tree.Marshal() returns empty bytes without any errors

[yukithm]

Describe the bug
tree.Marshal() returns empty bytes without any errors.

To Reproduce

package main

import (
	"fmt"
	"os"

	"github.com/pelletier/go-toml"
)

func main() {
	data := map[string]interface{}{
		"section": map[string]string{
			"name": "foo",
		},
	}

	tree, err := toml.TreeFromMap(data)
	if err != nil {
		panic(err)
	}

	fmt.Println(tree.Marshal()) //=> [] <nil>

	fmt.Println(tree.String())       // worked perfectly
	fmt.Println(tree.ToTomlString()) // worked perfectly
	tree.WriteTo(os.Stdout)          // worked perfectly
}

Expected behavior
It returns TOML content.

[section]
  name = "foo"

Versions

• go-toml: v1.4.1-0.20190827035702-3ded2e09ee1b
• go: go1.12.9 darwin/amd64
• operating system: macOS

[pelletier]

Thanks for the bug report! That definitely looks wrong.

[mbialon]

I don't understand why the Marshal method tries to process the Tree struct. The struct doesn't have exported fields so Marshal returns an empty result.

func (t *Tree) Marshal() ([]byte, error) {
	var buf bytes.Buffer
	err := NewEncoder(&buf).Encode(t)
	return buf.Bytes(), err
}

What do you think about replacing the encoding part with tree.WriteTo, similarly to ToTomlString?

func (t *Tree) Marshal() ([]byte, error) {
	var buf bytes.Buffer
	_, err := t.WriteTo(&buf)
	if err != nil {
		return nil, err
	}
	return buf.Bytes(), nil
}

[pelletier]

That makes sense. Looks like Tree.Marshal() should just call ToTomlString and cast to bytes.

This is the kind of function that I regret having published. There are 4 ways to emit a TOML document:

• Tree.ToTomlString()
• Tree.Marshal()
• Marshal()
• Encoder.Encode()

The last two are here to mirror the standard json library. The first two serve the same purpose (turn a tree into a TOML string/bytes). Clearly there should be just one.