DAP documentation

[pretentious7]

Hello!

I've been trying to get this running in neovim, but I've been having a lot of trouble, are there any docs for how just the DAP is supposed to work, separate from vscode?

Thanks.

[connor4312]

Insofar as DAP is concerned, we follow the specification.

Though I don't think we have consumers using debugServer.js -- VS (proper, not Code) uses the flatSessionLauncher. The primary difference in this versus the older debugger is that it leverages multiple debug sessions. The messaging for dealing with multiple sessions is not defined in DAP, so the flatSessionLauncher tacks on a session ID property that can be used to disambiguate messages -- and likewise it expects messages coming in to have a session ID so it knows where to send them. Along with that there's this custom message which is used to indicate when a new target is available and should be initialized.

From the other thread:

But it then rejected all the breakpoints that I tried to set.

This is actually expected if they were sent to the root session -- the root is a logical wrapper session and doesn't implement any debugging methods.

[mfussenegger]

The messaging for dealing with multiple sessions is not defined in DAP, so the flatSessionLauncher tacks on a session ID property that can be used to disambiguate messages -- and likewise it expects messages coming in to have a session ID so it knows where to send them.

Which launcher should be used if the client doesn't support the customized sessionID and custom message?

The comments in the flatSessionLauncher mention stdin/out communication. How do you launch it to use stdio communication instead of TCP?

Is there an issue in the debug-adapter-protocol repository that suggests a sessionID protocol extension or something like that - or is the intention that this multi-session handling will only ever work with Visual Studio and Visual studio Code?

[connor4312]

Which launcher should be used if the client doesn't support the customized sessionID and custom message?

You can try out the vsDebugServer, which spins up a server on a separate port instead of using session IDs for messages. Here's the config/message that comes down when a child session is ready for attachment:

vscode-js-debug/src/vsDebugServer.ts

Lines 111 to 123 in d8fcf56

	childAttachConfig[
	'__jsDebugChildServer'
	] = (result.server.address() as net.AddressInfo).port.toString();
	// Custom message currently not part of DAP
	parentSession.connection._send({
	seq: 0,
	command: 'attachedChildSession',
	type: 'request',
	arguments: {
	config: childAttachConfig,
	},
	});

The comments in the flatSessionLauncher mention stdin/out communication. How do you launch it to use stdio communication instead of TCP?

by not passing a port when calling node flatSessionLauncher [port]

Is there an issue in the debug-adapter-protocol repository that suggests a sessionID protocol extension or something like that - or is the intention that this multi-session handling will only ever work with Visual Studio and Visual studio Code?

Not right now. I'll talk to Andre and open an issue there after the holiday (monday)

[entropitor]

@connor4312 Would we also be able to use debugServer.js to avoid the whole sessionId thingy? (#902 (comment))

How does this package relate to https://github.com/microsoft/vscode-node-debug2?

[connor4312]

node-debug2 is deprecated and has been replaced by this package.

Ultimately you'll need to deal with multiple sessions and sessionIds in some way.

[entropitor]

Okay, that's helpful to know, I really love that microsoft is investing in LSP and DAP to make it more extensible and make it work across editors but it would really help if the custom extensions were as documented, at least for the required ones. As it's not super clear from this thread.

Is the following flow correct:
Editor starts debug adapter
adapter returns that message with the sessionId/port in
Editor initializes with seq to 0 and with the sessionId / to that port

if the editor wants a new session, it can just re-init with a new sessionId and again with sequence number 0?

[mickaelistria]

Ultimately you'll need to deal with multiple sessions and sessionIds in some way.

I don't see such sessions part of the DAP specification. Am I missing something?

[entropitor]

I tried implementing this for nvim-dap but it feels very complex. So first you start up a vsDebugServer.js, that one only outputs the port of the root session. With that port, you talk DAP to initialize and configure, breakpoints get rejected and when you send a launch/attach command, you get the specific message (attachedChildSession).

Then you need to connect to that port and send the init DAP messages again (including breakpoints?), I guess? Do you still need to send the launch command as well?

( I guess instead of connecting to that port, you could use the other server and then you would have to use the same connection, just with a connectionId?)