Preserve original body when resending

in_session.go

@@ -253,7 +253,7 @@ func (state inSession) resendMessages(session *session, beginSeqNo, endSeqNo int
 		}
 
 		session.log.OnEventf("Resending Message: %v", sentMessageSeqNum)
-		msgBytes = msg.build()
+		msgBytes = msg.buildWithBodyBytes(msg.bodyBytes) // workaround for maintaining repeating group field order
 		session.EnqueueBytesAndSend(msgBytes)
 
 		seqNum = sentMessageSeqNum + 1

message.go

@@ -210,6 +210,7 @@ func ParseMessageWithDataDictionary(
 
 	trailerBytes := []byte{}
 	foundBody := false
+	foundTrailer := false
 	for {
 		parsedFieldBytes = &msg.fields[fieldIndex]
 		if xmlDataLen > 0 {
@@ -228,6 +229,7 @@ func ParseMessageWithDataDictionary(
 			msg.Header.add(msg.fields[fieldIndex : fieldIndex+1])
 		case isTrailerField(parsedFieldBytes.tag, transportDataDictionary):
 			msg.Trailer.add(msg.fields[fieldIndex : fieldIndex+1])
+			foundTrailer = true
 		default:
 			foundBody = true
 			trailerBytes = rawBytes
@@ -247,6 +249,12 @@ func ParseMessageWithDataDictionary(
 		fieldIndex++
 	}
 
+	// This will happen if there are no fields in the body
+	if foundTrailer && !foundBody {
+		trailerBytes = rawBytes
+		msg.bodyBytes = nil
+	}
+
 	// Body length would only be larger than trailer if fields out of order.
 	if len(msg.bodyBytes) > len(trailerBytes) {
 		msg.bodyBytes = msg.bodyBytes[:len(msg.bodyBytes)-len(trailerBytes)]
@@ -417,6 +425,21 @@ func (m *Message) build() []byte {
 	return b.Bytes()
 }
 
+// Constructs a []byte from a Message instance, using the given bodyBytes.
+// This is a workaround for the fact that we currently rely on the generated Message types to properly serialize/deserialize RepeatingGroups.
+// In other words, we cannot go from bytes to a Message then back to bytes, which is exactly what we need to do in the case of a Resend.
+// This func lets us pull the Message from the Store, parse it, update the Header, and then build it back into bytes using the original Body.
+// Note: The only standard non-Body group is NoHops.  If that is used in the Header, this workaround may fail.
+func (m *Message) buildWithBodyBytes(bodyBytes []byte) []byte {
+	m.cook()
+
+	var b bytes.Buffer
+	m.Header.write(&b)
+	b.Write(bodyBytes)
+	m.Trailer.write(&b)
+	return b.Bytes()
+}
+
 func (m *Message) cook() {
 	bodyLength := m.Header.length() + m.Body.length() + m.Trailer.length()
 	m.Header.SetInt(tagBodyLength, bodyLength)

message_test.go

@@ -133,18 +133,54 @@ func (s *MessageSuite) TestReBuild() {
 
 	s.msg.Header.SetField(tagOrigSendingTime, FIXString("20140515-19:49:56.659"))
 	s.msg.Header.SetField(tagSendingTime, FIXString("20140615-19:49:56"))
+	s.msg.Header.SetField(tagPossDupFlag, FIXBoolean(true))
 
 	rebuildBytes := s.msg.build()
 
-	expectedBytes := []byte("8=FIX.4.2
9=126
35=D
34=2
49=TW
52=20140615-19:49:56
56=ISLD
122=20140515-19:49:56.659
11=100
21=1
40=1
54=1
55=TSLA
60=00010101-00:00:00.000
10=128
")
+	expectedBytes := []byte("8=FIX.4.2
9=131
35=D
34=2
43=Y
49=TW
52=20140615-19:49:56
56=ISLD
122=20140515-19:49:56.659
11=100
21=1
40=1
54=1
55=TSLA
60=00010101-00:00:00.000
10=122
")
 
-	s.True(bytes.Equal(expectedBytes, rebuildBytes), "Unexpected bytes,\n +%s\n-%s", rebuildBytes, expectedBytes)
+	s.True(bytes.Equal(expectedBytes, rebuildBytes), "Unexpected bytes,\n +%s\n -%s", rebuildBytes, expectedBytes)
 
 	expectedBodyBytes := []byte("11=100
21=1
40=1
54=1
55=TSLA
60=00010101-00:00:00.000
")
 
 	s.True(bytes.Equal(s.msg.bodyBytes, expectedBodyBytes), "Incorrect body bytes, got %s", string(s.msg.bodyBytes))
 }
 
+func (s *MessageSuite) TestReBuildWithRepeatingGroupForResend() {
+	// Given the following message with a repeating group
+	origHeader := "8=FIXT.1.1
9=161
35=8
34=3
49=ISLD
52=20240415-03:43:17.923
56=TW
"
+	origBody := "6=1.00
11=1
14=1.00
17=1
31=1.00
32=1.00
37=1
38=1.00
39=2
54=1
55=1
150=2
151=0.00
453=1
448=xyzzy
447=D
452=1
"
+	origTrailer := "10=014
"
+	rawMsg := bytes.NewBufferString(origHeader + origBody + origTrailer)
+
+	// When I reparse the message from the store during a resend request
+	s.Nil(ParseMessage(s.msg, rawMsg))
+
+	// And I update the headers for resend
+	s.msg.Header.SetField(tagOrigSendingTime, FIXString("20240415-03:43:17.923"))
+	s.msg.Header.SetField(tagSendingTime, FIXString("20240415-14:41:23.456"))
+	s.msg.Header.SetField(tagPossDupFlag, FIXBoolean(true))
+
+	// When I rebuild the message
+	rebuildBytes := s.msg.build()
+
+	// Then the repeating groups will not be in the correct order in the rebuilt message (note tags 447, 448, 452, 453)
+	expectedBytes := []byte("8=FIXT.1.1
9=192
35=8
34=3
43=Y
49=ISLD
52=20240415-14:41:23.456
56=TW
122=20240415-03:43:17.923
6=1.00
11=1
14=1.00
17=1
31=1.00
32=1.00
37=1
38=1.00
39=2
54=1
55=1
150=2
151=0.00
453=1
448=xyzzy
447=D
452=1
10=018
")
+	s.False(bytes.Equal(expectedBytes, rebuildBytes), "Unexpected bytes,\n expected: %s\n  but was: %s", expectedBytes, rebuildBytes)
+	expectedOutOfOrderBytes := []byte("8=FIXT.1.1
9=192
35=8
34=3
43=Y
49=ISLD
52=20240415-14:41:23.456
56=TW
122=20240415-03:43:17.923
6=1.00
11=1
14=1.00
17=1
31=1.00
32=1.00
37=1
38=1.00
39=2
54=1
55=1
150=2
151=0.00
447=D
448=xyzzy
452=1
453=1
10=018
")
+	s.True(bytes.Equal(expectedOutOfOrderBytes, rebuildBytes), "Unexpected bytes,\n expected: %s\n  but was: %s", expectedOutOfOrderBytes, rebuildBytes)
+
+	// But the bodyBytes will still be correct
+	origBodyBytes := []byte(origBody)
+	s.True(bytes.Equal(origBodyBytes, s.msg.bodyBytes), "Incorrect body bytes, \n expected: %s\n  but was: %s", origBodyBytes, s.msg.bodyBytes)
+
+	// So when I combine the updated header + the original bodyBytes + the as-is trailer
+	resendBytes := s.msg.buildWithBodyBytes(s.msg.bodyBytes)
+
+	// Then the reparsed, rebuilt message will retain the correct ordering of repeating group tags during resend
+	s.True(bytes.Equal(expectedBytes, resendBytes), "Unexpected bytes,\n expected: %s\n  but was: %s", expectedBytes, resendBytes)
+}
+
 func (s *MessageSuite) TestReverseRoute() {
 	s.Nil(ParseMessage(s.msg, bytes.NewBufferString("8=FIX.4.2
9=171
35=D
34=2
49=TW
50=KK
52=20060102-15:04:05
56=ISLD
57=AP
144=BB
115=JCD
116=CS
128=MG
129=CB
142=JV
143=RY
145=BH
11=ID
21=3
38=100
40=w
54=1
55=INTC
60=20060102-15:04:05
10=123
")))