return { -- overrides `require("mason-null-ls").setup(...)`
  "jay-babu/mason-null-ls.nvim",
  config = function(_, opts)
    local mason_null_ls = require("mason-null-ls")
    local null_ls = require "null-ls"
    mason_null_ls.setup(opts)
    mason_null_ls.setup_handlers { -- setup custom handlers
      prettier = function()
        require("null-ls").register(null_ls.builtins.formatting.prettier.with {
          condition = function(utils)
            return utils.root_has_file "package.json"
                or utils.root_has_file ".prettierrc"
                or utils.root_has_file ".prettierrc.json"
                or utils.root_has_file ".prettierrc.js"
          end,
        })
      end,
      -- For prettierd:
      -- prettierd = function()
      --   require("null-ls").register(require("null-ls").builtins.formatting.prettierd.with({
      --     condition = function(utils)
      --       return utils.root_has_file("package.json") or utils.root_has_file(".prettierrc") or utils.root_has_file(".prettierrc.json") or utils.root_has_file(".prettierrc.js")
      --     end
      --   }))
      -- end,
      -- For eslint_d:
      -- eslint_d = function()
      --   require("null-ls").register(require("null-ls").builtins.diagnostics.eslint_d.with({
      --     condition = function(utils)
      --       return utils.root_has_file("package.json") or utils.root_has_file(".eslintrc.json") or utils.root_has_file(".eslintrc.js")
      --     end
      --   }))
      -- end,
    }
  end,
}