TypeScript error on Firebase Cloud Function: Property 'toJSON' is missing in type 'FirebaseFirestore.Timestamp'

I am writing a Firebase Cloud Function, and I’m trying to convert a datetime string to a Firebase Timestamp.

I have been following advice from this and this answer, but TypeScript is complaining with this error:

Property ‘toJSON’ is missing in type ‘FirebaseFirestore.Timestamp’ but
required in type
‘import("/Users/John/Dev/my-app/node_modules/@firebase/firestore/dist/index").Timestamp’.
ts(2741)

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This is what my code looks like:

import * as admin from 'firebase-admin';
import { Timestamp } from 'firebase/firestore';
interface FirestoreSerp {
  createdAt: Timestamp;
  keyword: string;
}
const datetime = '2019-11-15 12:57:46 +00:00'
const firestoreSerp: FirestoreSerp = {
  createdAt: admin.firestore.Timestamp.fromDate(new Date(datetime)), // <-- ERROR HERE
  keyword: 'rickety cricket',
};

>Solution :

The client SDK (firebase/firestore) uses slightly different type definitions to the admin SDK (firebase-admin) and that is what is causing your conflict.

Use the same package to extract the types.

import * as admin from 'firebase-admin';

interface FirestoreSerp {
  createdAt: admin.firebase.Timestamp;
  keyword: string;
}

const datetime = '2019-11-15 12:57:46 +00:00'
const firestoreSerp: FirestoreSerp = {
  createdAt: admin.firestore.Timestamp.fromDate(new Date(datetime)),
  keyword: 'rickety cricket',
};

To alias the type:

type Timestamp = admin.firestore.Timestamp;