Minor fix to JacksonAnnotationIntrospector to allow use of @JsonSetter without masking name

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/databind/introspect/JacksonAnnotationIntrospector.java

@@ -1228,16 +1228,23 @@ public JsonPOJOBuilder.Value findPOJOBuilderConfig(AnnotatedClass ac)
     public PropertyName findNameForDeserialization(Annotated a)
     {
         // @JsonSetter has precedence over @JsonProperty, being more specific
-        // @JsonDeserialize implies that there is a property, but no name
+
+        boolean useDefault = false;
         JsonSetter js = _findAnnotation(a, JsonSetter.class);
         if (js != null) {
-            return PropertyName.construct(js.value());
+            String s = js.value();
+            // 04-May-2018, tatu: Need to allow for "nameless" `@JsonSetter` too
+            if (s.isEmpty()) {
+                useDefault = true;
+            } else {
+                return PropertyName.construct(s);
+            }
         }
         JsonProperty pann = _findAnnotation(a, JsonProperty.class);
         if (pann != null) {
             return PropertyName.construct(pann.value());
         }
-        if (_hasOneOf(a, ANNOTATIONS_TO_INFER_DESER)) {
+        if (useDefault || _hasOneOf(a, ANNOTATIONS_TO_INFER_DESER)) {
             return PropertyName.USE_DEFAULT;
         }
         return null;