Go Nullable

• Provide Go database null value for any data type as JSON thanks to the Golang generic features.
• Support data type github.com/google/uuid.UUID.
• Make possible to scan and store any structs' type into json and jsonb Postgresql data type.
• Support JSON marshaling and unMarshaling with conventional Javascript/Typescript value null instead of Valid:true/false, Type:value as database/sql does.

Usages

From the Go test

type Test[T any] struct {
	ID     int64                   `json:"id"`
	Name   *nullable.Of[string]    `json:"name"`
	DateTo *nullable.Of[time.Time] `json:"dateTo"`
	Data   *nullable.Of[T]         `json:"data"`
}

type testedType = struct {
	String string                      `json:"string"`
	Bool   *nullable.Of[bool]          `json:"bool"`
	Int    int64                       `json:"int"`
	JSON   *nullable.Of[nullable.JSON] `json:"json"`
}

data1 := testedType{
	String: "a string",
	Bool:   nullable.FromValue(true),
	Int:    768,
}

data1.JSON = nullable.FromValue[nullable.JSON](data1)

obj1 := Test[testedType]{
	Name:   nullable.FromValue("PLOP"),
	DateTo: nullable.FromValue(time.Now()),
	Data:   nullable.FromValue(data1),
}

obj2 := Test[testedType]{
	Name:   nullable.Null[string](),     // Null value
	DateTo: nullable.Null[time.Time](),  // Null value
	Data:   nullable.Null[testedType](), // Null value
}

Database Insertion

Comes from a test on Postgresql database with Time and JSON insertion :

// The model of the db table test
type Test[T nullable.JSON] struct {
	ID int64 `json:"id"`
	// This string can be null
	Name *nullable.Of[string] `json:"name"`
	// This timestamp can be null
	DateTo *nullable.Of[time.Time] `json:"dateTo"`
	// You can any interface you want in data
	Data *nullable.Of[T] `json:"data"`
}

type dataType = struct {
	String string `json:"string"`
	Bool   bool   `json:"bool"`
	Int    int64  `json:"int"`
}

data := dataType{
	String: "This is a string",
	Bool:   true,
	Int:    768,
}

obj := Test[dataType]{
	Name:      nullable.FromValue("My name"),
	DateTo:    nullable.FromValue(time.Now()),
	Data:      nullable.FromValue(data),
}

_, err = daoService.NamedExec("INSERT INTO test (name, date_to, data) VALUES (:name, :date_to, :data)", obj)

if err != nil…

Custom primitive data type

The library Nullable persist and read the structured types as JSON in/from the database but it is possible to workaround this feature.

Suppose you need the custom type type PhoneNumber string. If you use this type as is :

type Coordinate struct {
	Email      *nullable.Of[string]            `json:"email,omitempty"`
	Phone      *nullable.Of[phonenum.PhoneNum] `json:"phone"`
}

persisting a Coordinate in database will persist the field Phone in JSON, what we don't want. In order to persist (resp. read) the type Phone as a string, you must implement the native Go database driver.Valuer (reps. sql.Scanner) :

// Value implements the driver.Valuer interface.
func (pn *PhoneNumb) Value() (driver.Value, error) {
	return driver.Value(string(*pn)), nil
}

// Scan implements the sql.Scanner interface.
func (pn *PhoneNum) Scan(v any) error {
	switch val := v.(type) {
	case int, int64, uint64:
		*pn = PhoneNum(strconv.Itoa(val.(int)))
	case string:
		*pn = PhoneNum(val)
	default:
		return errors.New(fmt.Sprintf("can not scan phone number from type %T", val))
	}

	return nil
}

This Scanner can even read an integer from the database to fulfill the phone number as a string.

Notes

Similar Project

This project is inspired from gonull that fails scanning/storing some Postgresql type like enum, timestamp and json/jsonb.

Go Tests for Postgresql

Go tests storing and scanning data from/to Postgresql database are in progress and will be available soon in an other git repository.