Bug: struct with map (the only one field) encoded to null

[trim21]

package main

import (
	"fmt"
	"testing"

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

func main() {
	type Container struct {
		V any `json:"value"`
	}
	type MapOnly struct {
		Map map[string]int64 `json:"map"`
	}

	b, err := json.Marshal(Container{MapOnly{}})
	if err != nil {
		panic(err)
	}

	fmt.Println(string(b))
}

output: {"value":null}

[orisano]

what is your expectation?

I could not reproduce this problem in v0.9.8.

func TestIssue376(t *testing.T) {
	type Container struct {
		V any `json:"value"`
	}
	type MapOnly struct {
		b   bool
		Map map[string]int64 `json:"map"`
	}
	b, err := json.Marshal(Container{MapOnly{}})
	if err != nil {
		t.Fatal(err)
	}
	got := string(b)
	expected := `{"value":{"map":null}}`
	if got != expected {
		t.Errorf("unexpected result: %v != %v", got, expected)
	}
}

what version did you use?

[trim21]

Oh, sorry, I'm using 0.9.7.

This bug behavior differently in 0.9.8, try this: (remove MapOnly{}.b)

package main

import (
	"fmt"

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

func main() {
	type Container struct {
		V any `json:"value"`
	}
	type MapOnly struct {
		Map map[string]int64 `json:"map"`
	}

	b, err := json.Marshal(Container{MapOnly{}})
	if err != nil {
		panic(err)
	}

	fmt.Println(string(b))
}

[trim21]

@orisano can you re-produce with new example?

I just try this on master branch and it fail.

func TestIssue376(t *testing.T) {
	type Container struct {
		V interface{} `json:"value"`
	}
	type MapOnly struct {
		Map map[string]int64 `json:"map"`
	}
	b, err := json.Marshal(Container{MapOnly{}})
	if err != nil {
		t.Fatal(err)
	}
	got := string(b)
	expected := `{"value":{"map":null}}`
	if got != expected {
		t.Errorf("unexpected result: %v != %v", got, expected)
	}
}

[orisano]

thanks, I reproduced.