Suggestion: omit void 0 from output of new JSX transform (react-jsx)

[OliverJAsh]

Bug Report

🔎 Search Terms

• jsx
• React
• react-jsx
• transform
• void 0

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about JSX

⏯ Playground Link

Playground link with relevant code

💻 Code

export const el = <div>foo</div>;

tsconfig.json:

        "jsx": "react-jsx",

🙁 Actual behavior

import { jsx as _jsx } from "react/jsx-runtime";
export const el = _jsx("div", { children: "foo" }, void 0);

🙂 Expected behavior

import { jsx as _jsx } from "react/jsx-runtime";
export const el = _jsx("div", { children: "foo" });

---

This is how it works in Babel: Babel playground.

I just tried to migrate our codebase at Unsplash to use the new JSX transform but I noticed a cumulative increase of 5 KB across all chunks. If we can remove the extraneous void 0, this should help reduce the bundle size.

Twitter thread for reference: https://twitter.com/OliverJAsh/status/1481912497175203840

[RyanCavanaugh]

I'm not sure how that got there in the first place -- was it required at some point? Some background research to help us convince ourselves this is safe for all React versions would be good

[OliverJAsh]

The new JSX transform was implemented in #39199. I searched the code and comments but didn't find very much. Maybe @weswigham could chime in?

This issue was also mentioned here but it was never addressed: #40774

[DanielRosenwasser]

Thanks @a-tarasyuk!