Temporarily revert phase two of migration away from ReferenceUnions

*** Reason for rollback ***

This code is fine, and I will be resurrecting it unaltered next week.  It's only being rolled back for operational reasons related to the timing of our internal pushes.

*** Original change description ***

Switch over to non-ReferenceUnion fields on DomainBase

This is the second phase of a three phase migration to remove
ReferenceUnions. As of the end of this phase, ReferenceUnions are no longer read
from in any active code paths, but are still written to in case a rollback to
the previous version is necessary. The third and final phase will remove the
ReferenceUnions entirely.

***

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=136642759

java/google/registry/model/EppResourceUtils.java

@@ -347,10 +347,12 @@ public final class EppResourceUtils {
   public static List<Key<DomainBase>> queryDomainsUsingResource(
       Class<? extends EppResource> clazz, Key<? extends EppResource> key, DateTime now, int limit) {
     checkArgument(ContactResource.class.equals(clazz) || HostResource.class.equals(clazz));
-    return ofy()
-        .load()
-        .type(DomainBase.class)
-        .filter(clazz.equals(ContactResource.class) ? "allContacts.contact" : "nsHosts", key)
+    return ofy().load().type(DomainBase.class)
+        .filter(
+            clazz.equals(ContactResource.class)
+                ? "allContacts.contactId.linked"
+                : "nameservers.linked",
+            key)
         .filter("deletionTime >", now)
         .limit(limit)
         .keys()

java/google/registry/model/domain/DesignatedContact.java

@@ -72,6 +72,6 @@ public class DesignatedContact extends ImmutableObject {
   }
 
   public Key<ContactResource> getContactKey() {
-    return contact;
+    return contactId.getLinked();
   }
 }

java/google/registry/model/domain/DomainBase.java

@@ -183,7 +183,11 @@ public abstract class DomainBase extends EppResource {
   }
 
   public ImmutableSet<Key<HostResource>> getNameservers() {
-    return nullToEmptyImmutableCopy(nsHosts);
+    ImmutableSet.Builder<Key<HostResource>> builder = new ImmutableSet.Builder<>();
+    for (ReferenceUnion<HostResource> union : nullToEmptyImmutableCopy(nameservers)) {
+      builder.add(union.getLinked());
+    }
+    return builder.build();
   }
 
   /** Loads and returns the fully qualified host names of all linked nameservers. */
@@ -238,13 +242,13 @@ public abstract class DomainBase extends EppResource {
   @OnSave
   void dualSaveReferenceUnions() {
     for (DesignatedContact contact : nullToEmptyImmutableCopy(allContacts)) {
-      contact.contactId = ReferenceUnion.create(contact.contact);
+      contact.contact = contact.contactId.getLinked();
     }
-    ImmutableSet.Builder<ReferenceUnion<HostResource>> hosts = new ImmutableSet.Builder<>();
-    for (Key<HostResource> hostKey : nullToEmptyImmutableCopy(nsHosts)) {
-      hosts.add(ReferenceUnion.create(hostKey));
+    ImmutableSet.Builder<Key<HostResource>> hostKeys = new ImmutableSet.Builder<>();
+    for (ReferenceUnion<HostResource> refUnion : nullToEmptyImmutableCopy(nameservers)) {
+      hostKeys.add(refUnion.getLinked());
     }
-    nameservers = hosts.build();
+    nsHosts = hostKeys.build();
   }
 
   /** Predicate to determine if a given {@link DesignatedContact} is the registrant. */
@@ -303,7 +307,11 @@ public abstract class DomainBase extends EppResource {
     }
 
     public B setNameservers(ImmutableSet<Key<HostResource>> nameservers) {
-      getInstance().nsHosts = nameservers;
+      ImmutableSet.Builder<ReferenceUnion<HostResource>> builder = new ImmutableSet.Builder<>();
+      for (Key<HostResource> key : nullToEmpty(nameservers)) {
+        builder.add(ReferenceUnion.create(key));
+      }
+      getInstance().nameservers = builder.build();
       return thisCastToDerived();
     }
 

java/google/registry/rdap/RdapDomainSearchAction.java

@@ -269,7 +269,7 @@ public class RdapDomainSearchAction extends RdapActionBase {
     for (List<Key<HostResource>> chunk : Iterables.partition(hostKeys, 30)) {
       for (DomainResource domain : ofy().load()
           .type(DomainResource.class)
-          .filter("nsHosts in", chunk)
+          .filter("nameservers.linked in", chunk)
           .filter("deletionTime >", now)
           .limit(rdapResultSetMaxSize + 1)) {
         if (!domains.contains(domain)) {

javatests/google/registry/model/domain/DomainApplicationTest.java

@@ -145,16 +145,16 @@ public class DomainApplicationTest extends EntityTestCase {
 
   @Test
   public void testEmptySetsAndArraysBecomeNull() {
-    assertThat(emptyBuilder().setNameservers(null).build().nsHosts).isNull();
+    assertThat(emptyBuilder().setNameservers(null).build().nameservers).isNull();
     assertThat(emptyBuilder()
         .setNameservers(ImmutableSet.<Key<HostResource>>of())
         .build()
-        .nsHosts)
+        .nameservers)
             .isNull();
     assertThat(emptyBuilder()
         .setNameservers(ImmutableSet.of(Key.create(newHostResource("foo.example.tld"))))
         .build()
-        .nsHosts)
+        .nameservers)
             .isNotNull();
     // This behavior should also hold true for ImmutableObjects nested in collections.
     assertThat(emptyBuilder()

javatests/google/registry/model/domain/DomainResourceTest.java

@@ -207,13 +207,13 @@ public class DomainResourceTest extends EntityTestCase {
   @Test
   public void testEmptySetsAndArraysBecomeNull() {
     assertThat(newDomainResource("example.com").asBuilder()
-        .setNameservers(null).build().nsHosts).isNull();
+        .setNameservers(null).build().nameservers).isNull();
     assertThat(newDomainResource("example.com").asBuilder()
-        .setNameservers(ImmutableSet.<Key<HostResource>>of()).build().nsHosts)
+        .setNameservers(ImmutableSet.<Key<HostResource>>of()).build().nameservers)
             .isNull();
     assertThat(newDomainResource("example.com").asBuilder()
         .setNameservers(ImmutableSet.of(Key.create(newHostResource("foo.example.tld"))))
-            .build().nsHosts)
+            .build().nameservers)
                 .isNotNull();
     // This behavior should also hold true for ImmutableObjects nested in collections.
     assertThat(newDomainResource("example.com").asBuilder()
@@ -462,22 +462,21 @@ public class DomainResourceTest extends EntityTestCase {
   public void testDualSavingOfDesignatedContact() {
     ContactResource contact = persistActiveContact("time1006");
     DesignatedContact designatedContact = new DesignatedContact();
-    designatedContact.contact = Key.create(contact);
+    designatedContact.contactId = ReferenceUnion.create(Key.create(contact));
     designatedContact.type = Type.ADMIN;
     DomainResource domainWithContact =
         domain.asBuilder().setContacts(ImmutableSet.of(designatedContact)).build();
-    assertThat(getOnlyElement(domainWithContact.getContacts()).contactId).isNull();
+    assertThat(getOnlyElement(domainWithContact.getContacts()).contact).isNull();
     DomainResource reloadedDomain = persistResource(domainWithContact);
-    assertThat(getOnlyElement(reloadedDomain.getContacts()).contactId)
-        .isEqualTo(ReferenceUnion.create(Key.create(contact)));
+    assertThat(getOnlyElement(reloadedDomain.getContacts()).contact).isEqualTo(Key.create(contact));
   }
 
   @Test
   public void testDualSavingOfNameservers() {
     HostResource host = persistActiveHost("zzz.xxx.yyy");
     DomainResource domain = newDomainResource("python-django-unchained.com", host);
-    assertThat(domain.nameservers).isNull();
+    assertThat(domain.nsHosts).isNull();
     DomainResource djangoReloaded = persistResource(domain);
-    assertThat(djangoReloaded.nameservers).containsExactly(ReferenceUnion.create(Key.create(host)));
+    assertThat(djangoReloaded.nsHosts).containsExactly(Key.create(host));
   }
 }