Target es6 for esm build

Description of the bug

Previously, I could use postprocessing in my webpack bundling without any additional processing (e.g. babel). Recently, however, it appears the language target has moved to “esnext” which includes language features such as “??” and “?.” which are less compatible. Specifically, the build/postprocessing.esm.js generated file includes these esnext features.

To Reproduce

Run pnpm build and inspect the build/postprocessing.esm.js file to see that it includes ?? and ?. operators.

Expected behavior

Produce a plain “es6” target.

Library versions used

• Three: n/a
• Post Processing: main

Potential Solution

The https://github.com/pmndrs/postprocessing/blob/main/esbuild.mjs#L69 instructions do not include target: "es6", but I believe adding this would solve the issue.

[vanruesc]

Thanks for the repro 👍

I did some research and found that support for ?? and ?. was added to acorn in version 7. Webpack 4, however, is locked to version 6 and hence doesn’t support this syntax.

You should upgrade to webpack 5 if possible. I’ll set the build target to es2019 which will transpile the ?? and ?. syntax to ease the transition. but this will be reverted in the next major release.

[canadaduane]

Thanks! I had forgotten that Webpack is dependent on acorn. That was the piece I was missing in being able to explain to myself what was going on.

I believe our project can be updated to Webpack 5, but it will be a few months, so a little more time would be greatly appreciated.