5401 add terserutil clear by fhirpath (hapifhir#5402)

* begin with failing test

* test passes

* test passes

* changelog

* moar testor

hapi-fhir-base/src/main/java/ca/uhn/fhir/context/BaseRuntimeChildDefinition.java

@@ -20,6 +20,7 @@
 package ca.uhn.fhir.context;
 
 import ca.uhn.fhir.i18n.Msg;
+import ca.uhn.fhir.model.api.annotation.Child;
 import org.hl7.fhir.instance.model.api.IBase;
 import org.hl7.fhir.instance.model.api.IBaseReference;
 
@@ -78,6 +79,10 @@ public void setReplacedParentDefinition(BaseRuntimeChildDefinition myReplacedPar
 		this.myReplacedParentDefinition = myReplacedParentDefinition;
 	}
 
+	public boolean isMultipleCardinality() {
+		return this.getMax() > 1 || this.getMax() == Child.MAX_UNLIMITED;
+	}
+
 	public interface IAccessor {
 		List<IBase> getValues(IBase theTarget);
 

hapi-fhir-base/src/main/java/ca/uhn/fhir/parser/JsonParser.java

@@ -39,7 +39,6 @@
 import ca.uhn.fhir.model.api.ResourceMetadataKeyEnum;
 import ca.uhn.fhir.model.api.Tag;
 import ca.uhn.fhir.model.api.TagList;
-import ca.uhn.fhir.model.api.annotation.Child;
 import ca.uhn.fhir.model.base.composite.BaseCodingDt;
 import ca.uhn.fhir.model.base.composite.BaseContainedDt;
 import ca.uhn.fhir.model.primitive.IdDt;
@@ -659,9 +658,8 @@ private void encodeCompositeElementChildrenToStreamWriter(
 						theEventWriter.endArray();
 					}
 					BaseRuntimeChildDefinition replacedParentDefinition = nextChild.getReplacedParentDefinition();
-					if (isMultipleCardinality(nextChild.getMax())
-							|| (replacedParentDefinition != null
-									&& isMultipleCardinality(replacedParentDefinition.getMax()))) {
+					if (nextChild.isMultipleCardinality()
+							|| (replacedParentDefinition != null && replacedParentDefinition.isMultipleCardinality())) {
 						beginArray(theEventWriter, nextChildSpecificName);
 						inArray = true;
 						encodeChildElementToStreamWriter(
@@ -728,14 +726,14 @@ && isMultipleCardinality(replacedParentDefinition.getMax()))) {
 					List<HeldExtension> heldModExts = Collections.emptyList();
 					if (extensions.size() > i
 							&& extensions.get(i) != null
-							&& extensions.get(i).isEmpty() == false) {
+							&& !extensions.get(i).isEmpty()) {
 						haveContent = true;
 						heldExts = extensions.get(i);
 					}
 
 					if (modifierExtensions.size() > i
 							&& modifierExtensions.get(i) != null
-							&& modifierExtensions.get(i).isEmpty() == false) {
+							&& !modifierExtensions.get(i).isEmpty()) {
 						haveContent = true;
 						heldModExts = modifierExtensions.get(i);
 					}
@@ -746,7 +744,7 @@ && isMultipleCardinality(replacedParentDefinition.getMax()))) {
 					} else {
 						nextComments = null;
 					}
-					if (nextComments != null && nextComments.isEmpty() == false) {
+					if (nextComments != null && !nextComments.isEmpty()) {
 						haveContent = true;
 					}
 
@@ -804,10 +802,6 @@ private boolean isSupportsFhirComment() {
 		return myIsSupportsFhirComment;
 	}
 
-	private boolean isMultipleCardinality(int maxCardinality) {
-		return maxCardinality > 1 || maxCardinality == Child.MAX_UNLIMITED;
-	}
-
 	private void encodeCompositeElementToStreamWriter(
 			RuntimeResourceDefinition theResDef,
 			IBaseResource theResource,
@@ -917,10 +911,7 @@ private void encodeResourceToJsonStreamWriter(
 			// Undeclared extensions
 			extractUndeclaredExtensions(
 					theResourceId, extensions, modifierExtensions, null, null, theEncodeContext, theContainedResource);
-			boolean haveExtension = false;
-			if (!extensions.isEmpty()) {
-				haveExtension = true;
-			}
+			boolean haveExtension = !extensions.isEmpty();
 
 			if (theResourceId.hasFormatComment() || haveExtension) {
 				beginObject(theEventWriter, "_id");

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

@@ -351,6 +351,29 @@ public static void clearField(FhirContext theFhirContext, IBaseResource theResou
 		clear(childDefinition.getAccessor().getValues(theResource));
 	}
 
+	/**
+	 * Clears the specified field on the resource provided by the FHIRPath.  If more than one value matches
+	 * the FHIRPath, all values will be cleared.
+	 *
+	 * @param theFhirContext
+	 * @param theResource
+	 * @param theFhirPath
+	 */
+	public static void clearFieldByFhirPath(FhirContext theFhirContext, IBaseResource theResource, String theFhirPath) {
+
+		if (theFhirPath.contains(".")) {
+			String parentPath = theFhirPath.substring(0, theFhirPath.lastIndexOf("."));
+			String fieldName = theFhirPath.substring(theFhirPath.lastIndexOf(".") + 1);
+			FhirTerser terser = theFhirContext.newTerser();
+			List<IBase> parents = terser.getValues(theResource, parentPath);
+			for (IBase parent : parents) {
+				clearField(theFhirContext, fieldName, parent);
+			}
+		} else {
+			clearField(theFhirContext, theResource, theFhirPath);
+		}
+	}
+
 	/**
 	 * Clears the specified field on the element provided
 	 *
@@ -362,7 +385,16 @@ public static void clearField(FhirContext theFhirContext, String theFieldName, I
 		BaseRuntimeElementDefinition definition = theFhirContext.getElementDefinition(theBase.getClass());
 		BaseRuntimeChildDefinition childDefinition = definition.getChildByName(theFieldName);
 		Validate.notNull(childDefinition);
-		clear(childDefinition.getAccessor().getValues(theBase));
+		BaseRuntimeChildDefinition.IAccessor accessor = childDefinition.getAccessor();
+		clear(accessor.getValues(theBase));
+		List<IBase> newValue = accessor.getValues(theBase);
+
+		if (newValue != null && !newValue.isEmpty()) {
+			// Our clear failed, probably because it was an immutable SingletonList returned by a FieldPlainAccessor
+			// that cannot be cleared.
+			// Let's just null it out instead.
+			childDefinition.getMutator().setValue(theBase, null);
+		}
 	}
 
 	/**

hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/7_0_0/5401-terserutil-clear.yaml

@@ -0,0 +1,5 @@
+---
+type: add
+issue: 5401
+title: "Previously, it was only possible to clear a top-level field on a resource using TerserUtil.  A new method has been added
+to TerserUtil to support clearing a value by FhirPath."