Multi-line comment being stripped from generated code

[smcenlly]

Describe the bug

We create some popular developer tools (Quokka.js, Wallaby.js).

Our tools rely on code comments being correctly in code emitted by SWC.

It appears that SWC sometimes (not always) removes multi-line comment from generated code.

Input code

a() /* IMPORTANT_DO_NOT_REMOVE */ ;

Config

{
  "jsc": {
    "parser": {
      "syntax": "typescript",
      "tsx": false,
      "decorators": false,
      "dynamicImport": false
    }
  },
  "sourceMaps": true
}

Playground link

https://play.swc.rs/?version=1.2.144&code=H4sIAAAAAAAAA0vU0FTQ11Lw9A3wDwpx9AuJd%2FGP9%2FMPiQ9y9fUPc1XQ0lewBgAeBNe1IwAAAA%3D%3D&config=H4sIAAAAAAAAA0WMTQrEIAxG75K1286id5hDBCctFv9IUhgR714tlu7C915ehUMsrBUyshCPS0pU%2FMMKZAOKZZcVTNf6tKEXagYUeScdiiyd%2BZSEJjUQXHRbGSWbQmYSeRHG3T9m66GQfucYKmjJdAc%2F0N7G%2FHPynaLySe0Cj9ke9LUAAAA%3D

Expected behavior

Generated code should be:

a() /* IMPORTANT_DO_NOT_REMOVE */ ;

Actual behavior

Generated code is:

a();

Version

@swc/core@1.2.144

Additional context

No response

[kwonoj]

👋 I'm wallaby / quokka daily user.

We really don't have good defined behavior around comment. #2964 is one of the examples. There is internal consideration to revisit whole comment, but also it doesn't aim to fix specific issues around comment.

How much is this a blocker for you? Is there any workaround you can apply?

[smcenlly]

👋 I'm wallaby / quokka daily user.

That's awesome :)

---

One of Quokka/Wallaby key features is Live Comments, which gives users a mechanism to always log a value when Wallaby/Quokka runs their code.

We've been recommending people use swc over babel or TypeScript (see our blog post) because of the massive performance benefits. And we're also using swc in our own projects.

There's no real work around for us on this issue. It seems to work most of the time, but not always.

I wouldn't say it's a blocker for us per se but it'll definitely affect our customers and perhaps make them choose babel instead of swc when running their tests if they find it particularly painful.

[swc-bot]

This closed issue has been automatically locked because it had no new activity for a month. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.