Ensured that custom deserializer is invoked with actual type returned for field values.

Fixed a bug where a top-level object was constructed with default values even when the custom deserializer tried to set it to null.

gson/src/main/java/com/google/gson/JsonDeserializationVisitor.java

@@ -35,6 +35,7 @@ abstract class JsonDeserializationVisitor<T> implements ObjectNavigator.Visitor
   protected final JsonElement json;
   protected final Type targetType;
   protected final JsonDeserializationContext context;
+  protected boolean constructed;
 
   public JsonDeserializationVisitor(JsonElement json, Type targetType,
       ObjectNavigatorFactory factory, ObjectConstructor objectConstructor,
@@ -47,11 +48,13 @@ abstract class JsonDeserializationVisitor<T> implements ObjectNavigator.Visitor
     this.deserializers = deserializers;
     this.json = json;
     this.context = context;
+    this.constructed = false;
   }
 
   public T getTarget() {
-    if (target == null) {
+    if (!constructed) {
       target = constructTarget();
+      constructed = true;
     }
     return target;
   }
@@ -70,14 +73,21 @@ abstract class JsonDeserializationVisitor<T> implements ObjectNavigator.Visitor
     if (pair == null) {
       return false;
     }    
-    if (!json.isJsonNull()) {
+    Object value = invokeCustomDeserializer(json, pair);
-      JsonDeserializer deserializer = pair.getFirst();
+    target = (T) value;
-      Type objType = pair.getSecond().getType();
+    constructed = true;
-      target = (T) deserializer.deserialize(json, objType, context);
-    }
     return true;
   }
 
+  protected Object invokeCustomDeserializer(JsonElement element, 
+      Pair<JsonDeserializer<?>, ObjectTypePair> pair) {
+    if (element == null || element.isJsonNull()) {
+      return null;
+    }
+    Type objType = pair.getSecond().getType();
+    return (pair.getFirst()).deserialize(element, objType, context);
+  }
+
   final Object visitChildAsObject(Type childType, JsonElement jsonChild) {
     JsonDeserializationVisitor<?> childVisitor =
         new JsonObjectDeserializationVisitor<Object>(jsonChild, childType,

gson/src/main/java/com/google/gson/JsonObjectDeserializationVisitor.java

@@ -93,32 +93,32 @@ final class JsonObjectDeserializationVisitor<T> extends JsonDeserializationVisit
     return namingPolicy.translateName(f);
   }
 
-  public boolean visitFieldUsingCustomHandler(Field f, Type actualTypeOfField, Object parent) {
+  public boolean visitFieldUsingCustomHandler(Field f, Type declaredTypeOfField, Object parent) {
     try {
       String fName = getFieldName(f);
       if (!json.isJsonObject()) {
         throw new JsonParseException("Expecting object found: " + json); 
       }
       JsonElement child = json.getAsJsonObject().get(fName);
-      if (child == null) {
+      TypeInfo typeInfo = new TypeInfo(declaredTypeOfField);
+      if (child == null) { // Child will be null if the field wasn't present in Json
         return true;
       } else if (child.isJsonNull()) {
-        TypeInfo typeInfo = new TypeInfo(actualTypeOfField);
         if (!typeInfo.isPrimitive()) {
           f.set(parent, null);
         }
         return true;
       }
-      @SuppressWarnings("unchecked")
+      ObjectTypePair objTypePair = new ObjectTypePair(null, declaredTypeOfField, false);
-      JsonDeserializer deserializer = deserializers.getHandlerFor(actualTypeOfField);
+      Pair<JsonDeserializer<?>, ObjectTypePair> pair = objTypePair.getMatchingHandler(deserializers);
-      if (deserializer != null) {
+      if (pair == null) {
-        if (!child.isJsonNull()) {
+        return false;
-          Object value = deserializer.deserialize(child, actualTypeOfField, context);
+      }      
-          f.set(parent, value);
+      Object value = invokeCustomDeserializer(child, pair);
-        }
+      if (value != null || !typeInfo.isPrimitive()) {
-        return true;
+        f.set(parent, value);
       }
-      return false;
+      return true;
     } catch (IllegalAccessException e) {
       throw new RuntimeException();
     }

gson/src/test/java/com/google/gson/functional/CustomDeserializerTest.java

@@ -23,6 +23,8 @@ import com.google.gson.JsonDeserializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.google.gson.JsonParseException;
+import com.google.gson.common.TestTypes.Base;
+import com.google.gson.common.TestTypes.ClassWithBaseField;
 
 import junit.framework.TestCase;
 
@@ -144,4 +146,90 @@ public class CustomDeserializerTest extends TestCase {
     @SuppressWarnings("unused")
     String field2;    
   }
+  
+  public void testCustomDeserializerReturnsNullForTopLevelObject() {
+    Gson gson = new GsonBuilder()
+      .registerTypeAdapter(Base.class, new JsonDeserializer<Base>() {
+        public Base deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+            throws JsonParseException {
+          return null;
+        }
+      }).create();
+    String json = "{baseName:'Base',subName:'SubRevised'}";
+    Base target = gson.fromJson(json, Base.class);
+    assertNull(target);
+  }
+
+  public void testCustomDeserializerReturnsNull() {
+    Gson gson = new GsonBuilder()
+      .registerTypeAdapter(Base.class, new JsonDeserializer<Base>() {
+        public Base deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+            throws JsonParseException {
+          return null;
+        }
+      }).create();
+    String json = "{base:{baseName:'Base',subName:'SubRevised'}}";
+    ClassWithBaseField target = gson.fromJson(json, ClassWithBaseField.class);
+    assertNull(target.base);
+  }
+
+  public void testCustomDeserializerReturnsNullForTopLevelPrimitives() {
+    Gson gson = new GsonBuilder()
+      .registerTypeAdapter(long.class, new JsonDeserializer<Long>() {
+        public Long deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+            throws JsonParseException {
+          return null;
+        }
+      }).create();
+    String json = "10";
+    assertNull(gson.fromJson(json, long.class));
+  }
+
+  public void testCustomDeserializerReturnsNullForPrimitiveFields() {
+    Gson gson = new GsonBuilder()
+      .registerTypeAdapter(long.class, new JsonDeserializer<Long>() {
+        public Long deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+            throws JsonParseException {
+          return null;
+        }
+      }).create();
+    String json = "{field:10}";
+    ClassWithLong target = gson.fromJson(json, ClassWithLong.class);
+    assertEquals(0, target.field);
+  }
+  private static class ClassWithLong {
+    long field;
+  }
+ 
+  public void testCustomDeserializerReturnsNullForArrayElements() {
+    Gson gson = new GsonBuilder()
+      .registerTypeAdapter(Base.class, new JsonDeserializer<Base>() {
+        public Base deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+            throws JsonParseException {
+          return null;
+        }
+      }).create();
+    String json = "[{baseName:'Base'},{baseName:'Base'}]";
+    Base[] target = gson.fromJson(json, Base[].class);
+    assertNull(target[0]);
+    assertNull(target[1]);
+  }
+
+  public void testCustomDeserializerReturnsNullForArrayElementsForArrayField() {
+    Gson gson = new GsonBuilder()
+      .registerTypeAdapter(Base.class, new JsonDeserializer<Base>() {
+        public Base deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
+            throws JsonParseException {
+          return null;
+        }
+      }).create();
+    String json = "{bases:[{baseName:'Base'},{baseName:'Base'}]}";
+    ClassWithBaseArray target = gson.fromJson(json, ClassWithBaseArray.class);
+    assertNull(target.bases[0]);
+    assertNull(target.bases[1]);
+  }
+
+  private static class ClassWithBaseArray {
+    Base[] bases;
+  }
 }

gson/src/test/java/com/google/gson/functional/NullObjectAndFieldTest.java

@@ -200,7 +200,7 @@ public class NullObjectAndFieldTest extends TestCase {
         }).create();
     String json = "{value:'value1'}";
     ObjectWithField target = gson.fromJson(json, ObjectWithField.class);
-    assertFalse("value1".equals(target.value));
+    assertNull(target);
   }
 
   private static class ObjectWithField {