Output: Import statement must be with .js not .ts

[VienDinhCom]

Describe the bug

Input code

// sum.ts
export function sum(a: number, b: number) {
  return a + b;
}

// main.ts
import { sum } from './sum.ts';

console.log(sum(1, 2));

Config

{
  "jsc": {
    "parser": {
      "syntax": "typescript",
      "decorators": true
    },
    "transform": {
      "legacyDecorator": true,
      "decoratorMetadata": true
    }
  }
}

Result

// main.js
import { sum } from './sum.ts';

console.log(sum(1, 2));

Expected result

// main.js
import { sum } from './sum.js';

console.log(sum(1, 2));

The import statement must be with .js. Not .ts

Version
The version of @swc/core: 1.2.37

[kwonoj]

I believe this is related with #3043 also it's correct behavior as-is currently.

Linked issue's comment explains it

See @RyanCavanaugh's comment here: microsoft/TypeScript#41887 (comment)

TypeScript doesn't modify JavaScript code you write, the import path you write should be the one you want to appear in the output .js file

Actually, if you try latest tsc (https://www.typescriptlang.org/play?#code/JYWwDg9gTgLgBAKjgQwM5wEZwGZQiOAcgDoB6VfAU2JlUIG4g) you'll get error instead:

An import path cannot end with a '.ts' extension. Consider importing './some.js' instead.

If swc's bundler or other tool's resolver cannot resolve module with full extension (I believe for some cases it's failing) that's something to fix, but I believe swc should not try to modify import specifier by its own.

/cc @kdy1 , in my opinion I'd like to suggest to close this - and if we need, we can implement error out as same as tsc does.

[kdy1]

Yeah, I think you are right.
Thanks!

[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.