Add compatibility flag for ignoring missing source node in replace operation (#102)

Author: mbolgariw

src/main/java/com/flipkart/zjsonpatch/CompatibilityFlags.java

@@ -23,7 +23,8 @@
  */
 public enum CompatibilityFlags {
     MISSING_VALUES_AS_NULLS,
-    REMOVE_NONE_EXISTING_ARRAY_ELEMENT;
+    REMOVE_NONE_EXISTING_ARRAY_ELEMENT,
+    ALLOW_MISSING_TARGET_OBJECT_ON_REPLACE;
 
     public static EnumSet<CompatibilityFlags> defaults() {
         return EnumSet.noneOf(CompatibilityFlags.class);

src/main/java/com/flipkart/zjsonpatch/InPlaceApplyProcessor.java

@@ -88,7 +88,8 @@ public void replace(JsonPointer path, JsonNode value) throws JsonPointerEvaluati
         JsonNode parentNode = path.getParent().evaluate(target);
         JsonPointer.RefToken token = path.last();
         if (parentNode.isObject()) {
-            if (!parentNode.has(token.getField()))
+            if (!flags.contains(CompatibilityFlags.ALLOW_MISSING_TARGET_OBJECT_ON_REPLACE) &&
+                    !parentNode.has(token.getField()))
                 throw new JsonPatchApplicationException(
                         "Missing field \"" + token.getField() + "\"", Operation.REPLACE, path.getParent());
             ((ObjectNode) parentNode).replace(token.getField(), value);

src/test/java/com/flipkart/zjsonpatch/CompatibilityTest.java

@@ -24,8 +24,7 @@
 import java.io.IOException;
 import java.util.EnumSet;
 
-import static com.flipkart.zjsonpatch.CompatibilityFlags.MISSING_VALUES_AS_NULLS;
-import static com.flipkart.zjsonpatch.CompatibilityFlags.REMOVE_NONE_EXISTING_ARRAY_ELEMENT;
+import static com.flipkart.zjsonpatch.CompatibilityFlags.*;
 import static org.hamcrest.core.IsEqual.equalTo;
 import static org.junit.Assert.assertThat;
 
@@ -35,13 +34,15 @@ public class CompatibilityTest {
     JsonNode addNodeWithMissingValue;
     JsonNode replaceNodeWithMissingValue;
     JsonNode removeNoneExistingArrayElement;
+    JsonNode replaceNode;
 
     @Before
     public void setUp() throws Exception {
         mapper = new ObjectMapper();
         addNodeWithMissingValue = mapper.readTree("[{\"op\":\"add\",\"path\":\"/a\"}]");
         replaceNodeWithMissingValue = mapper.readTree("[{\"op\":\"replace\",\"path\":\"/a\"}]");
         removeNoneExistingArrayElement = mapper.readTree("[{\"op\": \"remove\",\"path\": \"/b/0\"}]");
+        replaceNode = mapper.readTree("[{\"op\":\"replace\",\"path\":\"/a\",\"value\":true}]");
     }
 
     @Test
@@ -76,4 +77,11 @@ public void withFlagIgnoreRemoveNoneExistingArrayElement() throws IOException {
         JsonNode result = JsonPatch.apply(removeNoneExistingArrayElement, source, EnumSet.of(REMOVE_NONE_EXISTING_ARRAY_ELEMENT));
         assertThat(result, equalTo(expected));
     }
+
+    @Test
+    public void withFlagReplaceShouldAddValueWhenMissingInTarget() throws Exception {
+        JsonNode expected = mapper.readTree("{\"a\": true}");
+        JsonNode result = JsonPatch.apply(replaceNode, mapper.createObjectNode(), EnumSet.of(ALLOW_MISSING_TARGET_OBJECT_ON_REPLACE));
+        assertThat(result, equalTo(expected));
+    }
 }