Fix #3421 (add JsonNodeFeature.READ_NULL_PROPERTIES)

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -8,6 +8,9 @@ Project: jackson-databind
 
 #3373: Change `TypeSerializerBase` to skip `generator.writeTypePrefix()`
   for `null` typeId
+#3405: Create DataTypeFeature abstraction (for JSTEP-7) with placeholder features
+#3421: Implement `JsonNodeFeature.READ_NULL_PROPERTIES` to allow skipping of
+  JSON `null` values on reading
 
 2.13.3 (not yet released)
 

src/main/java/com/fasterxml/jackson/databind/deser/std/JsonNodeDeserializer.java

@@ -4,7 +4,9 @@
 import java.util.Arrays;
 
 import com.fasterxml.jackson.core.*;
+
 import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.cfg.JsonNodeFeature;
 import com.fasterxml.jackson.databind.jsontype.TypeDeserializer;
 import com.fasterxml.jackson.databind.node.*;
 import com.fasterxml.jackson.databind.type.LogicalType;
@@ -402,6 +404,10 @@ protected final JsonNode updateObject(JsonParser p, DeserializationContext ctxt,
                 value = nodeFactory.booleanNode(false);
                 break;
             case JsonTokenId.ID_NULL:
+                // 20-Mar-2022, tatu: [databind#3421] Allow skipping `null`s from JSON
+                if (!ctxt.isEnabled(JsonNodeFeature.READ_NULL_PROPERTIES)) {
+                    continue;
+                }
                 value = nodeFactory.nullNode();
                 break;
             default:
@@ -485,6 +491,10 @@ protected final ContainerNode<?> _deserializeContainerNoRecursion(JsonParser p,
                         value = nodeFactory.booleanNode(false);
                         break;
                     case JsonTokenId.ID_NULL:
+                        // 20-Mar-2022, tatu: [databind#3421] Allow skipping `null`s from JSON
+                        if (!ctxt.isEnabled(JsonNodeFeature.READ_NULL_PROPERTIES)) {
+                            continue;
+                        }
                         value = nodeFactory.nullNode();
                         break;
                     default:

src/test/java/com/fasterxml/jackson/databind/node/NodeFeaturesTest.java

@@ -0,0 +1,50 @@
+package com.fasterxml.jackson.databind.node;
+
+import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.cfg.JsonNodeFeature;
+import com.fasterxml.jackson.databind.json.JsonMapper;
+
+// Tests for new (2.14) `JsonNodeFeature`
+public class NodeFeaturesTest extends BaseMapTest
+{
+    private final ObjectMapper MAPPER = newJsonMapper();
+    private final ObjectReader READER = MAPPER.reader();
+
+    private final ObjectNode DOC_EMPTY = MAPPER.createObjectNode();
+    private final ObjectNode DOC_WITH_NULL = MAPPER.createObjectNode();
+    {
+        DOC_WITH_NULL.putNull("nvl");
+    }
+    private final String JSON_WITH_NULL = a2q("{'nvl':null}");
+
+    public void testDefaultSettings() throws Exception
+    {
+        assertTrue(READER.isEnabled(JsonNodeFeature.READ_NULL_PROPERTIES));
+
+        assertFalse(READER.without(JsonNodeFeature.READ_NULL_PROPERTIES)
+                .isEnabled(JsonNodeFeature.READ_NULL_PROPERTIES));
+    }
+
+    public void testReadNulls() throws Exception
+    {
+        // so by default we'll get null included
+        assertEquals(DOC_WITH_NULL, READER.readTree(JSON_WITH_NULL));
+
+        ObjectMapper noNullsMapper = JsonMapper.builder()
+                .disable(JsonNodeFeature.READ_NULL_PROPERTIES)
+                .build();
+        ObjectReader r = noNullsMapper.reader();
+        assertFalse(r.isEnabled(JsonNodeFeature.READ_NULL_PROPERTIES));
+        assertEquals(DOC_EMPTY, r.readTree(JSON_WITH_NULL));
+
+        // but also verify we can "reset" reader's behavior
+        ObjectReader r2 = r.with(JsonNodeFeature.READ_NULL_PROPERTIES);
+        assertEquals(DOC_WITH_NULL, r2.readTree(JSON_WITH_NULL));
+
+        // and then bit more complex doc
+        ObjectNode exp = noNullsMapper.createObjectNode();
+        exp.put("a", 1);
+        exp.put("c", true);
+        assertEquals(exp, r.readTree(a2q("{'a':1,'b':null,'c':true}")));
+    }
+}