Fix handling of empty set of values as absence of the key

main.go

@@ -246,14 +246,23 @@ func (server *Server) addElements(dn string, attrs Entry) error {
 	}
 
 	for k, v := range attrs {
-		json, err := json.Marshal(v)
-		if err != nil {
-			return err
-		}
-		pair := &consul.KVPair{Key: prefix + "/attribute=" + k, Value: json}
-		_, err = server.kv.Put(pair, nil)
-		if err != nil {
-			return err
+		path := prefix + "/attribute=" + k
+		if len(v) == 0 {
+			// If we have zero values, delete associated k/v pair
+			_, err := server.kv.Delete(path, nil)
+			if err != nil {
+				return err
+			}
+		} else {
+			json, err := json.Marshal(v)
+			if err != nil {
+				return err
+			}
+			pair := &consul.KVPair{Key: path, Value: json}
+			_, err = server.kv.Put(pair, nil)
+			if err != nil {
+				return err
+			}
 		}
 	}
 	return nil
@@ -454,9 +463,9 @@ func applyFilter(entry Entry, filter message.Filter) (bool, error) {
 	} else if fPresent, ok := filter.(message.FilterPresent); ok {
 		what := string(fPresent)
 		// Case insensitive search
-		for desc := range entry {
+		for desc, values := range entry {
 			if strings.EqualFold(what, desc) {
-				return true, nil
+				return len(values) > 0, nil
 			}
 		}
 		return false, nil