Browsers don't allow whitespaces in <script type="module"> type attribute

[hiroshige-g]

According to the spec, <script type=" module "> should be executed, because leading and trailing ASCII whitespace stripped is applied to the type attribute value before comparing with "module".

However, Safari/Firefox/Chromium all reject such cases (WPT: https://wpt.fyi/results/html/semantics/scripting-1/the-script-element/module/type.html?label=experimental&label=master&aligned. the test expects module types with whitespaces NOT to be executed).

(Note: for classic scripts leading/trailing whitespaces are allowed on the all browsers above:
https://wpt.fyi/results/html/semantics/scripting-1/the-script-element/script-type-and-language-js.html?label=experimental&label=master&aligned)

Maybe we might want to change the spec, or fix impls?
(I found this during bug triaging and thus the priority is quite low anyway)

@domenic

[domenic]

Happy to change the spec here! I guess we should move the stripping from its current location in determining "the script block's type string", to the comparison step which checks "JavaScript MIME type essence match". And we should update the note that was just introduced for HTMLScriptElement.supports().

Would you like to submit a pull request for this?

[hiroshige-g]

Created a PR.