Bug 2045853 - Trigger postEnrolmentCalculation() on all enrollment changes

`postEnrolmentCalculation()` is responsible for recording the active
experiments and triggering the `onUpdatesApplied` observer -- which is
in turn used to invalidate the FML feature cache. Several enrolment
change mechanisms were not properly triggering `onUpdatesApplied`, which
has lead to stale feature value caching issues (see-also
mozilla-mobile/fenix#21838). These issues have
been band-aided by calling applyPendingExperiments() in most cases,
which results in ~correct behaviour but does a double update.

Now we trigger `postEnrolmentCalculation()` and therefore feature
invalidation on all enrollment changes.

Author: freshstrangemusic

components/nimbus/android/src/main/java/org/mozilla/experiments/nimbus/Nimbus.kt

@@ -165,7 +165,7 @@ open class Nimbus(
         get() = nimbusClient.getExperimentParticipation()
         set(active) {
             dbScope.launch {
-                nimbusClient.setExperimentParticipation(active)
+                setExperimentParticipationOnThisThread(active)
                 applyPendingExperimentsOnThisThread()
             }
         }
@@ -174,7 +174,7 @@ open class Nimbus(
         get() = nimbusClient.getRolloutParticipation()
         set(active) {
             dbScope.launch {
-                nimbusClient.setRolloutParticipation(active)
+                setRolloutParticipationOnThisThread(active)
                 applyPendingExperimentsOnThisThread()
             }
         }
@@ -458,9 +458,7 @@ open class Nimbus(
         prefUnenrollReason: PrefUnenrollReason,
     ) {
         dbScope.launch {
-            withCatchAll("unenrollForGeckoPref") {
-                unenrollForGeckoPrefOnThisThread(geckoPrefState, prefUnenrollReason)
-            }
+            unenrollForGeckoPrefOnThisThread(geckoPrefState, prefUnenrollReason)
         }
     }
 
@@ -469,10 +467,13 @@ open class Nimbus(
     internal fun unenrollForGeckoPrefOnThisThread(
         geckoPrefState: GeckoPrefState,
         prefUnenrollReason: PrefUnenrollReason,
-    ): List<EnrollmentChangeEvent> {
-        val events = nimbusClient.unenrollForGeckoPref(geckoPrefState, prefUnenrollReason)
-        recordExperimentTelemetryEvents(events)
-        return events
+    ): List<EnrollmentChangeEvent>? {
+        return withCatchAll("unenrollForGeckoPref") {
+            val enrollmentChangeEvents = nimbusClient.unenrollForGeckoPref(geckoPrefState, prefUnenrollReason)
+            recordExperimentTelemetryEvents(enrollmentChangeEvents)
+            postEnrolmentCalculation()
+            enrollmentChangeEvents
+        }
     }
 
     override fun registerPreviousGeckoPrefStates(geckoPrefStates: List<GeckoPrefState>) {
@@ -491,25 +492,42 @@ open class Nimbus(
 
     @WorkerThread
     @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
-    internal fun optOutOnThisThread(experimentId: String) = withCatchAll("optOut") {
-        nimbusClient.optOut(experimentId).also(::recordExperimentTelemetryEvents)
+    internal fun optOutOnThisThread(experimentId: String) {
+        withCatchAll("optOut") {
+            nimbusClient.optOut(experimentId).also(::recordExperimentTelemetryEvents)
+            postEnrolmentCalculation()
+        }
     }
 
+    @AnyThread
     override fun resetTelemetryIdentifiers() {
         dbScope.launch {
-            withCatchAll("resetTelemetryIdentifiers") {
-                nimbusClient.resetTelemetryIdentifiers().also { enrollmentChangeEvents ->
-                    recordExperimentTelemetryEvents(enrollmentChangeEvents)
-                }
-            }
+            resetTelemetryIdentifiersOnThisThread()
+        }
+    }
+
+    @WorkerThread
+    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
+    internal fun resetTelemetryIdentifiersOnThisThread() {
+        withCatchAll("resetTelemetryIdentifiers") {
+            val enrollmentChangeEvents = nimbusClient.resetTelemetryIdentifiers()
+            recordExperimentTelemetryEvents(enrollmentChangeEvents)
+            postEnrolmentCalculation()
         }
     }
 
     override fun optInWithBranch(experimentId: String, branch: String) {
         dbScope.launch {
-            withCatchAll("optIn") {
-                nimbusClient.optInWithBranch(experimentId, branch).also(::recordExperimentTelemetryEvents)
-            }
+            optInWithBranchOnThisThread(experimentId, branch)
+        }
+    }
+
+    @WorkerThread
+    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
+    internal fun optInWithBranchOnThisThread(experimentId: String, branch: String) {
+        withCatchAll("optIn") {
+            nimbusClient.optInWithBranch(experimentId, branch).also(::recordExperimentTelemetryEvents)
+            postEnrolmentCalculation()
         }
     }
 

components/nimbus/android/src/test/java/org/mozilla/experiments/nimbus/NimbusTests.kt

@@ -942,7 +942,8 @@ class NimbusTests {
             PrefUnenrollReason.FAILED_TO_SET,
         )
 
-        assertEquals(1, events.size)
+        assertNotNull(events)
+        assertEquals(1, events!!.size)
         assertEquals(EnrollmentChangeEventType.DISQUALIFICATION, events[0].change)
         assertEquals(0, handler.setValues?.size)
     }