Make loadByForeignKeyCached() return an Optional type

Next up (and a much larger commit) will be giving loadByForeignKey() the same
treatment.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=225182377

java/google/registry/model/EppResourceUtils.java

@@ -44,6 +44,7 @@ import google.registry.model.transfer.TransferData;
 import google.registry.model.transfer.TransferStatus;
 import java.util.List;
 import java.util.Map.Entry;
+import java.util.Optional;
 import java.util.Set;
 import java.util.function.Function;
 import javax.annotation.Nullable;
@@ -94,7 +95,7 @@ public final class EppResourceUtils {
   @Nullable
   public static <T extends EppResource> T loadByForeignKey(
       Class<T> clazz, String foreignKey, DateTime now) {
-    return loadByForeignKeyHelper(clazz, foreignKey, now, false);
+    return loadByForeignKeyHelper(clazz, foreignKey, now, false).orElse(null);
   }
 
   /**
@@ -120,15 +121,13 @@ public final class EppResourceUtils {
    * @param foreignKey id to match
    * @param now the current logical time to project resources at
    */
-  @Nullable
-  public static <T extends EppResource> T loadByForeignKeyCached(
+  public static <T extends EppResource> Optional<T> loadByForeignKeyCached(
       Class<T> clazz, String foreignKey, DateTime now) {
     return loadByForeignKeyHelper(
         clazz, foreignKey, now, RegistryConfig.isEppResourceCachingEnabled());
   }
 
-  @Nullable
-  private static <T extends EppResource> T loadByForeignKeyHelper(
+  private static <T extends EppResource> Optional<T> loadByForeignKeyHelper(
       Class<T> clazz, String foreignKey, DateTime now, boolean useCache) {
     checkArgument(
         ForeignKeyedEppResource.class.isAssignableFrom(clazz),
@@ -140,14 +139,14 @@ public final class EppResourceUtils {
             : ofy().load().type(ForeignKeyIndex.mapToFkiClass(clazz)).id(foreignKey).now();
     // The value of fki.getResourceKey() might be null for hard-deleted prober data.
     if (fki == null || isAtOrAfter(now, fki.getDeletionTime()) || fki.getResourceKey() == null) {
-      return null;
+      return Optional.empty();
     }
     T resource =
         useCache
             ? EppResource.loadCached(fki.getResourceKey())
             : ofy().load().key(fki.getResourceKey()).now();
     if (resource == null || isAtOrAfter(now, resource.getDeletionTime())) {
-      return null;
+      return Optional.empty();
     }
     // When setting status values based on a time, choose the greater of "now" and the resource's
     // UpdateAutoTimestamp. For non-mutating uses (info, whois, etc.), this is equivalent to rolling
@@ -155,8 +154,9 @@ public final class EppResourceUtils {
     // doesn't appear stale. For mutating flows, if we had to roll now forward then the flow will
     // fail when it tries to save anything via Ofy, since "now" is needed to be > the last update
     // time for writes.
-    return cloneProjectedAtTime(
-        resource, latestOf(now, resource.getUpdateAutoTimestamp().getTimestamp()));
+    return Optional.of(
+        cloneProjectedAtTime(
+            resource, latestOf(now, resource.getUpdateAutoTimestamp().getTimestamp())));
   }
 
   /**

java/google/registry/whois/DomainLookupCommand.java

@@ -33,9 +33,7 @@ public class DomainLookupCommand extends DomainOrHostLookupCommand {
 
   @Override
   protected Optional<WhoisResponse> getResponse(InternetDomainName domainName, DateTime now) {
-    final DomainResource domainResource =
-        loadByForeignKeyCached(DomainResource.class, domainName.toString(), now);
-    return Optional.ofNullable(
-        domainResource == null ? null : new DomainWhoisResponse(domainResource, fullOutput, now));
+    return loadByForeignKeyCached(DomainResource.class, domainName.toString(), now)
+        .map(domain -> new DomainWhoisResponse(domain, fullOutput, now));
   }
 }

java/google/registry/whois/NameserverLookupByHostCommand.java

@@ -30,9 +30,7 @@ public class NameserverLookupByHostCommand extends DomainOrHostLookupCommand {
 
   @Override
   protected Optional<WhoisResponse> getResponse(InternetDomainName hostName, DateTime now) {
-    final HostResource hostResource =
-        loadByForeignKeyCached(HostResource.class, hostName.toString(), now);
-    return Optional.ofNullable(
-        hostResource == null ? null : new NameserverWhoisResponse(hostResource, now));
+    return loadByForeignKeyCached(HostResource.class, hostName.toString(), now)
+        .map(host -> new NameserverWhoisResponse(host, now));
   }
 }

javatests/google/registry/whois/WhoisActionTest.java

@@ -15,6 +15,7 @@
 package google.registry.whois;
 
 import static com.google.common.truth.Truth.assertThat;
+import static com.google.common.truth.Truth8.assertThat;
 import static google.registry.model.EppResourceUtils.loadByForeignKeyCached;
 import static google.registry.model.registrar.Registrar.State.ACTIVE;
 import static google.registry.model.registrar.Registrar.Type.PDT;
@@ -146,9 +147,9 @@ public class WhoisActionTest {
     persistSimpleResources(makeRegistrarContacts(registrar));
     // Populate the cache for both the domain and contact.
     DomainResource domain =
-        loadByForeignKeyCached(DomainResource.class, "cat.lol", clock.nowUtc());
+        loadByForeignKeyCached(DomainResource.class, "cat.lol", clock.nowUtc()).get();
     ContactResource contact =
-        loadByForeignKeyCached(ContactResource.class, "5372808-ERL", clock.nowUtc());
+        loadByForeignKeyCached(ContactResource.class, "5372808-ERL", clock.nowUtc()).get();
     // Make a change to the domain and contact that won't be seen because the cache will be hit.
     persistResource(domain.asBuilder().setDeletionTime(clock.nowUtc().minusDays(1)).build());
     persistResource(
@@ -237,7 +238,7 @@ public class WhoisActionTest {
   @Test
   public void testRun_domainNotFound_usesCache() {
     // Populate the cache with the nonexistence of this domain.
-    assertThat(loadByForeignKeyCached(DomainResource.class, "cat.lol", clock.nowUtc())).isNull();
+    assertThat(loadByForeignKeyCached(DomainResource.class, "cat.lol", clock.nowUtc())).isEmpty();
     // Add a new valid cat.lol domain that won't be found because the cache will be hit instead.
     persistActiveDomain("cat.lol");
     newWhoisAction("domain cat.lol\r\n").run();
@@ -361,7 +362,7 @@ public class WhoisActionTest {
     persistResource(makeHostResource("ns1.cat.xn--q9jyb4c", "1.2.3.4"));
     // Populate the cache.
     HostResource host =
-        loadByForeignKeyCached(HostResource.class, "ns1.cat.xn--q9jyb4c", clock.nowUtc());
+        loadByForeignKeyCached(HostResource.class, "ns1.cat.xn--q9jyb4c", clock.nowUtc()).get();
     // Make a change to the persisted host that won't be seen because the cache will be hit.
     persistResource(
         host.asBuilder()