feat: add the ability to hotpatch mason-lspconfig.nvim with more lsp/package mappings

Author: mehalter

README.md

@@ -195,6 +195,21 @@ local opts = {
       },
     },
   },
+ -- Extra configuration for the `mason-lspconfig.nvim` plugin
+  mason_lspconfig = {
+    -- Allow registering more Mason packages as language servers for autodetection/setup
+    servers = {
+      -- The key is the lspconfig server name to register a package for
+      nextflow_ls = {
+        -- The Mason package name to register to the language server
+        package = "nextflow-language-server",
+        -- The filetypes that apply to the package and language server
+        filetypes = { "nextflow" },
+        -- (Optional) any default configuration changes that may need to happen (can be a table or a function that returns a table)
+        config = { cmd = { "nextflow-language-server" } }
+      }
+    }
+  }
   -- A list like table of servers that should be setup, useful for enabling language servers not installed with Mason.
   servers = { "dartls" },
   -- A custom `on_attach` function to be run after the default `on_attach` function, takes two parameters `client` and `bufnr`  (`:h lspconfig-setup`)
@@ -231,12 +246,16 @@ local opts = {
     {
       "williamboman/mason-lspconfig.nvim", -- MUST be set up before `nvim-lspconfig`
       dependencies = { "williamboman/mason.nvim" },
-      opts = function()
-        return {
-          -- use AstroLSP setup for mason-lspconfig
-          handlers = { function(server) require("astrolsp").lsp_setup(server) end },
-        }
-      end,
+      opts = {
+        -- use AstroLSP setup for mason-lspconfig
+        handlers = { function(server) require("astrolsp").lsp_setup(server) end },
+      },
+      config = function(_, opts)
+        -- Optionally tell AstroLSP to register new language servers before calling the `setup` function
+        -- this enables the `mason-lspconfig.servers` option in the AstroLSP configuration
+        require("astrolsp.mason-lspconfig").register_servers()
+        require("mason-lspconfig").setup(opts)
+      end
     },
   },
   config = function()

lua/astrolsp/config.lua

@@ -59,6 +59,16 @@
 ---@field hover vim.lsp.buf.hover.Opts? control the default options for `vim.lsp.buf.hover()` (`:h vim.lsp.buf.hover.Opts`)
 ---@field signature_help vim.lsp.buf.signature_help.Opts? control the default options for `vim.lsp.buf.signature_help()` (`:h vim.lsp.buf.signature_help.Opts`)
 
+---@class AstroLSPMasonLspconfigServer
+---@field public package string the Mason package name
+---@field filetypes string|string[] the filetype(s) that the server applies to
+---@field config? table|(fun(): table) extensions tothe default language server configuration
+
+---@alias AstroLSPMasonLspconfigServers { [string]: AstroLSPMasonLspconfigServer }
+
+---@class AstroLSPMasonLspconfigOpts
+---@field servers AstroLSPMasonLspconfigServers? a table of servers to register with mason-lspconfig.nvim
+
 ---@class AstroLSPOpts
 ---Configuration of auto commands
 ---The key into the table is the group name for the auto commands (`:h augroup`) and the value
@@ -284,6 +294,21 @@
 ---}
 ---```
 ---@field mappings AstroLSPMappings?
+---Extra options for the `mason-lspconfig.nvim` plugin such as registering new packages as language servers.
+---Example:
+--
+---```lua
+---mason_lspconfig = {
+---  servers = {
+---    nextflow_ls = {
+---      package = "nextflow-language-server",
+---      filetypes = "nextflow",
+---      config = { cmd = { "nextflow-language-server" } }
+---    }
+---  }
+---}
+---```
+---@field mason_lspconfig AstroLSPMasonLspconfigOpts?
 ---A list like table of servers that should be setup, useful for enabling language servers not installed with Mason.
 ---Example:
 --
@@ -324,6 +349,7 @@ local M = {
   handlers = {},
   lsp_handlers = {},
   mappings = {},
+  mason_lspconfig = {},
   servers = {},
   on_attach = nil,
 }

lua/astrolsp/mason-lspconfig.lua

@@ -0,0 +1,58 @@
+---Utilities for working with mason-lspconfig.nvim
+---
+---This module can be loaded with `local astrolsp_mason_lspconfig = require "astrolsp.mason-lspconfig"`
+---
+---copyright 2025
+---license GNU General Public License v3.0
+---@class astrolsp.mason-lspconfig
+local M = {}
+
+local function resolve_config() return require("astrolsp").config.mason_lspconfig or {} end
+
+--- Register a new language server with mason-lspconfig
+---@param server string the server name in lspconfig
+---@param spec AstroLSPMasonLspconfigServer the details for registering the server
+function M.register_server(server, spec)
+  local filetype_mappings_avail, filetype_mappings = pcall(require, "mason-lspconfig.mappings.filetype")
+  local server_mappings_avail, server_mappings = pcall(require, "mason-lspconfig.mappings.server")
+
+  if not (filetype_mappings_avail and server_mappings_avail) then
+    vim.notify("Unable to properly load required `mason-lspconfig` modules", vim.log.levels.ERROR)
+  end
+
+  -- register server in the filetype maps
+  local filetypes = spec.filetypes
+  if type(filetypes) ~= "table" then filetypes = { filetypes } end
+  for _, filetype in ipairs(filetypes) do
+    if not filetype_mappings[filetype] then filetype_mappings[filetype] = {} end
+    table.insert(filetype_mappings, server)
+  end
+  -- register the mappings between lspconfig server name and mason package name
+  server_mappings.lspconfig_to_package[server] = spec.package
+  server_mappings.package_to_lspconfig[spec.package] = server
+  -- if a config is provided, set up a mason-lspconfig server configuration module
+  if spec.config then
+    local module = spec.config
+    if type(module) == "table" then
+      local orig_function = module
+      module = function() return orig_function end
+    end
+    local module_name = "mason-lspconfig.server_configurations." .. server
+    if package.loaded[module_name] == nil then
+      package.preload[module_name] = function() return module end
+    else
+      package.loaded[module_name] = module
+    end
+  end
+end
+
+--- Register multiple new language servers with mason-lspconfig
+---@param server_specs? AstroLSPMasonLspconfigServers
+function M.register_servers(server_specs)
+  if not server_specs then server_specs = resolve_config().servers or {} end
+  for server, spec in pairs(server_specs) do
+    M.register_server(server, spec)
+  end
+end
+
+return M