Make user.ext.prebid.buyeruids bidder name case insensitive

[Sonali-More-Xandr]

We need to handle case insensitivity for user.ext.prebid.buyeruids biddernames. This PR updates the biddername look up to use the normalized names for buyeruids.BIDDER.

partially resolves #2400

[Sonali-More-Xandr]

@bsardo We need this PR to go out with PBS 2.0. Can you please help me understand me why this PR is marked blocked and if there is something pending from my side

[bsardo]

Hi @Sonali-More-Xandr. We originally blocked this because we thought it conflicted with #3107 and we wanted to see that merged first, but on second look it appears that was a mistake so I'll remove the label.

[gargcreation1992]

I see that you have two test case files that you added for this PR. Would it mean that it also needs to be added in this function?

[Sonali-More-Xandr]

Good catch! Added it in 07427d6

[gargcreation1992]

Also add a test case for the request that has an alias in the request.ext.prebid.aliases field.

[Sonali-More-Xandr]

Added in b43a4cf

[VeronikaSolovei9]

Nitpick: in this PR here https://github.com/prebid/prebid-server/pull/3187/files#diff-785f5ab5ebde657757f3b3c34bf30a939782678d61bf1ea43f844c4f22a012d9R155:~:text=normalizeBidderName%20%20%20%20%20%20%20normalizeBidderName @SyntaxNode introduced a new function in endpoint deps.
This validation function already has deps. Could you please pull latest changes from main branch and call normalize bidder name through the normalizedCoreBidder, _ := deps.normalizeBidderName(bidderName). With this change code will be more consistent.

Other than this looks good, local testing looks good too.

[Sonali-More-Xandr]

Thank you, Veronika! Updated it in 49a8d0e

[VeronikaSolovei9]

Sonali, thank you for your updates!
I want to apologize. At the moment I tested your PR at the first time, I misunderstood how this should work.
(I did the same mistake for my StoredBidResponses PR and had to fix it... )

Here is a desired behavior.
Let's say we have a request with one imp. In the imp.ext we have this config:

"ext": {
                        "prebid": {
                            "bidder": {
                                "APPnexus": {
                                    "placementId": 1
                                },
                                "appNEXUS": {
                                    "placementId": 2
                                },
                                "amx": {}
                            }
                        }
                    }

We also have this config in user.ext.prebid.buyerids:

"user": {
                "id": "userId",
                "ext": {
                    "prebid": {
                        "buyeruids": {
                            "APPnexUS": "12345"
                        }
                    }
                }
            }

in this case "buyeruids": {"APPnexUS": "12345"} should be applied to both "APPnexus" and "appNEXUS", because we need to support case-insesitive comparisons, not case sensitive as it is now.
My mistake was to check that user.ext.prebid."buyeruids": { "APPnexus": "12345" } will be only applied to "APPnexus". This is not right, it should be applied to any "appnexus" in imp.ext.

In order to fix this, add next change on top of existing ones in this PR: utils.go -> func prepareUser should be changed to this:

func prepareUser(req *openrtb2.BidRequest, givenBidder, syncerKey string, explicitBuyerUIDs map[string]string, usersyncs IdFetcher) bool {
	cookieId, hadCookie, _ := usersyncs.GetUID(syncerKey)

	buyerIdSet := false
	for bidderName, id := range explicitBuyerUIDs {
		if strings.EqualFold(bidderName, givenBidder) {
			req.User = copyWithBuyerUID(req.User, id)
			buyerIdSet = true
                         break 
		}
	}
	if !buyerIdSet && hadCookie {
		req.User = copyWithBuyerUID(req.User, cookieId)
	}

	return hadCookie
}

Also I would like you to add a test that explicitly tests what data goes to what bidder. Put this test in exchange/exchangetest/ directory. This test has 3 bidders in imp.ext. 2 of them are "apnexus" in different casing and one amx. It also has a req.user.ext.prebid.buyerids{"APPnexUS": "12345"}.
In outgoingRequests there are 3 requests we expect to be executed: APPnexus, appNEXUS and amx. Only APPnexus and appNEXUS will receive user.buyeruid: "12345" -> test_buyerids.json

[onkarvhanumante]

master code

func prepareUser(req *openrtb2.BidRequest, givenBidder, syncerKey string, explicitBuyerUIDs map[string]string, usersyncs IdFetcher) bool {
  cookieId, hadCookie, _ := usersyncs.GetUID(syncerKey)

  if id, ok := explicitBuyerUIDs[givenBidder]; ok {
  	req.User = copyWithBuyerUID(req.User, id)
  } else if hadCookie {
  	req.User = copyWithBuyerUID(req.User, cookieId)
  }

  return hadCookie
}

suggested code #3152 (comment)

func prepareUser(req *openrtb2.BidRequest, givenBidder, syncerKey string, explicitBuyerUIDs map[string]string, usersyncs IdFetcher) bool {
	cookieId, hadCookie, _ := usersyncs.GetUID(syncerKey)

	buyerIdSet := false
	for bidderName, id := range explicitBuyerUIDs {
		if strings.EqualFold(bidderName, givenBidder) {
			req.User = copyWithBuyerUID(req.User, id)
			buyerIdSet = true
                         break 
		}
	}
	if !buyerIdSet && hadCookie {
		req.User = copyWithBuyerUID(req.User, cookieId)
	}

	return hadCookie
}

Thanks @VeronikaSolovei9 for above suggestion. But something to note is this will change increase time complexity of prepareUser(). Also prepareUser() is called within the loop.

prebid-server/exchange/utils.go

Lines 331 to 364 in 1944dbb

	for bidder, imps := range impsByBidder {
	coreBidder := resolveBidder(bidder, aliases)
	reqCopy := *req.BidRequest
	reqCopy.Imp = imps
	sChainWriter.Write(&reqCopy, bidder)
	reqCopy.Ext, err = buildRequestExtForBidder(bidder, req.BidRequest.Ext, requestExt, bidderParamsInReqExt, auctionRequest.Account.AlternateBidderCodes)
	if err != nil {
	return nil, []error{err}
	}
	if err := removeUnpermissionedEids(&reqCopy, bidder, requestExt); err != nil {
	errs = append(errs, fmt.Errorf("unable to enforce request.ext.prebid.data.eidpermissions because %v", err))
	continue
	}
	bidderRequest := BidderRequest{
	BidderName: openrtb_ext.BidderName(bidder),
	BidderCoreName: coreBidder,
	BidRequest: &reqCopy,
	BidderLabels: metrics.AdapterLabels{
	Source: auctionRequest.LegacyLabels.Source,
	RType: auctionRequest.LegacyLabels.RType,
	Adapter: coreBidder,
	PubID: auctionRequest.LegacyLabels.PubID,
	CookieFlag: auctionRequest.LegacyLabels.CookieFlag,
	AdapterBids: metrics.AdapterBidPresent,
	},
	}
	syncerKey := bidderToSyncerKey[string(coreBidder)]
	if hadSync := prepareUser(&reqCopy, bidder, syncerKey, explicitBuyerUIDs, auctionRequest.UserSyncs); !hadSync && req.BidRequest.App == nil {

How about preparing lowercase key map from explicitBuyerUIDs outside impsByBidder loop and could lookup using strings.ToLower() in prepareUser(). Preparing lowercase key map will incur less complexity.

lowerCaseExplicitBuyerUIDs = ... code to have lower case bidder name keys from explicitBuyerUIDs map

 for bidder, imps := range impsByBidder { 
 	coreBidder := resolveBidder(bidder, aliases) 
  
 	reqCopy := *req.BidRequest 
 	reqCopy.Imp = imps 
  
 	sChainWriter.Write(&reqCopy, bidder) 
        ...
        if hadSync := prepareUser(&reqCopy, bidder, syncerKey, explicitBuyerUIDs, auctionRequest.UserSyncs); !hadSync && req.BidRequest.App == nil { 
...

func prepareUser(req *openrtb2.BidRequest, givenBidder, syncerKey string, lowerCaseExplicitBuyerUIDs map[string]string, usersyncs IdFetcher) bool {
	cookieId, hadCookie, _ := usersyncs.GetUID(syncerKey)

	if id, ok := lowerCaseExplicitBuyerUIDs [strings.ToLower(givenBidder)]; ok {
		req.User = copyWithBuyerUID(req.User, id)
	} else if hadCookie {
		req.User = copyWithBuyerUID(req.User, cookieId)
	}

	return hadCookie
}

[VeronikaSolovei9]

Sure, if this gives the same result! As long as attached test passes and data is returned as expected.