Let's remove outdated @babel/plugin-proposal-xxx in modern build?

[kkocdko]

Duplicates

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Latest version

• I have tested the latest version

Summary 💡

In a word, some @babel/plugin-proposal-xxx in babel.config.js maybe outdated and should be removed.

Docs said "the modern folder targets the latest released versions of evergreen browsers".
However I found the rest property (like const { a, ...others } = obj) in modern build is also transpiled to use babel's polyfill (_objectWithoutProperties(xxx)). See modern/Accordion in unpkg.

This's because of:

material-ui/babel.config.js

Lines 65 to 70 in 9f5ae34

	// Need the following 3 proposals for all targets in .browserslistrc.
	// With our usage the transpiled loose mode is equivalent to spec mode.
	['@babel/plugin-proposal-class-properties', { loose: true }],
	['@babel/plugin-proposal-private-methods', { loose: true }],
	['@babel/plugin-proposal-private-property-in-object', { loose: true }],
	['@babel/plugin-proposal-object-rest-spread', { loose: true }],

These code was written 3 years ago, at that time these syntaxes were still in the proposal stage.

In babel's docs of object-rest-spread plugin, "This plugin is included in @babel/preset-env, in ES2018" (and some others were included in ES2021 or 2022). So I try to remove these line of code. The output is satisfied, without polyfill. Certainly, the node and legacy build, was not changed.

Examples 🌈

No response

Motivation 🔦

Smaller bundle size & better performance on modern platform.

[kkocdko]

So what I want is: remove the plugins that already included in @babel/preset-env. This will be a small change, should I take a PR?

I think this change is still follow our compatibility promise, so no breaking changes happen.