Include @babel/plugin-proposal-class-properties in @babel/preset-typescript

[dilyanpalauzov]

I want to use Babel 7.11.5 only to strip TypeScript declarations, as fast alternative to running tsc. With X.ts:

class X {
    #y(n: number) {
      console.log(n + 2);
    }
}

This fails:

babel --presets @babel/preset-typescript --extensions '.ts' X.ts
SyntaxError: X.ts: Support for the experimental syntax 'classPrivateProperties' isn't currently enabled (2:5):

  1 | class X {
> 2 |     #y(n: number) {
    |     ^
  3 |       console.log( n + 2);
  4 |     }
  5 | }

Add @babel/plugin-proposal-class-properties (https://git.io/vb4SL) to the 'plugins' section of your Babel config to enable transformation.
If you want to leave it as-is, add @babel/plugin-syntax-class-properties (https://git.io/vb4yQ) to the 'plugins' section to enable parsing.
  at Object._raise ...
  loc: Position { line: 2, column: 4 },
  pos: 14,
  missingPlugin: [ 'classPrivateProperties', 'classPrivateMethods' ],
  code: 'BABEL_PARSE_ERROR'
}

This works:

babel --plugins @babel/plugin-syntax-class-properties --presets @babel/preset-typescript --extensions '.ts' X.ts

• Extend babel/cli --presets @babel/preset-typescript or @babel/plugin-transform-typescript to only strip the TypeScript declarations and leave the rest as it is, so that adding @babel/plugin-syntax-class-properties is not necessary for the stripping.

[babel-bot]

Hey @dilyanpalauzov! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite."

[dilyanpalauzov]

Do I see correctly, that #13232 enables @babel/plugin-syntax-class-properties by default (no-op), so that the typescript-preset can now be used just to strip the type annotations, and it understands this convoluted syntax?

[dilyanpalauzov]

This is implemented in 7.14.0.