Fix #4184: setCurrentValue() for empty POJO called at wrong time (#4186)

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -4,6 +4,12 @@ Project: jackson-databind
 === Releases === 
 ------------------------------------------------------------------------
 
+(not yet released)
+
+#4184: `BeanDeserializer` updates `currentValue` incorrectly when
+  deserialising empty Object
+ (reported by @nocny-x)
+
 2.16.0-rc1 (20-Oct-2023)
 
 #2502: Add a way to configure caches Jackson uses

src/main/java/com/fasterxml/jackson/databind/deser/BeanDeserializer.java

@@ -296,9 +296,10 @@ private final Object vanillaDeserialize(JsonParser p,
         throws IOException
     {
         final Object bean = _valueInstantiator.createUsingDefault(ctxt);
-        // [databind#631]: Assign current value, to be accessible by custom serializers
-        p.setCurrentValue(bean);
         if (p.hasTokenId(JsonTokenId.ID_FIELD_NAME)) {
+            // [databind#631]: Assign current value, to be accessible by custom serializers
+            // [databind#4184]: but only if we have at least one property
+            p.setCurrentValue(bean);
             String propName = p.currentName();
             do {
                 p.nextToken();

src/test/java/com/fasterxml/jackson/databind/ser/filter/CurrentValueDeser4184Test.java

@@ -0,0 +1,97 @@
+package com.fasterxml.jackson.databind.ser.filter;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.core.*;
+
+import com.fasterxml.jackson.databind.*;
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+
+// [databind#4184]
+public class CurrentValueDeser4184Test extends BaseMapTest
+{
+    static class User {
+        public Role role;
+        public UserType type;
+    }
+
+    static class Role {
+        public String name;
+    }
+
+    @JsonDeserialize(using = UserTypeDeserializer.class)
+    enum UserType {
+        ADMIN(1),
+        USER(2);
+
+        final int value;
+
+        UserType(int value) {
+            this.value = value;
+        }
+
+        public Integer getValue() {
+            return this.value;
+        }
+
+        public String getName() {
+            return this.name();
+        }
+    }
+
+    static class UserTypeDeserializer extends JsonDeserializer<UserType> {
+        @Override
+        public UserType deserialize(JsonParser p, DeserializationContext ctxt) throws IOException {
+            Object currentValue;
+            if (p.currentToken().isStructStart()) {
+                currentValue = p.getParsingContext().getParent().getCurrentValue();
+            } else {
+                currentValue = p.getParsingContext().getCurrentValue();
+            }
+            if (null == currentValue) {
+                ctxt.reportInputMismatch(UserType.class, "No currentValue() available");
+            }
+            if (!(currentValue instanceof User)) {
+                ctxt.reportInputMismatch(UserType.class, "currentValue() of wrong type, not User but: "
+                        +currentValue.getClass().getName());
+            }
+            JsonNode node = ctxt.readTree(p);
+            int value = node.path("value").asInt(-1);
+            switch (value) {
+            case 1:
+                return UserType.ADMIN;
+            case 2:
+                return UserType.USER;
+            }
+            throw new IllegalArgumentException("Bad value: "+value);
+        }
+    }
+
+    /*
+    /**********************************************************************
+    /* Test methods
+    /**********************************************************************
+     */
+
+    private final ObjectMapper MAPPER = newJsonMapper();
+
+    // [databind#4184]
+    public void testCurrentValue4184FullPojo() throws Exception
+    {
+        String json = "{\"role\": {\"name\": \"Manager\"}, \"type\": {\"value\":1}}";
+
+        User user = MAPPER.readValue(json, User.class);
+        assertNotNull(user);
+        assertEquals(UserType.ADMIN, user.type);
+    }
+
+    // [databind#4184]
+    public void testCurrentValue4184EmptyPojo() throws Exception
+    {
+        String json = "{\"role\": {}, \"type\": {\"value\":1}}";
+
+        User user = MAPPER.readValue(json, User.class);
+        assertNotNull(user);
+        assertEquals(UserType.ADMIN, user.type);
+    }
+}