Make RDE generation resilient to missing contact rows

This will prevent RDE from failing once we delete all contacts, just as a
fail-safe.

BUG= http://b/439636188

Author: CydeWeys

core/src/main/java/google/registry/rde/DomainToXjcConverter.java

@@ -168,20 +168,18 @@ static XjcRdeDomain convertDomain(Domain model, RdeMode mode) {
         //    as the holder of the domain name object.
         Optional<VKey<Contact>> registrant = model.getRegistrant();
         if (registrant.isPresent()) {
-          Contact registrantContact = tm().transact(() -> tm().loadByKey(registrant.get()));
-          checkState(
-              registrantContact != null,
-              "Registrant contact %s on domain %s does not exist",
-              registrant,
-              domainName);
-          bean.setRegistrant(registrantContact.getContactId());
+          Optional<Contact> registrantContact =
+              tm().transact(() -> tm().loadByKeyIfPresent(registrant.get()));
+          registrantContact.ifPresent(c -> bean.setRegistrant(c.getContactId()));
         }
 
         // o  Zero or more OPTIONAL <contact> elements that contain identifiers
         //    for the human or organizational social information objects
         //    associated with the domain name object.
         for (DesignatedContact contact : model.getContacts()) {
-          bean.getContacts().add(convertDesignatedContact(contact, domainName));
+          Optional<XjcDomainContactType> contactType =
+              convertDesignatedContact(contact, domainName);
+          contactType.ifPresent(c -> bean.getContacts().add(c));
         }
 
         // o  An OPTIONAL <secDNS> element that contains the public key
@@ -292,23 +290,21 @@ private static XjcSecdnsDsDataType convertDelegationSignerData(DomainDsData mode
   }
 
   /** Converts {@link DesignatedContact} to {@link XjcDomainContactType}. */
-  private static XjcDomainContactType convertDesignatedContact(
+  private static Optional<XjcDomainContactType> convertDesignatedContact(
       DesignatedContact model, String domainName) {
     XjcDomainContactType bean = new XjcDomainContactType();
     checkState(
         model.getContactKey() != null,
         "Contact key for type %s is null on domain %s",
         model.getType(),
         domainName);
-    Contact contact = tm().transact(() -> tm().loadByKey(model.getContactKey()));
-    checkState(
-        contact != null,
-        "Contact %s on domain %s does not exist",
-        model.getContactKey(),
-        domainName);
+    Optional<Contact> contact = tm().transact(() -> tm().loadByKeyIfPresent(model.getContactKey()));
+    if (contact.isEmpty()) {
+      return Optional.empty();
+    }
     bean.setType(XjcDomainContactAttrType.fromValue(Ascii.toLowerCase(model.getType().toString())));
-    bean.setValue(contact.getContactId());
-    return bean;
+    bean.setValue(contact.get().getContactId());
+    return Optional.of(bean);
   }
 
   private DomainToXjcConverter() {}

core/src/test/java/google/registry/rde/DomainToXjcConverterTest.java

@@ -14,9 +14,11 @@
 
 package google.registry.rde;
 
+import static com.google.common.collect.ImmutableSet.toImmutableSet;
 import static com.google.common.io.BaseEncoding.base16;
 import static com.google.common.truth.Truth.assertThat;
 import static com.google.common.truth.Truth.assertWithMessage;
+import static google.registry.persistence.transaction.TransactionManagerFactory.tm;
 import static google.registry.testing.DatabaseHelper.createTld;
 import static google.registry.testing.DatabaseHelper.persistEppResource;
 import static google.registry.testing.DatabaseHelper.persistResource;
@@ -69,6 +71,7 @@
 import google.registry.xjc.rdedomain.XjcRdeDomainElement;
 import google.registry.xjc.rgp.XjcRgpStatusType;
 import google.registry.xjc.secdns.XjcSecdnsDsDataType;
+import google.registry.xml.XmlException;
 import java.io.ByteArrayOutputStream;
 import java.util.Optional;
 import org.joda.money.Money;
@@ -198,6 +201,21 @@ void testMarshalThin() throws Exception {
     wrapDeposit(bean).marshal(new ByteArrayOutputStream(), UTF_8);
   }
 
+  @Test
+  void testConvertAbsentContacts() throws XmlException {
+    Domain domain = makeDomain(clock);
+    tm().transact(
+            () ->
+                tm().delete(
+                        domain.getAllContacts().stream()
+                            .map(DesignatedContact::getContactKey)
+                            .collect(toImmutableSet())));
+    XjcRdeDomain bean = DomainToXjcConverter.convertDomain(domain, RdeMode.FULL);
+    assertThat(bean.getRegistrant()).isNull();
+    assertThat(bean.getContacts()).isEmpty();
+    wrapDeposit(bean).marshal(new ByteArrayOutputStream(), UTF_8);
+  }
+
   XjcRdeDeposit wrapDeposit(XjcRdeDomain domain) {
     XjcRdeDeposit deposit = new XjcRdeDeposit();
     deposit.setId("984302");