必须正确处理承诺错误

Question

I am trying to write this timer based function. Once a week, it should run and create almost duplicates of existing documents. Every time I try to launch it, I keep getting the "Promises must be handled appropriately" error, but I can't understand what it is that I am doing wrong? There's a return at any stage possible. Where is there a promises which I don't satisfy?

I've previously launched about 40 cloud functions, so I do have some understanding of how promises work, but I'm obviously missing something here, and for the life of me, I can't understand what it is.

This is the function:

exports.createRecurringDeals = functions.pubsub.schedule('0 0 * * 7').timeZone('Asia/Jerusalem').onRun((context) => {
    db.collection('recurring_deals').get().then(querySnapshot => {

        querySnapshot.forEach(bus => {
            const businessListDoc = bus.data();

            if (businessListDoc !== undefined) {
                const dealsList = businessListDoc.list as Array<String>

                return db.doc('businesses/' + bus.id).get().then(busDoc => {

                    const business = busDoc.data();

                    if (business !== undefined) {

                        dealsList.forEach(deal => {
                            return db.doc('deals/' + deal).get().then(snapshot => {
                                const oldDeal = snapshot.data();
                                if (oldDeal !== undefined) {

                                    const promises: any = [];

                                    const startTime = oldDeal.startTime + oldDeal.interval;
                                    const endTime = oldDeal.endTime + oldDeal.interval;

                                    const newDealDoc = db.collection('deals').doc();

                                    const newDeal = {
                                        id: newDealDoc.id,
                                        business_ID: business.id,
                                        business_name: business.name,
                                        business_address_text: business.address_text,
                                        business_address_lat: business.address_lat,
                                        business_address_long: business.address_long,
                                        business_phone_number: business.phone_number,
                                        business_image: business.restaurant_photos[0],
                                        business_categories: business.categories,
                                        business_sub_categories: business.sub_categories,
                                        discount: oldDeal.discount,
                                        timestamp_start: startTime,
                                        timestamp_end: endTime,
                                        gmt: oldDeal.gmt,
                                        amount: oldDeal.amount,
                                        claimers: [],
                                        active: true
                                    };

                                    promises.push(newDealDoc.set(newDeal));

                                    promises.push(db.doc('recurring_deals/' + business.id).update({ list: FieldValue.arrayRemove(oldDeal.id) }));

                                    promises.push(db.doc('recurring_deals/' + business.id).update({ list: FieldValue.arrayUnion(newDeal.id) }));

                                    return Promise.all(promises);

                                } else {
                                    return null;
                                };
                            });
                        });
                        return null;
                    } else {
                        return null;
                    };
                });
            } else {
                return null;
            };
        });
        return null;
    });
});

Answer 1

I'm guessing that it wants you to add a .catch() clause after the .then in case the Promise fails for whatever reason. So for example, try changing

return db.doc('deals/' + deal).get().then(snapshot => {
    ...
});

to

return db.doc('deals/' + deal).get().then(snapshot => {
    ...
}).catch(err => console.log(err));

Answer 2

lets start with the notion that every promise has to be handled- either by .catch or .then . So the first thing you're missing is a handler for the Promise.all() call you have near the end.

Furthermore, in the latest versions of JS, you have to place a catch block after a pomise to handle rejection, even if it does nothing and even if you have a .then . Here you're missing .catch both for the main promise on top ( db.collection('recurring_deals').get() ), and for the promise.all() call.

Add those and the error should disappear.