Add target: ES2021

[saschanaz]

Fixes #41238

We may never have year 2021 but TypeScript will.

[typescript-bot]

Thanks for the PR! It looks like you've changed the TSServer protocol in some way. Please ensure that any changes here don't break consumers of the current TSServer API. For some extra review, we'll ping @sheetalkamat, @amcasey, @mjbvz, @minestarks for you. Feel free to loop in other consumers/maintainers if necessary

[jueinin]

you committed so much code...hard work!

[saschanaz]

General feedback: Could we stop putting esnext to file paths so that we can stop renaming it whenever new standard happens? It causes unnecessary and boring changes 😬

[sandersn]

Just one question about commandLineParser's remapping esnext.promise -> es2021.promise, plus the esnext transformer looks correct to me, but @rbuckton might have an opinion about it.

[typescript-bot]

The TypeScript team hasn't accepted the linked issue #41238. If you can get it accepted, this PR will have a better chance of being reviewed.

[minestarks]

@uniqueiniquity the internal TypeScript / TypeScript-VS repos will need to be updated to match.

[Kingwl]

@saschanaz My bad. Got it!😂

[sandersn]

@minestarks @uniqueiniquity This is merged now, so the internal repos need to update.

[rbuckton]

I would note that ES2021 is still not official, per the ECMA. ES2021 is currently under the ECMA Royalty-Free Patent policy opt-out period which will last for two months, effective yesterday (March 9th, 2021). It won't officially become a standard until approximately May 9th, 2021. Nothing new can be added in that time, but its possible (though unlikely) that there could be a patent-related objection during the opt-out period that would result in a feature being removed.