:03 handler.go:11: A request of textDocument/didOpen type came...
[ glsp ]2025/09/09 00:07:03 handler.go:29: opend file :file://
[ glsp ]2025/09/09 00:07:07 handler.go:11: A request of textDocument/didClose type came...
[ glsp ]2025/09/09 00:17:21 handler.go:11: A request of textDocument/didOpen type came...
[ glsp ]2025/09/09 00:17:21 handler.go:29: opend file :file://
[ glsp ]2025/09/09 00:17:25 handler.go:11: A request of textDocument/didClose type came...
[ glsp ]2025/09/09 00:48:17 handler.go:11: A request of shutdown type came...
st.md
[ glsp ]2025/09/08 23:55:40 handler.go:11: A request of textDocument/didChange type came...
[ glsp ]2025/09/08 23:55:40 handler.go:37: changed file :file:///home/shekhar/Personal/glsp/test.md
[ glsp ]2025/09/08 23:55:40 handler.go:11: A request of textDocument/didChange type came...
[ glsp ]2025/09/08 23:55:40 handler.go:37: changed file :file:///home/shekhar/Personal/glsp/test.md
[ glsp ]2025/09/08 23:55:41 handler.go:11: A request of textDocument/didChange type came...
[ glsp ]2025/09/08 23:55:41 handler.go:37: changed file :file:///home/shekhar/Personal/glsp/test.md
[ glsp ]2025/09/08 23:55:41 handler.go:11: A request of textDocument/didChange type came...
[ glsp ]2025/09/08 23:55:41 handler.go:37: changed file :file:///home/shekhar/Personal/glsp/test.md
[ glsp ]2025/09/08 23:55:42 handler.go:11: A request of textDocument/didChange type came...
[ glsp ]2025/09/08 23:55:42 handler.go:37: changed file :file:///home/shekhar/Personal/glsp/test.md
[ glsp ]2025/09/08 23:55:43 handler.go:11: A request of textDocument/didChange type came...
[ glsp ]2025/09/08 23:55:43 handler.go:37: changed file :file:///home/shekhar/Personal/glsp/test.md
[ glsp ]2025/09/08 23:55:44 handler.go:11: A request of textDocument/didChange type came...
[ glsp ]2025/09/08 23:55:44 handler.go:37: changed file :file:///home/shekhar/Personal/glsp/test.md
[ glsp ]2025/09/08 23:55:44 handler.go:11: A request of textDocument/didChange type came...
[ glsp ]2025/09/08 23:55:44 handler.go:37: changed file :file:///home/shekhar/Personal/glsp/test.md
[ glsp ]2025/09/08 23:55:46 handler.go:11: A request of textDocument/definition type came...
[ glsp ]2025/09/08 23:55:47 handler.go:11: A request of textDocument/definition type came...
[ glsp ]2025/09/08 23:55:52 handler.go:11: A request of textDocument/definition type came...
[ glsp ]2025/09/08 23:56:03 handler.go:11: A request of textDocument/definition type came...
[ glsp ]2025/09/08 23:56:05 handler.go:11: A request of textDocument/hover type came...
[ glsp ]2025/09/08 23:56:05 handler.go:11: A request of textDocument/didOpen type came...
[ glsp ]2025/09/08 23:56:05 handler.go:29: opend file :file://