disconnect command listener not working with debugpy and long-running programs

[abhinavnatarajan]

Debug adapter definition and debug configuration

Using the following minimal configuration for nvim-dap with the debugpy adapter, I cannot get the disconnect listener to work correctly.

return {
	"mfussenegger/nvim-dap",
	keys = {
		{ "<Leader>Dt", function() require("dap").toggle_breakpoint() end, desc = "Toggle Breakpoint" },
		{ "<Leader>Ds", function() require("dap").continue() end, desc = "Start" },
		{
			"<Leader>Dd",
			function()
				require("dap").disconnect({ terminateDebuggee = false })
				require("dap").close()
			end,
			desc = "Disconnect debugger"
		},
	},
	config = function(_, opts)
		local dap = require("dap")

		dap.listeners.before.disconnect.cb =
				function()
					vim.notify("disconnected")
				end
		dap.listeners.before.event_terminated.cb = 
				function()
					vim.notify("terminated")
				end
		dap.listeners.before.event_exited.cb = 
				function()
					vim.notify("exited")
				end
		dap.adapters.python = {
					type = 'executable',
					command = vim.fn.exepath('debugpy-adapter'), -- debugpy installed via Mason
					options = {
						source_filetype = 'python',
					},
				},
		dap.configurations.python = {
			{
				type = 'python',
				request = 'launch',
				name = "Launch file",
				program = "${file}",
				python = '/usr/bin/python3'
			},
		}
	end
}

Debug adapter version

debugpy v1.8.1

Steps to Reproduce

Add a breakpoint on line 2 of the following file, and start the debugger.

import time
time.sleep(5) # set a breakpoint on this line
print('Nothing in particular')

When the debugger stops at the breakpoint, hit <leader>Dd to disconnect.

Expected Result

I should get a notification with the message disconnected.

Actual Result

No notification is raised, but I get [Process exited 0] in the DAP terminal.
The behaviour also depends on the sleep time. If I change the second line in the python file to time.sleep(0.1), the line Nothing in particular is printed to the DAP terminal before the process exit. I tried increasing the value of disconnect_timeout_sec in the adapter options, but this did not change the behaviour.

[mfussenegger]

That's up to the debug adapter. nvim-dap closes the connection after disconnect_timeout_sec to avoid waiting indefinitely. If the adapter doesn't send it there is nothing the client can do about it.