JQuery 2.1.x not recommended for Lift

[j...@joescii.com]

Hello fellow Lifters! 

TL;DR

Upgrade to JQuery 2.2.x if you are using 2.1.x and you rely on Lift's comet feature.

Full version

One of my clients noticed that whenever someone put their MacBook to sleep, comet would not resume after waking the Mac. Sleeping the Mac for as little as one moment was enough to cause the issue.

After investigation, I learned that the browser (Chrome is what I used to investigate, but Safari behaved similarly) cancels the ajax request made for comet. After instrumenting code, I noticed that Lift's cometFailureFunc JS function was not getting called immediately after waking the laptop. This was NOT what I observed in my test projects. There I would see our error function called moments after waking the laptop.

For those unfamiliar with Lift's comet implementation details: Comet works by the client initiating an ajax request back to the server. Lift then uses jquery to handle the ajax call (unless of course you have configured your Lift app differently). Hence if jquery is broken, Lift isn't going to behave well.

So I went down the path of investigating what JQuery version was in play. If you find yourself investigating this, execute "jQuery.fn.jquery" in the browser console to echo the exact version that is active in your app (thanks Stack Overflow). That's how I tracked down that the version they were using (2.1.1) was broken, the latest 2.1.x (2.1.4 at this time) had the same behavior, but the latest 2.x (2.2.4 at this time) does NOT have this issue of calling the error handler in a timely fashion.

I hope this helps someone else!

Joe

 

[Matt Farmer]

Good catch Joe! Thanks for the heads up!

Should we put something in the README on lift/framework about this?

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[Donald McLean]

What about newer versions of JQuery?

I'm using 3.1.1, but I see that 3.3.1 is the current version.

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[Antonio Salazar Cardozo]

What is the actual issue in jquery? Might there be a workaround that we can let people know about?

Nice find!
Thanks,
Antonio

[Tim Nelson]

FYI, there is a vulnerability in jQuery <3.0.0 [1], so you should upgrade above that if you can. I just upgraded our codebase and with the help of their migration library, I didn't have to make many changes, so it's not too bad.

Tim

1 - https://snyk.io/vuln/npm:jquery:20150627

[Antonio Salazar Cardozo]

Yipes. Yeah, maybe not worth supporting that version then.

[Joe Barnes]

Following up on some questions...

> What about newer versions of JQuery?

I only tested the versions I mentioned. This particular project has a LOT of front end code and the task of trying later versions of JQuery is on someone else's plate. I've followed up and I'm letting folks here know about the security vulnerability Tim pointed out. I'll reply back with any findings.

> What is the actual issue in jquery? Might there be a workaround that we can let people know about?

I didn't bother to track it down tbh. Once I saw that our error function wasn't getting called, I started kicking JQuery versions until it worked again :) 

> Should we put something in the README on lift/framework about this?

Most definitely in light of the issue Tim shared with us! We probably need to update our template projects and so forth to, don't y'all think? 

Joe

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