Fix NPE bug in DomainCommand.cloneAndLinkReferences()

See b/30806813 for more context.  Copied from there:  This appears to be happening if we get an EPP domain create command that is missing any contacts (but has a registrant; with no registrant we exercise a different codepath).  In that case, JAXB leaves the contacts field on the Create null, and we try to pass it into Sets.union() as a result of Corey's refactoring in [] that changed contact loading to load the contacts and registrant all at once.  The fix is just to apply nullToEmpty() first.

Note that it's always an error to try to create a domain without any non-registrant contacts, but that's supposed to happen later on in BaseDomainCreateFlow.verifyCreateIsAllowed() via validateRequiredContactsPresent(), which will produce a nice error message.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=130309019

java/google/registry/model/domain/DomainCommand.java

@@ -22,7 +22,9 @@ import static com.google.common.collect.Sets.difference;
 import static com.google.common.collect.Sets.intersection;
 import static google.registry.model.ofy.ObjectifyService.ofy;
 import static google.registry.util.CollectionUtils.difference;
+import static google.registry.util.CollectionUtils.forceEmptyToNull;
 import static google.registry.util.CollectionUtils.nullSafeImmutableCopy;
+import static google.registry.util.CollectionUtils.nullToEmpty;
 import static google.registry.util.CollectionUtils.nullToEmptyImmutableCopy;
 import static google.registry.util.CollectionUtils.union;
 
@@ -204,12 +206,12 @@ public class DomainCommand {
         registrantPlaceholder.contactId = clone.registrantContactId;
         registrantPlaceholder.type = DesignatedContact.Type.REGISTRANT;
         Set<DesignatedContact> contacts = linkContacts(
-            union(clone.foreignKeyedDesignatedContacts, registrantPlaceholder),
+            union(nullToEmpty(clone.foreignKeyedDesignatedContacts), registrantPlaceholder),
             now);
         for (DesignatedContact contact : contacts) {
           if (DesignatedContact.Type.REGISTRANT.equals(contact.getType())) {
             clone.registrant = contact.getContactRef();
-            clone.contacts = difference(contacts, contact);
+            clone.contacts = forceEmptyToNull(difference(contacts, contact));
             break;
           }
         }
@@ -511,6 +513,7 @@ public class DomainCommand {
     private final Class<?> type;
 
     InvalidReferencesException(Class<?> type, ImmutableSet<String> foreignKeys) {
+      super(String.format("Invalid %s reference IDs: %s", type.getSimpleName(), foreignKeys));
       this.type = checkNotNull(type);
       this.foreignKeys = foreignKeys;
     }

javatests/google/registry/flows/domain/DomainCreateFlowTest.java

@@ -1025,6 +1025,14 @@ public class DomainCreateFlowTest extends ResourceFlowTestCase<DomainCreateFlow,
     runFlow();
   }
 
+  @Test
+  public void testFailure_missingNonRegistrantContacts() throws Exception {
+    thrown.expect(MissingAdminContactException.class);
+    setEppInput("domain_create_missing_non_registrant_contacts.xml");
+    persistContactsAndHosts();
+    runFlow();
+  }
+
   @Test
   public void testFailure_badIdn() throws Exception {
     thrown.expect(InvalidIdnDomainLabelException.class);

javatests/google/registry/flows/domain/testdata/domain_create_missing_non_registrant_contacts.xml

@@ -0,0 +1,20 @@
+<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
+  <command>
+    <create>
+      <domain:create
+       xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
+        <domain:name>example.tld</domain:name>
+        <domain:period unit="y">2</domain:period>
+        <domain:ns>
+          <domain:hostObj>ns1.example.net</domain:hostObj>
+          <domain:hostObj>ns2.example.net</domain:hostObj>
+        </domain:ns>
+        <domain:registrant>jd1234</domain:registrant>
+        <domain:authInfo>
+          <domain:pw>2fooBAR</domain:pw>
+        </domain:authInfo>
+      </domain:create>
+    </create>
+    <clTRID>ABC-12345</clTRID>
+  </command>
+</epp>

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

@@ -14,11 +14,42 @@
 
 package google.registry.model.domain;
 
+import static google.registry.testing.DatastoreHelper.persistActiveContact;
+import static google.registry.testing.DatastoreHelper.persistActiveHost;
+import static org.joda.time.DateTimeZone.UTC;
+
 import google.registry.model.ResourceCommandTestCase;
+import google.registry.model.eppinput.EppInput;
+import google.registry.model.eppinput.EppInput.ResourceCommandWrapper;
+import google.registry.model.eppinput.ResourceCommand;
+import google.registry.model.ofy.Ofy;
+import google.registry.testing.AppEngineRule;
+import google.registry.testing.EppLoader;
+import google.registry.testing.FakeClock;
+import google.registry.testing.InjectRule;
+import org.joda.time.DateTime;
+import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
 
-/** Test xml roundtripping of commands. */
+/** Tests for DomainCommand. */
 public class DomainCommandTest extends ResourceCommandTestCase {
+
+  @Rule
+  public final AppEngineRule appEngine = AppEngineRule.builder()
+      .withDatastore()
+      .build();
+
+  @Rule
+  public InjectRule inject = new InjectRule();
+
+  private FakeClock clock = new FakeClock(DateTime.now(UTC));
+
+  @Before
+  public void beforeDomainCommandTest() throws Exception {
+    inject.setStaticField(Ofy.class, "clock", clock);
+  }
+
   @Test
   public void testCreate() throws Exception {
     doXmlRoundtripTest("domain_create.xml");
@@ -64,6 +95,47 @@ public class DomainCommandTest extends ResourceCommandTestCase {
     doXmlRoundtripTest("domain_create_flags.xml");
   }
 
+  @Test
+  public void testCreate_emptyCommand() throws Exception {
+    // This EPP command wouldn't be allowed for policy reasons, but should marshal/unmarshal fine.
+    doXmlRoundtripTest("domain_create_empty.xml");
+  }
+
+  @Test
+  public void testCreate_missingNonRegistrantContacts() throws Exception {
+    // This EPP command wouldn't be allowed for policy reasons, but should marshal/unmarshal fine.
+    doXmlRoundtripTest("domain_create_missing_non_registrant_contacts.xml");
+  }
+
+  @Test
+  public void testCreate_cloneAndLinkReferences() throws Exception {
+    persistActiveHost("ns1.example.net");
+    persistActiveHost("ns2.example.net");
+    persistActiveContact("sh8013");
+    persistActiveContact("jd1234");
+    DomainCommand.Create create =
+        (DomainCommand.Create) loadEppResourceCommand("domain_create.xml");
+    create.cloneAndLinkReferences(clock.nowUtc());
+  }
+
+  @Test
+  public void testCreate_emptyCommand_cloneAndLinkReferences() throws Exception {
+    // This EPP command wouldn't be allowed for policy reasons, but should clone-and-link fine.
+    DomainCommand.Create create =
+        (DomainCommand.Create) loadEppResourceCommand("domain_create_empty.xml");
+    create.cloneAndLinkReferences(clock.nowUtc());
+  }
+
+  @Test
+  public void testCreate_missingNonRegistrantContacts_cloneAndLinkReferences() throws Exception {
+    persistActiveContact("jd1234");
+    // This EPP command wouldn't be allowed for policy reasons, but should clone-and-link fine.
+    DomainCommand.Create create =
+        (DomainCommand.Create)
+            loadEppResourceCommand("domain_create_missing_non_registrant_contacts.xml");
+    create.cloneAndLinkReferences(clock.nowUtc());
+  }
+
   @Test
   public void testDelete() throws Exception {
     doXmlRoundtripTest("domain_delete.xml");
@@ -84,6 +156,31 @@ public class DomainCommandTest extends ResourceCommandTestCase {
     doXmlRoundtripTest("domain_update_flags.xml");
   }
 
+  @Test
+  public void testUpdate_emptyCommand() throws Exception {
+    // This EPP command wouldn't be allowed for policy reasons, but should marshal/unmarshal fine.
+    doXmlRoundtripTest("domain_update_empty.xml");
+  }
+
+  @Test
+  public void testUpdate_cloneAndLinkReferences() throws Exception {
+    persistActiveHost("ns1.example.com");
+    persistActiveHost("ns2.example.com");
+    persistActiveContact("mak21");
+    persistActiveContact("sh8013");
+    DomainCommand.Update update =
+        (DomainCommand.Update) loadEppResourceCommand("domain_update.xml");
+    update.cloneAndLinkReferences(clock.nowUtc());
+  }
+
+  @Test
+  public void testUpdate_emptyCommand_cloneAndLinkReferences() throws Exception {
+    // This EPP command wouldn't be allowed for policy reasons, but should clone-and-link fine.
+    DomainCommand.Update update =
+        (DomainCommand.Update) loadEppResourceCommand("domain_update_empty.xml");
+    update.cloneAndLinkReferences(clock.nowUtc());
+  }
+
   @Test
   public void testInfo() throws Exception {
     doXmlRoundtripTest("domain_info.xml");
@@ -178,4 +275,11 @@ public class DomainCommandTest extends ResourceCommandTestCase {
   public void testRenew_fee() throws Exception {
     doXmlRoundtripTest("domain_renew_fee.xml");
   }
+
+  /** Loads the EppInput from the given filename and returns its ResourceCommand element. */
+  private ResourceCommand loadEppResourceCommand(String filename) throws Exception {
+    EppInput eppInput = new EppLoader(this, filename).getEpp();
+    return ((ResourceCommandWrapper) eppInput.getCommandWrapper().getCommand())
+        .getResourceCommand();
+  }
 }

javatests/google/registry/model/domain/testdata/domain_create_empty.xml

@@ -0,0 +1,14 @@
+<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
+  <command>
+    <create>
+      <domain:create
+       xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
+        <domain:name>example.com</domain:name>
+        <domain:authInfo>
+          <domain:pw>2fooBAR</domain:pw>
+        </domain:authInfo>
+      </domain:create>
+    </create>
+    <clTRID>ABC-12345</clTRID>
+  </command>
+</epp>

javatests/google/registry/model/domain/testdata/domain_create_missing_non_registrant_contacts.xml

@@ -0,0 +1,15 @@
+<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
+  <command>
+    <create>
+      <domain:create
+       xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
+        <domain:name>example.com</domain:name>
+        <domain:registrant>jd1234</domain:registrant>
+        <domain:authInfo>
+          <domain:pw>2fooBAR</domain:pw>
+        </domain:authInfo>
+      </domain:create>
+    </create>
+    <clTRID>ABC-12345</clTRID>
+  </command>
+</epp>

javatests/google/registry/model/domain/testdata/domain_update_empty.xml

@@ -0,0 +1,11 @@
+<epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
+  <command>
+    <update>
+      <domain:update
+       xmlns:domain="urn:ietf:params:xml:ns:domain-1.0">
+        <domain:name>example.com</domain:name>
+      </domain:update>
+    </update>
+    <clTRID>ABC-12345</clTRID>
+  </command>
+</epp>