incorrect way of loading mac address.

[d0zer11st]

Getting mac address not the same I stored before.

I think, the issue is in the Stringer.Scan() func, for macaddr the underlying type is net.HardwareAddr, simple type conversion is not the way to use it.

bob/types/marshal.go

Lines 76 to 89 in 5263402

	func (s *Stringer[T]) Scan(value any) error {
	switch x := value.(type) {
	case string:
	s.Val = T(x)
	return nil
	case []byte:
	s.Val = T(x)
	return nil
	case nil:
	return nil
	default:
	return fmt.Errorf("cannot scan type %T: %v", value, value)
	}
	}

how to reproduce:

1. bob version: github.com/stephenafamo/bob v0.27.1
2. postgres 16.2
3. Table

create table example
(
    id bigint primary key generated always as identity,
    mac           macaddr not null,
    hostname text not null
)

4. Code example.

	macToTest := "1b:1b:63:84:45:e6"
	hwAddr, parseMacErr := net.ParseMAC(macToTest)
	if parseMacErr != nil {
		log.Fatal(parseMacErr)
	}
	log.Printf("parsed mac: %s", hwAddr)
	hostNameString := uuid.New().String()
	exampleSetter := &models.ExampleSetter{
		Mac:      omit.From(types.Stringer[net.HardwareAddr]{Val: hwAddr}),
		Hostname: omit.From(hostNameString),
	}

	_, err := models.Examples.InsertMany(ctx, bobDB, exampleSetter)
	if err != nil {
		log.Fatal(err)
	}

	selectQueryWhere := psql.Select(
		sm.From(models.TableNames.Examples),
		sm.Where(
			models.ExampleColumns.Hostname.EQ(
				psql.Arg(hostNameString),
			),
		),
	)

	all, err := bob.All(ctx, bobDB, selectQueryWhere, scan.StructMapper[*models.Example]())
	if err != nil {
		log.Fatal(err)
	}

	hwAddrStrConv := net.HardwareAddr(macToTest)

	fmt.Printf("strconv: %s\n", hwAddrStrConv.String())  // the same way it implemented in Stringer.Scan()
	fmt.Printf("     db: %s\n", all[0].Mac.Val.String()) // loaded value
	fmt.Printf(" parsed: %s\n", hwAddr.String())         // parsed

	if !strings.EqualFold(all[0].Mac.Val.String(), hwAddr.String()) {
		log.Fatalf("%s is not the same as %s", all[0].Mac.Val.String(), hwAddr.String())
	}

Print results:

strconv: 31:62:3a:31:62:3a:36:33:3a:38:34:3a:34:35:3a:65:36
     db: 31:62:3a:31:62:3a:36:33:3a:38:34:3a:34:35:3a:65:36
 parsed: 1b:1b:63:84:45:e6

I also tried to insert Mac with just type conversion like this:

	hostNameString := uuid.New().String()

        macToTest := "1b:1b:63:84:45:e6"
	hwAddr := net.HardwareAddr(macToTest)

	exampleSetter := &models.ExampleSetter{
		Mac:      omit.From(types.Stringer[net.HardwareAddr]{Val: hwAddr}),
		Hostname: omit.From(hostNameString),
	}

	_, err := models.Examples.InsertMany(ctx, bobDB, exampleSetter)
	if err != nil {
		log.Fatal(err)
	}

that leads to error

ERROR: invalid input syntax for type macaddr: "31:62:3a:31:62:3a:36:33:3a:38:34:3a:34:35:3a:65:36" (SQLSTATE 22P02)

[stephenafamo]

Yeah, I see the issue.

I should not have assumed that it would be able to work like this, types.Stringer as a whole probably does not work. I would probably have to create a dedicated type for it.

I wish net.HardwareAddr implemented Text or Binary Marshaler.

[d0zer11st]

yeah, as I see there is only one usage of Stringer and it is for macaddr.
the dedicated type would work better.