State Transitions to sync correctly from source to target. (#763)

* State Transitions to sync correctly from source to target.

Author: praveenkumarct

src/integration-test/java/com/commercetools/sync/integration/externalsource/states/StateSyncIT.java

@@ -912,6 +912,42 @@ void sync_WithEmptyNewTransition_ShouldRemoveTransitions() {
         .join();
   }
 
+  @Test
+  void sync_WithNullTransitions_TargetStateTransitionsShouldBeNull() {
+
+    final StateDraft stateDraft = createStateDraft(keyA);
+    final State state = createStateInSource(stateDraft);
+
+    final StateSyncOptions stateSyncOptions =
+        StateSyncOptionsBuilder.of(CTP_TARGET_CLIENT).batchSize(3).build();
+
+    final StateSync stateSync = new StateSync(stateSyncOptions);
+    final List<StateDraft> stateDrafts =
+        StateTransformUtils.toStateDrafts(
+                CTP_SOURCE_CLIENT, referenceIdToKeyCache, Arrays.asList(state))
+            .join();
+    // test
+    final StateSyncStatistics stateSyncStatistics =
+        stateSync.sync(stateDrafts).toCompletableFuture().join();
+
+    assertThat(stateSyncStatistics).hasValues(1, 1, 0, 0, 0);
+
+    CtpQueryUtils.queryAll(
+            CTP_TARGET_CLIENT,
+            StateQueryBuilder.of().plusPredicates(q -> q.key().is(keyA)).build(),
+            Function.identity())
+        .thenApply(
+            fetchedCategories ->
+                fetchedCategories.stream().flatMap(List::stream).collect(Collectors.toList()))
+        .thenAccept(
+            resultStates -> {
+              Assertions.assertThat(resultStates.size()).isEqualTo(1);
+              Assertions.assertThat(resultStates.get(0).getTransitions()).isNull();
+            })
+        .toCompletableFuture()
+        .join();
+  }
+
   @Test
   void sync_WithStateWithoutKey_ShouldAddErrorMessage() {
     String nameA = "state-A";
@@ -1165,8 +1201,9 @@ private StateDraft createStateDraftReferencingStateDrafts(
   }
 
   private StateDraft createStateDraft(final String key, final State... transitionStates) {
-    List<Reference<State>> references = new ArrayList<>();
+    List<Reference<State>> references = null;
     if (transitionStates.length > 0) {
+      references = new ArrayList<>();
       for (State transitionState : transitionStates) {
         references.add(referenceOfId(transitionState.getId()));
       }
@@ -1178,7 +1215,7 @@ private StateDraft createStateDraftWithReference(
       final String key, final List<Reference<State>> references) {
     return StateDraftBuilder.of(key, StateType.REVIEW_STATE)
         .roles(Collections.singleton(StateRole.REVIEW_INCLUDED_IN_STATISTICS))
-        .transitions(new HashSet<>(references))
+        .transitions(null == references ? null : new HashSet<>(references))
         .initial(true)
         .build();
   }

src/main/java/com/commercetools/sync/states/utils/StateReferenceResolutionUtils.java

@@ -77,8 +77,11 @@ public static List<StateDraft> mapToStateDrafts(
   private static Set<Reference<State>> replaceTransitionIdsWithKeys(
       @Nonnull final State state, @Nonnull final ReferenceIdToKeyCache referenceIdToKeyCache) {
     final Set<Reference<State>> transitions = state.getTransitions();
+
+    if (transitions == null) return null;
+
     final Set<Reference<State>> newTransitions = new HashSet<>();
-    if (transitions != null && !transitions.isEmpty()) {
+    if (!transitions.isEmpty()) {
       transitions.forEach(
           transition -> {
             newTransitions.add(

src/test/java/com/commercetools/sync/states/utils/StateReferenceResolutionUtilsTest.java

@@ -92,20 +92,29 @@ void mapToStateDrafts_WithAllNonExpandedReferences_ShouldReturnReferencesWithout
   }
 
   @Test
-  void mapToStateDrafts_WithNullOrEmptyReferences_ShouldNotFail() {
+  void mapToStateDrafts_WithEmptyReferences_ShouldNotFail() {
     // preparation
-    final State mockState1 = mock(State.class);
-    when(mockState1.getTransitions()).thenReturn(null);
-
-    final State mockState2 = mock(State.class);
-    when(mockState2.getTransitions()).thenReturn(Collections.emptySet());
+    final State mockState = mock(State.class);
+    when(mockState.getTransitions()).thenReturn(Collections.emptySet());
 
     // test
     final List<StateDraft> referenceReplacedDrafts =
-        mapToStateDrafts(Arrays.asList(mockState1, mockState2), referenceIdToKeyCache);
+        mapToStateDrafts(Arrays.asList(mockState), referenceIdToKeyCache);
 
     assertThat(referenceReplacedDrafts.get(0).getTransitions()).isEqualTo(Collections.emptySet());
-    assertThat(referenceReplacedDrafts.get(1).getTransitions()).isEqualTo(Collections.emptySet());
+  }
+
+  @Test
+  void mapToStateDrafts_WithNullReferences_ShouldNotFail() {
+    // preparation
+    final State mockState = mock(State.class);
+    when(mockState.getTransitions()).thenReturn(null);
+
+    // test
+    final List<StateDraft> referenceReplacedDrafts =
+        mapToStateDrafts(Arrays.asList(mockState), referenceIdToKeyCache);
+
+    assertThat(referenceReplacedDrafts.get(0).getTransitions()).isEqualTo(null);
   }
 
   @Nonnull