Repository: googleapis/java-datastore (java)
Issue: Cloud Datastore Java SDK - parent keys are created without the correct database ID
#### Environment details

Java version: 17
SDK version: 2.19.4-SNAPSHOT

#### Steps to reproduce

  1. Create a key with a parent and a non-default database ID
  2. Compare the database ID of the key to the database ID of the parent
  3. Observe the values are different. They should be the same.

#### Code example

```java
Key entityKey = DatastoreOptions.newBuilder()
        .setDatabaseId("my-database-id")
        .build()
        .getService()
        .newKeyFactory()
        .setKind("EntityKind")
        .addAncestor(PathElement.of("ParentKind", 1L))
        .newKey(2L);
System.out.printf("Entity database ID: %s%n", entityKey.getDatabaseId());
System.out.printf("Parent database ID: %s%n", entityKey.getParent().getDatabaseId());
```

Pull request description: fix: set the correct database id on the key parent when calling Key#getParent
Fixes #1456 ☕️

This is to fix the bug where the database ID is not set correctly on the parent key. The bug causes problems in Objectify by preventing you from fetching an entity from a non-default database, using a parent key.

Patch:
diff --git a/google-cloud-datastore/src/main/java/com/google/cloud/datastore/IncompleteKey.java b/google-cloud-datastore/src/main/java/com/google/cloud/datastore/IncompleteKey.java
index db9973cb..71e31b94 100644
--- a/google-cloud-datastore/src/main/java/com/google/cloud/datastore/IncompleteKey.java
+++ b/google-cloud-datastore/src/main/java/com/google/cloud/datastore/IncompleteKey.java
@@ -91,9 +91,11 @@ public class IncompleteKey extends BaseKey {
     PathElement parent = ancestors.get(ancestors.size() - 1);
     Key.Builder keyBuilder;
     if (parent.hasName()) {
-      keyBuilder = Key.newBuilder(getProjectId(), parent.getKind(), parent.getName());
+      keyBuilder =
+          Key.newBuilder(getProjectId(), parent.getKind(), parent.getName(), getDatabaseId());
     } else {
-      keyBuilder = Key.newBuilder(getProjectId(), parent.getKind(), parent.getId());
+      keyBuilder =
+          Key.newBuilder(getProjectId(), parent.getKind(), parent.getId(), getDatabaseId());
     }
     String namespace = getNamespace();
     if (namespace != null) {


Test patch:
diff --git a/google-cloud-datastore/src/test/java/com/google/cloud/datastore/IncompleteKeyTest.java b/google-cloud-datastore/src/test/java/com/google/cloud/datastore/IncompleteKeyTest.java
index a1f8956b..75549e5e 100644
--- a/google-cloud-datastore/src/test/java/com/google/cloud/datastore/IncompleteKeyTest.java
+++ b/google-cloud-datastore/src/test/java/com/google/cloud/datastore/IncompleteKeyTest.java
@@ -25,15 +25,17 @@ import org.junit.Test;
 
 public class IncompleteKeyTest {
 
-  private static IncompleteKey pk1, pk2, pk4;
-  private static Key parent1;
+  private static IncompleteKey pk1, pk2, pk4, pk5;
+  private static Key parent1, parent2;
 
   @Before
   public void setUp() {
     pk1 = IncompleteKey.newBuilder("ds", "kind1").build();
     parent1 = Key.newBuilder("ds", "kind2", 10).setNamespace("ns").build();
+    parent2 = Key.newBuilder("ds", "kind2", 10, "test-db").setNamespace("ns").build();
     pk2 = IncompleteKey.newBuilder(parent1, "kind3").build();
     pk4 = IncompleteKey.newBuilderWithDatabaseId("ds", "kind3", "test-db").build();
+    pk5 = IncompleteKey.newBuilder(parent2, "kind4").build();
   }
 
   @Test
@@ -59,12 +61,18 @@ public class IncompleteKeyTest {
     assertEquals("test-db", pk4.getDatabaseId());
     assertEquals("kind3", pk4.getKind());
     assertTrue(pk4.getAncestors().isEmpty());
+
+    assertEquals("ds", pk5.getProjectId());
+    assertEquals("test-db", pk5.getDatabaseId());
+    assertEquals("kind4", pk5.getKind());
+    assertEquals(parent2.getPath(), pk5.getAncestors());
   }
 
   @Test
   public void testParent() {
     assertNull(pk1.getParent());
     assertEquals(parent1, pk2.getParent());
+    assertEquals(parent2, pk5.getParent());
     Key parent2 = Key.newBuilder("ds", "kind3", "name").setNamespace("ns").build();
     IncompleteKey pk3 = IncompleteKey.newBuilder(parent2, "kind3").build();
     assertEquals(parent2, pk3.getParent());