Trouble with js promises (bluebird)

Question

I'm trying to create merge fields in MailChimp from a list if they don't already exist. If they don't exist, I want them to be pushed to a list of promises, where I use promises.all to make sure that all the necessary list items have been added.

This isn't working though. What am I doing wrong?

var productDict = []

var getMergeNumPromise = new Promise( 
    function(resolve, reject) {
        // call to mailchimp to get the number of merge fields
        rp({
            uri: MAILCHIMP_MERGEFIELDS_URI, 
            qs:{count:1}, 
            json:true, 
            headers:MAILCHIMP_HEADER
        })
        .then(function( mergeFieldList ) {
            console.log("total items: " + mergeFieldList.total_items)
            resolve(mergeFieldList.total_items)
        })
        .catch(function(err) {
            console.log("error getting merge field count: " + err)
            reject(err)
        })
    }
)

var getMergeFieldsPromise = new Promise( 
    function( resolve, reject ) {
        getMergeNumPromise.then(function( total, err ){
            //gets just the name and tag for all merge fields in the list
            rp({
                uri: MAILCHIMP_MERGEFIELDS_URI, 
                qs:{
                    count: total,
                    fields: "merge_fields.tag,merge_fields.name"
                },
                headers: MAILCHIMP_HEADER
            })
            .then(function( fullFieldList ) {
                console.log("FULL FIELD BODY" + fullFieldList)
                var body = JSON.parse(fullFieldList)
                resolve(body.merge_fields)
            })
            .catch(function(err){
                console.log("error getting fields: " + err)
                reject(err)
            })
        })
    }
)

function addMergeField (prodName , dictPos) {
    return new Promise (
        function(resolve, reject) {
            fieldBody = { name : prodName , type : "number"}

            //post request to make the new merge field
            rp({
                method: "POST", 
                uri: MAILCHIMP_MERGEFIELDS_URI, 
                json: true, 
                headers: MAILCHIMP_HEADER, 
                body: fieldBody
            })
            .then(function(body) {
                //update product dictionary
                productDict[dictPos] = {tag : body.tag, name : body.name}
                console.log("MERGE FIELD RESPONSE " + JSON.stringify(body))
                resolve(body)
            })
           .catch(function(err) {
                console.log("error creating merge field for product id: " + err)
                reject(err)
            })
        }
    )
}

var updateMergeFields = getMergeFieldsPromise.then( 
    function( mergeFieldList ) {
        // resolved ids keeps track of ids that have already been added
        var resolvedIDS = {}
        //holds result of find to look for product ids
        var foundMCMatch
        // holds productIDS[i]
        var product
        //console.log("merge field list" + JSON.stringify(mergeFieldList))

        for(var i = 0; i < productIDS.length; i++) {
            console.log("checking if product id " + productIDS[i] + "exists")
            product = productIDS[i]
            // tries to find a match to see if fields are already in mailchimp
            foundMCMATCH = mergeFieldList.find(x => x.name == product)

            if(foundMCMATCH) {
                console.log("foundMCMATCH" + JSON.stringify(foundMCMATCH))

                //updates product dict with matching tag/name from mailchimp
                productDict[i] = {
                    tag : foundMCMATCH.tag, 
                    name : foundMCMATCH.name
                }
                //console.log("PRODUCT DICT " + JSON.stringify(productDict))
            }

            //if field isn't on mailchimp
            else if (!resolvedIDS[product])
            {
                resolvedIDS[product] = true

                // adds product id as merge field becasue it doesn't exist
                allProductIDPromises.push(
                    addMergeField(product,i)
                )
            }
        }
    }
)

allProductIDPromises.push( getMergeFieldsPromise, getMergeNumPromise, updateMergeFields ) 
Promise.all(allProductIDPromises) 
.then(function() { 
    //function here that's running out of order
}

NB: I'm using request promise to make my post requests, so they are already promisified.

Answer 1

The then callback of getMergeFieldsPromise is not returning anything, so once getMergeFieldsPromise is resolved, it does not await the addMergeField promises, but instead resolves immediately (with undefined as promised value).

To solve this, make allProductIDPromises a local variable inside the then callback and call Promise.all on it, and return it there:

var updateMergeFields = getMergeFieldsPromise.then( 
    function( mergeFieldList ) {
        // **** make the array of promises local to this function
        var allProductIDPromises = [];
        // resolved ids keeps track of ids that have already been added
        var resolvedIDS = {}
        //holds result of find to look for product ids
        var foundMCMatch
        // holds productIDS[i]
        var product
        //console.log("merge field list" + JSON.stringify(mergeFieldList))

        for(var i = 0; i < productIDS.length; i++) {
            console.log("checking if product id " + productIDS[i] + "exists")
            product = productIDS[i]
            // tries to find a match to see if fields are already in mailchimp
            foundMCMATCH = mergeFieldList.find(x => x.name == product)

            if(foundMCMATCH) {
                console.log("foundMCMATCH" + JSON.stringify(foundMCMATCH))

                //updates product dict with matching tag/name from mailchimp
                productDict[i] = {
                    tag : foundMCMATCH.tag, 
                    name : foundMCMATCH.name
                }
                //console.log("PRODUCT DICT " + JSON.stringify(productDict))
            }

            //if field isn't on mailchimp
            else if (!resolvedIDS[product])
            {
                resolvedIDS[product] = true

                // adds product id as merge field becasue it doesn't exist
                allProductIDPromises.push(
                    addMergeField(product,i)
                )
            }
        }
        // **** call Promise.all here, and return it
        return Promise.all(allProductIDPromises);
    }
)

Then after that, you should remove this:

allProductIDPromises.push( ... )

... and since your main three promises are already chained with then, you only need to perform a then on the last one:

updateMergeFields.then(function(addedMergeFields) { 
    // ... all is ready now.
}

Finally, read about the Promise constructor anti-pattern, which you are using several times: you should not use new Promise when in fact you can return a promise (e.g. return rp()).