feat: Adds support for client-side prerequisite events

contract-tests/src/main/java/com/launchdarkly/sdktest/TestService.java

@@ -35,7 +35,8 @@ public class TestService extends NanoHTTPD {
             "tags",
             "auto-env-attributes",
             "inline-context",
-            "anonymous-redaction"
+            "anonymous-redaction",
+            "client-prereq-events"
     };
     private static final String MIME_JSON = "application/json";
     static final Gson gson = new GsonBuilder()

launchdarkly-android-client-sdk/src/androidTest/java/com/launchdarkly/sdk/android/LDClientEventTest.java

@@ -196,6 +196,48 @@ public void variationFlagTrackReasonGeneratesEventWithReason() throws IOExceptio
         }
     }
 
+    @Test
+    public void flagEvaluationWithPrereqProducesPrereqEvents() throws IOException, InterruptedException {
+        try (MockWebServer mockEventsServer = new MockWebServer()) {
+            mockEventsServer.start();
+            // Enqueue a successful empty response
+            mockEventsServer.enqueue(new MockResponse());
+
+            // Setup flag store with test flag
+            Flag flagA = new FlagBuilder("flagA").version(1)
+                    .variation(1).value(LDValue.of(true)).reason(EvaluationReason.targetMatch()).build();
+            Flag flagAB = new FlagBuilder("flagAB").prerequisites(new String[]{"flagA"}).version(1)
+                    .variation(1).value(LDValue.of(true)).reason(EvaluationReason.targetMatch()).build();
+            Flag flagAC = new FlagBuilder("flagAC").prerequisites(new String[]{"flagA"}).version(1)
+                    .variation(1).value(LDValue.of(true)).reason(EvaluationReason.targetMatch()).build();
+            Flag flagABD = new FlagBuilder("flagABD").prerequisites(new String[]{"flagAB"}).version(1)
+                    .variation(1).value(LDValue.of(true)).reason(EvaluationReason.targetMatch()).build();
+            PersistentDataStore store = new InMemoryPersistentDataStore();
+            TestUtil.writeFlagUpdateToStore(store, mobileKey, ldContext, flagA);
+            TestUtil.writeFlagUpdateToStore(store, mobileKey, ldContext, flagAB);
+            TestUtil.writeFlagUpdateToStore(store, mobileKey, ldContext, flagAC);
+            TestUtil.writeFlagUpdateToStore(store, mobileKey, ldContext, flagABD);
+            LDConfig ldConfig = baseConfigBuilder(mockEventsServer)
+                    .persistentDataStore(store).build();
+
+            try (LDClient client = LDClient.init(application, ldConfig, ldContext, 0)) {
+                assertTrue(client.boolVariation("flagA", false));
+                assertTrue(client.boolVariation("flagAB", false));
+                assertTrue(client.boolVariation("flagAC", false));
+                assertTrue(client.boolVariation("flagABD", false));
+                client.blockingFlush();
+
+                LDValue[] events = getEventsFromLastRequest(mockEventsServer, 2);
+                LDValue summaryEvent = events[1];
+                assertSummaryEvent(summaryEvent);
+                assertEquals(LDValue.of(4), summaryEvent.get("features").get("flagA").get("counters").get(0).get("count"));
+                assertEquals(LDValue.of(2), summaryEvent.get("features").get("flagAB").get("counters").get(0).get("count"));
+                assertEquals(LDValue.of(1), summaryEvent.get("features").get("flagAC").get("counters").get(0).get("count"));
+                assertEquals(LDValue.of(1), summaryEvent.get("features").get("flagABD").get("counters").get(0).get("count"));
+            }
+        }
+    }
+
     @Test
     public void additionalHeadersIncludedInEventsRequest() throws IOException, InterruptedException {
         try (MockWebServer mockEventsServer = new MockWebServer()) {

launchdarkly-android-client-sdk/src/main/java/com/launchdarkly/sdk/android/DataModel.java

@@ -39,6 +39,7 @@ public static final class Flag {
         private final Boolean trackEvents;
         private final Boolean trackReason;
         private final Long debugEventsUntilDate;
+        private final String[] prerequisites;
         private final Boolean deleted;
 
         private Flag(
@@ -51,6 +52,7 @@ private Flag(
                 boolean trackEvents,
                 boolean trackReason,
                 Long debugEventsUntilDate,
+                String[] prerequisites,
                 boolean deleted
         ) {
             this.key = key;
@@ -62,6 +64,7 @@ private Flag(
             this.trackEvents = trackEvents ? Boolean.TRUE : null;
             this.trackReason = trackReason ? Boolean.TRUE : null;
             this.debugEventsUntilDate = debugEventsUntilDate;
+            this.prerequisites = prerequisites;
             this.deleted = deleted ? Boolean.TRUE : null;
         }
 
@@ -76,6 +79,7 @@ private Flag(
          * @param trackReason true if events must include evaluation reasons
          * @param debugEventsUntilDate non-null if debugging is enabled
          * @param reason evaluation reason of the result, or null if not available
+         * @param prerequisites flag keys of prerequisites
          */
         public Flag(
                 @NonNull String key,
@@ -86,9 +90,10 @@ public Flag(
                 boolean trackEvents,
                 boolean trackReason,
                 @Nullable Long debugEventsUntilDate,
-                @Nullable EvaluationReason reason
+                @Nullable EvaluationReason reason,
+                @Nullable String[] prerequisites
         ) {
-            this(key, value, version, flagVersion, variation, reason, trackEvents, trackReason, debugEventsUntilDate, false);
+            this(key, value, version, flagVersion, variation, reason, trackEvents, trackReason, debugEventsUntilDate, prerequisites, false);
         }
 
         /**
@@ -97,7 +102,7 @@ public Flag(
          * @return a placeholder {@link Flag} to represent a deleted flag
          */
         public static Flag deletedItemPlaceholder(@NonNull String key, int version) {
-            return new Flag(key, null, version, null, null, null, false, false, null, true);
+            return new Flag(key, null, version, null, null, null, false, false, null, null, true);
         }
 
         String getKey() {
@@ -122,6 +127,7 @@ Integer getVariation() {
             return variation;
         }
 
+        @Nullable
         EvaluationReason getReason() {
             return reason;
         }
@@ -132,6 +138,7 @@ boolean isTrackEvents() {
 
         boolean isTrackReason() { return trackReason != null && trackReason.booleanValue(); }
 
+        @Nullable
         Long getDebugEventsUntilDate() {
             return debugEventsUntilDate;
         }
@@ -140,6 +147,11 @@ int getVersionForEvents() {
             return flagVersion == null ? version : flagVersion.intValue();
         }
 
+        @Nullable
+        String[] getPrerequisites() {
+            return prerequisites;
+        }
+
         boolean isDeleted() {
             return deleted != null && deleted.booleanValue();
         }
@@ -161,6 +173,7 @@ public boolean equals(Object other) {
                         trackEvents == o.trackEvents &&
                         trackReason == o.trackReason &&
                         Objects.equals(debugEventsUntilDate, o.debugEventsUntilDate) &&
+                        Objects.equals(prerequisites, o.prerequisites) &&
                         deleted == o.deleted;
             }
             return false;

launchdarkly-android-client-sdk/src/main/java/com/launchdarkly/sdk/android/EnvironmentData.java

@@ -83,7 +83,7 @@ public static EnvironmentData fromJson(String json) throws SerializationExceptio
             if (f.getKey() == null) {
                 f = new Flag(e.getKey(), f.getValue(), f.getVersion(), f.getFlagVersion(),
                         f.getVariation(), f.isTrackEvents(), f.isTrackReason(), f.getDebugEventsUntilDate(),
-                        f.getReason());
+                        f.getReason(), f.getPrerequisites());
                 dataMap.put(e.getKey(), f);
             }
         }

launchdarkly-android-client-sdk/src/main/java/com/launchdarkly/sdk/android/LDClient.java

@@ -518,6 +518,7 @@ private <T> EvaluationDetail<T> convertDetailType(EvaluationDetail<LDValue> deta
         return EvaluationDetail.fromValue(converter.toType(detail.getValue()), detail.getVariationIndex(), detail.getReason());
     }
 
+    // TODO: when implementing hooks support in the future, verify prerequisite evaluations do not trigger the evaluation hooks
     private EvaluationDetail<LDValue> variationDetailInternal(@NonNull String key, @NonNull LDValue defaultValue, boolean checkType, boolean needsReason) {
         LDContext context = clientContextImpl.getEvaluationContext();
         Flag flag = contextDataManager.getNonDeletedFlag(key); // returns null for nonexistent *or* deleted flag
@@ -530,6 +531,13 @@ private EvaluationDetail<LDValue> variationDetailInternal(@NonNull String key, @
                     null, defaultValue, false, null);
             result = EvaluationDetail.fromValue(defaultValue, EvaluationDetail.NO_VARIATION, EvaluationReason.error(EvaluationReason.ErrorKind.FLAG_NOT_FOUND));
         } else {
+            if (flag.getPrerequisites() != null) {
+                // recurse on prerequisites to emulate prereq evaluations occurring with desirable side effects such as events for prereqs
+                for (String prereqKey : flag.getPrerequisites()) {
+                    variationDetailInternal(prereqKey, LDValue.ofNull(), false, false);
+                }
+            }
+
             LDValue value = flag.getValue();
             int variation = flag.getVariation() == null ? EvaluationDetail.NO_VARIATION : flag.getVariation();
             if (value.isNull()) {

launchdarkly-android-client-sdk/src/main/java/com/launchdarkly/sdk/android/integrations/TestData.java

@@ -509,7 +509,7 @@ Flag createFlag(int version, LDContext context) {
             EvaluationReason reason = targetedVariation == null ? EvaluationReason.fallthrough() :
                     EvaluationReason.targetMatch();
             return new Flag(key, value, version, null, variation,
-                    false, false, null, reason);
+                    false, false, null, reason, null);
         }
 
         private static int variationForBoolean(boolean value) {

launchdarkly-android-client-sdk/src/test/java/com/launchdarkly/sdk/android/ConnectivityManagerTest.java

@@ -41,6 +41,7 @@
 import java.io.IOException;
 import java.util.List;
 import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.TimeUnit;
@@ -568,24 +569,23 @@ public void refreshDataSourceWhileInBackgroundWithBackgroundPollingDisabled() {
     @Test
     public void notifyListenersWhenStatusChanges() throws Exception {
         createTestManager(false, false, makeSuccessfulDataSourceFactory());
-
         awaitStartUp();
 
         LDStatusListener mockListener = mock(LDStatusListener.class);
-        // expected initial connection
+        // expected initial connection mode
         mockListener.onConnectionModeChanged(anyObject(ConnectionInformation.class));
-        // expected second connection after identify
+        // expected second connection mode after identify
         mockListener.onConnectionModeChanged(anyObject(ConnectionInformation.class));
         expectLastCall();
         replayAll();
 
-        AwaitableCallback<Void> identifyListenersCalled = new AwaitableCallback<>();
+        CountDownLatch latch = new CountDownLatch(2);
         connectivityManager.registerStatusListener(mockListener);
         connectivityManager.registerStatusListener(new LDStatusListener() {
             @Override
             public void onConnectionModeChanged(ConnectionInformation connectionInformation) {
                 // since the callback system is on another thread, need to use awaitable callback
-                identifyListenersCalled.onSuccess(null);
+                latch.countDown();
             }
 
             @Override
@@ -597,7 +597,7 @@ public void onInternalFailure(LDFailure ldFailure) {
         LDContext context2 = LDContext.create("context2");
         contextDataManager.switchToContext(context2);
         connectivityManager.switchToContext(context2, new AwaitableCallback<>());
-        identifyListenersCalled.await();
+        latch.await(500, TimeUnit.MILLISECONDS);
 
         verifyAll();
     }

launchdarkly-android-client-sdk/src/test/java/com/launchdarkly/sdk/android/EnvironmentDataTest.java

@@ -3,6 +3,7 @@
 import static com.launchdarkly.sdk.android.AssertHelpers.assertJsonEqual;
 import static org.hamcrest.CoreMatchers.hasItems;
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -54,14 +55,15 @@ public void toJson() {
                 .trackEvents(true)
                 .trackReason(true)
                 .debugEventsUntilDate(1000L)
+                .prerequisites(new String[]{"flagA", "flagB"})
                 .build();
         Flag flag2 = new FlagBuilder("flag2").version(200).value(false).build();
         EnvironmentData data = new DataSetBuilder().add(flag1).add(flag2).build();
         String json = data.toJson();
 
         String expectedJson = "{" +
                 "\"flag1\":{\"key\":\"flag1\",\"version\":100,\"flagVersion\":222,\"value\":true," +
-                "\"variation\":1,\"reason\":{\"kind\":\"OFF\"},\"trackEvents\":true," +
+                "\"variation\":1,\"prerequisites\":[\"flagA\",\"flagB\"],\"reason\":{\"kind\":\"OFF\"},\"trackEvents\":true," +
                 "\"trackReason\":true,\"debugEventsUntilDate\":1000}," +
                 "\"flag2\":{\"key\":\"flag2\",\"version\":200,\"value\":false}" +
                 "}";
@@ -72,7 +74,7 @@ public void toJson() {
     public void fromJson() throws Exception {
         String json = "{" +
                 "\"flag1\":{\"key\":\"flag1\",\"version\":100,\"flagVersion\":222,\"value\":true," +
-                "\"variation\":1,\"reason\":{\"kind\":\"OFF\"},\"trackEvents\":true," +
+                "\"variation\":1,\"prerequisites\":[\"flagA\",\"flagB\"],\"reason\":{\"kind\":\"OFF\"},\"trackEvents\":true," +
                 "\"trackReason\":true,\"debugEventsUntilDate\":1000}," +
                 "\"flag2\":{\"key\":\"flag2\",\"version\":200,\"value\":false}" +
                 "}";
@@ -87,6 +89,7 @@ public void fromJson() throws Exception {
         assertEquals(Integer.valueOf(222), flag1.getFlagVersion());
         assertEquals(LDValue.of(true), flag1.getValue());
         assertEquals(Integer.valueOf(1), flag1.getVariation());
+        assertArrayEquals(new String[]{"flagA", "flagB"}, flag1.getPrerequisites());
         assertTrue(flag1.isTrackEvents());
         assertTrue(flag1.isTrackReason());
         assertEquals(Long.valueOf(1000), flag1.getDebugEventsUntilDate());

launchdarkly-android-client-sdk/src/test/java/com/launchdarkly/sdk/android/FlagTest.java

@@ -3,6 +3,7 @@
 import static com.launchdarkly.sdk.internal.GsonHelpers.gsonInstance;
 
 import com.google.gson.Gson;
+import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonPrimitive;
@@ -20,6 +21,7 @@
 import java.util.List;
 import java.util.Map;
 
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
@@ -206,6 +208,23 @@ public void trackReasonDefaultWhenOmitted() {
         assertFalse(r.isTrackReason());
     }
 
+    @Test
+    public void prerequisitesIsSerialized() {
+        final Flag r = new FlagBuilder("flag").prerequisites(new String[]{"flagB", "flagC"}).build();
+        final JsonObject json = gson.toJsonTree(r).getAsJsonObject();
+        final JsonArray array = json.getAsJsonArray("prerequisites");
+        assertEquals(2, array.size());
+        assertEquals("flagB", array.get(0).getAsString());
+        assertEquals("flagC", array.get(1).getAsString());
+    }
+
+    @Test
+    public void prerequisitesIsDeserialized() {
+        final String jsonStr = "{\"version\": 99, \"prerequisites\": [\"flagA\",\"flagB\"]}";
+        final Flag r = gson.fromJson(jsonStr, Flag.class);
+        assertArrayEquals(new String[]{"flagA","flagB"}, r.getPrerequisites());
+    }
+
     @Test
     public void debugEventsUntilDateIsSerialized() {
         final long date = 12345L;

launchdarkly-android-client-sdk/src/test/java/com/launchdarkly/sdk/android/PersistentDataStoreWrapperTest.java

@@ -36,7 +36,7 @@ public class PersistentDataStoreWrapperTest extends EasyMockSupport {
     private static final String EXPECTED_INDEX_KEY = "index";
     private static final String EXPECTED_GENERATED_CONTEXT_KEY_PREFIX = "anonKey_";
     private static final Flag FLAG = new Flag("flagkey", LDValue.of(true), 1,
-            null, 0, false, false, null, null);
+            null, 0, false, false, null, null, null);
 
     private final PersistentDataStore mockPersistentStore;
     private final PersistentDataStoreWrapper wrapper;

shared-test-code/src/main/java/com/launchdarkly/sdk/android/DataSetBuilder.java

@@ -24,7 +24,7 @@ public DataSetBuilder add(Flag flag) {
 
     public DataSetBuilder add(String flagKey, int version, LDValue value, int variation) {
         return add(new Flag(flagKey, value, version, null, variation,
-                false, false, null, null));
+                false, false, null, null, null));
     }
 
     public DataSetBuilder add(String flagKey, LDValue value, int variation) {

shared-test-code/src/main/java/com/launchdarkly/sdk/android/FlagBuilder.java

@@ -17,6 +17,7 @@ public final class FlagBuilder {
     private boolean trackReason = false;
     private Long debugEventsUntilDate = null;
     private EvaluationReason reason = null;
+    private String[] prerequisites = null;
 
     public FlagBuilder(@NonNull String key) {
         this.key = key;
@@ -66,7 +67,12 @@ public FlagBuilder reason(EvaluationReason reason) {
         return this;
     }
 
+    public FlagBuilder prerequisites(String[] prerequisites) {
+        this.prerequisites = prerequisites;
+        return this;
+    }
+
     public Flag build() {
-        return new Flag(key, value, version, flagVersion, variation, trackEvents, trackReason, debugEventsUntilDate, reason);
+        return new Flag(key, value, version, flagVersion, variation, trackEvents, trackReason, debugEventsUntilDate, reason, prerequisites);
     }
 }