[BUG] discovery = false not respected when non-fs buffer is added

[angles-n-daemons]

NeoVim Version

NVIM v0.10.1
Build type: Release
LuaJIT 2.1.1713484068
Run "nvim -V1 -v" for more info

Describe the bug
I'm working on a large codebase so I have discovery = { enabled = false } setup. When using dap/dapui to debug a test, a buffer open triggers the autocmd here in the client. This buffer's file property is always set to "", and therefore the file_path variable is set to "/path/to/my/project" (a directory, and not a file specifically). Because of this, at the end of the nio.run call _update_positions is called with the root of my project, causing a full walk of the repository.

To Reproduce

local lazypath = '/tmp/lazy/lazy.nvim'

if not vim.loop.fs_stat(lazypath) then
  vim.fn.system {
    'git',
    'clone',
    '--filter=blob:none',
    'https://github.com/folke/lazy.nvim.git',
    '--branch=stable', -- latest stable release
    lazypath,
  }
end

vim.opt.rtp:prepend(lazypath)

require('lazy').setup {
  {
    'nvim-neotest/neotest',
    dependencies = {
      'nvim-lua/plenary.nvim',
      'nvim-treesitter/nvim-treesitter',
      'fredrikaverpil/neotest-golang',
      {
        'mfussenegger/nvim-dap',
        dependencies = {
          'rcarriga/nvim-dap-ui',
          'nvim-neotest/nvim-nio',
          'williamboman/mason.nvim',
          'folke/neoconf.nvim',
          {
            'leoluz/nvim-dap-go',
            config = true,
          },
          {
            'williamboman/mason.nvim',
            cmd = 'Mason',
            build = ':MasonUpdate',
            config = function(_, opts)
              require('mason').setup(opts)
              local mr = require 'mason-registry'
              if not mr.get_package('delve'):is_installed() then
                mr.get_package('delve'):install()
              end
            end,
          },
        },
        keys = {
          -- requires neotest to be installed
          {
            '<leader>td',
            function()
              require('neotest').run.run { strategy = 'dap' }
            end,
            desc = 'Debug Nearest',
          },
        },
        config = function()
          local dap, dapui = require 'dap', require 'dapui'
          print 'setting up dap go'
          require('dap-go').setup {}
          dapui.setup()
          dap.listeners.after.event_initialized['dapui_config'] = dapui.open
          dap.listeners.before.event_terminated['dapui_config'] = dapui.close
          dap.listeners.before.event_exited['dapui_config'] = dapui.close
        end,
      },
    },
    config = function()
      -- Install any required parsers
      require('nvim-treesitter.configs').setup {
        ensure_installed = { 'go' },
      }

      require('neotest').setup {
        adapters = { require 'neotest-golang' {} },
        discovery = {
          enabled = false,
        },
      }
    end,
  },
}

This reproduction may be tricky, for some reason the above file worked eventually but was tricky to wrestle with.

Steps to reproduce the behavior:

1. Clone the cockroach database repo.
2. Run the build setup.
3. Open an iterator test file: nvim pkg/ts/iterator_test.go.
4. *Debug the tests in that file.

Expected behavior
When discovery is explicitly disabled, neotest should not recursively update positions of all files in the working path.

More concretely, BufAdd autocmd events with no file name should not trigger an _update_positions call which walks the codebase.

I feel like there are a couple approaches to addressing this:

1. Ignoring buffer events without file names.
2. Only continuing in BufAdd or BufWritePost if the file_path is a file and not a directory.
3. Skipping update_positions directory branch if discovery is disabled.

Logs
Cannot retrieve logs as walking causes vim to freeze.