Can not enable syntax-class-properties with other fields related plugins

[JounQin]

Bug Report

• I would like to work on a fix!

Current behavior

• REPL

Input Code

export class Foo {
  #bar = 'bar'
}

Expected behavior

I'd like to keep class properties as-is.

Babel Configuration (babel.config.js, .babelrc, package.json#babel, cli command, .eslintrc)

• Filename: babel.config.js

module.exports = {
  plugins: [
    '@babel/syntax-class-properties',
    '@babel/proposal-private-methods',
  ],
}

Environment

- Babel version(s): v7.12.10
- Node/npm version: Node v12.20.0/npm 6.14.9
- OS: macOS 11.2 Beta
- Monorepo: no
- How you are using Babel: API directly

Possible Solution

Check syntax-class-properties instead of proposal-class-properties for class fields

Additional context

[babel-bot]

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[fedeci]

I think we should check if the property is private here, like we do for methods.

babel/packages/babel-helper-create-class-features-plugin/src/features.js

Lines 171 to 176 in b727e67

	if (path.isProperty()) {
	if (!hasFeature(file, FEATURES.fields)) {
	throw path.buildCodeFrameError("Class fields are not enabled.");
	}
	}
	}

[JounQin]

@fedeci

class-static-block and private-property-in-object are both affected too.

[fedeci]

@JounQin Cannot reproduce those😕

[JounQin]

@fedeci Sorry my fault, private-property-in-object is affected but not class-static-block.

REPL

[nicolo-ribaudo]

This is probably fixed by part of #12250, I can split that PR in two separate PRs.

[nicolo-ribaudo]

I'm preparing #13260 as an alternative for #12250, which gives better and easier control on how the different class features transforms interact.