[RUM-16486] Diff account, context, featureFlags, and usr in RUMViewUpdateEvent

Author: maxep

DatadogRUM/Sources/RUMMonitor/Scopes/RUMViewEvent+Update.swift

@@ -17,24 +17,22 @@ extension RUMViewEvent {
     /// - Fields equal between `self` and `event` are set to `nil` (meaning "unchanged").
     ///   `self.dd.documentVersion` is incremented by one.
     ///
-    /// Fields containing `[String: Encodable]` (account, context, featureFlags, usr)
-    /// cannot be cheaply compared and are always forwarded from `event`.
     func update(from event: RUMViewEvent) -> RUMViewUpdateEvent {
         RUMViewUpdateEvent(
             dd: .init(documentVersion: dd.documentVersion + 1, from: event.dd),
-            account: event.account,
+            account: diff(account, event.account),
             application: .init(event.application),
             buildId: diff(buildId, event.buildId),
             buildVersion: diff(buildVersion, event.buildVersion),
             ciTest: diff(ciTest, event.ciTest),
             connectivity: diff(connectivity, event.connectivity),
             container: diffMap(container, event.container, RUMViewUpdateEvent.Container.init),
-            context: event.context,
+            context: diff(context, event.context),
             date: event.date,
             ddtags: diff(ddtags, event.ddtags),
             device: diff(device, event.device),
             display: diffMap(display, event.display, RUMViewUpdateEvent.Display.init),
-            featureFlags: event.featureFlags.map { .init($0) },
+            featureFlags: diffMap(featureFlags, event.featureFlags, RUMViewUpdateEvent.FeatureFlags.init),
             os: diff(os, event.os),
             privacy: diffMap(privacy, event.privacy, RUMViewUpdateEvent.Privacy.init),
             service: diff(service, event.service),
@@ -43,7 +41,7 @@ extension RUMViewEvent {
             stream: diffMap(stream, event.stream, RUMViewUpdateEvent.Stream.init),
             synthetics: diff(synthetics, event.synthetics),
             tab: diffMap(tab, event.tab, RUMViewUpdateEvent.TAB.init),
-            usr: event.usr,
+            usr: diff(usr, event.usr),
             version: diff(version, event.version),
             view: .init(old: view, new: event.view)
         )

DatadogRUM/Tests/RUMMonitor/Scopes/RUMViewScope_Tests.swift

@@ -109,7 +109,7 @@ class RUMViewScope_Tests: XCTestCase {
         DDTAssertValidRUMUUID(update.view.id)
         XCTAssertEqual(update.view.url, "UIViewController")
         XCTAssertEqual(update.dd.documentVersion, 2)
-        XCTAssertEqual(update.context?.contextInfo as? [String: String], ["foo": "bar"])
+        XCTAssertNil(update.context)  // context unchanged between full event and stop → diffed to nil
 
         // Delta fields that changed.
         XCTAssertFalse(try XCTUnwrap(update.view.isActive))
@@ -264,12 +264,13 @@ class RUMViewScope_Tests: XCTestCase {
             "The command should be ignored."
         )
 
-        // context is always forwarded in update events — attributes must be the initial ones.
+        // Full view events always carry context.
         writer.events(ofType: RUMViewEvent.self).forEach {
             XCTAssertEqual($0.context?.contextInfo as? [String: String], initialAttributes)
         }
+        // Update events diff context — unchanged between full event and stop → nil.
         writer.events(ofType: RUMViewUpdateEvent.self).forEach {
-            XCTAssertEqual($0.context?.contextInfo as? [String: String], initialAttributes)
+            XCTAssertNil($0.context)
         }
     }