I'm working on an interview project for which I have to add an endpoint that lets me POST an array of products (listings) and it should create them (MongoDB Mongoose) or update them accordingly. The problem is I'm clearly not dealing with Promises properly and I'm getting a timeout on my test. Here's the spec:

    it.only('should create listings or update them if they already exist, incrementing the quantity with the difference '  
      'between the current sold_quantity and the initial_sold_quantity', (done) => {
      var iPhone = { ... };
      var samsung = { ... };
      request(app).post('/listings/myEndpoint').send([iPhone, samsung]).expect(200, {
        created: 1,
        updated: 1
      }, done);
    });

exports.myEndpoint = (req, res) => {
  var listings = req.body;
  var created, updated = 0;

  listings.forEach(reqListing => {
    Listing.findOne({ listing_id: reqListing.listing_id })
      .then(foundListing => {
        if (!foundListing) {
          var newListing = reqListing;
          newListing.initial_sold_quantity = newListing.sold_quantity;
          Listing.create(newListing);
          created  ;
        } else {
          var newQuantity = reqListing.sold_quantity - foundListing._doc.initial_sold_quantity;
          if (foundListing._doc.quantity != newQuantity) {
            foundListing._doc.quantity = newQuantity;
            foundListing.save();
            updated  ;
          }
        }
      });
      return {
        created: created,
        updated: updated
      };
  });
};

THINGS I'VE TRIED:

1. Giving it more time. I tried changing the default timeout for Mocha tests but it doesn't really matter if it's 2 seconds or 20, it'll still timeout.

2. Isolating the update vs the creation. Really doesn't matter either if I'm only updating a product or if I'm only creating one, it'll still timeout.

3. Removing the logic. As far as I've checked it doesn't really matter what happens inside the if/else blocks because it'll still give me a timeout. So even if the code looks like this:

exports.myEndpoint = (req, res) => {
  var listings = req.body;
  var created, updated = 0;

  listings.forEach(reqListing => {
    Listing.findOne({ listing_id: reqListing.listing_id })
      .then(foundListing => {
        if (!foundListing) {
          console.log("creating");
        } else {
          console.log("updating");
        }
      });
      return {
        created: created,
        updated: updated
      };
  });
};

it'll still timeout.

CodePudding user response：

After asking some questions in the Nodeiflux Discord server I managed to find a solution, maybe not the prettiest because it doesn't make use of async/await but I'm not supposed to change the style of the project too much so I'll leave it without async/await.

First, the silly problem which came after fixing the post's question:

var created = 0, updated = 0;

instead of not initializing created.

Second, making use of forEach with Promises inside didn't make too much sense because it would discard whatever was returning inside so I put the return outside the forEach clause and changed the forEach iteration for a map instead. I also made use of Promise.all() to get all promises to resolve before returning:

exports.upsert = (req, res) => {
  var listings = req.body;
  var created = 0, updated = 0;
  var allowedArrayLength = 50;
  return Promise.all(listings.map(reqListing =>
    Listing.findOne({
        listing_id: reqListing.listing_id
      })
      .then(foundListing => {
        if (!foundListing) {
          createListing(reqListing);
          created  ;
        } else {
          var prevQuantity = foundListing.quantity;
          if (updateListing(reqListing, foundListing).quantity > prevQuantity) {
            updated  ;
          }
        }
      })
  )).then(() => ({ created: created, updated: updated }));
};