improve data type conversion (#236)

* improve data type conversion

* update doc

tools/goctl/model/sql/converter/types.go

@@ -41,12 +41,34 @@ var (
 	}
 )
 
-func ConvertDataType(dataBaseType string) (goDataType string, err error) {
+func ConvertDataType(dataBaseType string, isDefaultNull bool) (string, error) {
 	tp, ok := commonMysqlDataTypeMap[strings.ToLower(dataBaseType)]
 	if !ok {
-		err = fmt.Errorf("unexpected database type: %s", dataBaseType)
-		return
+		return "", fmt.Errorf("unexpected database type: %s", dataBaseType)
+	}
+
+	return mayConvertNullType(tp, isDefaultNull), nil
+}
+
+func mayConvertNullType(goDataType string, isDefaultNull bool) string {
+	if !isDefaultNull {
+		return goDataType
+	}
+
+	switch goDataType {
+	case "int64":
+		return "sql.NullInt64"
+	case "int32":
+		return "sql.NullInt32"
+	case "float64":
+		return "sql.NullFloat64"
+	case "bool":
+		return "sql.NullBool"
+	case "string":
+		return "sql.NullString"
+	case "time.Time":
+		return "sql.NullTime"
+	default:
+		return goDataType
 	}
-	goDataType = tp
-	return
 }

tools/goctl/model/sql/converter/types_test.go

@@ -7,14 +7,22 @@ import (
 )
 
 func TestConvertDataType(t *testing.T) {
-	v, err := ConvertDataType("tinyint")
+	v, err := ConvertDataType("tinyint", false)
 	assert.Nil(t, err)
 	assert.Equal(t, "int64", v)
 
-	v, err = ConvertDataType("timestamp")
+	v, err = ConvertDataType("tinyint", true)
+	assert.Nil(t, err)
+	assert.Equal(t, "sql.NullInt64", v)
+
+	v, err = ConvertDataType("timestamp", false)
 	assert.Nil(t, err)
 	assert.Equal(t, "time.Time", v)
 
-	_, err = ConvertDataType("float32")
+	v, err = ConvertDataType("timestamp", true)
+	assert.Nil(t, err)
+	assert.Equal(t, "sql.NullTime", v)
+
+	_, err = ConvertDataType("float32", false)
 	assert.NotNil(t, err)
 }