Panic when using a custom type with MarshalJSON() + omitempty + specific order of fields in a struct

[knadh]

The panic happens when:

• There's a custom type with a MarshalJSON + there's an omitempty in the field + the field (Field2) has a value

The panic does not happen when:

• Field2 is empty.
• The order of Field1 and Field2 in the struct definition are interchanged (!)

package main

import (
	"fmt"

	gojson "github.com/goccy/go-json"
)

type NullStr string

type Test struct {
	Field1 string  `json:"field1"`
	Field2 NullStr `json:"field2,omitempty"`
}

func main() {

	b, err := gojson.Marshal(Test{
		Field1: "a",
		Field2: "b",
	})

	fmt.Println(string(b), err)
}

func (v *NullStr) MarshalJSON() ([]byte, error) {
	if *v == "" {
		return []byte("null"), nil
	}

	return []byte(*v), nil
}

$ go run main.go                                                                                                                                      
runtime: out of memory: cannot allocate 2317421039983788032-byte block (66781184 in use)
fatal error: out of memory

goroutine 1 [running]:
runtime.throw(0x55eca4, 0xd)
        /usr/local/go/src/runtime/panic.go:1117 +0x72 fp=0xc000414190 sp=0xc000414160 pc=0x4335f2
runtime.(*mcache).allocLarge(0x7fa7bf2fe108, 0x202922285b206000, 0x400100, 0x545180)
        /usr/local/go/src/runtime/mcache.go:226 +0x29e fp=0xc0004141e8 sp=0xc000414190 pc=0x4162be
runtime.mallocgc(0x202922285b206000, 0x0, 0x0, 0x538c36)
        /usr/local/go/src/runtime/malloc.go:1078 +0x925 fp=0xc000414270 sp=0xc0004141e8 pc=0x40d445
runtime.rawbyteslice(0x202922285b205020, 0x0, 0x0, 0x0)
        /usr/local/go/src/runtime/string.go:276 +0xb1 fp=0xc0004142b0 sp=0xc000414270 pc=0x44dc91
runtime.stringtoslicebyte(0x0, 0x40202b20736d6862, 0x202922285b205020, 0x545180, 0x545100, 0x7fa798632858)
        /usr/local/go/src/runtime/string.go:171 +0xbf fp=0xc0004142f8 sp=0xc0004142b0 pc=0x44d65f
main.(*NullStr).MarshalJSON(0x55d516, 0x545180, 0x55d516, 0x7fa798632858, 0x55d516, 0xc000404000)
        /code/go/my/go-json-benchmark/main.go:31 +0x90 fp=0xc000414338 sp=0xc0004142f8 pc=0x535ed0
github.com/goccy/go-json.encodeRunEscaped(0xc000406000, 0xc000404000, 0xe, 0x400, 0xc0000102f0, 0x1, 0x0, 0x0, 0x0, 0x0, ...)
        /code/go/pkg/mod/github.com/goccy/go-json@v0.4.7/encode_vm_escaped.go:5195 +0x3c9ef fp=0xc000415cc8 sp=0xc000414338 pc=0x52ed2f
github.com/goccy/go-json.encodeRunCode(0xc000406000, 0xc000404000, 0x0, 0x400, 0xc0000102f0, 0x1, 0x5352f7, 0x553d60, 0xc000406000, 0x8, ...)
        /code/go/pkg/mod/github.com/goccy/go-json@v0.4.7/encode.go:276 +0x74 fp=0xc000415d30 sp=0xc000415cc8 pc=0x49fc34
github.com/goccy/go-json.encode(0xc000406000, 0x54a640, 0xc000026040, 0x1, 0xc000026040, 0x20, 0x20, 0x54a640, 0x6316e0)
        /code/go/pkg/mod/github.com/goccy/go-json@v0.4.7/encode.go:205 +0x1df fp=0xc000415df8 sp=0xc000415d30 pc=0x49f8ff
github.com/goccy/go-json.marshal(0x54a640, 0xc000026040, 0x1, 0x40aadf, 0x54a640, 0xc000026040, 0xc000064f58, 0xc000026040)
        /code/go/pkg/mod/github.com/goccy/go-json@v0.4.7/encode.go:131 +0x85 fp=0xc000415e80 sp=0xc000415df8 pc=0x49f5a5
github.com/goccy/go-json.MarshalWithOption(0x54a640, 0xc000026040, 0x0, 0x0, 0x0, 0x7fa7bf2fe108, 0x60, 0xc00001e060, 0xc000036748, 0x64a4a0)
        /code/go/pkg/mod/github.com/goccy/go-json@v0.4.7/json.go:171 +0x76 fp=0xc000415ed8 sp=0xc000415e80 pc=0x5346f6
github.com/goccy/go-json.Marshal(...)
        /code/go/pkg/mod/github.com/goccy/go-json@v0.4.7/json.go:157
main.main()
        /code/go/my/go-json-benchmark/main.go:18 +0xce fp=0xc000415f88 sp=0xc000415ed8 pc=0x535d4e
runtime.main()
        /usr/local/go/src/runtime/proc.go:225 +0x256 fp=0xc000415fe0 sp=0xc000415f88 pc=0x435e36
runtime.goexit()
        /usr/local/go/src/runtime/asm_amd64.s:1371 +0x1 fp=0xc000415fe8 sp=0xc000415fe0 pc=0x465041
exit status 2

[goccy]

Thank you for the reporting.
Currently, I will try to fix any encoder's bug with #148 .
This issue will fix by that PR .

[goccy]

I fixed this issue with #148