Fix interaction start/end time being wrong on spa payloads of 3+ inte…

…ractions

src/features/soft_navigations/aggregate/index.js

@@ -70,11 +70,11 @@ export class Aggregate extends AggregateBase {
   serializer (eventBuffer) {
     // The payload depacker takes the first ixn of a payload (if there are multiple ixns) and positively offset the subsequent ixns timestamps by that amount.
     // In order to accurately portray the real start & end times of the 2nd & onward ixns, we hence need to negatively offset their start timestamps with that of the 1st ixn.
-    let firstIxnStartTime = 0 // the very 1st ixn does not require any offsetting
+    let firstIxnStartTime
     const serializedIxnList = []
     for (const interaction of eventBuffer) {
       serializedIxnList.push(interaction.serialize(firstIxnStartTime))
-      if (!firstIxnStartTime) firstIxnStartTime = Math.floor(interaction.start)
+      if (firstIxnStartTime === undefined) firstIxnStartTime = Math.floor(interaction.start) // careful not to match or overwrite on 0 value!
     }
     return `bel.7;${serializedIxnList.join(';')}`
   }

src/features/soft_navigations/aggregate/interaction.js

@@ -115,6 +115,7 @@ export class Interaction extends BelNode {
   get navTiming () {}
 
   serialize (firstStartTimeOfPayload) {
+    const isFirstIxnOfPayload = firstStartTimeOfPayload === undefined
     const addString = getAddStringContext(this.agentIdentifier)
     const nodeList = []
     let ixnType
@@ -126,7 +127,7 @@ export class Interaction extends BelNode {
     const fields = [
       numeric(this.belType),
       0, // this will be overwritten below with number of attached nodes
-      numeric(this.start - firstStartTimeOfPayload), // relative to first node
+      numeric(this.start - (isFirstIxnOfPayload ? 0 : firstStartTimeOfPayload)), // the very 1st ixn does not require offset so it should fallback to a 0 while rest is offset by the very 1st ixn's start
       numeric(this.end - this.start), // end -- relative to start
       numeric(this.callbackEnd), // cbEnd -- relative to start; not used by BrowserInteraction events
       numeric(this.callbackDuration), // not relative
@@ -145,9 +146,9 @@ export class Interaction extends BelNode {
     const allAttachedNodes = addCustomAttributes(this.customAttributes || {}, addString) // start with all custom attributes
     if (getInfo(this.agentIdentifier).atts) allAttachedNodes.push('a,' + addString(getInfo(this.agentIdentifier).atts)) // add apm provided attributes
     /* Querypack encoder+decoder quirkiness:
-       - If first ixn node of payload is being processed, we use this node's start to offset. (firstStartTime should be 0--or undefined.)
-       - Else for subsequent ixn nodes, we use the first ixn node's start to offset. */
-    this.children.forEach(node => allAttachedNodes.push(node.serialize(firstStartTimeOfPayload || this.start))) // recursively add the serialized string of every child of this (ixn) bel node
+       - If first ixn node of payload is being processed, its children's start time must be offset by this node's start. (firstStartTime should be undefined.)
+       - Else for subsequent ixns in the same payload, we go back to using that first ixn node's start to offset their children's start. */
+    this.children.forEach(node => allAttachedNodes.push(node.serialize(isFirstIxnOfPayload ? this.start : firstStartTimeOfPayload))) // recursively add the serialized string of every child of this (ixn) bel node
 
     fields[1] = numeric(allAttachedNodes.length)
     nodeList.push(fields)

tests/components/soft_navigations/api.test.js

@@ -267,7 +267,7 @@ test('.actionText and .setAttribute add attributes to ixn specifically', () => {
 
 // This isn't just an API test; it double serves as data validation on the querypack payload output.
 test('multiple finished ixns retain the correct start/end timestamps in payload', () => {
-  softNavAggregate.ee.emit(`${INTERACTION_API}-get`, [100])
+  softNavAggregate.ee.emit(`${INTERACTION_API}-get`, [0])
   let ixnContext = getIxnContext(newrelic.interaction())
   ixnContext.associatedInteraction.nodeId = 1
   ixnContext.associatedInteraction.id = 'some_id'
@@ -290,7 +290,7 @@ test('multiple finished ixns retain the correct start/end timestamps in payload'
 
   expect(softNavAggregate.interactionsToHarvest.get().length).toEqual(3)
   // WARN: Double check decoded output & behavior or any introduced bugs before changing the follow line's static string.
-  expect(softNavAggregate.makeHarvestPayload().body).toEqual("bel.7;1,,2s,2s,,,'api,'http://localhost/,1,1,,2,!!!!'some_id,'1,!!;;1,,5k,5k,,,'api,'http://localhost/,1,1,,2,!!!!'some_other_id,'2,!!;;1,,go,8c,,,'api,'http://localhost/,1,1,,2,!!!!'some_another_id,'3,!!;")
+  expect(softNavAggregate.makeHarvestPayload().body).toEqual("bel.7;1,,,5k,,,'api,'http://localhost/,1,1,,2,!!!!'some_id,'1,!!;;1,,8c,5k,,,'api,'http://localhost/,1,1,,2,!!!!'some_other_id,'2,!!;;1,,jg,8c,,,'api,'http://localhost/,1,1,,2,!!!!'some_another_id,'3,!!;")
 })
 
 // This isn't just an API test; it double serves as data validation on the querypack payload output.