FIx a failure in FhirTerser when visiting custom types

hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java

@@ -728,7 +728,12 @@ public class FhirTerser {
 									continue;
 								}
 								BaseRuntimeElementDefinition<?> childElementDef;
-								childElementDef = nextChild.getChildElementDefinitionByDatatype(nextValue.getClass());
+								Class<? extends IBase> valueType = nextValue.getClass();
+								childElementDef = nextChild.getChildElementDefinitionByDatatype(valueType);
+								while (childElementDef == null && IBase.class.isAssignableFrom(valueType)) {
+									childElementDef = nextChild.getChildElementDefinitionByDatatype(valueType);
+									valueType = (Class<? extends IBase>) valueType.getSuperclass();
+								}
 
 								if (childElementDef == null) {
 									StringBuilder b = new StringBuilder();

hapi-fhir-structures-r4/src/test/java/ca/uhn/fhir/util/FhirTerserR4Test.java

@@ -3,12 +3,10 @@ package ca.uhn.fhir.util;
 import ca.uhn.fhir.context.BaseRuntimeChildDefinition;
 import ca.uhn.fhir.context.BaseRuntimeElementDefinition;
 import ca.uhn.fhir.context.FhirContext;
+import ca.uhn.fhir.model.api.annotation.Block;
 import ca.uhn.fhir.parser.DataFormatException;
 import org.hamcrest.Matchers;
-import org.hl7.fhir.instance.model.api.IBase;
+import org.hl7.fhir.instance.model.api.*;
-import org.hl7.fhir.instance.model.api.IBaseExtension;
-import org.hl7.fhir.instance.model.api.IBaseReference;
-import org.hl7.fhir.instance.model.api.IBaseResource;
 import org.hl7.fhir.r4.model.*;
 import org.hl7.fhir.r4.model.Patient.LinkType;
 import org.junit.AfterClass;
@@ -20,9 +18,7 @@ import org.slf4j.LoggerFactory;
 
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
-import java.util.ArrayList;
+import java.util.*;
-import java.util.Collection;
-import java.util.List;
 import java.util.stream.Collectors;
 
 import static org.hamcrest.Matchers.containsInAnyOrder;
@@ -989,6 +985,43 @@ public class FhirTerserR4Test {
 		Assert.assertEquals("nestedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
 	}
 
+	@Test
+	public void testVisitWithCustomSubclass() {
+
+		ValueSet.ValueSetExpansionComponent component = new MyValueSetExpansionComponent();
+		ValueSet vs = new ValueSet();
+		vs.setExpansion(component);
+		vs.getExpansion().setIdentifier("http://foo");
+
+		Set<String> strings = new HashSet<>();
+		ourCtx.newTerser().visit(vs, new IModelVisitor() {
+			@Override
+			public void acceptElement(IBaseResource theResource, IBase theElement, List<String> thePathToElement, BaseRuntimeChildDefinition theChildDefinition, BaseRuntimeElementDefinition<?> theDefinition) {
+				if (theElement instanceof IPrimitiveType) {
+					strings.add(((IPrimitiveType) theElement).getValueAsString());
+				}
+			}
+		});
+		assertThat(strings, Matchers.contains("http://foo"));
+
+		strings.clear();
+		ourCtx.newTerser().visit(vs, new IModelVisitor2() {
+			@Override
+			public boolean acceptElement(IBase theElement, List<IBase> theContainingElementPath, List<BaseRuntimeChildDefinition> theChildDefinitionPath, List<BaseRuntimeElementDefinition<?>> theElementDefinitionPath) {
+				if (theElement instanceof IPrimitiveType) {
+					strings.add(((IPrimitiveType) theElement).getValueAsString());
+				}
+				return true;
+			}
+
+			@Override
+			public boolean acceptUndeclaredExtension(IBaseExtension<?, ?> theNextExt, List<IBase> theContainingElementPath, List<BaseRuntimeChildDefinition> theChildDefinitionPath, List<BaseRuntimeElementDefinition<?>> theElementDefinitionPath) {
+				return true;
+			}
+		});
+		assertThat(strings, Matchers.contains("http://foo"));
+	}
+
 	@Test
 	public void testVisitWithModelVisitor2() {
 		IModelVisitor2 visitor = mock(IModelVisitor2.class);
@@ -1038,6 +1071,11 @@ public class FhirTerserR4Test {
 		}
 	}
 
+	@Block
+	public static class MyValueSetExpansionComponent extends ValueSet.ValueSetExpansionComponent {
+		private static final long serialVersionUID = 2624360513249904086L;
+	}
+
 	@AfterClass
 	public static void afterClassClearContext() {
 		TestUtil.clearAllStaticFieldsForUnitTest();

src/changes/changes.xml

@@ -133,8 +133,12 @@
 				and version were still returned to the user. This has been corrected so that no details about
 				the resource are leaked.
 			</action>
+			<action type="fix">
+				Fix a failure in FhirTerser#visit when fields in model classes being visited contain custom subclasses of the
+				expected type.
+			</action>
 		</release>
-		<release version="4.0.1" date="2019-09-03" description="Igloo (Point Release)">
+		<release version="4.0.3" date="2019-09-03" description="Igloo (Point Release)">
 			<action type="fix">
 				This release contains no new or updated functionality, but addressed a dependency 
 				version that was left incorrectly requiring a SNAPSHOT maven build of the