Why is jsc.baseUrl not resolving the require path?

[devjiwonchoi]

Hello, fellow engineers and appreciatable SWC maintainers,

I wish to understand if the following behavior is intended and if so, the reason for it:

TL;DR

Why is jsc.baseUrl not resolving the require path as either relative or absolute?

Context

Using transform or transformSync from @swc/core.

Based on this error message:

Error: failed to handle: base_dir(`.`) must be absolute. Please ensure that `jsc.baseUrl` is specified correctly.

I've understood that the baseUrl path must be absolute which differs from tsconfig.json, so I'm passing process.cwd().

Code

import { foo } from "src/foo"
console.log(foo)

await transform(code, { jsx: { baseUrl: process.cwd() } })

Expected:

import { foo } from "./src/foo" // or a resolved absolute path?
console.log(foo)

Output:

import { foo } from "src/foo"
console.log(foo)

[kdy1]

If you invoke transform with relative jsc.baseUrl, which directory it should be resolved from? Current working directory? Input file? There's no clear default, so we require absolute url.

[devjiwonchoi]

Yes true! I understand why baseUrl needs to be an absolute path since SWC is compile-focused, and I think the error log is very clear and reasonable.

Since using jsc.baseUrl and jsc.paths do resolve the import path from @/foo to ./src/foo, why not src/foo to ./src/foo on the same baseUrl?

[devjiwonchoi]

I can guess that for paths it gives keys to resolve (e.g. @) but when only baseUrl, SWC needs to validate whether src/foo is from node_modules or is on the baseUrl, which is an extra step non-related to compilation... right?

By the way, this is 100% what I was looking for: #7302

[kdy1]

I think it's a bug, and swc should resolve it. But IIRC, there's a wrong check for jsc.paths that prevents swc from resolving it

[devjiwonchoi]

Sounds great that SWC can support it, let me know anything I can assist you on behalf of solving this issue!