nvim/lua/lsp/metals.lua

local status, metals = pcall(require, "metals")
if (not status) then return function() end end

return function(on_attach)
  metals_config = metals.bare_config()
  metals_config.init_options.statusBarProvider = "on"
  metals_config.settings = {
    showImplicitArguments = true,
    superMethodLensesEnabled = true,
  }
  metals_config.on_attach = function(client, bufnr)
    require("metals").setup_dap()
    on_attach(client, bufnr)
  end
  metals_config.capabilities = require("cmp_nvim_lsp").default_capabilities()
  -- Debug settings if you're using nvim-dap
  local dap = require("dap")
  dap.configurations.scala = {
    {
      type = "scala",
      request = "launch",
      name = "RunOrTest",
      metals = {
        runType = "runOrTestFile",
        --args = { "firstArg", "secondArg", "thirdArg" }, -- here just as an example
      },
    },
    {
      type = "scala",
      request = "launch",
      name = "Test Target",
      metals = {
        runType = "testTarget",
      },
    },
  }


  -- Autocmd that will actually be in charging of starting the whole thing
  local nvim_metals_group = vim.api.nvim_create_augroup("nvim-metals", { clear = true })
  vim.api.nvim_create_autocmd("FileType", {
    -- NOTE: You may or may not want java included here. You will need it if you
    -- want basic Java support but it may also conflict if you are using
    -- something like nvim-jdtls which also works on a java filetype autocmd.
    pattern = { "scala", "sbt" },
    callback = function()
      require("metals").initialize_or_attach(metals_config)
    end,
    group = nvim_metals_group,
  })

  return metals_config
end