Stop passing null as second argument to document.createElement()

[darobin]

When using the two-parameter variant of document.createElement() (which is used for Custom Elements), if null is passed as the second parameter then Firefox will stringify it to the DOM as an is="null" attribute. I don't believe that this causes any manner of problem, but it is surprising (as exemplified in this discussion thread.

This change simply changes the call to avoid passing null.

[gaearon]

Can we just always pass props.is? It would be undefined unless specified, which is indistinguishable from not passing it at all.

cc @jimfb

[darobin]

I tried that, it was my first guess: Firefox helpfully gives you is="undefined" in return.

[gaearon]

Haha, got it. Let’s split into two branches to make it a bit easier on eyes?

} else if (props.is) {
  ...
} else {
  ...
}

[darobin]

Sure thing, done.

[gaearon]

Is there any way to test this with jsdom so we don’t regress?

[ghost]

@darobin updated the pull request.

[darobin]

Not that I can think of, at least not without intercepting createElement, which is doable but perhaps a bit brutal. Note that Firefox's behaviour is incorrect as per (current) spec, and therefore likely to change at some point.

[gaearon]

Thanks!

[zpao]

Do you know if this Firefox bug been reported to Mozilla?

[darobin]

Yes, I discussed it on #whatwg this morning to double-check, and reported it in bugzilla.