Generated tags include superfluous metadata

[karol-majewski]

• emotion version: 9.0.2
• react version: 16.3.1

Relevant code:

emotion/packages/create-emotion/src/sheet.js

Lines 44 to 57 in 3544dd6

	function makeStyleTag(opts: Options): HTMLStyleElement {
	let tag = document.createElement('style')
	tag.type = 'text/css'
	tag.setAttribute('data-emotion', opts.key || '')
	if (opts.nonce !== undefined) {
	tag.setAttribute('nonce', opts.nonce)
	}
	tag.appendChild(document.createTextNode(''))
	// $FlowFixMe
	;(opts.container !== undefined ? opts.container : document.head).appendChild(
	tag
	)
	return tag
	}

What you did:

1. Used react-emotion in my application.
2. Validated the serialized DOM with Nu HTML Checker

What happened:

It returned dozens of warning concerning the type attribute that is no longer necessary in HTML5.

Warning: The type attribute for the style element is not needed and should be omitted.
;}</style><style type="text/css" data-emotion="">.css-v

Reproduction:

Not sure if it's needed (the code doing it is right there), but if you'd like to see it in the wild, go to https://validator.w3.org/nu/ and check https://zefenify.com/about.html mentioned in the README.

Problem description:

As W3 docs say:

In HTML5, the type attribute is no longer required for CSS. The default value is "text/css".

Suggested solution:

Delete the line 46.

emotion/packages/create-emotion/src/sheet.js

Line 46 in 3544dd6

tag.type = 'text/css'

[emmatown]

Thanks for the issue!! If you submit a PR removing that line and updating any necessary snapshots, I'd be happy to merge it.