Fix #3005

Author: cowtowncoder

release-notes/VERSION-2.x

@@ -6,6 +6,8 @@ Project: jackson-databind
 
 2.12.2 (not yet released)
 
+#3005: String property deserializes null as "null" for
+   `JsonTypeInfo.As.EXTERNAL_PROPERTY`
 #3022: Property ignorals cause `BeanDeserializer `to forget how to read
   from arrays (not copying `_arrayDelegateDeserializer`)
  (reported by Gian M)

src/main/java/com/fasterxml/jackson/databind/deser/impl/ExternalTypeHandler.java

@@ -172,7 +172,9 @@ public boolean handlePropertyValue(JsonParser p, DeserializationContext ctxt,
         ExtTypedProperty prop = _properties[index];
         boolean canDeserialize;
         if (prop.hasTypePropertyName(propName)) {
-            _typeIds[index] = p.getText();
+            // 19-Feb-2021, tatu: as per [databind#3005], don't use "getText()"
+            //    since that'll coerce null value into String "null"...
+            _typeIds[index] = p.getValueAsString();
             p.skipChildren();
             canDeserialize = (bean != null) && (_tokens[index] != null);
         } else {
@@ -270,7 +272,12 @@ public Object complete(JsonParser p, DeserializationContext ctxt,
             final ExtTypedProperty extProp = _properties[i];
             if (typeId == null) {
                 // let's allow missing both type and property (may already have been set, too)
-                if (_tokens[i] == null) {
+                TokenBuffer tb = _tokens[i];
+                if ((tb == null)
+                        // 19-Feb-2021, tatu: Both missing value and explicit `null`
+                        //    should be accepted...
+                        || (tb.firstToken() == JsonToken.VALUE_NULL)
+                    ) {
                     continue;
                 }
                 // but not just one

src/main/java/com/fasterxml/jackson/databind/util/TokenBuffer.java

@@ -299,6 +299,17 @@ public JsonToken firstToken() {
         return _first.type(0);
     }
 
+    /**
+     * Accessor for checking whether this buffer has one or more tokens
+     * or not.
+     *
+     * @return True if this buffer instance has no tokens
+     *
+     * @since 2.13
+     */
+    public boolean isEmpty() {
+        return (_appendAt == 0) && (_first == _last);
+    }
     /*
     /**********************************************************
     /* Other custom methods not needed for implementing interfaces

src/test/java/com/fasterxml/jackson/databind/jsontype/ext/ExternalTypeIdTest.java

@@ -10,6 +10,7 @@
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.MapperFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.ObjectReader;
 import com.fasterxml.jackson.databind.json.JsonMapper;
 
 // Tests for External type id, one that exists at same level as typed Object,
@@ -537,4 +538,40 @@ public void testBigDecimal965() throws Exception
             w.value.getClass().getSimpleName(), w.value.toString(), w2.value.getClass().getSimpleName(), w2.value.toString()),
             w.value.equals(w2.value));
     }
+
+    static class Box3008 {
+        public String type;
+        public Fruit3008 fruit;
+
+        public Box3008(@JsonProperty("type") String type,
+                @JsonTypeInfo(use = Id.NAME, include = As.EXTERNAL_PROPERTY, property = "type")
+                @JsonSubTypes({@JsonSubTypes.Type(value = Orange.class, name = "orange")})
+                @JsonProperty("fruit")
+                Fruit3008 fruit) {
+            this.type = type;
+            this.fruit = fruit;
+        }
+    }
+
+    // [databind#3008]: allow
+    interface Fruit3008 {}
+
+    static class Orange implements Fruit3008 {
+        public String name;
+        public String color;
+
+        public Orange(@JsonProperty("name") String name, @JsonProperty("name") String color) {
+            this.name = name;
+            this.color = color;
+        }
+    }
+
+    // for [databind#3008]
+    public void testIssue3008() throws Exception
+    {
+        ObjectReader r = MAPPER.readerFor(Box3008.class);
+        Box3008 deserOrangeBox = r.readValue("{\"type\":null,\"fruit\":null}}");
+        assertNull(deserOrangeBox.fruit);
+        assertNull(deserOrangeBox.type); // error: "expected null, but was:<null>"
+    }
 }

src/test/java/com/fasterxml/jackson/databind/util/TestTokenBuffer.java

@@ -37,6 +37,7 @@ public void testBasicConfig() throws IOException
         assertSame(MAPPER, buf.getCodec());
         assertNotNull(buf.getOutputContext());
         assertFalse(buf.isClosed());
+        assertTrue(buf.isEmpty());
 
         buf.setCodec(null);
         assertNull(buf.getCodec());
@@ -57,7 +58,8 @@ public void testBasicConfig() throws IOException
     public void testSimpleWrites() throws IOException
     {
         TokenBuffer buf = new TokenBuffer(null, false); // no ObjectCodec
-        
+        assertTrue(buf.isEmpty());
+
         // First, with empty buffer
         JsonParser p = buf.asParser();
         assertNull(p.currentToken());
@@ -66,6 +68,7 @@ public void testSimpleWrites() throws IOException
 
         // Then with simple text
         buf.writeString("abc");
+        assertFalse(buf.isEmpty());
 
         p = buf.asParser();
         assertNull(p.currentToken());
@@ -657,6 +660,7 @@ public void testEmbeddedObjectCoerceCheck() throws Exception
         TokenBuffer buf = new TokenBuffer(null, false);
         Object inputPojo = new Sub1730();
         buf.writeEmbeddedObject(inputPojo);
+        assertEquals(JsonToken.VALUE_EMBEDDED_OBJECT, buf.firstToken());
 
         // first: raw value won't be transformed in any way:
         JsonParser p = buf.asParser();
@@ -666,4 +670,19 @@ public void testEmbeddedObjectCoerceCheck() throws Exception
         p.close();
         buf.close();
     }
+
+    public void testIsEmpty() throws Exception
+    {
+        // Let's check that segment boundary won't ruin it
+        try (TokenBuffer buf = new TokenBuffer(null, false)) {
+            assertTrue(buf.isEmpty());
+
+            for (int i = 0; i < 100; ++i) {
+                buf.writeNumber(i);
+                assertFalse(buf.isEmpty());
+            }
+
+            assertEquals(JsonToken.VALUE_NUMBER_INT, buf.firstToken());
+        }
+    }
 }