Bug: "Unspecified error" some of the time in IE11 in iframe

[mparizeau-pdftron]

React version: 16.12

Steps To Reproduce

1. Open http://cygnetuat.sterlingdatarooms.com/PDFTronClientTest/ in IE11
2. Wait for the application to load in the iframe

The current behavior

Sometimes an "Unspecified error" will appear in the console and the viewer in the iframe won't load

Unfortunately it is not 100% reproducible. Sometimes the error won't occur. I'm also having trouble creating a minimal sample to reproduce this.

The expected behavior

There is no error.

Investigation

The relevant line in the callstack where the error is occurring is here

react/packages/react-dom/src/client/ReactDOMInput.js

Line 415 in 03de849

node.ownerDocument.activeElement !== node

I suspect it might be the same issue discussed here Availity/react-block-ui#18

This was a real pain to track down, but apparently IE 11 will just throw Unspecified error. when accessing document.activeElement from an <iframe>, sometimes.

The solution they used to fix the error was to use this function instead of accessing document.activeElement directly https://gist.github.com/Alex1990/046a6553dc83e22dd6f4

Ideally this function could be used inside React as well. I am also happy to use a workaround if there is one.

[dhavalsingh]

is anyone working on this? or can i give it a shot?

[pfongkye]

@dhavalsingh are you working on this issue?

[hemakshis]

Hi, is this issue available? If yes, I wanna take it up as my first issue to the React project. Thanks!

[pfongkye]

Hi @hemakshis, I was waiting for @dhavalsingh to reply. I think you can go for it. I can help if needed.

[eps1lon]

@hemakshis All yours. If you get stuck at any point in time feel free to share your progress.

[hemakshis]

Thanks a lot @pfongkye and @eps1lon. Will definitely reach out if I face any issues.

[hemakshis]

Hi, I am unable to reproduce this error, can someone help me with it? And how can I contact you - Discord, IRC, or some other means?
Thanks.

[eps1lon]

Hi, I am unable to reproduce this error, can someone help me with it?

Looking at the initial issue description this might be tough to accomplish:

Unfortunately it is not 100% reproducible. Sometimes the error won't occur. I'm also having trouble creating a minimal sample to reproduce this.

I guess @bvaughn envisioned that this could just be solved by replacing the current read with https://gist.github.com/Alex1990/046a6553dc83e22dd6f4.

But reproducing a IE11-iframe bug that only "sometimes" occurs seems like a pretty hard task to me.

[hemakshis]

Hi,
Thanks for your inputs. I was going through the code and found that there is already a very similar implementation done in this file:

getActiveElement.js

react/packages/react-dom/src/client/getActiveElement.js

Lines 10 to 20 in c641b61

	export default function getActiveElement(doc: ?Document): ?Element {
	doc = doc || (typeof document !== 'undefined' ? document : undefined);
	if (typeof doc === 'undefined') {
	return null;
	}
	try {
	return doc.activeElement || doc.body;
	} catch (e) {
	return doc.body;
	}
	}

This function is being called in a few places but not where the reporter has mentioned the change needs to be done. I think we can reuse this function in mentioned line of description. Please let me know if this sounds correct or not.

[hemakshis]

Hi,
Created #19664
Request you to please review it.
Thanks

[hemakshis]

Hi @pfongkye, @eps1lon, I want to continue contributing so do you think I can take up some other issue, if yes, please let me know? Maybe not as trivial as this one.

[eps1lon]

Closed in #19664

Hi @pfongkye, @eps1lon, I want to continue contributing so do you think I can take up some other issue, if yes, please let me know? Maybe not as trivial as this one.

You can look through the issues marked as "bug" and see if something catches your eye. The conversations might have some hints how a fix might look or whether this this isn't worth fixing because an upcoming refactor might fix it incidentally.

Also triaging issues or simply checking if they're still valid or need an updated reproduction is a form of contributing as well.