firebase_cloud_functions_recursive_delete.ts

const deepDeleteDoc = async (store: admin.firestore.Firestore, docPath: string, batchSize: number): Promise<any> => {
    const doc = store.doc(docPath);
    const snap = await doc.get();
    if (!snap.exists) return;
    console.log('Found doc - ' + docPath);
    // Check if this doc has subcollections
    const subCollections = await snap.ref.listCollections();
    const promises: Promise<void>[] = [];
    if (subCollections) {
        for (const subCollection of subCollections) {
            console.log('Found sub collection - ' + subCollection.path);
            const subQuery = subCollection.limit(batchSize);
            // Delete all sub collection docs
            promises.push(deleteQueryBatch(store, subQuery, batchSize));
        }
    }
    await Promise.all(promises);
    console.log('All collections are done for doc and now deleting it - ' + docPath);
    return doc.delete();
}

const deepDeleteCollection = (store: admin.firestore.Firestore, collectionPath: string, batchSize: number): Promise<any> => {
    const collection = store.collection(collectionPath);
    const query = collection.limit(batchSize);
    return deleteQueryBatch(store, query, batchSize);
}

const deleteQueryBatch = async (store: admin.firestore.Firestore, query: admin.firestore.Query, batchSize: number): Promise<any> => {
    const snaps = await query.get();
    // When there are no documents left, we are done
    if (snaps.size === 0) {
        return;
    }
    const promises1: Promise<any>[] = [];
    for (const doc of snaps.docs) {
        // Check if this doc has subcollections
        const subCollections = await doc.ref.listCollections();
        const promises2: Promise<void>[] = [];
        if (subCollections) {
            for (const subCollection of subCollections) {
                console.log('Found sub collection - ' + subCollection.path);
                const subQuery = subCollection.limit(batchSize);
                // Delete all sub collection docs
                promises2.push(deleteQueryBatch(store, subQuery, batchSize));
            }
        }
        await Promise.all(promises2);
        // And delete the document only if all subcollections deleted succesfully
        console.log('All collections are done for doc and now deleting it - ' + doc.ref.path);
        promises1.push(doc.ref.delete());
    }
    return Promise.all(promises1);
}