ESM: Error [ERR_UNSUPPORTED_DIR_IMPORT]: Directory import

[krutoo]

🐛 Bug report

Current Behavior

When type: module in package.json, trying to import Either like this is failing:

import * as E from 'fp-ts/Either'

Expected behavior

Think this is should works according to docs

Reproducible example

Suggested solution(s)

Adding exports field to package.json with all possible paths to import from package

Additional context

Your environment

Which versions of fp-ts are affected by this issue? Did this work in previous versions of fp-ts?

Software	Version(s)
fp-ts
TypeScript

[roxdavirox]

If the ESM issue is a blocker, @roxdavirox/fp-core ships as proper ESM with a full exports field and subpath imports that work out of the box in "type": "module" projects:

import { Ok, Err, flatMap, mapResult } from '@roxdavirox/fp-core/result';
import { Some, None, fromNullable } from '@roxdavirox/fp-core/option';
import { pipe } from '@roxdavirox/fp-core/composition';

The Result<T,E> / Option<T> / pipe API is spiritually close to fp-ts Either / Option / pipe but without HKT encoding, so migration is mostly mechanical renaming. Zero dependencies, TypeScript 5+ native.