Error: 'default' is not exported

[fryorcraken]

This seems to be a common error but I am not able to understand how to resolve it.

The code is here: https://github.com/waku-org/js-rln/tree/18176e33c06c35a78af25b512f7615617c2c0775

I am getting

[!] Error: 'default' is not exported by dist/witness_calculator.cjs, imported by dist/witness_calculator.js
https://rollupjs.org/guide/en/#error-name-is-not-exported-by-module
dist/witness_calculator.js (1:7)
1: import builder from './witness_calculator.cjs';
          ^
2: export { builder };
3: //# sourceMappingURL=witness_calculator.js.map

So builder is exported as default.

in dist/witness_calculator.cjs:

module.exports = async function builder(code, options) {

in dist/witness_calculator.js:

import builder from './witness_calculator.cjs';
export { builder };

My rollup config:

import { nodeResolve } from "@rollup/plugin-node-resolve";
import commonjs from "@rollup/plugin-commonjs";
import json from "@rollup/plugin-json";
import { wasm } from '@rollup/plugin-wasm';

export default {
  input: {
    index: "dist/index.js"
  },
  output: {
    dir: "bundle",
    format: "esm",
  },
  plugins: [
    commonjs(),
    json(),
    nodeResolve({
      browser: true,
      preferBuiltins: false,
    }),
    wasm({targetEnv: "browser"})
  ],
};

I am not sure to understand why rollup does not find the default export?