Attach to debugpy

[AckslD]

I'm trying to attach to a debugpy server started by the python process itself but can't get it working for some reason. I'm pretty new to this so probably doing something wrong and was wondering if someone might have some ideas.

Basically I'm running:

# tmp.py
x = 5
import debugpy
debugpy.listen(38000)
debugpy.wait_for_client()
debugpy.breakpoint()

and then I'm runnning

# tmp.lua
local dap = require('dap')
dap.run({
  name = 'Attach',
  type = 'python',
  request = 'attach',
  port = 38000,
  server = '127.0.0.1',
  pythonPath = 'python',
  console = 'integratedTerminal',
})

But I get:

Debug adapter didn't respond. Either the adapter is slow (then wait and ignore this) or there is a problem with your adapter or `python` configuration. Check the logs for errors (:help dap.set_log_level)

and then

Error on attach: Timed out waiting for debug server to connect.

I can see the python process waiting for a client and that there is a port 38000 open.

[mfussenegger]

How does your adapter definition look like? debugpy is a bit special in regards to the attach handling. For most adapters you still launch the debug-adapter the same way, and then the debug-adapter attaches to the process. For debugpy the process using debugpy.listen() (or when using python -m debugpy --listen ...) launches the service that speaks DAP.

Because of that you'll need to switch over to a adapter definition of type server. I'd recommend to use nvim-dap-python which does that:

https://github.com/mfussenegger/nvim-dap-python/blob/d4400d075c21ed8fb8e8ac6a5ff56f58f6e93531/lua/dap-python.lua#L130-L153

[AckslD]

Thanks @mfussenegger (and sorry for late reply). This did indeed work 👍

[verajosemanuel]

same issue here. Any step by step help I could use?

[AckslD]

@verajosemanuel did you try @mfussenegger's answer above?

[verajosemanuel]

Not sure of how to do so (a bit newbie). Here my debug config:

return {
{
'mfussenegger/nvim-dap',
events = 'VeryLazy',
dependencies = {
  -- Creates a beautiful debugger UI
  'rcarriga/nvim-dap-ui',
  events = 'BufRead',

  -- Installs the debug adapters for you
  'williamboman/mason.nvim',
  {
    'mfussenegger/nvim-dap-python',
    events = 'BufRead',
    keys = {
      {
        '<leader>dPt',
        function()
          require('dap-python').test_method()
        end,
        desc = 'Debug Method',
        ft = 'python',
      },
      {
        '<leader>dPc',
        function()
          require('dap-python').test_class()
        end,
        desc = 'Debug Class',
        ft = 'python',
      },
    },
  },
  {
    'theHamsta/nvim-dap-virtual-text',
    events = 'BufRead',
    opts = {},
  },
  'jay-babu/mason-nvim-dap.nvim',

  -- Add your own debuggers here
},
config = function()
  local dap = require 'dap'
  local dapui = require 'dapui'

require('mason-nvim-dap').setup {
    automatic_setup = true,
    handlers = {},
    ensure_installed = {"debugpy"},
    config = function()
      local path = require('mason-registry').get_package('debugpy'):get_install_path()
      require('dap-python').setup(path .. '/Scripts/python')
    end,
    }

  -- Basic debugging keymaps, feel free to change to your liking!
  vim.keymap.set('n', '<F5>', dap.continue, { desc = 'Debug: Start/Continue' })
  vim.keymap.set('n', '<F1>', dap.step_into, { desc = 'Debug: Step Into' })
  vim.keymap.set('n', '<F2>', dap.step_over, { desc = 'Debug: Step Over' })
  vim.keymap.set('n', '<F3>', dap.step_out, { desc = 'Debug: Step Out' })

  -- Dap UI setup
  -- For more information, see |:help nvim-dap-ui|
  dapui.setup {
    -- Set icons to characters that are more likely to work in every terminal.
    --    Feel free to remove or use ones that you like more! :)
    --    Don't feel like these are good choices.
    icons = { expanded = '▾', collapsed = '▸', current_frame = '*' },
    controls = {
      icons = {
        pause = '⏸',
        play = '▶',
        step_into = '⏎',
        step_over = '⏭',
        step_out = '⏮',
        step_back = 'b',
        run_last = '▶▶',
        terminate = '⏹',
        disconnect = '⏏',
      },
    },
  }

  -- Toggle to see last session result. Without this, you can't see session output in case of unhandled exception.
  vim.keymap.set(
    'n',
    '<F7>',
    dapui.toggle,
    { desc = 'Debug: See last session result.' }
  )

  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,
},
{
 'jay-babu/mason-nvim-dap.nvim',
 events = 'BufRead',
 config = function(_, opts)
  require('mason-nvim-dap').setup(opts)
  local dap = require 'dap'
  dap.adapters.python = function(cb, config)
    if config.request == 'attach' then
      ---@diagnostic disable-next-line: undefined-field
      local port = (config.connect or config).port
      ---@diagnostic disable-next-line: undefined-field
      local host = (config.connect or config).host or '127.0.0.1'
      cb {
        type = 'server',
        port = assert(
          port,
          '`connect.port` is required for a python `attach` configuration'
        ),
        host = host,
        options = {
          source_filetype = 'python',
        },
      }
    else
      cb {
        type = 'executable',
        command = 'C:\\Users\\joe\\Anaconda3\\envs\\market\\pythonw.exe',
        args = { '-m', 'debugpy.adapter' },
        options = {
          source_filetype = 'python',
        },
      }
    end
  end
  dap.configurations.python = {
    {
      -- The first three options are required by nvim-dap
      type = 'python', -- the type here established the link to the adapter definition: `dap.adapters.python`
      request = 'launch',
      name = 'Launch file',

      -- Options below are for debugpy, see https://github.com/microsoft/debugpy/wiki/Debug-configuration- settings for supported options
      justMyCode = false,
      program = '${file}', -- This configuration will launch the current file if used.
      pythonPath = function()
        -- debugpy supports launching an application with a different interpreter then the one used to launch  debugpy itself.
        -- The code below looks for a `venv` or `.venv` folder in the current directly and uses the python within.
        -- You could adapt this - to for example use the `VIRTUAL_ENV` environment variable.
        local cwd = vim.fn.getcwd()
        if vim.fn.executable(cwd .. '/venv/Scripts/pythonw.exe') == 1 then
          return cwd .. '/venv/Scripts/pythonw.exe'
        elseif vim.fn.executable(cwd .. '/.venv/Scripts/pythonw.exe') == 1 then
          return cwd .. '/.venv/Scripts/pythonw.exe'
        else
          return 'C:\\Users\\joe\\Anaconda3\\envs\\market\\pythonw.exe'
        end
      end,
    },
  }
 end,
  },
 }

[AckslD]

I think the easiest is to use nvim-dap-python, see for example what I do in my config:
https://gitlab.com/AckslD/config/-/blob/master/nvim/lua/acksld/plugins/dap.lua?ref_type=heads#L40
or copy what that plugin does if you want to customise it.

[AM-I-Human]

I found issue too using dap-python. I solve it now by adding a port.
I place my dap config for reference (this then goes to Lazy)

return {
    {
        'mfussenegger/nvim-dap',
        dependencies = {
            'rcarriga/nvim-dap-ui',
            'theHamsta/nvim-dap-virtual-text',
            'nvim-neotest/nvim-nio',
            'williamboman/mason.nvim',
            'jay-babu/mason-nvim-dap.nvim',
            'mfussenegger/nvim-dap-python',
            'leoluz/nvim-dap-go',
        },
        config = function()
            local dap = require 'dap'
            local dapui = require 'dapui'
            local dap_python = require 'dap-python'

            local mason_path = vim.fn.glob(vim.fn.stdpath 'data' .. '/mason/')
            local debugpy_path = mason_path .. 'packages/debugpy/venv/Scripts/python'

            dapui.setup()
            dap_python.setup(debugpy_path)
            dap_python.default_port = 38000


            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,},}

and I discovered if I use this it will break again:

            require('mason-nvim-dap').setup {
                automatic_installation = true,
                automatic_setup = true,
                handlers = {},
                ensure_installed = {
                    'delve',
                },
            }