Fix: Prepared statements now support NULL arguments

connection.go

@@ -622,11 +622,15 @@ func (c *Connection) sendPreparedQuery(ps *preparedStatement, arguments ...inter
 
 	w.Write(int16(len(arguments)))
 	for i, oid := range ps.ParameterOids {
-		transcoder := ValueTranscoders[oid]
-		if transcoder == nil {
-			transcoder = defaultTranscoder
+		if arguments[i] != nil {
+			transcoder := ValueTranscoders[oid]
+			if transcoder == nil {
+				transcoder = defaultTranscoder
+			}
+			transcoder.EncodeTo(w, arguments[i])
+		} else {
+			w.Write(int32(-1))
 		}
-		transcoder.EncodeTo(w, arguments[i])
 	}
 
 	w.Write(int16(len(ps.FieldDescriptions)))

value_transcoder_test.go

@@ -5,6 +5,30 @@ import (
 	"time"
 )
 
+func TestNilTranscode(t *testing.T) {
+	conn := getSharedConnection(t)
+
+	var inputNil interface{}
+	inputNil = nil
+
+	result := mustSelectValue(t, conn, "select $1::integer", inputNil)
+	if result != nil {
+		t.Errorf("Did not transcode nil successfully for normal query: %v", result)
+	}
+
+	mustPrepare(t, conn, "testTranscode", "select $1::integer")
+	defer func() {
+		if err := conn.Deallocate("testTranscode"); err != nil {
+			t.Fatalf("Unable to deallocate prepared statement: %v", err)
+		}
+	}()
+
+	result = mustSelectValue(t, conn, "testTranscode", inputNil)
+	if result != nil {
+		t.Errorf("Did not transcode nil successfully for prepared query: %v", result)
+	}
+}
+
 func TestDateTranscode(t *testing.T) {
 	conn := getSharedConnection(t)