What is the version 9 equivalent of this in firebase?

Question

Im trying to convert my version 8 working code to version 9 but I cant figure out why im getting the error: 'FirebaseError: Expected type 'Query', but it was: a custom DocumentReference object'. It seems not like messagesRes but I put in a query and I think im correctly getting the subcollection.

version 8: working
 export async function getServerSideProps(context) {
   const chatRef = db.collection('chats').doc(context.query.id);

   const messagesRes = await chatRef
     .collection('messages')
     .orderBy('timestamp', 'asc')
     .get();

   const messages = messagesRes.docs
    .map(doc => ({
       id: doc.id,
       ...doc.data(),
    }))
       .map(messages => ({
       ...messages,
       timestamp: messages.timestamp.toDate().getTime(),
     }));

   const chatRes = await chatRef.get();

   const chat = {
     id: chatRes.id,
     ...chatRes.data(),
   };

   return {
     props: {
       messages: JSON.stringify(messages),
       chat,
     },
   };
 }
version 9: 
export async function getServerSideProps(context) {
  const chatRef = doc(db, 'chats', context.query.id);

  const messagesRes = await getDocs(
    query(collection(chatRef, 'messages'), orderBy('timestamp', 'asc'))
  );

  const messages = messagesRes.docs
    .map(doc => ({
      id: doc.id,
      ...doc.data(),
    }))
    .map(messages => ({
      ...messages,
      timestamp: messages.timestamp.toDate().getTime(),
    }));

  const chatRes = await getDocs(chatRef);

  const chat = {
    id: chatRes.id,
    ...chatRes.data(),
  };

  return {
    props: {
      messages: JSON.stringify(messages),
      chat,
    },
  };
}

Answer 1

According to the API documentation:

export declare function getDocs<T>(query: Query<T>): Promise<QuerySnapshot<T>>;

And in your code you are doing:

const chatRes = await getDocs(chatRef);

That is why you are seeing the error:

'FirebaseError: Expected type 'Query', but it was: a custom DocumentReference object'.

because you are passing in your document reference and not a query.

Like you did here:

const messagesRes = await getDocs(
    query(collection(chatRef, 'messages'), orderBy('timestamp', 'asc'))
  );

You can see the correct usage of the API here.