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Mason provides a user-friendly interface for installing and managing LSP servers, formatters, linters, and DAP adapters.

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Configuration

The Mason setup is located in lua/user/lsp/mason.lua.

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Server List

Define which LSP servers to automatically install:
lua/user/lsp/mason.lua
local servers = {
  "lua_ls",
  -- "cssls",
  -- "html",
  -- "tsserver",
  "pyright",
  -- "bashls",
  "jsonls",
  -- "yamlls",
}

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Mason Settings

Customize the Mason UI and behavior:
lua/user/lsp/mason.lua
local settings = {
  ui = {
    border = "none",
    icons = {
      package_installed = "◍",
      package_pending = "◍",
      package_uninstalled = "◍",
    },
  },
  log_level = vim.log.levels.INFO,
  max_concurrent_installers = 4,
}

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Initialization

lua/user/lsp/mason.lua
require("mason").setup(settings)
require("mason-lspconfig").setup({
  ensure_installed = servers,
  automatic_installation = true,
})

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Server Configuration

Each server is configured with handlers and capabilities:
lua/user/lsp/mason.lua
for _, server in pairs(servers) do
  opts = {
    on_attach = require("user.lsp.handlers").on_attach,
    capabilities = require("user.lsp.handlers").capabilities,
  }

  server = vim.split(server, "@")[1]

  -- Load server-specific settings if available
  local require_ok, conf_opts = pcall(require, "user.lsp.settings." .. server)
  if require_ok then
    opts = vim.tbl_deep_extend("force", conf_opts, opts)
  end

  lspconfig[server].setup(opts)
end

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Adding New LSP Servers

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Step 1: Add to Server List

Uncomment or add a new server to the servers table:
lua/user/lsp/mason.lua
local servers = {
  "lua_ls",
  "pyright",
  "jsonls",
  "tsserver",  -- Added TypeScript support
}

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Step 2: Create Server Settings (Optional)

For custom configuration, create a settings file:
lua/user/lsp/settings/tsserver.lua
return {
  settings = {
    typescript = {
      inlayHints = {
        includeInlayParameterNameHints = "all",
        includeInlayFunctionParameterTypeHints = true,
      },
    },
  },
}

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Step 3: Restart Neovim

Mason will automatically install the new server on next launch.

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Server-Specific Settings

The configuration includes custom settings for several servers:

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Lua Language Server

Configured for Neovim development in lua/user/lsp/settings/lua_ls.lua:1: 
return {
  settings = {
    Lua = {
      diagnostics = {
        globals = { "vim" },  -- Recognize 'vim' global
      },
      workspace = {
        library = {
          [vim.fn.expand("$VIMRUNTIME/lua")] = true,
          [vim.fn.stdpath("config") .. "/lua"] = true,
        },
      },
    },
  },
}

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Pyright

Python type checking configured in lua/user/lsp/settings/pyright.lua:1: 
return {
  settings = {
    python = {
      analysis = {
        typeCheckingMode = "off",
      },
    },
  },
}

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JSON Language Server

Includes extensive schema validation in lua/user/lsp/settings/jsonls.lua:1:
  • TypeScript config (tsconfig.json)
  • Package.json
  • ESLint, Prettier, Babel configs
  • AWS CloudFormation templates
  • GitHub workflow templates
  • And many more…

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Mason Commands

CommandDescription
:MasonOpen Mason UI
:MasonInstall <server>Install a specific server
:MasonUninstall <server>Remove a server
:MasonUpdateUpdate all installed packages
:LspInfoShow attached LSP servers
:LspInstallInfoShow Mason install info

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Troubleshooting

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Server Not Starting

  1. Check if installed: :Mason
  2. View LSP logs: :LspInfo
  3. Check file type: :set filetype?

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Installation Fails

Increase log level for debugging: 
log_level = vim.log.levels.DEBUG,

LSP Handlers

Configure LSP keybindings and behavior

Null-ls Setup

Add formatters and linters

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