fix: generate es2015 output

[domoritz]

Fixes #7437

Undoes #7266

[hydrosquall]

Thanks for updating this! I tried downgrading to 5.0.0 in a local build, and confirmed that it imports without error in create-react-app's default typescript template.

[domoritz]

CRA is still on Webpack 4 but hopefully will update to Webpack 5 soon.

[hydrosquall]

Would it be possible to release this as a 5.1.1? I have a project where we can't downgrade to 5.0.0 because it has strictNullChecks enabled, so we would be aiming to have the other feature from 5.1.0 #7352 in the bundle too.

[domoritz]

@kanitw Can you merge and make a patch release?

[hydrosquall]

I tried deploying a copy of this branch to check the output, but there are non es2015 symbols still making their way into the built bundle, specifically nullish coalescing (??). It's possible that I'm somehow running the build step differently (e.g. with a different node version) This may create issues for create-react-app / webpack4 users.

https://www.runpkg.com/?@hydrosquall/vega-lite@5.1.0-canary-0/build/vega-lite.js

image

I'm not very familiar with rollup / how it transforms the original output of tsc, so I just wanted to flag it as a possible additional detail to investigate before releasing.