Hidden input name=_charset_ case sensitivity

[josepharhar]

According to the spec, the check for the _charset_ string in <input type=hidden name="_charset_"> should be case sensitive, but in chrome and safari, the check is case insensitive.

I was going to make the check case sensitive in chrome to match the spec, but I did an HTTPArchive query and found that there are a few sites which use _CHARSET_ instead of _charset_. Considering that I might be breaking some websites by making the check case sensitive, could we instead change the spec to make the check case insensitive?

[annevk]

It seems reasonable to change this. Could you update the test to check for the exact encoding emitted (as well as expecting an encoding for the case-insensitive matches of course).

I filed https://bugzilla.mozilla.org/show_bug.cgi?id=1665014 to track this in Firefox.

[domenic]

Note that the section linked here is for authoring conformance requirements, not processing model. The processing model is in https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#constructing-form-data-set:attr-fe-name-charset. (But, they are both case-sensitive and would need updating.)

[josepharhar]

Thanks for filing the firefox bug @annevk!
Opened a pr: #5948
Opened a wpt pr: web-platform-tests/wpt#25797