[Bug]: Cannot set properties of undefined (setting 'identifier') error when using plugin-proposal-decorators legacy with plugin-transform-block-scoping

[charlessuh]

💻

• Would you like to work on a fix?

How are you using Babel?

@babel/cli

Input code

try {
    class C {
        @Dummy foo() {
            throw new Error();
        }
    }

    let c = new C();
    c.foo();
} catch (e) {
    console.error(e);
}

Configuration file name

.babelrc

Configuration

{
  //"presets": [
  //  ["@babel/preset-env", {"targets": "firefox 50"}]
  //],
  "plugins": [
    ["@babel/plugin-proposal-decorators", {"legacy": true}],
    ["@babel/transform-block-scoping"]
  ]	
}

Current and expected behavior

Current:

TypeError: /Users/chsuh/decorators-bug/index.js: Cannot set properties of undefined (setting 'identifier')
    at PluginPass.ClassDeclaration (/Users/chsuh/decorators-bug/node_modules/@babel/plugin-proposal-decorators/lib/transformer-legacy.js:148:26)
    at newFn (/Users/chsuh/decorators-bug/node_modules/@babel/traverse/lib/visitors.js:159:21)
    at NodePath._call (/Users/chsuh/decorators-bug/node_modules/@babel/traverse/lib/path/context.js:46:20)
    at NodePath.call (/Users/chsuh/decorators-bug/node_modules/@babel/traverse/lib/path/context.js:36:17)
    at NodePath.visit (/Users/chsuh/decorators-bug/node_modules/@babel/traverse/lib/path/context.js:84:31)
    at TraversalContext.visitQueue (/Users/chsuh/decorators-bug/node_modules/@babel/traverse/lib/context.js:96:16)
    at TraversalContext.visitMultiple (/Users/chsuh/decorators-bug/node_modules/@babel/traverse/lib/context.js:67:17)
    at TraversalContext.visit (/Users/chsuh/decorators-bug/node_modules/@babel/traverse/lib/context.js:119:19)
    at traverseNode (/Users/chsuh/decorators-bug/node_modules/@babel/traverse/lib/traverse-node.js:18:17)
    at NodePath.visit (/Users/chsuh/decorators-bug/node_modules/@babel/traverse/lib/path/context.js:90:52) {
  code: 'BABEL_TRANSFORM_ERROR'
}

Environment

System:
OS: macOS 13.1
Binaries:
Node: 16.14.0 - ~/.nvm/versions/node/v16.14.0/bin/node
npm: 8.3.1 - ~/.nvm/versions/node/v16.14.0/bin/npm
npmPackages:
@babel/cli: ^7.19.3 => 7.19.3
@babel/plugin-proposal-decorators: ^7.20.5 => 7.20.5
@babel/plugin-transform-block-scoping: ^7.20.5 => 7.20.5

Possible solution

No response

Additional context

No response

[babel-bot]

Hey @charlessuh! 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.

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[charlessuh]

This line appears to be throwing the error: https://github.com/babel/babel/pull/8566/files#diff-fb3ce34c7f7df7457153d3f43ef3fe7f02074361968b11b045932930db4e44fdR334

[liuxingbaoyu]

I can reproduce it with the latest release, but not in the main branch, not sure if it's because of #15200.

[nicolo-ribaudo]

Lets try releasing and see if it fixes the bug then :)

[liuxingbaoyu]

After the update the problem disappeared.😂

[nicolo-ribaudo]

@charlessuh Can you confirm that updating all your Babel dependencies fixed this for you?

[cjones26]

It may not be fully related, but we are seeing something similar here: storybookjs/storybook#20382.

We were able to resolve by reverting to an older version of @babel/plugin-transform-block-scoping@7.18.9.

[liuxingbaoyu]

@cjones26 #15299 Can you try v7.20.8?

[cjones26]

@liuxingbaoyu I just tried v7.20.8 with no luck, but v7.20.5 does in fact work properly.

[liuxingbaoyu]

@cjones26 v7.20.9 has been released, has the problem been solved?

[necatisarhanli]

@liuxingbaoyu I don't see the new release (v7.20.9) on npm , where can we find it?

[liuxingbaoyu]

@necatisarhanli https://www.npmjs.com/package/@babel/plugin-transform-block-scoping

[eductech]

Hello. We use 3rd party bundling tool that has depth "@babel/preset-env": "^7.11.5". Now it installs @babel/plugin-transform-block-scoping@7.20.7 which seems to be corrupted by the issue raised and build fails. How we can resolve this?

[nicolo-ribaudo]

Delete @babel/plugin-transform-block-scoping from your lockfile and reinstall your dependencies

[eductech]

@nicolo-ribaudo thanks. With @babel/plugin-transform-block-scoping@7.20.9 issue was resolved in our case