So I'm trying to upgrade my modules to ESM, which I've done by setting "type": "module" in package.json, and "module": "Node16" in tsconfig.json's compilerOptions.

However I'm running into a few type issues.

If I import Bucket from @google-cloud/storage, it will correctly access the bucket in the ESM path.
But the Bucket type from firebase-admin's storage().bucket() will point to a CJS path.

Typescript will then complain that the two types are not compatible.

import { storage } from 'firebase-admin'
import { Bucket } from '@google-cloud/storage'
const bucket: Bucket = storage().bucket()

Type 'import("@google-cloud/storage/build/cjs/src/bucket").Bucket' is not assignable to type 'import("@google-cloud/storage/build/esm/src/bucket", { with: { "resolution-mode": "import" } }).Bucket'.
The types returned by 'storage.channel(...)' are incompatible between these types.
    Type 'import("@google-cloud/storage/build/cjs/src/channel").Channel' is not assignable to type 'import("@google-cloud/storage/build/esm/src/channel", { with: { "resolution-mode": "import" } }).Channel'.
      Types have separate declarations of a private property 'createMethod'.ts(2322)

How do I solve this "correctly"?

I can solve the above Bucket type problem by doing:

import type { Storage } from 'firebase-admin/storage'
type Bucket = ReturnType<Storage['bucket']>

but this quickly gets very complicated, as the next type I need to extract is UploadOptions which is
the return type found on Bucket.upload which is a Promise<UploadOptions>. No idea how to extract that type, and I rather wouldn't.

Help would be appreciated.