Adding .mjs to list of known MIME types

[shirhatti]

https://datatracker.ietf.org/doc/html/draft-ietf-dispatch-javascript-mjs has been submitted for publication to the IESG. We anticipate that browsers may start enforcing the correct Content-Type header for javascript modules prior to execution.

As an aside, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules#aside_%E2%80%94_.mjs_versus_.js

👀 @MylesBorins

[MylesBorins]

this looks great @shirhatti The only thing I'll point out is that browsers already do enforce the correct Content-Type header for JavaScript modules which is exactly what makes the lack of .mjs support from mime type database an issue (and a primary motivation for standardization at the IETF)

[shirhatti]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[javiercn]

@shirhatti this also needs tooling support, since VS will not colorize .mjs files

[halter73]

Triage note: This is different than .js which is still "application/json". We're okay with this since we expect we'll eventually address .js when we resolve #34323.

We anticipate that browsers may start enforcing the correct Content-Type header for javascript modules prior to execution.

@shirhatti Do you really think this is likely? Why would a browser be that strict and reject "application/json".

[shirhatti]

@shirhatti Do you really think this is likely? Why would a browser be that strict and reject "application/json".

That was phrased poorly. I don't expect browsers to stop executing application/javascript, but they will not serve mjs files without text/javascript or application/javascript