[debug]: Cannot stop debug session of `vscode-mock-debug`

[kittaakos]

Bug Description:

It's impossible to terminate the debug session in Theia. It works very well from Code.

Steps to Reproduce:

1. Start the Microsoft/vscode-mock-debug debugger in Theia.
2. Stop the debug session.
3. It cannot terminate and will timeout after 5 sec

2022-11-18T11:59:05.246Z root ERROR Error on disconnect

{
    "type": "response",
    "seq": 0,
    "request_seq": 12,
    "success": false,
    "command": "disconnect",
    "message": "Request #12: disconnect timed out"
}

---

If you do not want to build the vscode-mock-debug extension on your own, you can use the VS Code extension mock debugger from #11871

Additional Information

• Operating System: macOS, 12.5.1
• Theia Version: fe8e4c1

[kittaakos]

I will handle this.

[kittaakos]

After microsoft/vscode#166137, I can confirm Theia's behavior is the same as Code.

I was positive the debug session's fast termination was due to no await in Code's implementation, then microsoft/vscode#166137 popped up. I debugged into the non-minified version of the mock-debug implementation, and I can confirm no disconnect response was sent back to the client. So a timeout is expected. See here. I downloaded latest Code Insider, and now I can see the 2-sec delay after terminating the debug session. The differences are that Theia uses 5000ms while Code 2000ms. Code ignores errors, Theia does not.

Theia should adjust the UX, though. Shall Theia ignore the error and timeout after 2000ms (or make the timeout easily configurable from downstream code)?

We can close the issue. It's up to core committers. Thanks!

[msujew]

Code ignores errors, Theia does not.

Note that Theia also "ignores" the error. I wouldn't say that logging the error to console really counts as error handling. We don't show anything to the user or anything similar.

[kittaakos]

Note that Theia also "ignores" the error.

Yes, thanks for the correction. What I meant is logging the error is misleading. No malfunction is happening when terminating the debug session with 'disconnect' and there is a timeout.

[kittaakos]

Let's leave this open. There are other places we could improve Theia. For example, when a request is timed out, the error object used for rejection does not have an error message. However, DAP has a spacial ErrorResponse, Theia could benefit from it:

	/** On error (whenever `success` is false), the body can provide more details. */
	interface ErrorResponse extends Response {
		body: {
			/** A structured error message. */
			error?: Message;
		};
	}

Current code:

theia/packages/debug/src/browser/debug-session-connection.ts

Lines 224 to 232 in b2c52e2

	const error: DebugProtocol.Response = {
	type: 'response',
	seq: 0,
	request_seq: request.seq,
	success: false,
	command,
	message: `Request #${request.seq}: ${request.command} timed out`
	};
	pendingRequest.reject(error);

Also, it should be easier for downstream to specify a timeout for terminate and disconnect. I would also like to increase the visibility of the isStopped to improve the APIs for downstream:

theia/packages/debug/src/browser/debug-session.tsx

Line 75 in b2c52e2

private isStopping: boolean = false;