From cd6d4302c34c38727265148b04d8b82d6e136b8c Mon Sep 17 00:00:00 2001
From: Diederik Muylwyk <diederik.muylwyk@gmail.com>
Date: Fri, 19 Oct 2018 15:13:51 -0400
Subject: [PATCH 1/6] Incremental work on FhirTerser.getValues(...)
 enhancements.

---
 .../java/ca/uhn/fhir/util/FhirTerser.java     | 150 +++++++---
 .../ca/uhn/fhir/util/FhirTerserDstu3Test.java | 264 ++++++++++++++++--
 2 files changed, 348 insertions(+), 66 deletions(-)

diff --git a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
index bf8df49e182..082daaf122c 100644
--- a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
+++ b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
@@ -1,36 +1,5 @@
 package ca.uhn.fhir.util;
 
-import static org.apache.commons.lang3.StringUtils.defaultString;
-import static org.apache.commons.lang3.StringUtils.isBlank;
-import static org.apache.commons.lang3.StringUtils.isNotBlank;
-
-/*
- * #%L
- * HAPI FHIR - Core Library
- * %%
- * Copyright (C) 2014 - 2018 University Health Network
- * %%
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- * 
- *      http://www.apache.org/licenses/LICENSE-2.0
- * 
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- * #L%
- */
-import java.util.*;
-import java.util.function.Predicate;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
-
-import org.apache.commons.lang3.Validate;
-import org.hl7.fhir.instance.model.api.*;
-
 import ca.uhn.fhir.context.*;
 import ca.uhn.fhir.context.BaseRuntimeElementDefinition.ChildTypeEnum;
 import ca.uhn.fhir.model.api.ExtensionDt;
@@ -40,6 +9,35 @@ import ca.uhn.fhir.model.base.composite.BaseContainedDt;
 import ca.uhn.fhir.model.base.composite.BaseResourceReferenceDt;
 import ca.uhn.fhir.model.primitive.StringDt;
 import ca.uhn.fhir.parser.DataFormatException;
+import org.apache.commons.lang3.Validate;
+import org.hl7.fhir.instance.model.api.*;
+
+import java.util.*;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+import static org.apache.commons.lang3.StringUtils.*;
+
+/*
+ * #%L
+ * HAPI FHIR - Core Library
+ * %%
+ * Copyright (C) 2014 - 2018 University Health Network
+ * %%
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * #L%
+ */
 
 public class FhirTerser {
 
@@ -215,8 +213,12 @@ public class FhirTerser {
 		return retVal.get(0);
 	}
 
-	@SuppressWarnings("unchecked")
 	private <T> List<T> getValues(BaseRuntimeElementCompositeDefinition<?> theCurrentDef, Object theCurrentObj, List<String> theSubList, Class<T> theWantedClass) {
+		return getValues(theCurrentDef, theCurrentObj, theSubList, theWantedClass, false);
+	}
+
+	@SuppressWarnings("unchecked")
+	private <T> List<T> getValues(BaseRuntimeElementCompositeDefinition<?> theCurrentDef, Object theCurrentObj, List<String> theSubList, Class<T> theWantedClass, boolean theCreate) {
 		String name = theSubList.get(0);
 		List<T> retVal = new ArrayList<>();
 
@@ -227,14 +229,71 @@ public class FhirTerser {
 				extensionUrl = extensionUrl.substring(0, endIndex);
 			}
 
-			List<ExtensionDt> extensions= Collections.emptyList();
+			// DSTU2
+			List<ExtensionDt> extensionDts = Collections.emptyList();
 			if (theCurrentObj instanceof ISupportsUndeclaredExtensions) {
-				extensions = ((ISupportsUndeclaredExtensions) theCurrentObj).getUndeclaredExtensionsByUrl(extensionUrl);
+				extensionDts = ((ISupportsUndeclaredExtensions) theCurrentObj).getUndeclaredExtensionsByUrl(extensionUrl);
+
+				if (extensionDts.isEmpty() && theCreate) {
+					// FIXME: Add a new extension with extensionUrl and null value.
+					// FIXME: Discern between extensions and modifier extensions.
+				}
 			} else if (theCurrentObj instanceof IBaseExtension) {
-				extensions = ((IBaseExtension)theCurrentObj).getExtension();
+				extensionDts = ((IBaseExtension) theCurrentObj).getExtension();
+
+				if (extensionDts.isEmpty() && theCreate) {
+					// FIXME: Add a new extension with extensionUrl and null value.
+				}
 			}
 
-			for (ExtensionDt next : extensions) {
+			for (ExtensionDt next : extensionDts) {
+				if (theWantedClass.isAssignableFrom(next.getClass())) {
+					retVal.add((T) next);
+				}
+			}
+
+			// DSTU3+
+			final String extensionUrlForLambda = extensionUrl;
+			List<IBaseExtension> extensions = Collections.emptyList();
+			if (theCurrentObj instanceof IBaseHasExtensions) {
+				extensions = ((IBaseHasExtensions) theCurrentObj).getExtension()
+					.stream()
+					.filter(t -> t.getUrl().equals(extensionUrlForLambda))
+					.distinct()
+					.collect(Collectors.toList());
+
+				if (extensions.isEmpty() && theCreate) {
+					IBaseExtension extension = ((IBaseHasExtensions) theCurrentObj).addExtension();
+					extension.setUrl(extensionUrl);
+					extensions.add(extension);
+				}
+			}
+//			List<IBaseExtension> modifierExtensions = Collections.emptyList();
+//			if (theCurrentObj instanceof IBaseHasModifierExtensions) {
+//				modifierExtensions = ((IBaseHasModifierExtensions) theCurrentObj).getModifierExtension()
+//					.stream()
+//					.filter(t -> t.getUrl().equals(extensionUrlForLambda))
+//					.collect(Collectors.toList());
+//
+//				if (modifierExtensions.isEmpty() && theCreate) {
+//					IBaseExtension modifierExtension = ((IBaseHasModifierExtensions) theCurrentObj).addModifierExtension();
+//					modifierExtension.setUrl(extensionUrl);
+//					modifierExtensions.add(modifierExtension);
+//				}
+//			}
+//
+//			List<IBaseExtension> allExtensions = Stream.of(extensions, modifierExtensions)
+//				.flatMap(Collection::stream)
+//				.distinct()
+//				.collect(Collectors.toList());
+//
+//			for (IBaseExtension next : allExtensions) {
+//				if (theWantedClass.isAssignableFrom(next.getClass())) {
+//					retVal.add((T) next);
+//				}
+//			}
+
+			for (IBaseExtension next : extensions) {
 				if (theWantedClass.isAssignableFrom(next.getClass())) {
 					retVal.add((T) next);
 				}
@@ -256,6 +315,14 @@ public class FhirTerser {
 		BaseRuntimeChildDefinition nextDef = theCurrentDef.getChildByNameOrThrowDataFormatException(name);
 		List<? extends IBase> values = nextDef.getAccessor().getValues(theCurrentObj);
 
+		if (values.isEmpty() && theCreate) {
+			IBase value = nextDef.getChildByName(name).newInstance();
+			nextDef.getMutator().addValue(theCurrentObj, value);
+			List<IBase> list = new ArrayList<>();
+			list.add(value);
+			values = list;
+		}
+
 		if (theSubList.size() == 1) {
 			if (nextDef instanceof RuntimeChildChoiceDefinition) {
 				for (IBase next : values) {
@@ -297,7 +364,12 @@ public class FhirTerser {
 		Class<Object> wantedClass = Object.class;
 
 		return getValues(theResource, thePath, wantedClass);
+	}
 
+	public List<Object> getValues(IBaseResource theResource, String thePath, boolean theCreate) {
+		Class<Object> wantedClass = Object.class;
+
+		return getValues(theResource, thePath, wantedClass, theCreate);
 	}
 
 	public <T> List<T> getValues(IBaseResource theResource, String thePath, Class<T> theWantedClass) {
@@ -306,6 +378,12 @@ public class FhirTerser {
 		return getValues(def, theResource, parts, theWantedClass);
 	}
 
+	public <T> List<T> getValues(IBaseResource theResource, String thePath, Class<T> theWantedClass, boolean theCreate) {
+		RuntimeResourceDefinition def = myContext.getResourceDefinition(theResource);
+		List<String> parts = parsePath(def, thePath);
+		return getValues(def, theResource, parts, theWantedClass, theCreate);
+	}
+
 	private List<String> parsePath(BaseRuntimeElementCompositeDefinition<?> theElementDef, String thePath) {
 		List<String> parts = new ArrayList<>();
 
diff --git a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
index dadc87e9b62..2cdfcba8030 100644
--- a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
+++ b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
@@ -1,41 +1,27 @@
 package ca.uhn.fhir.util;
 
-import static org.hamcrest.Matchers.containsInAnyOrder;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertSame;
-import static org.junit.Assert.assertThat;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.when;
+import ca.uhn.fhir.context.BaseRuntimeChildDefinition;
+import ca.uhn.fhir.context.BaseRuntimeElementDefinition;
+import ca.uhn.fhir.context.FhirContext;
+import ca.uhn.fhir.parser.DataFormatException;
+import org.hl7.fhir.dstu3.model.*;
+import org.hl7.fhir.dstu3.model.Patient.LinkType;
+import org.hl7.fhir.instance.model.api.IBase;
+import org.hl7.fhir.instance.model.api.IBaseExtension;
+import org.hl7.fhir.instance.model.api.IBaseReference;
+import org.junit.AfterClass;
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
 
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
 import java.util.ArrayList;
 import java.util.List;
 
-import org.hl7.fhir.dstu3.model.Bundle;
-import org.hl7.fhir.dstu3.model.Extension;
-import org.hl7.fhir.dstu3.model.Identifier;
-import org.hl7.fhir.dstu3.model.MarkdownType;
-import org.hl7.fhir.dstu3.model.Money;
-import org.hl7.fhir.dstu3.model.Observation;
-import org.hl7.fhir.dstu3.model.Organization;
-import org.hl7.fhir.dstu3.model.Patient;
-import org.hl7.fhir.dstu3.model.Patient.LinkType;
-import org.hl7.fhir.dstu3.model.Quantity;
-import org.hl7.fhir.dstu3.model.Reference;
-import org.hl7.fhir.dstu3.model.StringType;
-import org.hl7.fhir.instance.model.api.IBase;
-import org.hl7.fhir.instance.model.api.IBaseReference;
-import org.junit.AfterClass;
-import org.junit.Test;
-import org.mockito.ArgumentCaptor;
-
-import ca.uhn.fhir.context.BaseRuntimeChildDefinition;
-import ca.uhn.fhir.context.BaseRuntimeElementDefinition;
-import ca.uhn.fhir.context.FhirContext;
-import ca.uhn.fhir.parser.DataFormatException;
+import static org.hamcrest.Matchers.containsInAnyOrder;
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 public class FhirTerserDstu3Test {
 
@@ -183,6 +169,224 @@ public class FhirTerserDstu3Test {
 		assertSame(ref, refs.get(0));
 	}
 
+	@Test
+	public void testGetValues() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addExtension()
+			.setUrl("http://acme.org/extension")
+			.setValue(new StringType("value"));
+		p.addExtension()
+			.setUrl("http://acme.org/otherExtension")
+			.setValue(new StringType("otherValue"));
+//		p.addModifierExtension()
+//			.setUrl("http://acme.org/extension")
+//			.setValue(new StringType("modifierValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof PrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertTrue(((BooleanType) values.get(0)).booleanValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+//		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/extension')");
+//		assertEquals(1, values.size());
+//		assertTrue(values.get(0) instanceof IBaseExtension);
+//		assertTrue(values.get(0) instanceof Extension);
+//		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+//		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesAndModify() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addExtension()
+			.setUrl("http://acme.org/extension")
+			.setValue(new StringType("value"));
+		p.addExtension()
+			.setUrl("http://acme.org/otherExtension")
+			.setValue(new StringType("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof PrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertTrue(((BooleanType) values.get(0)).booleanValue());
+
+		((BooleanType) values.get(0)).setValue(Boolean.FALSE);
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof PrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertFalse(((BooleanType) values.get(0)).booleanValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		((Extension) values.get(0)).setValue(new StringType("modifiedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifiedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesWithWantedClass() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addExtension()
+			.setUrl("http://acme.org/extension")
+			.setValue(new StringType("value"));
+		p.addExtension()
+			.setUrl("http://acme.org/otherExtension")
+			.setValue(new StringType("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<PrimitiveType> values = ourCtx.newTerser().getValues(p, "Patient.active", PrimitiveType.class);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertTrue(((BooleanType) values.get(0)).booleanValue());
+
+		List<Extension> extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertEquals("value", ((StringType) (extValues.get(0).getValue())).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesWithWantedClassAndModify() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addExtension()
+			.setUrl("http://acme.org/extension")
+			.setValue(new StringType("value"));
+		p.addExtension()
+			.setUrl("http://acme.org/otherExtension")
+			.setValue(new StringType("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<PrimitiveType> values = ourCtx.newTerser().getValues(p, "Patient.active", PrimitiveType.class);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertTrue(((BooleanType) values.get(0)).booleanValue());
+
+		((BooleanType) values.get(0)).setValue(Boolean.FALSE);
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.active", PrimitiveType.class);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertFalse(((BooleanType) values.get(0)).booleanValue());
+
+		List<Extension> extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertEquals("value", ((StringType) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues.get(0).setValue(new StringType("modifiedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertEquals("modifiedValue", ((StringType) (extValues.get(0).getValue())).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesWithWantedClassAndTheCreate() {
+		Patient p = new Patient();
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<PrimitiveType> values = ourCtx.newTerser().getValues(p, "Patient.active", PrimitiveType.class, true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertNull(((BooleanType) values.get(0)).getValue());
+
+		List<Extension> extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", Extension.class, true);
+		assertEquals(1, extValues.size());
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertNull(extValues.get(0).getValue());
+	}
+
+	@Test
+	public void testGetValuesWithTheCreate() {
+   	Patient p = new Patient();
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+   	List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active", true);
+   	assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof PrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertNull(((BooleanType) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+		assertNull(((Extension) values.get(0)).getValue());
+	}
+
+	@Test
+	public void testGetValuesWithTheCreateAndNoOverwrite() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addExtension()
+			.setUrl("http://acme.org/extension")
+			.setValue(new StringType("value"));
+		p.addExtension()
+			.setUrl("http://acme.org/otherExtension")
+			.setValue(new StringType("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof PrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertTrue(((BooleanType) values.get(0)).booleanValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+	}
+
 	@Test
 	public void testVisitWithModelVisitor2() {
 		IModelVisitor2 visitor = mock(IModelVisitor2.class);

From 225007d681fb1cd45511cfc02d524dc28852a9ac Mon Sep 17 00:00:00 2001
From: Diederik Muylwyk <diederik.muylwyk@gmail.com>
Date: Fri, 19 Oct 2018 18:24:26 -0400
Subject: [PATCH 2/6] Completed work on FhirTerser.getValues(...) enhancements.

---
 .../java/ca/uhn/fhir/util/FhirTerser.java     | 184 +++++++++----
 .../ca/uhn/fhir/util/FhirTerserDstu2Test.java | 245 ++++++++++++++++--
 .../ca/uhn/fhir/util/FhirTerserDstu3Test.java | 133 +++++++++-
 3 files changed, 481 insertions(+), 81 deletions(-)

diff --git a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
index 082daaf122c..44550187d2b 100644
--- a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
+++ b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
@@ -230,72 +230,100 @@ public class FhirTerser {
 			}
 
 			// DSTU2
-			List<ExtensionDt> extensionDts = Collections.emptyList();
-			if (theCurrentObj instanceof ISupportsUndeclaredExtensions) {
-				extensionDts = ((ISupportsUndeclaredExtensions) theCurrentObj).getUndeclaredExtensionsByUrl(extensionUrl);
+			if (myContext.getVersion().getVersion().isOlderThan(FhirVersionEnum.DSTU3)) {
+				List<ExtensionDt> extensionDts = Collections.emptyList();
+				if (theCurrentObj instanceof ISupportsUndeclaredExtensions) {
+					extensionDts = ((ISupportsUndeclaredExtensions) theCurrentObj).getUndeclaredExtensionsByUrl(extensionUrl);
 
-				if (extensionDts.isEmpty() && theCreate) {
-					// FIXME: Add a new extension with extensionUrl and null value.
-					// FIXME: Discern between extensions and modifier extensions.
+					if (extensionDts.isEmpty() && theCreate) {
+						// We assume the extension is not a modifier extension.
+						extensionDts = new ArrayList<>(); // Implementation of ISupportsUndeclaredExtensions.getUndeclaredExtensionsByUrl(...) returns unmodifiable list.
+						ExtensionDt extensionDt = ((ISupportsUndeclaredExtensions) theCurrentObj).addUndeclaredExtension(false, extensionUrl);
+						extensionDts.add(extensionDt);
+					}
+				} else if (theCurrentObj instanceof IBaseExtension) {
+					extensionDts = ((IBaseExtension) theCurrentObj).getExtension();
+
+					if (extensionDts.isEmpty() && theCreate) {
+						// We assume the extension is not a modifier extension.
+						ExtensionDt extensionDt = new ExtensionDt();
+						extensionDt.setUrl(extensionUrl);
+						((IBaseExtension) theCurrentObj).getExtension().add(extensionDt);
+						extensionDts.add(extensionDt);
+					}
 				}
-			} else if (theCurrentObj instanceof IBaseExtension) {
-				extensionDts = ((IBaseExtension) theCurrentObj).getExtension();
 
-				if (extensionDts.isEmpty() && theCreate) {
-					// FIXME: Add a new extension with extensionUrl and null value.
+				for (ExtensionDt next : extensionDts) {
+					if (theWantedClass.isAssignableFrom(next.getClass())) {
+						retVal.add((T) next);
+					}
+				}
+			} else {
+				// DSTU3+
+				final String extensionUrlForLambda = extensionUrl;
+				List<IBaseExtension> extensions = Collections.emptyList();
+				if (theCurrentObj instanceof IBaseHasExtensions) {
+					extensions = ((IBaseHasExtensions) theCurrentObj).getExtension()
+						.stream()
+						.filter(t -> t.getUrl().equals(extensionUrlForLambda))
+						.collect(Collectors.toList());
+
+					if (extensions.isEmpty() && theCreate) {
+						IBaseExtension extension = ((IBaseHasExtensions) theCurrentObj).addExtension();
+						extension.setUrl(extensionUrl);
+						extensions.add(extension);
+					}
+				}
+
+				for (IBaseExtension next : extensions) {
+					if (theWantedClass.isAssignableFrom(next.getClass())) {
+						retVal.add((T) next);
+					}
 				}
 			}
 
-			for (ExtensionDt next : extensionDts) {
-				if (theWantedClass.isAssignableFrom(next.getClass())) {
-					retVal.add((T) next);
+			if (theSubList.size() > 1) {
+				List<T> values = retVal;
+				retVal = new ArrayList<>();
+				for (T nextElement : values) {
+					BaseRuntimeElementCompositeDefinition<?> nextChildDef = (BaseRuntimeElementCompositeDefinition<?>) myContext.getElementDefinition((Class<? extends IBase>) nextElement.getClass());
+					List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass);
+					retVal.addAll(foundValues);
 				}
 			}
 
+			return retVal;
+		}
+
+		if (name.startsWith("modifierExtension('")) {
+			String extensionUrl = name.substring("modifierExtension('".length());
+			int endIndex = extensionUrl.indexOf('\'');
+			if (endIndex != -1) {
+				extensionUrl = extensionUrl.substring(0, endIndex);
+			}
+
 			// DSTU3+
-			final String extensionUrlForLambda = extensionUrl;
-			List<IBaseExtension> extensions = Collections.emptyList();
-			if (theCurrentObj instanceof IBaseHasExtensions) {
-				extensions = ((IBaseHasExtensions) theCurrentObj).getExtension()
-					.stream()
-					.filter(t -> t.getUrl().equals(extensionUrlForLambda))
-					.distinct()
-					.collect(Collectors.toList());
+			if (myContext.getVersion().getVersion().isEqualOrNewerThan(FhirVersionEnum.DSTU3)) {
+				final String extensionUrlForLambda = extensionUrl;
+				List<IBaseExtension> extensions = Collections.emptyList();
 
-				if (extensions.isEmpty() && theCreate) {
-					IBaseExtension extension = ((IBaseHasExtensions) theCurrentObj).addExtension();
-					extension.setUrl(extensionUrl);
-					extensions.add(extension);
+				if (theCurrentObj instanceof IBaseHasModifierExtensions) {
+					extensions = ((IBaseHasModifierExtensions) theCurrentObj).getModifierExtension()
+						.stream()
+						.filter(t -> t.getUrl().equals(extensionUrlForLambda))
+						.collect(Collectors.toList());
+
+					if (extensions.isEmpty() && theCreate) {
+						IBaseExtension modifierExtension = ((IBaseHasModifierExtensions) theCurrentObj).addModifierExtension();
+						modifierExtension.setUrl(extensionUrl);
+						extensions.add(modifierExtension);
+					}
 				}
-			}
-//			List<IBaseExtension> modifierExtensions = Collections.emptyList();
-//			if (theCurrentObj instanceof IBaseHasModifierExtensions) {
-//				modifierExtensions = ((IBaseHasModifierExtensions) theCurrentObj).getModifierExtension()
-//					.stream()
-//					.filter(t -> t.getUrl().equals(extensionUrlForLambda))
-//					.collect(Collectors.toList());
-//
-//				if (modifierExtensions.isEmpty() && theCreate) {
-//					IBaseExtension modifierExtension = ((IBaseHasModifierExtensions) theCurrentObj).addModifierExtension();
-//					modifierExtension.setUrl(extensionUrl);
-//					modifierExtensions.add(modifierExtension);
-//				}
-//			}
-//
-//			List<IBaseExtension> allExtensions = Stream.of(extensions, modifierExtensions)
-//				.flatMap(Collection::stream)
-//				.distinct()
-//				.collect(Collectors.toList());
-//
-//			for (IBaseExtension next : allExtensions) {
-//				if (theWantedClass.isAssignableFrom(next.getClass())) {
-//					retVal.add((T) next);
-//				}
-//			}
 
-			for (IBaseExtension next : extensions) {
-				if (theWantedClass.isAssignableFrom(next.getClass())) {
-					retVal.add((T) next);
+				for (IBaseExtension next : extensions) {
+					if (theWantedClass.isAssignableFrom(next.getClass())) {
+						retVal.add((T) next);
+					}
 				}
 			}
 
@@ -360,24 +388,74 @@ public class FhirTerser {
 		return retVal;
 	}
 
+	/**
+	 * Returns values stored in an element identified by its path. The list of values is of
+	 * type {@link Object}.
+	 *
+	 * <p>Note: this method does not support creation of null-valued modifier extensions for
+	 * versions of FHIR prior to DSTU3.</p>
+	 *
+	 * @param theResource The resource instance to be accessed. Must not be null.
+	 * @param thePath The path for the element to be accessed.
+	 * @return A list of values of type {@link Object}.
+	 */
 	public List<Object> getValues(IBaseResource theResource, String thePath) {
 		Class<Object> wantedClass = Object.class;
 
 		return getValues(theResource, thePath, wantedClass);
 	}
 
+	/**
+	 * Returns values stored in an element identified by its path. The list of values is of
+	 * type {@link Object}.
+	 *
+	 * <p>Note: this method does not support creation of null-valued modifier extensions for
+	 * versions of FHIR prior to DSTU3.</p>
+	 *
+	 * @param theResource The resource instance to be accessed. Must not be null.
+	 * @param thePath The path for the element to be accessed.
+	 * @param theCreate When set to <code>true</code>, the terser will create a null-valued element where none exists.
+	 * @return A list of values of type {@link Object}.
+	 */
 	public List<Object> getValues(IBaseResource theResource, String thePath, boolean theCreate) {
 		Class<Object> wantedClass = Object.class;
 
 		return getValues(theResource, thePath, wantedClass, theCreate);
 	}
 
+	/**
+	 * Returns values stored in an element identified by its path. The list of values is of
+	 * type <code>theWantedClass</code>.
+	 *
+	 * <p>Note: this method does not support creation of null-valued modifier extensions for
+	 * versions of FHIR prior to DSTU3.</p>
+	 *
+	 * @param theResource The resource instance to be accessed. Must not be null.
+	 * @param thePath The path for the element to be accessed.
+	 * @param theWantedClass The desired class to be returned in a list.
+	 * @param <T> Type declared by <code>theWantedClass</code>
+	 * @return A list of values of type <code>theWantedClass</code>.
+	 */
 	public <T> List<T> getValues(IBaseResource theResource, String thePath, Class<T> theWantedClass) {
 		RuntimeResourceDefinition def = myContext.getResourceDefinition(theResource);
 		List<String> parts = parsePath(def, thePath);
 		return getValues(def, theResource, parts, theWantedClass);
 	}
 
+	/**
+	 * Returns values stored in an element identified by its path. The list of values is of
+	 * type <code>theWantedClass</code>.
+	 *
+	 * <p>Note: this method does not support creation of null-valued modifier extensions for
+	 * versions of FHIR prior to DSTU3.</p>
+	 *
+	 * @param theResource The resource instance to be accessed. Must not be null.
+	 * @param thePath The path for the element to be accessed.
+	 * @param theWantedClass The desired class to be returned in a list.
+	 * @param theCreate When set to <code>true</code>, the terser will create a null-valued element where none exists.
+	 * @param <T> Type declared by <code>theWantedClass</code>
+	 * @return A list of values of type <code>theWantedClass</code>.
+	 */
 	public <T> List<T> getValues(IBaseResource theResource, String thePath, Class<T> theWantedClass, boolean theCreate) {
 		RuntimeResourceDefinition def = myContext.getResourceDefinition(theResource);
 		List<String> parts = parsePath(def, thePath);
diff --git a/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java b/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
index d4816152d0a..0139b2d6b13 100644
--- a/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
+++ b/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
@@ -1,24 +1,5 @@
 package ca.uhn.fhir.util;
 
-import static org.hamcrest.Matchers.containsInAnyOrder;
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertSame;
-import static org.junit.Assert.assertThat;
-import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.when;
-
-import java.lang.reflect.ParameterizedType;
-import java.lang.reflect.Type;
-import java.util.List;
-
-import org.hl7.fhir.instance.model.api.IBase;
-import org.hl7.fhir.instance.model.api.IBaseReference;
-import org.junit.AfterClass;
-import org.junit.Test;
-import org.mockito.ArgumentCaptor;
-
 import ca.uhn.fhir.context.BaseRuntimeChildDefinition;
 import ca.uhn.fhir.context.BaseRuntimeElementDefinition;
 import ca.uhn.fhir.context.FhirContext;
@@ -31,9 +12,26 @@ import ca.uhn.fhir.model.dstu2.resource.Bundle;
 import ca.uhn.fhir.model.dstu2.resource.Observation;
 import ca.uhn.fhir.model.dstu2.resource.Organization;
 import ca.uhn.fhir.model.dstu2.resource.Patient;
+import ca.uhn.fhir.model.primitive.BooleanDt;
 import ca.uhn.fhir.model.primitive.MarkdownDt;
 import ca.uhn.fhir.model.primitive.StringDt;
 import ca.uhn.fhir.parser.DataFormatException;
+import org.hl7.fhir.instance.model.api.IBase;
+import org.hl7.fhir.instance.model.api.IBaseExtension;
+import org.hl7.fhir.instance.model.api.IBaseReference;
+import org.hl7.fhir.instance.model.api.IPrimitiveType;
+import org.junit.AfterClass;
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.List;
+
+import static org.hamcrest.Matchers.containsInAnyOrder;
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 public class FhirTerserDstu2Test {
 
@@ -180,6 +178,215 @@ public class FhirTerserDstu2Test {
 		assertEquals(1, refs.size());
 		assertSame(ref, refs.get(0));
 	}
+
+	@Test
+	public void testGetValues() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesAndModify() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		((BooleanDt) values.get(0)).setValue(Boolean.FALSE);
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertFalse(((BooleanDt) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		((ExtensionDt) values.get(0)).setValue(new StringDt("modifiedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifiedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesMultiple() {
+		Patient p = new Patient();
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value1"));
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value2"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value1", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(1)).getUrl());
+		assertEquals("value2", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesWithWantedClass() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<IPrimitiveType> values = ourCtx.newTerser().getValues(p, "Patient.active", IPrimitiveType.class);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		List<ExtensionDt> extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertEquals("value", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesWithWantedClassAndModify() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<IPrimitiveType> values = ourCtx.newTerser().getValues(p, "Patient.active", IPrimitiveType.class);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		((BooleanDt) values.get(0)).setValue(Boolean.FALSE);
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.active", IPrimitiveType.class);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertFalse(((BooleanDt) values.get(0)).getValue());
+
+		List<ExtensionDt> extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertEquals("value", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues.get(0).setValue(new StringDt("modifiedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertEquals("modifiedValue", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesWithWantedClassAndTheCreate() {
+		Patient p = new Patient();
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<IPrimitiveType> values = ourCtx.newTerser().getValues(p, "Patient.active", IPrimitiveType.class, true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertNull(((BooleanDt) values.get(0)).getValue());
+
+		List<ExtensionDt> extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", ExtensionDt.class, true);
+		assertEquals(1, extValues.size());
+		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
+		assertNull(extValues.get(0).getValue());
+	}
+
+	@Test
+	public void testGetValuesWithTheCreate() {
+		Patient p = new Patient();
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertNull(((BooleanDt) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertNull(((ExtensionDt) values.get(0)).getValue());
+	}
+
+	@Test
+	public void testGetValuesWithTheCreateAndNoOverwrite() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+	}
 	
 	@Test
 	public void testVisitWithModelVisitor2() {
diff --git a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
index 2cdfcba8030..bf0ffde4ee0 100644
--- a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
+++ b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
@@ -179,9 +179,9 @@ public class FhirTerserDstu3Test {
 		p.addExtension()
 			.setUrl("http://acme.org/otherExtension")
 			.setValue(new StringType("otherValue"));
-//		p.addModifierExtension()
-//			.setUrl("http://acme.org/extension")
-//			.setValue(new StringType("modifierValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -198,12 +198,12 @@ public class FhirTerserDstu3Test {
 		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
 		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
 
-//		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/extension')");
-//		assertEquals(1, values.size());
-//		assertTrue(values.get(0) instanceof IBaseExtension);
-//		assertTrue(values.get(0) instanceof Extension);
-//		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
-//		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -216,6 +216,9 @@ public class FhirTerserDstu3Test {
 		p.addExtension()
 			.setUrl("http://acme.org/otherExtension")
 			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -252,6 +255,68 @@ public class FhirTerserDstu3Test {
 		assertTrue(values.get(0) instanceof Extension);
 		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
 		assertEquals("modifiedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		((Extension) values.get(0)).setValue(new StringType("modifiedModifierValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifiedModifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+	}
+
+	@Test
+	public void testGetValuesMultiple() {
+		Patient p = new Patient();
+		p.addExtension()
+			.setUrl("http://acme.org/extension")
+			.setValue(new StringType("value1"));
+		p.addExtension()
+			.setUrl("http://acme.org/extension")
+			.setValue(new StringType("value2"));
+		p.addExtension()
+			.setUrl("http://acme.org/otherExtension")
+			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue1"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue2"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+		assertEquals("value1", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(1)).getUrl());
+		assertEquals("value2", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue1", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(1)).getUrl());
+		assertEquals("modifierValue2", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -264,6 +329,9 @@ public class FhirTerserDstu3Test {
 		p.addExtension()
 			.setUrl("http://acme.org/otherExtension")
 			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -277,6 +345,12 @@ public class FhirTerserDstu3Test {
 		assertTrue(extValues.get(0).getValue() instanceof StringType);
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
 		assertEquals("value", ((StringType) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertEquals("modifierValue", ((StringType) (extValues.get(0).getValue())).getValueAsString());
 	}
 
 	@Test
@@ -289,6 +363,9 @@ public class FhirTerserDstu3Test {
 		p.addExtension()
 			.setUrl("http://acme.org/otherExtension")
 			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -321,6 +398,22 @@ public class FhirTerserDstu3Test {
 		assertTrue(extValues.get(0).getValue() instanceof StringType);
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
 		assertEquals("modifiedValue", ((StringType) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertEquals("modifierValue", ((StringType) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues.get(0).setValue(new StringType("modifiedModifierValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertEquals("modifiedModifierValue", ((StringType) (extValues.get(0).getValue())).getValueAsString());
 	}
 
 	@Test
@@ -338,6 +431,11 @@ public class FhirTerserDstu3Test {
 		assertEquals(1, extValues.size());
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
 		assertNull(extValues.get(0).getValue());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", Extension.class, true);
+		assertEquals(1, extValues.size());
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertNull(extValues.get(0).getValue());
 	}
 
 	@Test
@@ -358,6 +456,13 @@ public class FhirTerserDstu3Test {
 		assertTrue(values.get(0) instanceof Extension);
 		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
 		assertNull(((Extension) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertNull(((Extension) values.get(0)).getValue());
 	}
 
 	@Test
@@ -370,6 +475,9 @@ public class FhirTerserDstu3Test {
 		p.addExtension()
 			.setUrl("http://acme.org/otherExtension")
 			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -385,6 +493,13 @@ public class FhirTerserDstu3Test {
 		assertTrue(values.get(0) instanceof Extension);
 		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
 		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
 	}
 
 	@Test

From 688e159493b16bf290a1cb6c2fe6284645862f4f Mon Sep 17 00:00:00 2001
From: Diederik Muylwyk <diederik.muylwyk@gmail.com>
Date: Mon, 22 Oct 2018 18:22:03 -0400
Subject: [PATCH 3/6] Additional work on FhirTerser.getValues(...)
 enhancements.

---
 .../java/ca/uhn/fhir/util/FhirTerser.java     |   6 +-
 .../ca/uhn/fhir/util/FhirTerserDstu2Test.java |  88 ++++++++++++-
 .../ca/uhn/fhir/util/FhirTerserDstu3Test.java | 121 +++++++++++++++++-
 3 files changed, 208 insertions(+), 7 deletions(-)

diff --git a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
index 44550187d2b..ca32e26447c 100644
--- a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
+++ b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
@@ -287,7 +287,7 @@ public class FhirTerser {
 				retVal = new ArrayList<>();
 				for (T nextElement : values) {
 					BaseRuntimeElementCompositeDefinition<?> nextChildDef = (BaseRuntimeElementCompositeDefinition<?>) myContext.getElementDefinition((Class<? extends IBase>) nextElement.getClass());
-					List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass);
+					List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass, theCreate);
 					retVal.addAll(foundValues);
 				}
 			}
@@ -332,7 +332,7 @@ public class FhirTerser {
 				retVal = new ArrayList<>();
 				for (T nextElement : values) {
 					BaseRuntimeElementCompositeDefinition<?> nextChildDef = (BaseRuntimeElementCompositeDefinition<?>) myContext.getElementDefinition((Class<? extends IBase>) nextElement.getClass());
-					List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass);
+					List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass, theCreate);
 					retVal.addAll(foundValues);
 				}
 			}
@@ -381,7 +381,7 @@ public class FhirTerser {
 		} else {
 			for (IBase nextElement : values) {
 				BaseRuntimeElementCompositeDefinition<?> nextChildDef = (BaseRuntimeElementCompositeDefinition<?>) myContext.getElementDefinition(nextElement.getClass());
-				List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass);
+				List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass, theCreate);
 				retVal.addAll(foundValues);
 			}
 		}
diff --git a/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java b/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
index 0139b2d6b13..e66eabdc9cd 100644
--- a/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
+++ b/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
@@ -185,6 +185,7 @@ public class FhirTerserDstu2Test {
 		p.setActive(true);
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -200,6 +201,13 @@ public class FhirTerserDstu2Test {
 		assertTrue(values.get(0) instanceof ExtensionDt);
 		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
 		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -208,6 +216,7 @@ public class FhirTerserDstu2Test {
 		p.setActive(true);
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -244,6 +253,24 @@ public class FhirTerserDstu2Test {
 		assertTrue(values.get(0) instanceof ExtensionDt);
 		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
 		assertEquals("modifiedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		((ExtensionDt) values.get(0)).setValue(new StringDt("modifiedNestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifiedNestedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -252,6 +279,8 @@ public class FhirTerserDstu2Test {
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value1"));
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value2"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue1"));
+		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue2"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -265,6 +294,17 @@ public class FhirTerserDstu2Test {
 		assertTrue(values.get(1) instanceof ExtensionDt);
 		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(1)).getUrl());
 		assertEquals("value2", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("nestedValue1", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(1)).getUrl());
+		assertEquals("nestedValue2", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -273,6 +313,7 @@ public class FhirTerserDstu2Test {
 		p.setActive(true);
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -285,7 +326,13 @@ public class FhirTerserDstu2Test {
 		assertEquals(1, extValues.size());
 		assertTrue(extValues.get(0).getValue() instanceof StringDt);
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
-		assertEquals("value", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
+		assertEquals("value", ((StringDt) extValues.get(0).getValue()).getValueAsString());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/childExtension", extValues.get(0).getUrl());
+		assertEquals("nestedValue", ((StringDt) extValues.get(0).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -294,6 +341,7 @@ public class FhirTerserDstu2Test {
 		p.setActive(true);
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -326,6 +374,22 @@ public class FhirTerserDstu2Test {
 		assertTrue(extValues.get(0).getValue() instanceof StringDt);
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
 		assertEquals("modifiedValue", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/childExtension", extValues.get(0).getUrl());
+		assertEquals("nestedValue", ((StringDt) extValues.get(0).getValue()).getValueAsString());
+
+		extValues.get(0).setValue(new StringDt("modifiedNestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/childExtension", extValues.get(0).getUrl());
+		assertEquals("modifiedNestedValue", ((StringDt) extValues.get(0).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -343,6 +407,11 @@ public class FhirTerserDstu2Test {
 		assertEquals(1, extValues.size());
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
 		assertNull(extValues.get(0).getValue());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", ExtensionDt.class, true);
+		assertEquals(1, extValues.size());
+		assertEquals("http://acme.org/childExtension", extValues.get(0).getUrl());
+		assertNull(extValues.get(0).getValue());
 	}
 
 	@Test
@@ -363,6 +432,13 @@ public class FhirTerserDstu2Test {
 		assertTrue(values.get(0) instanceof ExtensionDt);
 		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
 		assertNull(((ExtensionDt) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertNull(((ExtensionDt) values.get(0)).getValue());
 	}
 
 	@Test
@@ -371,6 +447,7 @@ public class FhirTerserDstu2Test {
 		p.setActive(true);
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -380,12 +457,19 @@ public class FhirTerserDstu2Test {
 		assertTrue(values.get(0) instanceof BooleanDt);
 		assertTrue(((BooleanDt) values.get(0)).getValue());
 
-		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", true);
 		assertEquals(1, values.size());
 		assertTrue(values.get(0) instanceof IBaseExtension);
 		assertTrue(values.get(0) instanceof ExtensionDt);
 		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
 		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
 	}
 	
 	@Test
diff --git a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
index bf0ffde4ee0..923762241f8 100644
--- a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
+++ b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
@@ -182,6 +182,11 @@ public class FhirTerserDstu3Test {
 		p.addModifierExtension()
 			.setUrl("http://acme.org/modifierExtension")
 			.setValue(new StringType("modifierValue"));
+		p.addExtension()
+			.setUrl("http://acme.org/parentExtension")
+			.addExtension()
+			.setUrl("http://acme.org/childExtension")
+			.setValue(new StringType("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -204,6 +209,13 @@ public class FhirTerserDstu3Test {
 		assertTrue(values.get(0) instanceof Extension);
 		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
 		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -219,6 +231,11 @@ public class FhirTerserDstu3Test {
 		p.addModifierExtension()
 			.setUrl("http://acme.org/modifierExtension")
 			.setValue(new StringType("modifierValue"));
+		p.addExtension()
+			.setUrl("http://acme.org/parentExtension")
+			.addExtension()
+			.setUrl("http://acme.org/childExtension")
+			.setValue(new StringType("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -273,6 +290,24 @@ public class FhirTerserDstu3Test {
 		assertTrue(values.get(0) instanceof Extension);
 		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
 		assertEquals("modifiedModifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		((Extension) values.get(0)).setValue(new StringType("modifiedNestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifiedNestedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -293,6 +328,16 @@ public class FhirTerserDstu3Test {
 		p.addModifierExtension()
 			.setUrl("http://acme.org/modifierExtension")
 			.setValue(new StringType("modifierValue2"));
+		p.addExtension()
+			.setUrl("http://acme.org/parentExtension")
+			.addExtension()
+			.setUrl("http://acme.org/childExtension")
+			.setValue(new StringType("nestedValue1"));
+		p.addExtension()
+			.setUrl("http://acme.org/parentExtension")
+			.addExtension()
+			.setUrl("http://acme.org/childExtension")
+			.setValue(new StringType("nestedValue2"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -317,6 +362,17 @@ public class FhirTerserDstu3Test {
 		assertTrue(values.get(1) instanceof Extension);
 		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(1)).getUrl());
 		assertEquals("modifierValue2", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("nestedValue1", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof  IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(1)).getUrl());
+		assertEquals("nestedValue2", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -332,6 +388,11 @@ public class FhirTerserDstu3Test {
 		p.addModifierExtension()
 			.setUrl("http://acme.org/modifierExtension")
 			.setValue(new StringType("modifierValue"));
+		p.addExtension()
+			.setUrl("http://acme.org/parentExtension")
+			.addExtension()
+			.setUrl("http://acme.org/childExtension")
+			.setValue(new StringType("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -351,6 +412,12 @@ public class FhirTerserDstu3Test {
 		assertTrue(extValues.get(0).getValue() instanceof StringType);
 		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
 		assertEquals("modifierValue", ((StringType) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/childExtension", extValues.get(0).getUrl());
+		assertEquals("nestedValue", ((StringType) extValues.get(0).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -366,6 +433,11 @@ public class FhirTerserDstu3Test {
 		p.addModifierExtension()
 			.setUrl("http://acme.org/modifierExtension")
 			.setValue(new StringType("modifierValue"));
+		p.addExtension()
+			.setUrl("http://acme.org/parentExtension")
+			.addExtension()
+			.setUrl("http://acme.org/childExtension")
+			.setValue(new StringType("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -414,6 +486,22 @@ public class FhirTerserDstu3Test {
 		assertTrue(extValues.get(0).getValue() instanceof StringType);
 		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
 		assertEquals("modifiedModifierValue", ((StringType) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/childExtension", extValues.get(0).getUrl());
+		assertEquals("nestedValue", ((StringType) extValues.get(0).getValue()).getValueAsString());
+
+		extValues.get(0).setValue(new StringType("modifiedNestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", Extension.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringType);
+		assertEquals("http://acme.org/childExtension", extValues.get(0).getUrl());
+		assertEquals("modifiedNestedValue", ((StringType) extValues.get(0).getValue()).getValueAsString());
 	}
 
 	@Test
@@ -436,6 +524,11 @@ public class FhirTerserDstu3Test {
 		assertEquals(1, extValues.size());
 		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
 		assertNull(extValues.get(0).getValue());
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", Extension.class, true);
+		assertEquals(1, extValues.size());
+		assertEquals("http://acme.org/childExtension", extValues.get(0).getUrl());
+		assertNull(extValues.get(0).getValue());
 	}
 
 	@Test
@@ -463,6 +556,18 @@ public class FhirTerserDstu3Test {
 		assertTrue(values.get(0) instanceof Extension);
 		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
 		assertNull(((Extension) values.get(0)).getValue());
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", true);
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(0)).getUrl());
+		assertNull(((Extension) values.get(0)).getValue());
 	}
 
 	@Test
@@ -478,6 +583,11 @@ public class FhirTerserDstu3Test {
 		p.addModifierExtension()
 			.setUrl("http://acme.org/modifierExtension")
 			.setValue(new StringType("modifierValue"));
+		p.addExtension()
+			.setUrl("http://acme.org/parentExtension")
+			.addExtension()
+			.setUrl("http://acme.org/childExtension")
+			.setValue(new StringType("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
 
@@ -487,19 +597,26 @@ public class FhirTerserDstu3Test {
 		assertTrue(values.get(0) instanceof BooleanType);
 		assertTrue(((BooleanType) values.get(0)).booleanValue());
 
-		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", true);
 		assertEquals(1, values.size());
 		assertTrue(values.get(0) instanceof IBaseExtension);
 		assertTrue(values.get(0) instanceof Extension);
 		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
 		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
 
-		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", true);
 		assertEquals(1, values.size());
 		assertTrue(values.get(0) instanceof IBaseExtension);
 		assertTrue(values.get(0) instanceof Extension);
 		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
 		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
 	}
 
 	@Test

From 4e414a16fb7d08021f5467a12dede76659f3a155 Mon Sep 17 00:00:00 2001
From: Diederik Muylwyk <diederik.muylwyk@gmail.com>
Date: Mon, 22 Oct 2018 18:37:34 -0400
Subject: [PATCH 4/6] More additional work on FhirTerser.getValues(...)
 enhancements. Ready for review.

---
 .../test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java    | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
index 923762241f8..047256fff6d 100644
--- a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
+++ b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
@@ -535,8 +535,6 @@ public class FhirTerserDstu3Test {
 	public void testGetValuesWithTheCreate() {
    	Patient p = new Patient();
 
-		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
-
    	List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active", true);
    	assertEquals(1, values.size());
 		assertTrue(values.get(0) instanceof PrimitiveType);
@@ -557,12 +555,7 @@ public class FhirTerserDstu3Test {
 		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
 		assertNull(((Extension) values.get(0)).getValue());
 
-		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
-
 		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", true);
-
-		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
-
 		assertEquals(1, values.size());
 		assertTrue(values.get(0) instanceof  IBaseExtension);
 		assertTrue(values.get(0) instanceof Extension);

From 21a0390e6e906e88c1525ae308b92abb30f85fcc Mon Sep 17 00:00:00 2001
From: Diederik Muylwyk <diederik.muylwyk@gmail.com>
Date: Wed, 24 Oct 2018 11:43:19 -0400
Subject: [PATCH 5/6] Even more additional work on FhirTerser.getValues(...)
 enhancements. Almost ready for review.

---
 .../api/ISupportsUndeclaredExtensions.java    |   7 +-
 .../java/ca/uhn/fhir/util/FhirTerser.java     | 183 ++++++++---
 .../ca/uhn/fhir/util/FhirTerserDstu2Test.java | 298 ++++++++++++++++++
 .../ca/uhn/fhir/util/FhirTerserDstu3Test.java | 234 ++++++++++++++
 4 files changed, 681 insertions(+), 41 deletions(-)

diff --git a/hapi-fhir-base/src/main/java/ca/uhn/fhir/model/api/ISupportsUndeclaredExtensions.java b/hapi-fhir-base/src/main/java/ca/uhn/fhir/model/api/ISupportsUndeclaredExtensions.java
index afd252ed349..ee6402578bc 100644
--- a/hapi-fhir-base/src/main/java/ca/uhn/fhir/model/api/ISupportsUndeclaredExtensions.java
+++ b/hapi-fhir-base/src/main/java/ca/uhn/fhir/model/api/ISupportsUndeclaredExtensions.java
@@ -20,10 +20,10 @@ package ca.uhn.fhir.model.api;
  * #L%
  */
 
-import java.util.List;
-
 import org.hl7.fhir.instance.model.api.IBaseDatatype;
 
+import java.util.List;
+
 public interface ISupportsUndeclaredExtensions extends IElement {
 	
 	/**
@@ -42,7 +42,8 @@ public interface ISupportsUndeclaredExtensions extends IElement {
 	/**
 	 * Returns an <b>immutable</b> list containing all extensions (modifier and non-modifier).
 	 * 
-	 * @see #getUndeclaredExtensions() To return a mutable list which may be used to remove extensions
+	 * @see #getUndeclaredExtensions() To return a mutable list which may be used to remove undeclared non-modifier extensions
+	 * @see #getUndeclaredModifierExtensions() To return a mutable list which may be used to remove undeclared modifier extensions
 	 */
 	List<ExtensionDt> getAllUndeclaredExtensions();
 
diff --git a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
index ca32e26447c..354d52d6201 100644
--- a/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
+++ b/hapi-fhir-base/src/main/java/ca/uhn/fhir/util/FhirTerser.java
@@ -58,7 +58,41 @@ public class FhirTerser {
 		newList.add(theChildDefinition.getElementName());
 		return newList;
 	}
-	
+
+	private ExtensionDt createEmptyExtensionDt(IBaseExtension theBaseExtension, String theUrl) {
+		return createEmptyExtensionDt(theBaseExtension, false, theUrl);
+	}
+
+	@SuppressWarnings("unchecked")
+	private ExtensionDt createEmptyExtensionDt(IBaseExtension theBaseExtension, boolean theIsModifier, String theUrl) {
+		ExtensionDt retVal = new ExtensionDt(theIsModifier, theUrl);
+		theBaseExtension.getExtension().add(retVal);
+		return retVal;
+	}
+
+	private ExtensionDt createEmptyExtensionDt(ISupportsUndeclaredExtensions theSupportsUndeclaredExtensions, String theUrl) {
+		return createEmptyExtensionDt(theSupportsUndeclaredExtensions, false, theUrl);
+	}
+
+	private ExtensionDt createEmptyExtensionDt(ISupportsUndeclaredExtensions theSupportsUndeclaredExtensions, boolean theIsModifier, String theUrl) {
+		return theSupportsUndeclaredExtensions.addUndeclaredExtension(theIsModifier, theUrl);
+	}
+
+	private IBaseExtension createEmptyExtension(IBaseHasExtensions theBaseHasExtensions, String theUrl) {
+		return (IBaseExtension) theBaseHasExtensions.addExtension().setUrl(theUrl);
+	}
+
+	private IBaseExtension createEmptyModifierExtension(IBaseHasModifierExtensions theBaseHasModifierExtensions, String theUrl) {
+		return (IBaseExtension) theBaseHasModifierExtensions.addModifierExtension().setUrl(theUrl);
+	}
+
+	private ExtensionDt createEmptyModifierExtensionDt(IBaseExtension theBaseExtension, String theUrl) {
+		return createEmptyExtensionDt(theBaseExtension, true, theUrl);
+	}
+
+	private ExtensionDt createEmptyModifierExtensionDt(ISupportsUndeclaredExtensions theSupportsUndeclaredExtensions, String theUrl) {
+		return createEmptyExtensionDt(theSupportsUndeclaredExtensions, true, theUrl);
+	}
 
 	/**
 	 * Clones all values from a source object into the equivalent fields in a target object
@@ -214,11 +248,11 @@ public class FhirTerser {
 	}
 
 	private <T> List<T> getValues(BaseRuntimeElementCompositeDefinition<?> theCurrentDef, Object theCurrentObj, List<String> theSubList, Class<T> theWantedClass) {
-		return getValues(theCurrentDef, theCurrentObj, theSubList, theWantedClass, false);
+		return getValues(theCurrentDef, theCurrentObj, theSubList, theWantedClass, false, false);
 	}
 
 	@SuppressWarnings("unchecked")
-	private <T> List<T> getValues(BaseRuntimeElementCompositeDefinition<?> theCurrentDef, Object theCurrentObj, List<String> theSubList, Class<T> theWantedClass, boolean theCreate) {
+	private <T> List<T> getValues(BaseRuntimeElementCompositeDefinition<?> theCurrentDef, Object theCurrentObj, List<String> theSubList, Class<T> theWantedClass, boolean theCreate, boolean theAddExtension) {
 		String name = theSubList.get(0);
 		List<T> retVal = new ArrayList<>();
 
@@ -229,27 +263,35 @@ public class FhirTerser {
 				extensionUrl = extensionUrl.substring(0, endIndex);
 			}
 
-			// DSTU2
 			if (myContext.getVersion().getVersion().isOlderThan(FhirVersionEnum.DSTU3)) {
+				// DTSU2
+				final String extensionDtUrlForLambda = extensionUrl;
 				List<ExtensionDt> extensionDts = Collections.emptyList();
 				if (theCurrentObj instanceof ISupportsUndeclaredExtensions) {
-					extensionDts = ((ISupportsUndeclaredExtensions) theCurrentObj).getUndeclaredExtensionsByUrl(extensionUrl);
+					extensionDts = ((ISupportsUndeclaredExtensions) theCurrentObj).getUndeclaredExtensions()
+						.stream()
+						.filter(t -> t.getUrl().equals(extensionDtUrlForLambda))
+						.collect(Collectors.toList());
+
+					if (theAddExtension
+						 && (!(theCurrentObj instanceof IBaseExtension) || (extensionDts.isEmpty() && theSubList.size() == 1))) {
+						extensionDts.add(createEmptyExtensionDt((ISupportsUndeclaredExtensions) theCurrentObj, extensionUrl));
+					}
 
 					if (extensionDts.isEmpty() && theCreate) {
-						// We assume the extension is not a modifier extension.
-						extensionDts = new ArrayList<>(); // Implementation of ISupportsUndeclaredExtensions.getUndeclaredExtensionsByUrl(...) returns unmodifiable list.
-						ExtensionDt extensionDt = ((ISupportsUndeclaredExtensions) theCurrentObj).addUndeclaredExtension(false, extensionUrl);
-						extensionDts.add(extensionDt);
+						extensionDts.add(createEmptyExtensionDt((ISupportsUndeclaredExtensions) theCurrentObj, extensionUrl));
 					}
+
 				} else if (theCurrentObj instanceof IBaseExtension) {
 					extensionDts = ((IBaseExtension) theCurrentObj).getExtension();
 
+					if (theAddExtension
+						 && (extensionDts.isEmpty() && theSubList.size() == 1)) {
+						extensionDts.add(createEmptyExtensionDt((IBaseExtension) theCurrentObj, extensionUrl));
+					}
+
 					if (extensionDts.isEmpty() && theCreate) {
-						// We assume the extension is not a modifier extension.
-						ExtensionDt extensionDt = new ExtensionDt();
-						extensionDt.setUrl(extensionUrl);
-						((IBaseExtension) theCurrentObj).getExtension().add(extensionDt);
-						extensionDts.add(extensionDt);
+						extensionDts.add(createEmptyExtensionDt((IBaseExtension) theCurrentObj, extensionUrl));
 					}
 				}
 
@@ -268,10 +310,13 @@ public class FhirTerser {
 						.filter(t -> t.getUrl().equals(extensionUrlForLambda))
 						.collect(Collectors.toList());
 
+					if (theAddExtension
+						 && (!(theCurrentObj instanceof IBaseExtension) || (extensions.isEmpty() && theSubList.size() == 1))) {
+						extensions.add(createEmptyExtension((IBaseHasExtensions) theCurrentObj, extensionUrl));
+					}
+
 					if (extensions.isEmpty() && theCreate) {
-						IBaseExtension extension = ((IBaseHasExtensions) theCurrentObj).addExtension();
-						extension.setUrl(extensionUrl);
-						extensions.add(extension);
+						extensions.add(createEmptyExtension((IBaseHasExtensions) theCurrentObj, extensionUrl));
 					}
 				}
 
@@ -287,7 +332,7 @@ public class FhirTerser {
 				retVal = new ArrayList<>();
 				for (T nextElement : values) {
 					BaseRuntimeElementCompositeDefinition<?> nextChildDef = (BaseRuntimeElementCompositeDefinition<?>) myContext.getElementDefinition((Class<? extends IBase>) nextElement.getClass());
-					List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass, theCreate);
+					List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass, theCreate, theAddExtension);
 					retVal.addAll(foundValues);
 				}
 			}
@@ -302,8 +347,45 @@ public class FhirTerser {
 				extensionUrl = extensionUrl.substring(0, endIndex);
 			}
 
-			// DSTU3+
-			if (myContext.getVersion().getVersion().isEqualOrNewerThan(FhirVersionEnum.DSTU3)) {
+			if (myContext.getVersion().getVersion().isOlderThan(FhirVersionEnum.DSTU3)) {
+				// DSTU2
+				final String extensionDtUrlForLambda = extensionUrl;
+				List<ExtensionDt> extensionDts = Collections.emptyList();
+				if (theCurrentObj instanceof ISupportsUndeclaredExtensions) {
+					extensionDts = ((ISupportsUndeclaredExtensions) theCurrentObj).getUndeclaredModifierExtensions()
+						.stream()
+						.filter(t -> t.getUrl().equals(extensionDtUrlForLambda))
+						.collect(Collectors.toList());
+
+					if (theAddExtension
+						&& (!(theCurrentObj instanceof IBaseExtension) || (extensionDts.isEmpty() && theSubList.size() == 1))) {
+						extensionDts.add(createEmptyModifierExtensionDt((ISupportsUndeclaredExtensions) theCurrentObj, extensionUrl));
+					}
+
+					if (extensionDts.isEmpty() && theCreate) {
+						extensionDts.add(createEmptyModifierExtensionDt((ISupportsUndeclaredExtensions) theCurrentObj, extensionUrl));
+					}
+
+				} else if (theCurrentObj instanceof IBaseExtension) {
+					extensionDts = ((IBaseExtension) theCurrentObj).getExtension();
+
+					if (theAddExtension
+						&& (extensionDts.isEmpty() && theSubList.size() == 1)) {
+						extensionDts.add(createEmptyExtensionDt((IBaseExtension) theCurrentObj, extensionUrl));
+					}
+
+					if (extensionDts.isEmpty() && theCreate) {
+						extensionDts.add(createEmptyExtensionDt((IBaseExtension) theCurrentObj, extensionUrl));
+					}
+				}
+
+				for (ExtensionDt next : extensionDts) {
+					if (theWantedClass.isAssignableFrom(next.getClass())) {
+						retVal.add((T) next);
+					}
+				}
+			} else {
+				// DSTU3+
 				final String extensionUrlForLambda = extensionUrl;
 				List<IBaseExtension> extensions = Collections.emptyList();
 
@@ -313,10 +395,13 @@ public class FhirTerser {
 						.filter(t -> t.getUrl().equals(extensionUrlForLambda))
 						.collect(Collectors.toList());
 
+					if (theAddExtension
+						 && (!(theCurrentObj instanceof IBaseExtension) || (extensions.isEmpty() && theSubList.size() == 1))) {
+						extensions.add(createEmptyModifierExtension((IBaseHasModifierExtensions) theCurrentObj, extensionUrl));
+					}
+
 					if (extensions.isEmpty() && theCreate) {
-						IBaseExtension modifierExtension = ((IBaseHasModifierExtensions) theCurrentObj).addModifierExtension();
-						modifierExtension.setUrl(extensionUrl);
-						extensions.add(modifierExtension);
+						extensions.add(createEmptyModifierExtension((IBaseHasModifierExtensions) theCurrentObj, extensionUrl));
 					}
 				}
 
@@ -332,7 +417,7 @@ public class FhirTerser {
 				retVal = new ArrayList<>();
 				for (T nextElement : values) {
 					BaseRuntimeElementCompositeDefinition<?> nextChildDef = (BaseRuntimeElementCompositeDefinition<?>) myContext.getElementDefinition((Class<? extends IBase>) nextElement.getClass());
-					List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass, theCreate);
+					List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass, theCreate, theAddExtension);
 					retVal.addAll(foundValues);
 				}
 			}
@@ -381,7 +466,7 @@ public class FhirTerser {
 		} else {
 			for (IBase nextElement : values) {
 				BaseRuntimeElementCompositeDefinition<?> nextChildDef = (BaseRuntimeElementCompositeDefinition<?>) myContext.getElementDefinition(nextElement.getClass());
-				List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass, theCreate);
+				List<T> foundValues = getValues(nextChildDef, nextElement, theSubList.subList(1, theSubList.size()), theWantedClass, theCreate, theAddExtension);
 				retVal.addAll(foundValues);
 			}
 		}
@@ -392,9 +477,6 @@ public class FhirTerser {
 	 * Returns values stored in an element identified by its path. The list of values is of
 	 * type {@link Object}.
 	 *
-	 * <p>Note: this method does not support creation of null-valued modifier extensions for
-	 * versions of FHIR prior to DSTU3.</p>
-	 *
 	 * @param theResource The resource instance to be accessed. Must not be null.
 	 * @param thePath The path for the element to be accessed.
 	 * @return A list of values of type {@link Object}.
@@ -409,9 +491,6 @@ public class FhirTerser {
 	 * Returns values stored in an element identified by its path. The list of values is of
 	 * type {@link Object}.
 	 *
-	 * <p>Note: this method does not support creation of null-valued modifier extensions for
-	 * versions of FHIR prior to DSTU3.</p>
-	 *
 	 * @param theResource The resource instance to be accessed. Must not be null.
 	 * @param thePath The path for the element to be accessed.
 	 * @param theCreate When set to <code>true</code>, the terser will create a null-valued element where none exists.
@@ -425,10 +504,23 @@ public class FhirTerser {
 
 	/**
 	 * Returns values stored in an element identified by its path. The list of values is of
-	 * type <code>theWantedClass</code>.
+	 * type {@link Object}.
 	 *
-	 * <p>Note: this method does not support creation of null-valued modifier extensions for
-	 * versions of FHIR prior to DSTU3.</p>
+	 * @param theResource The resource instance to be accessed. Must not be null.
+	 * @param thePath The path for the element to be accessed.
+	 * @param theCreate When set to <code>true</code>, the terser will create a null-valued element where none exists.
+	 * @param theAddExtension When set to <code>true</code>, the terser will add a null-valued extension where one or more such extensions already exist.
+	 * @return A list of values of type {@link Object}.
+	 */
+	public List<Object> getValues(IBaseResource theResource, String thePath, boolean theCreate, boolean theAddExtension) {
+		Class<Object> wantedClass = Object.class;
+
+		return getValues(theResource, thePath, wantedClass, theCreate, theAddExtension);
+	}
+
+	/**
+	 * Returns values stored in an element identified by its path. The list of values is of
+	 * type <code>theWantedClass</code>.
 	 *
 	 * @param theResource The resource instance to be accessed. Must not be null.
 	 * @param thePath The path for the element to be accessed.
@@ -446,9 +538,6 @@ public class FhirTerser {
 	 * Returns values stored in an element identified by its path. The list of values is of
 	 * type <code>theWantedClass</code>.
 	 *
-	 * <p>Note: this method does not support creation of null-valued modifier extensions for
-	 * versions of FHIR prior to DSTU3.</p>
-	 *
 	 * @param theResource The resource instance to be accessed. Must not be null.
 	 * @param thePath The path for the element to be accessed.
 	 * @param theWantedClass The desired class to be returned in a list.
@@ -459,7 +548,25 @@ public class FhirTerser {
 	public <T> List<T> getValues(IBaseResource theResource, String thePath, Class<T> theWantedClass, boolean theCreate) {
 		RuntimeResourceDefinition def = myContext.getResourceDefinition(theResource);
 		List<String> parts = parsePath(def, thePath);
-		return getValues(def, theResource, parts, theWantedClass, theCreate);
+		return getValues(def, theResource, parts, theWantedClass, theCreate, false);
+	}
+
+	/**
+	 * Returns values stored in an element identified by its path. The list of values is of
+	 * type <code>theWantedClass</code>.
+	 *
+	 * @param theResource The resource instance to be accessed. Must not be null.
+	 * @param thePath The path for the element to be accessed.
+	 * @param theWantedClass The desired class to be returned in a list.
+	 * @param theCreate When set to <code>true</code>, the terser will create a null-valued element where none exists.
+	 * @param theAddExtension When set to <code>true</code>, the terser will add a null-valued extension where one or more such extensions already exist.
+	 * @param <T> Type declared by <code>theWantedClass</code>
+	 * @return A list of values of type <code>theWantedClass</code>.
+	 */
+	public <T> List<T> getValues(IBaseResource theResource, String thePath, Class<T> theWantedClass, boolean theCreate, boolean theAddExtension) {
+		RuntimeResourceDefinition def = myContext.getResourceDefinition(theResource);
+		List<String> parts = parsePath(def, thePath);
+		return getValues(def, theResource, parts, theWantedClass, theCreate, theAddExtension);
 	}
 
 	private List<String> parsePath(BaseRuntimeElementCompositeDefinition<?> theElementDef, String thePath) {
diff --git a/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java b/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
index e66eabdc9cd..f1312e16850 100644
--- a/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
+++ b/hapi-fhir-structures-dstu2/src/test/java/ca/uhn/fhir/util/FhirTerserDstu2Test.java
@@ -185,6 +185,7 @@ public class FhirTerserDstu2Test {
 		p.setActive(true);
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(true, "http://acme.org/modifierExtension", new StringDt("modifierValue"));
 		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
@@ -202,6 +203,13 @@ public class FhirTerserDstu2Test {
 		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
 		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
 
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
 		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
 		assertEquals(1, values.size());
 		assertTrue(values.get(0) instanceof IBaseExtension);
@@ -216,6 +224,7 @@ public class FhirTerserDstu2Test {
 		p.setActive(true);
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(true, "http://acme.org/modifierExtension", new StringDt("modifierValue"));
 		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
@@ -254,6 +263,24 @@ public class FhirTerserDstu2Test {
 		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
 		assertEquals("modifiedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
 
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		((ExtensionDt) values.get(0)).setValue(new StringDt("modifiedModifierValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifiedModifierValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
 		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
 		assertEquals(1, values.size());
 		assertTrue(values.get(0) instanceof IBaseExtension);
@@ -279,6 +306,8 @@ public class FhirTerserDstu2Test {
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value1"));
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value2"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(true, "http://acme.org/modifierExtension", new StringDt("modifierValue1"));
+		p.addUndeclaredExtension(true, "http://acme.org/modifierExtension", new StringDt("modifierValue2"));
 		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue1"));
 		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue2"));
 
@@ -295,6 +324,17 @@ public class FhirTerserDstu2Test {
 		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(1)).getUrl());
 		assertEquals("value2", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
 
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifierValue1", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(1)).getUrl());
+		assertEquals("modifierValue2", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
+
 		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
 		assertEquals(2, values.size());
 		assertTrue(values.get(0) instanceof IBaseExtension);
@@ -313,6 +353,7 @@ public class FhirTerserDstu2Test {
 		p.setActive(true);
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(true, "http://acme.org/modifierExtension", new StringDt("modifierValue"));
 		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
@@ -328,6 +369,12 @@ public class FhirTerserDstu2Test {
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
 		assertEquals("value", ((StringDt) extValues.get(0).getValue()).getValueAsString());
 
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertEquals("modifierValue", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
+
 		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", ExtensionDt.class);
 		assertEquals(1, extValues.size());
 		assertTrue(extValues.get(0).getValue() instanceof StringDt);
@@ -341,6 +388,7 @@ public class FhirTerserDstu2Test {
 		p.setActive(true);
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(true, "http://acme.org/modifierExtension", new StringDt("modifierValue"));
 		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
@@ -375,6 +423,22 @@ public class FhirTerserDstu2Test {
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
 		assertEquals("modifiedValue", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
 
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertEquals("modifierValue", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
+
+		extValues.get(0).setValue(new StringDt("modifiedModifierValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", ExtensionDt.class);
+		assertEquals(1, extValues.size());
+		assertTrue(extValues.get(0).getValue() instanceof StringDt);
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertEquals("modifiedModifierValue", ((StringDt) (extValues.get(0).getValue())).getValueAsString());
+
 		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", ExtensionDt.class);
 		assertEquals(1, extValues.size());
 		assertTrue(extValues.get(0).getValue() instanceof StringDt);
@@ -408,12 +472,125 @@ public class FhirTerserDstu2Test {
 		assertEquals("http://acme.org/extension", extValues.get(0).getUrl());
 		assertNull(extValues.get(0).getValue());
 
+		extValues = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", ExtensionDt.class, true);
+		assertEquals(1, extValues.size());
+		assertEquals("http://acme.org/modifierExtension", extValues.get(0).getUrl());
+		assertNull(extValues.get(0).getValue());
+
 		extValues = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", ExtensionDt.class, true);
 		assertEquals(1, extValues.size());
 		assertEquals("http://acme.org/childExtension", extValues.get(0).getUrl());
 		assertNull(extValues.get(0).getValue());
 	}
 
+	@Test
+	public void testGetValuesWithTheAddExtensionAndModify() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(true, "http://acme.org/modifierExtension", new StringDt("modifierValue"));
+		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		// No change.
+		values = ourCtx.newTerser().getValues(p, "Patient.active", false, true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", false, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(1)).getUrl());
+		assertNull(((ExtensionDt) values.get(1)).getValue());
+
+		((ExtensionDt) values.get(1)).setValue(new StringDt("addedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(1)).getUrl());
+		assertEquals("addedValue", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", false, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(1)).getUrl());
+		assertNull(((ExtensionDt) values.get(1)).getValue());
+
+		((ExtensionDt) values.get(1)).setValue(new StringDt("addedModifierValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(1)).getUrl());
+		assertEquals("addedModifierValue", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", false, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof  IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(1)).getUrl());
+		assertNull(((ExtensionDt) values.get(1)).getValue());
+
+		((ExtensionDt) values.get(1)).setValue(new StringDt("addedNestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof  IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(1)).getUrl());
+		assertEquals("addedNestedValue", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
+	}
+
 	@Test
 	public void testGetValuesWithTheCreate() {
 		Patient p = new Patient();
@@ -433,6 +610,13 @@ public class FhirTerserDstu2Test {
 		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
 		assertNull(((ExtensionDt) values.get(0)).getValue());
 
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertNull(((ExtensionDt) values.get(0)).getValue());
+
 		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", true);
 		assertEquals(1, values.size());
 		assertTrue(values.get(0) instanceof IBaseExtension);
@@ -441,12 +625,119 @@ public class FhirTerserDstu2Test {
 		assertNull(((ExtensionDt) values.get(0)).getValue());
 	}
 
+	@Test
+	public void testGetValuesWithTheCreateAndTheAddExtensionAndModify() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
+		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(true, "http://acme.org/modifierExtension", new StringDt("modifierValue"));
+		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		// No change.
+		values = ourCtx.newTerser().getValues(p, "Patient.active", true, true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IPrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanDt);
+		assertTrue(((BooleanDt) values.get(0)).getValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", true, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(1)).getUrl());
+		assertNull(((ExtensionDt) values.get(1)).getValue());
+
+		((ExtensionDt) values.get(1)).setValue(new StringDt("addedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(1)).getUrl());
+		assertEquals("addedValue", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", true, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(1)).getUrl());
+		assertNull(((ExtensionDt) values.get(1)).getValue());
+
+		((ExtensionDt) values.get(1)).setValue(new StringDt("addedModifierValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(1)).getUrl());
+		assertEquals("addedModifierValue", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", true, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof  IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(1)).getUrl());
+		assertNull(((ExtensionDt) values.get(1)).getValue());
+
+		((ExtensionDt) values.get(1)).setValue(new StringDt("addedNestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof  IBaseExtension);
+		assertTrue(values.get(1) instanceof ExtensionDt);
+		assertEquals("http://acme.org/childExtension", ((ExtensionDt) values.get(1)).getUrl());
+		assertEquals("addedNestedValue", ((StringDt) ((ExtensionDt) values.get(1)).getValue()).getValueAsString());
+	}
+
 	@Test
 	public void testGetValuesWithTheCreateAndNoOverwrite() {
 		Patient p = new Patient();
 		p.setActive(true);
 		p.addUndeclaredExtension(false, "http://acme.org/extension", new StringDt("value"));
 		p.addUndeclaredExtension(false, "http://acme.org/otherExtension", new StringDt("otherValue"));
+		p.addUndeclaredExtension(true, "http://acme.org/modifierExtension", new StringDt("modifierValue"));
 		p.addUndeclaredExtension(false, "http://acme.org/parentExtension").addUndeclaredExtension(false, "http://acme.org/childExtension", new StringDt("nestedValue"));
 
 		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
@@ -464,6 +755,13 @@ public class FhirTerserDstu2Test {
 		assertEquals("http://acme.org/extension", ((ExtensionDt) values.get(0)).getUrl());
 		assertEquals("value", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
 
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof ExtensionDt);
+		assertEquals("http://acme.org/modifierExtension", ((ExtensionDt) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringDt) ((ExtensionDt) values.get(0)).getValue()).getValueAsString());
+
 		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", true);
 		assertEquals(1, values.size());
 		assertTrue(values.get(0) instanceof IBaseExtension);
diff --git a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
index 047256fff6d..b8cece751d7 100644
--- a/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
+++ b/hapi-fhir-structures-dstu3/src/test/java/ca/uhn/fhir/util/FhirTerserDstu3Test.java
@@ -531,6 +531,124 @@ public class FhirTerserDstu3Test {
 		assertNull(extValues.get(0).getValue());
 	}
 
+	@Test
+	public void testGetValuesWithTheAddExtensionAndModify() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addExtension()
+			.setUrl("http://acme.org/extension")
+			.setValue(new StringType("value"));
+		p.addExtension()
+			.setUrl("http://acme.org/otherExtension")
+			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
+		p.addExtension()
+			.setUrl("http://acme.org/parentExtension")
+			.addExtension()
+			.setUrl("http://acme.org/childExtension")
+			.setValue(new StringType("nestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof PrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertTrue(((BooleanType) values.get(0)).booleanValue());
+
+		// No change.
+		values = ourCtx.newTerser().getValues(p, "Patient.active", false, true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof PrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertTrue(((BooleanType) values.get(0)).booleanValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", false, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(1)).getUrl());
+		assertNull(((Extension) values.get(1)).getValue());
+
+		((Extension) values.get(1)).setValue(new StringType("addedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(1)).getUrl());
+		assertEquals("addedValue", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", false, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(1)).getUrl());
+		assertNull(((Extension) values.get(1)).getValue());
+
+		((Extension) values.get(1)).setValue(new StringType("addedModifierValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(1)).getUrl());
+		assertEquals("addedModifierValue", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", false, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof  IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(1)).getUrl());
+		assertNull(((Extension) values.get(1)).getValue());
+
+		((Extension) values.get(1)).setValue(new StringType("addedNestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof  IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(1)).getUrl());
+		assertEquals("addedNestedValue", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
+	}
+
 	@Test
 	public void testGetValuesWithTheCreate() {
    	Patient p = new Patient();
@@ -563,6 +681,122 @@ public class FhirTerserDstu3Test {
 		assertNull(((Extension) values.get(0)).getValue());
 	}
 
+	@Test
+	public void testGetValuesWithTheCreateAndTheAddExtensionAndModify() {
+		Patient p = new Patient();
+		p.setActive(true);
+		p.addExtension()
+			.setUrl("http://acme.org/extension")
+			.setValue(new StringType("value"));
+		p.addExtension()
+			.setUrl("http://acme.org/otherExtension")
+			.setValue(new StringType("otherValue"));
+		p.addModifierExtension()
+			.setUrl("http://acme.org/modifierExtension")
+			.setValue(new StringType("modifierValue"));
+		p.addExtension()
+			.setUrl("http://acme.org/parentExtension")
+			.addExtension()
+			.setUrl("http://acme.org/childExtension")
+			.setValue(new StringType("nestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		List<Object> values = ourCtx.newTerser().getValues(p, "Patient.active");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof PrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertTrue(((BooleanType) values.get(0)).booleanValue());
+
+		// No change.
+		values = ourCtx.newTerser().getValues(p, "Patient.active", true, true);
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof PrimitiveType);
+		assertTrue(values.get(0) instanceof BooleanType);
+		assertTrue(((BooleanType) values.get(0)).booleanValue());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/extension')", true, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(0)).getUrl());
+		assertEquals("value", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(1)).getUrl());
+		assertNull(((Extension) values.get(1)).getValue());
+
+		((Extension) values.get(1)).setValue(new StringType("addedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/extension", ((Extension) values.get(1)).getUrl());
+		assertEquals("addedValue", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.modifierExtension('http://acme.org/modifierExtension')", true, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("modifierValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(1)).getUrl());
+		assertNull(((Extension) values.get(1)).getValue());
+
+		((Extension) values.get(1)).setValue(new StringType("addedModifierValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/modifierExtension", ((Extension) values.get(1)).getUrl());
+		assertEquals("addedModifierValue", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')");
+		assertEquals(1, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+
+		values = ourCtx.newTerser().getValues(p, "Patient.extension('http://acme.org/parentExtension').extension('http://acme.org/childExtension')", true, true);
+		assertEquals(2, values.size());
+		assertTrue(values.get(0) instanceof  IBaseExtension);
+		assertTrue(values.get(0) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(0)).getUrl());
+		assertEquals("nestedValue", ((StringType) ((Extension) values.get(0)).getValue()).getValueAsString());
+		assertTrue(values.get(1) instanceof  IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(1)).getUrl());
+		assertNull(((Extension) values.get(1)).getValue());
+
+		((Extension) values.get(1)).setValue(new StringType("addedNestedValue"));
+
+		System.out.println(ourCtx.newJsonParser().setPrettyPrint(true).encodeResourceToString(p));
+
+		assertTrue(values.get(1) instanceof  IBaseExtension);
+		assertTrue(values.get(1) instanceof Extension);
+		assertEquals("http://acme.org/childExtension", ((Extension) values.get(1)).getUrl());
+		assertEquals("addedNestedValue", ((StringType) ((Extension) values.get(1)).getValue()).getValueAsString());
+	}
+
 	@Test
 	public void testGetValuesWithTheCreateAndNoOverwrite() {
 		Patient p = new Patient();

From c669bba4bdd099adf78d792aca9425fb9900d778 Mon Sep 17 00:00:00 2001
From: Diederik Muylwyk <diederik.muylwyk@gmail.com>
Date: Wed, 24 Oct 2018 12:08:17 -0400
Subject: [PATCH 6/6] FhirTerser.getValues(...) enhancements are completed.
 Added changelog entry.

---
 src/changes/changes.xml | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/changes/changes.xml b/src/changes/changes.xml
index 9a8f49cd6e1..539e91b4d02 100644
--- a/src/changes/changes.xml
+++ b/src/changes/changes.xml
@@ -116,6 +116,16 @@
 				<![CDATA[<a href="https://github.com/hapifhir/hapi-fhir-jpaserver-starter/blob/master/src/main/java/ca/uhn/fhir/jpa/demo/FhirServerConfig.java#L62">the example project</a>]]>
 				if they are not already.
 			</action>
+			<action type="add">
+				The FhirTerser <![CDATA[<code>getValues(...)</code>]]> methods have been overloaded. The terser can now be
+				used to create a null-valued element where none exists. Additionally, the terser can now add a null-valued
+				extension where one or more such extensions already exist. These changes allow better population of FHIR
+				elements provided an arbitrary FHIR path.
+			</action>
+			<action type="fix">
+				The FhirTerser <![CDATA[<code>getValues(...)</code>]]> methods were not properly handling modifier
+				extensions for verions of FHIR prior to DSTU3. This has been corrected.
+			</action>
 		</release>
 
 		<release version="3.5.0" date="2018-09-17">