Couldn't resolve workspace module when platform is "neutral"

[g-mero]

Reproduction link or steps

https://github.com/g-mero/tsdown-issue-workspace-no-external

run pnpm -F main build

What is expected?

should bundle workspace package correctly

What is actually happening?

[UNRESOLVED_IMPORT] Warning: Could not resolve 'utils' in src/index.ts
╭─[ src/index.ts:1:21 ]
│
1 │ import { foo } from "utils";
│ ───┬───
│ ╰───── Module not found, treating it as an external dependency

Any additional comments?

No response

[sxzz]

It's a upstream issue, and you can add exports field as a workaround.

"exports": {
  ".": "./dist/index.js"
}