Old Content-Type headers are retained after email MIME content is generated with Bytes() #131
Description
When parsing an email having a Content-Type and boundary, the old boundary value is still returned by the Email instance even though the call to Bytes() generates a new one.
Here is some sample code that demonstrate the issue:
package main
import (
"bufio"
"bytes"
"fmt"
"net/textproto"
"github.com/jordan-wright/email"
)
func main() {
var content = []byte(`Content-Type: multipart/alternative; boundary="000000000000a8b374056d65d2cc"
--000000000000a8b374056d65d2cc
Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes
Hello world !
--000000000000a8b374056d65d2cc
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
<html><body>Hello world !</body></html>
--000000000000a8b374056d65d2cc--
`)
// Original CT headers, kept in 'e'
e, _ := email.NewEmailFromReader(bytes.NewReader((content)))
fmt.Println(e.Headers.Get("Content-Type"))
// Generated headers when using bytes
body, _ := e.Bytes()
tp := textproto.NewReader(bufio.NewReader(bytes.NewReader(body)))
hdrs, _ := tp.ReadMIMEHeader()
fmt.Println(hdrs.Get("Content-Type"))
// But e still holds old headers
fmt.Println(e.Headers.Get("Content-Type"))
}(try it on https://play.golang.org/p/Wa9nvCf5rz5).
$ go run test.go
multipart/alternative; boundary="000000000000a8b374056d65d2cc"
multipart/alternative; boundary=1d6ee4a2d342ba18c1ecd4e7070573e9fb57ed43211843becbc7fb6635fe
multipart/alternative; boundary="000000000000a8b374056d65d2cc"
This is a bit misleading, and a somewhat detrimental in certain situations.
May be a call to e.Bytes() could replace MIME Headers with the new Content-Type/multipart value ?