feat(GODT-3193): preserve attachment encoding.

pkg/message/parser.go

@@ -205,6 +205,10 @@ func convertForeignEncodings(p *parser.Parser) error {
 			return p.ConvertMetaCharset()
 		}).
 		RegisterContentTypeHandler("text/.*", func(p *parser.Part) error {
+			if p.IsAttachment() {
+				return nil
+			}
+
 			return p.ConvertToUTF8()
 		}).
 		Walk()

pkg/message/parser_test.go

@@ -837,6 +837,17 @@ func TestPatchNewLineWithHtmlBreaks(t *testing.T) {
 	}
 }
 
+func TestParseCp1250Attachment(t *testing.T) {
+	r := require.New(t)
+	f := getFileReader("text_plain_xml_attachment_cp1250.eml")
+
+	m, err := Parse(f)
+	r.NoError(err)
+
+	r.Len(m.Attachments, 1)
+	r.Equal("text/xml; charset=windows-1250; name=\"cp1250.xml\"", m.Attachments[0].Header.Get("Content-Type"))
+}
+
 func getFileReader(filename string) io.Reader {
 	f, err := os.Open(filepath.Join("testdata", filename))
 	if err != nil {

pkg/message/testdata/text_plain_xml_attachment_cp1250.eml

@@ -0,0 +1,22 @@
+From: Sender <sender@pm.me>
+To: Receiver <receiver@pm.me>
+Content-Type: multipart/mixed; boundary="------------iOaeSk0jVHjMucH3kQFwS1LB"
+
+This is a multi-part message in MIME format.
+--------------iOaeSk0jVHjMucH3kQFwS1LB
+Content-Type: text/plain; charset=UTF-8; format=flowed
+Content-Transfer-Encoding: 8bit
+
+created by me 😎
+
+--------------iOaeSk0jVHjMucH3kQFwS1LB
+Content-Type: text/xml; charset=windows-1250; name="cp1250.xml"
+Content-Disposition: attachment; filename="cp1250.xml"
+Content-Transfer-Encoding: 8bit
+
+<?xml version="1.0" encoding="WINDOWS-1250" ?>
+<pvpoj xmlns="http://schemas.cssz.cz/POJ/PVPOJ2023">
+<ulice>Horní námìstí</ulice>
+<prijmeni>ŠCheckCharsá</prijmeni>
+</pvpoj>
+--------------iOaeSk0jVHjMucH3kQFwS1LB--