IE 11 vs preProcessedHeaders.split(/\r?\n/)

[pierremanceaux]

Hello devs, and thank you for this great polyfill.

I am facing a strange bug in IE 11 (on Browserstack, no access to and old Windows system).

In short, the behaviour of preProcessedHeaders.split(/\r?\n/).forEach(...) seem to be inconsistent between for instance Chrome's last version (my reference point) and IE11 on Browserstack.

IE 11 -> Incorrect

Chrome -> Correct

Meaning that the polyfill simply doesn't work for me on IE 11.

If you want to try yourself assuming you have an access to an IE 11 browser:

'preProcessedHeaders'.split(/\r?\n/)
'preProcessedHeaders\n'.split(/\r?\n/)
'preProcessedHeaders\r'.split(/\r?\n/)
'preProcessedHeaders\r\n'.split(/\r?\n/)

Is anyone able to reproduce this?

Thank you for your time in advance.

Note
Polyfill version: 3.0.0
Here is the IE11 build I tested with:

[dgraham]

The regular expression works for me in a newer patch version of IE 11, so this might be a bug in the older version Browserstack seems to be using.

[pierremanceaux]

Thank you for having taken the time to test! More tests from more people are welcome here, as it is nearly impossible to obtain information about IE11 builds market shares.
I will notify Browserstack about it, and if they provide me with any interesting information I'll add it in here for other people.

[charlesbjohnson]

I'm running into the same thing on the newer version of IE 11 that was posted.

[pierremanceaux]

@charlesbjohnson your version is exactly the same as mine. Edit: or do you simply confirm that you run into this issue too?

[charlesbjohnson]

@charlesbjohnson your version is exactly the same as mine. Edit: or do you simply confirm that you run into this issue too?

Confirming that I'm running into this issue on the same version that you posted. I don't know how to confirm if this is the latest IE 11, but I downloaded it today from here.

[charlesbjohnson]

Correction: My version is the same as @dgraham's (here), and not the version @pierremanceaux originally posted in the PR description.

[pierremanceaux]

Yeah, didn't find a way to confirm the build date either, but for everything I see, seems pretty recent to me, if not the last one. I would bet it is the last one because:

• Well, I expect Browserstack to keep things up to date
• All google results are from end of last year until now
• Also just found a similar issue here: IE11 + core-js@3.6.4 String.prototype.split doesn't work with regexp zloirock/core-js#751

Seems like something is broken in IE11's last build...

[ansbar]

@pierremanceaux I use a newer version it seems, see image.

Cant reproduce your problem but still have the problem in fetch:

[pierremanceaux]

Interesting @ansbar , so in your version, preProcessedHeaders\r\n'.split(/\r?\n/) would work fine?

[pierremanceaux]

@dgraham maybe we should re-open this issue?

[ansbar]

preProcessedHeaders.split(/\r?\n/) works with your examples but not in my real life test.
For now I use:
preProcessedHeaders.split('\r\n')
which works.

[steveworkman]

The core-js ticket isn't getting any progress right now. Is there a way to work around this issue by not using the polyfilled regex and doing it a different way?

[JakeChampion]

This project does not use core-js at all, the issue you are seeing is one from core-js itself I believe and not something in this project.

[steveworkman]

@JakeChampion we do know of the issue though and it's common to use core-js polyfills and this polyfill. If we can use different code that doesn't trigger the bug - surely that's a win?

[JakeChampion]

@JakeChampion we do know of the issue though and it's common to use core-js polyfills and this polyfill. If we can use different code that doesn't trigger the bug - surely that's a win?

I'm happy to accept a pull-request for that change 👍