[Bug]: @babel/preset-typescript@7.22.15 fails when exporting namespace

[snitin315]

💻

• Would you like to work on a fix?

How are you using Babel?

@rollup/plugin-babel

Input code

Building the following code with @babel/preset-typescript fails:

import type { Brand, NativeOrWebBrand } from './types';

namespace Platform {
  export type Name = 'web';
}

export { Platform };

with the following error:

However if I move the export to declaration itself, it builds successful:

import type { Brand, NativeOrWebBrand } from './types';

export namespace Platform {
  export type Name = 'web';
}

Configuration file name

.babelrc.js

Configuration

{
      presets: [
        ['@babel/preset-env', { modules: false }],
        '@babel/preset-typescript',
        ['@babel/preset-react', { runtime: 'automatic' }],
      ],
      plugins: [
        [
          '@babel/plugin-transform-runtime',
          {
            helpers: true,
            regenerator: true,
          },
        ],
        [
          'babel-plugin-styled-components',
          {
            displayName: true,
            pure: true,
            ssr: true,
          },
        ],
      ],
    },

Current and expected behavior

Currently it throws error with v7.22

It should not throw error like in v7.16

Environment

System:
    OS: macOS 13.4.1
  Binaries:
    Node: 20.2.0 - ~/.nvm/versions/node/v20.2.0/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 9.6.6 - ~/.nvm/versions/node/v20.2.0/bin/npm
  npmPackages:
    @babel/core: 7.22.15 => 7.22.15 
    @babel/plugin-transform-react-jsx: 7.22.15 => 7.22.15 
    @babel/plugin-transform-runtime: 7.22.15 => 7.22.15 
    @babel/preset-env: 7.22.15 => 7.22.15 
    @babel/preset-react: 7.22.15 => 7.22.15 
    @babel/preset-typescript: 7.22.15 => 7.22.15 
    @babel/runtime: 7.22.15 => 7.22.15 
    babel-jest: 29.6.1 => 29.6.1 
    babel-loader: 8.2.3 => 8.2.3 
    babel-plugin-module-resolver: 4.1.0 => 4.1.0 
    babel-plugin-styled-components: 1.12.0 => 1.12.0 
    jest: 29.6.1 => 29.6.1 
    metro-react-native-babel-preset: 0.76.7 => 0.76.7 
    react-native: 0.72.3 => 0.72.3

Possible solution

No response

Additional context

No response

[babel-bot]

Hey @snitin315! 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.

[nicolo-ribaudo]

This has been probably caused by #15799, but the old output was wrong too.

We might have to add a "is namespace && will be stripped because it only contains types" check in

babel/packages/babel-plugin-transform-typescript/src/index.ts

Line 389 in 85a35ad

} else if (

, or call registerGlobalType in

babel/packages/babel-plugin-transform-typescript/src/namespace.ts

Line 27 in 85a35ad

path.remove();

.

I see that you marked "Would you like to work on a fix?", let me know if you need further help :)

[snitin315]

We might have to add a "is namespace && will be stripped because it only contains types" check in

@nicolo-ribaudo How do I check it's a namespace, currently stmt doesn't have access to the kind property

[nicolo-ribaudo]

You can use stmt.isTSModuleDeclaration() for that

[nicolo-ribaudo]

@snitin315 Are you still working on this?

[snitin315]

@nicolo-ribaudo not as of now. Feel free to pick this up.

[nicolo-ribaudo]

For anyone that wants to help :)

If it is the first time that you contribute to Babel, follow these steps: (you need to have make and yarn available on your machine)

1. Write a comment there to let other possible contributors know that you are working on this bug.
2. Fork the repo
3. Run git clone https://github.com/<YOUR_USERNAME>/babel.git && cd babel
4. Run yarn && make bootstrap
5. Wait ⏳
6. Run make watch (or make build whenever you change a file)
7. Add a test in https://github.com/babel/babel/tree/main/packages/babel-plugin-transform-typescript/test/fixtures/namespace (only input.ts; output.js will be automatically generated)
8. Update the code!
9. yarn jest transform-typescript to run the tests
   • If some test outputs don't match but the new results are correct, you can delete the bad output.js files and run the tests again
   • If you prefer, you can run OVERWRITE=true yarn jest transform-typescript and they will be automatically updated.
10. If it is working, run make test to run all the tests
11. Run git push and open a PR!

[niftytyro]

hey there can I pick this up?

[nicolo-ribaudo]

Sure! Feel free to write here if you need more help :)

[CheadleCheadle]

I could try taking a stab at it if niftytyro isn't working on it anymore!

[niftytyro]

Yes sure please! I'm not working on it right now. Feel free to take it