Error from body writer is ignored

[oschwald]

Description

If you set a body writer with SetBodyWriter and the writer fails with an error, (*Msg).WriteTo will not return an error itself.

To Reproduce

Run:

package main

import (
	"errors"
	"fmt"
	"io"

	"github.com/wneessen/go-mail"
)

func main() {
	m := mail.NewMsg()

	m.SetBodyWriter(
		mail.TypeTextPlain,
		func(io.Writer) (int64, error) {
			return 0, errors.New("failed!")
		},
	)

	_, err := m.WriteTo(io.Discard)
	fmt.Println(err)
}

Expected behaviour

The above prints out <nil>. I would expect the body writer error to cause WriteTo to return an error, resulting in the program outputting failed! or a wrapped version of it. Right now, there is no indication that an error occurred.

Screenshots

No response

Attempted Fixes

No response

Additional context

No response

[wneessen]

Thanks for the report. That indeed doesn't sound right. I'll have a look what's going on there.

[oschwald]

Thanks for the quick fix on this.