Allownil in []byte is useless

[lxyshuai]

No description provided.

[lxyshuai]

package main

import (
	"fmt"
)

//go:generate msgp

type A struct {
	Bytes   []byte   `msg:"bytes,omitempty,allownil"`
	Strings []string `msg:"strings,omitempty,allownil"`
	Ints    []int    `msg:"ints,omitempty,allownil"`
}

func main() {
	a := A{
		Bytes:   make([]byte, 0),
		Strings: make([]string, 0),
		Ints:    make([]int, 0),
	}

	aBytes, _ := a.MarshalMsg(nil)
	aTemp := A{}
	aTemp.UnmarshalMsg(aBytes)

	fmt.Println(aTemp)
}

Allownil in []byte is useless

[klauspost]

omitempty and allownil doesn't make sense together, since both operate on the nil value. Adding it will do:

	// check for omitted fields
	zb0001Len := uint32(3)
	var zb0001Mask uint8 /* 3 bits */
	_ = zb0001Mask
	if z.Bytes == nil {
		zb0001Len--
		zb0001Mask |= 0x1
	}

Resulting in the same output, since all are included as 0 length arrays, and therefore it will never emit nil values.

omitempty will not omit 0-length slices. This is stated in the docs is that it checks against the zero value. The zero value of a []byte is nil.

[klauspost]

There is a quirk in ReadBytesBytes, where if the array size is 0 a new slice is not allocated if scratch is nil. I will send a fix for that.

[lxyshuai]

@klauspost Thank you！

when scratch is nil,readBytesBytes return nil

[klauspost]

Yes.

[lxyshuai]

Should we reopen this issue?