Why @babel/proposal-class-properties add plugins ?

[astroplex]

After babel-preset-env version 7.10.0 @babel/plugin-proposal-class-properties included.

but when I not include plugin I got this error.

 Missing class properties transform.
  14 | 
  15 | export class ErrorBoundary extends Component<Props, State> {
> 16 |   state = {
     |   ^

...

My .babelrc setting is

// not working 🚨
{
  "plugins": [
    "lodash"
  ],
  "presets": [
    "@babel/preset-env",
    "@babel/preset-react",
    "@babel/preset-typescript"
  ]
}

// working 🙆‍♂️
{
  "plugins": [
    "@babel/proposal-class-properties",
    "lodash"
  ],
  "presets": [
    "@babel/preset-env",
    "@babel/preset-react",
    "@babel/preset-typescript"
  ]
}

[nicolo-ribaudo]

Since class properties are not standard ECMAScript yet, you have to explicitly enable support for proposals that are already shipped in browsers:

{
  "plugins": [
    "lodash"
  ],
  "presets": [
    ["@babel/preset-env", { "shippedProposals": true }],
    "@babel/preset-react",
    "@babel/preset-typescript"
  ]
}