3.2 JSON Parse error: Unrecognized token '<' Password bug

Charlie

If you have any insight, I would greatly appreciate it.

chrishamm

@Charlie Some response doesn't seem right, no valid JSON should start with '<' so you're getting an error. Try to open the developer console with F12 and check the log for further details. You should be able to see an error trace in there.

What browser are you using? Can you open DWC from a different device?

Charlie

@chrishamm

Thank you for your response.

I opened the developer console in Safari (Develop > Show Web Inspector > Console). I found the following errors and warnings:

Screen Shot 2021-01-08 at 12.58.28 PM.png

Im currently using Safari.

Charlie

The first error does not seem to be the cause of the issue, and was resolved by inserting a blank "dwc-plugins.json" file in the sys/ folder using DWC.

The subsequent errors seem to be the cause of the issue. Ive diffchecked both the "pollconnector.js" and the "BaseConnector.js" files against the files in GitHub and they appear to be identical. Im pretty out of my depth when it comes to coding, so any help would be greatly appreciated.

Phaedrux

Can you test with Chrome just to see if it's isolated to safari on your machine? What MacOS and Safari version are you running?

Sindarius

The 401 error would mean the < you are getting is because it's sending an HTML 401 error page response.

What happens if you take out the M551 in your config? Maybe there is an issue going on with passwords?

Charlie

@Phaedrux

I will try to see if I can replicate the issue on Chrome, though its difficult to reliably replicate the issue. I am using macOS Big Sur 11.1 and Safari 14.0.2 (most up to date I believe).

alankilian

(I'm NOT a JavaScript guy, so....))

It looks like the code is trying to parse a JSON tesponse, but the response is not JSON, it's text.

I notice in PollConnector.js this code:

				if (xhr.status >= 200 && xhr.status < 300) {
					if (responseType === 'json') {
						try {
							if (!xhr.responseText) {
								resolve(null);
							} else {
								resolve(JSON.parse(xhr.responseText));
							}
						} catch (e) {
							reject(e);
						}
					} else {
						resolve(xhr.response);
					}

But in BaseConnector.js I see this code:

				if (xhr.status >= 200 && xhr.status < 300) {
					try {
						if (!xhr.responseText) {
							resolve(null);
						} else {
							resolve(JSON.parse(xhr.responseText));
						}
					} catch (e) {
						reject(e);
					}

Maybe if you use the code from PollConnector.js in BaseConnector.js you'll fix the issue.

Charlie

@Phaedrux

It appears as though this is NOT occurring in Chrome, though Ive been having issues replicating the error recently.

Phaedrux

Wouldn't be the first time Safari has behaved oddly.

Charlie

@Phaedrux

Hahaha! Very true.

I am testing out the solution by @Sindarius and I will report back the results.

Charlie

@Sindarius

Your solution appears to have worked! I deleted M551 and no more error messages in Safari.

Charlie

@alankilian

Thank you so much for your response, but I have no clue how I would go about changing this, as I have no clue where these files (don't even know if the files sit on the Duet, lol).

alankilian

@Charlie "Ive diffchecked both the "pollconnector.js" and the "BaseConnector.js" files against the files in GitHub and they appear to be identical. Im pretty out of my depth when it comes to coding, so any help would be greatly appreciated."

Oh, I figured if you checked those files you'd be ready-to-go. My machine is at the lab and I haven't been going in there due to COVID-19, so I can't check.

I don't know where the files are either, but the .zip file has them in: store\machine\connector

Is that a place on your Duet?

chrishamm

@Charlie Thanks for the log, I'll try to reproduce this in Safari but I am surprised it tries to parse invalid JSON at some point - even because it should never attempt to parse anything once it gets back HTTP code 401.

@alankilian BaseConnector is the base class of PollConnector and that particular function is only used when connecting. The JS files are bundled by Webpack into very few files to accelerate the initial page load.

Charlie

@alankilian

This is what I have on the SD card, and a search of the file names turned up nothing. I could be looking in the wrong place though, since I have no clue where those files sit, or how to modify them.

Screen Shot 2021-01-09 at 12.13.10 PM.png

alankilian

@chrishamm said in 3.2 JSON Parse error: Unrecognized token '<':

The JS files are bundled by Webpack into very few files to accelerate the initial page load.

I don't know what this message from @chrishamm means.

I'm guessing that when the firmware is built a bunch of these files get packed together somehow, renamed and put somewhere on the Duet.

Sorry I'm not better versed in the Internets-part of 3D printing.

Charlie

@alankilian

Neither do I.

No worries! You've been super helpful, and way more knowledgeable than myself! I greatly appreciate your time.

Since changing the browser or removing the password GCode fixed this issue, Im super happy.

xenon2008

Hello Guys,
have the same Problem.
Updated to the latest RFF Version since 2-3 Days and now i always get this error!

I already uploaded the whole ZIP file again, deleted all gcodes files on the Duet Webinterface but nothing works.
Created also a new Thread here:

https://forum.duet3d.com/topic/21024/json-error-and-connection-drops/4

I am using Google Chrome and get this error, so i think it is not a Browser Problem..

Kind Regards

Sindarius

@xenon2008 do you happen to have a m551 in your config setting a password. The last person who was having problems removed it and it worked. Wonder if there is an issue with passwords.