Maintain repeating group field order when parsing messages

Makefile

@@ -25,6 +25,10 @@ linters-install:
 lint: linters-install
 	golangci-lint run
 
+# An easy way to run the linter without going through the install process -
+# docker run -t --rm -v $(pwd):/app -w /app golangci/golangci-lint:v1.57.2 golangci-lint run -v
+# See https://golangci-lint.run/welcome/install/ for more details.
+
 # ---------------------------------------------------------------
 # Targets related to running acceptance tests -
 

in_session.go

@@ -232,7 +232,11 @@ func (state inSession) resendMessages(session *session, beginSeqNo, endSeqNo int
 	nextSeqNum := seqNum
 	msg := NewMessage()
 	for _, msgBytes := range msgs {
-		_ = ParseMessageWithDataDictionary(msg, bytes.NewBuffer(msgBytes), session.transportDataDictionary, session.appDataDictionary)
+		err = ParseMessageWithDataDictionary(msg, bytes.NewBuffer(msgBytes), session.transportDataDictionary, session.appDataDictionary)
+		if err != nil {
+			session.log.OnEventf("Resend Msg Parse Error: %v, %v", err.Error(), bytes.NewBuffer(msgBytes).String())
+			return // We cant continue with a message that cant be parsed correctly.
+		}
 		msgType, _ := msg.Header.GetBytes(tagMsgType)
 		sentMessageSeqNum, _ := msg.Header.GetInt(tagMsgSeqNum)
 

message.go

@@ -27,6 +27,19 @@ import (
 // Header is first section of a FIX Message.
 type Header struct{ FieldMap }
 
+// msgparser contains message parsing vars needed to parse a string into a message.
+type msgParser struct {
+	msg                     *Message
+	transportDataDictionary *datadictionary.DataDictionary
+	appDataDictionary       *datadictionary.DataDictionary
+	rawBytes                []byte
+	fieldIndex              int
+	parsedFieldBytes        *TagValue
+	trailerBytes            []byte
+	foundBody               bool
+	foundTrailer            bool
+}
+
 // in the message header, the first 3 tags in the message header must be 8,9,35.
 func headerFieldOrdering(i, j Tag) bool {
 	var ordering = func(t Tag) uint32 {
@@ -152,124 +165,134 @@ func ParseMessageWithDataDictionary(
 	msg *Message,
 	rawMessage *bytes.Buffer,
 	transportDataDictionary *datadictionary.DataDictionary,
-	_ *datadictionary.DataDictionary,
+	appDataDictionary *datadictionary.DataDictionary,
 ) (err error) {
-	msg.Header.Clear()
-	msg.Body.Clear()
-	msg.Trailer.Clear()
-	msg.rawMessage = rawMessage
+	// Create msgparser before we go any further.
+	mp := &msgParser{
+		msg:                     msg,
+		transportDataDictionary: transportDataDictionary,
+		appDataDictionary:       appDataDictionary,
+	}
+	mp.msg.rawMessage = rawMessage
+	mp.rawBytes = rawMessage.Bytes()
 
-	rawBytes := rawMessage.Bytes()
+	return doParsing(mp)
+}
 
-	// Allocate fields in one chunk.
+// doParsing executes the message parsing process.
+func doParsing(mp *msgParser) (err error) {
+	// Initialize for parsing.
+	mp.msg.Header.Clear()
+	mp.msg.Body.Clear()
+	mp.msg.Trailer.Clear()
+
+	// Allocate expected message fields in one chunk.
 	fieldCount := 0
-	for _, b := range rawBytes {
+	for _, b := range mp.rawBytes {
 		if b == '\001' {
 			fieldCount++
 		}
 	}
-
 	if fieldCount == 0 {
-		return parseError{OrigError: fmt.Sprintf("No Fields detected in %s", string(rawBytes))}
+		return parseError{OrigError: fmt.Sprintf("No Fields detected in %s", string(mp.rawBytes))}
 	}
-
-	if cap(msg.fields) < fieldCount {
-		msg.fields = make([]TagValue, fieldCount)
+	if cap(mp.msg.fields) < fieldCount {
+		mp.msg.fields = make([]TagValue, fieldCount)
 	} else {
-		msg.fields = msg.fields[0:fieldCount]
+		mp.msg.fields = mp.msg.fields[0:fieldCount]
 	}
 
-	fieldIndex := 0
-
 	// Message must start with begin string, body length, msg type.
-	if rawBytes, err = extractSpecificField(&msg.fields[fieldIndex], tagBeginString, rawBytes); err != nil {
+	// Get begin string.
+	if mp.rawBytes, err = extractSpecificField(&mp.msg.fields[mp.fieldIndex], tagBeginString, mp.rawBytes); err != nil {
 		return
 	}
+	mp.msg.Header.add(mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1])
 
-	msg.Header.add(msg.fields[fieldIndex : fieldIndex+1])
-	fieldIndex++
-
-	parsedFieldBytes := &msg.fields[fieldIndex]
-	if rawBytes, err = extractSpecificField(parsedFieldBytes, tagBodyLength, rawBytes); err != nil {
+	// Get body length.
+	mp.fieldIndex++
+	mp.parsedFieldBytes = &mp.msg.fields[mp.fieldIndex]
+	if mp.rawBytes, err = extractSpecificField(mp.parsedFieldBytes, tagBodyLength, mp.rawBytes); err != nil {
 		return
 	}
+	mp.msg.Header.add(mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1])
 
-	msg.Header.add(msg.fields[fieldIndex : fieldIndex+1])
-	fieldIndex++
-
-	parsedFieldBytes = &msg.fields[fieldIndex]
-	if rawBytes, err = extractSpecificField(parsedFieldBytes, tagMsgType, rawBytes); err != nil {
+	// Get msg type.
+	mp.fieldIndex++
+	mp.parsedFieldBytes = &mp.msg.fields[mp.fieldIndex]
+	if mp.rawBytes, err = extractSpecificField(mp.parsedFieldBytes, tagMsgType, mp.rawBytes); err != nil {
 		return
 	}
+	mp.msg.Header.add(mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1])
 
+	// Start parsing.
+	mp.fieldIndex++
 	xmlDataLen := 0
 	xmlDataMsg := false
-
-	msg.Header.add(msg.fields[fieldIndex : fieldIndex+1])
-	fieldIndex++
-
-	trailerBytes := []byte{}
-	foundBody := false
-	foundTrailer := false
+	mp.trailerBytes = []byte{}
+	mp.foundBody = false
+	mp.foundTrailer = false
 	for {
-		parsedFieldBytes = &msg.fields[fieldIndex]
+		mp.parsedFieldBytes = &mp.msg.fields[mp.fieldIndex]
 		if xmlDataLen > 0 {
-			rawBytes, err = extractXMLDataField(parsedFieldBytes, rawBytes, xmlDataLen)
+			mp.rawBytes, err = extractXMLDataField(mp.parsedFieldBytes, mp.rawBytes, xmlDataLen)
 			xmlDataLen = 0
 			xmlDataMsg = true
 		} else {
-			rawBytes, err = extractField(parsedFieldBytes, rawBytes)
+			mp.rawBytes, err = extractField(mp.parsedFieldBytes, mp.rawBytes)
 		}
 		if err != nil {
 			return
 		}
 
 		switch {
-		case isHeaderField(parsedFieldBytes.tag, transportDataDictionary):
-			msg.Header.add(msg.fields[fieldIndex : fieldIndex+1])
-		case isTrailerField(parsedFieldBytes.tag, transportDataDictionary):
-			msg.Trailer.add(msg.fields[fieldIndex : fieldIndex+1])
-			foundTrailer = true
+		case isHeaderField(mp.parsedFieldBytes.tag, mp.transportDataDictionary):
+			mp.msg.Header.add(mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1])
+		case isTrailerField(mp.parsedFieldBytes.tag, mp.transportDataDictionary):
+			mp.msg.Trailer.add(mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1])
+			mp.foundTrailer = true
+		case isNumInGroupField(mp.msg, []Tag{mp.parsedFieldBytes.tag}, mp.appDataDictionary):
+			parseGroup(mp, []Tag{mp.parsedFieldBytes.tag})
 		default:
-			foundBody = true
-			trailerBytes = rawBytes
-			msg.Body.add(msg.fields[fieldIndex : fieldIndex+1])
+			mp.foundBody = true
+			mp.trailerBytes = mp.rawBytes
+			mp.msg.Body.add(mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1])
 		}
-		if parsedFieldBytes.tag == tagCheckSum {
+		if mp.parsedFieldBytes.tag == tagCheckSum {
 			break
 		}
 
-		if !foundBody {
-			msg.bodyBytes = rawBytes
+		if !mp.foundBody {
+			mp.msg.bodyBytes = mp.rawBytes
 		}
 
-		if parsedFieldBytes.tag == tagXMLDataLen {
-			xmlDataLen, _ = msg.Header.GetInt(tagXMLDataLen)
+		if mp.parsedFieldBytes.tag == tagXMLDataLen {
+			xmlDataLen, _ = mp.msg.Header.GetInt(tagXMLDataLen)
 		}
-		fieldIndex++
+		mp.fieldIndex++
 	}
 
 	// This will happen if there are no fields in the body
-	if foundTrailer && !foundBody {
-		trailerBytes = rawBytes
-		msg.bodyBytes = nil
+	if mp.foundTrailer && !mp.foundBody {
+		mp.trailerBytes = mp.rawBytes
+		mp.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)]
+	if len(mp.msg.bodyBytes) > len(mp.trailerBytes) {
+		mp.msg.bodyBytes = mp.msg.bodyBytes[:len(mp.msg.bodyBytes)-len(mp.trailerBytes)]
 	}
 
 	length := 0
-	for _, field := range msg.fields {
+	for _, field := range mp.msg.fields {
 		switch field.tag {
 		case tagBeginString, tagBodyLength, tagCheckSum: // Tags do not contribute to length.
 		default:
 			length += field.length()
 		}
 	}
 
-	bodyLength, err := msg.Header.GetInt(tagBodyLength)
+	bodyLength, err := mp.msg.Header.GetInt(tagBodyLength)
 	if err != nil {
 		err = parseError{OrigError: err.Error()}
 	} else if length != bodyLength && !xmlDataMsg {
@@ -279,6 +302,149 @@ func ParseMessageWithDataDictionary(
 	return
 }
 
+// parseGroup iterates through a repeating group to maintain correct order of those fields.
+func parseGroup(mp *msgParser, tags []Tag) {
+	mp.foundBody = true
+	dm := mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1]
+	fields := getGroupFields(mp.msg, tags, mp.appDataDictionary)
+
+	for {
+		mp.fieldIndex++
+		mp.parsedFieldBytes = &mp.msg.fields[mp.fieldIndex]
+		mp.rawBytes, _ = extractField(mp.parsedFieldBytes, mp.rawBytes)
+		mp.trailerBytes = mp.rawBytes
+
+		// Is this field a member for the group.
+		if isGroupMember(mp.parsedFieldBytes.tag, fields) {
+			// Is this field a nested repeating group.
+			if isNumInGroupField(mp.msg, append(tags, mp.parsedFieldBytes.tag), mp.appDataDictionary) {
+				dm = append(dm, *mp.parsedFieldBytes)
+				tags = append(tags, mp.parsedFieldBytes.tag)
+				fields = getGroupFields(mp.msg, tags, mp.appDataDictionary)
+				continue
+			}
+			// Add the field member to the group.
+			dm = append(dm, *mp.parsedFieldBytes)
+		} else if isHeaderField(mp.parsedFieldBytes.tag, mp.transportDataDictionary) {
+			// Found a header tag for some reason..
+			mp.msg.Body.add(dm)
+			mp.msg.Header.add(mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1])
+			break
+		} else if isTrailerField(mp.parsedFieldBytes.tag, mp.transportDataDictionary) {
+			// Found the trailer at the end of the message.
+			mp.msg.Body.add(dm)
+			mp.msg.Trailer.add(mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1])
+			mp.foundTrailer = true
+			break
+		} else {
+			// Found a body field outside the group.
+			searchTags := []Tag{mp.parsedFieldBytes.tag}
+			// Is this a new group not inside the existing group.
+			if isNumInGroupField(mp.msg, searchTags, mp.appDataDictionary) {
+				// Add the current repeating group.
+				mp.msg.Body.add(dm)
+				// Cycle again with the new group.
+				dm = mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1]
+				fields = getGroupFields(mp.msg, searchTags, mp.appDataDictionary)
+				continue
+			}
+			if len(tags) > 1 {
+				searchTags = tags[:len(tags)-1]
+			}
+			// Did this tag occur after a nested group and belongs to the parent group.
+			if isNumInGroupField(mp.msg, searchTags, mp.appDataDictionary) {
+				// Add the field member to the group.
+				dm = append(dm, *mp.parsedFieldBytes)
+				// Continue parsing the parent group.
+				fields = getGroupFields(mp.msg, searchTags, mp.appDataDictionary)
+				continue
+			}
+			// Add the repeating group.
+			mp.msg.Body.add(dm)
+			// Add the next body field.
+			mp.msg.Body.add(mp.msg.fields[mp.fieldIndex : mp.fieldIndex+1])
+
+			break
+		}
+	}
+}
+
+// isNumInGroupField evaluates if this tag is the start of a repeating group.
+// tags slice will contain multiple tags if the tag in question is found while processing a group already.
+func isNumInGroupField(msg *Message, tags []Tag, appDataDictionary *datadictionary.DataDictionary) bool {
+	if appDataDictionary != nil {
+		msgt, err := msg.MsgType()
+		if err != nil {
+			return false
+		}
+		mm, ok := appDataDictionary.Messages[msgt]
+		if ok {
+			fields := mm.Fields
+			for idx, tag := range tags {
+				fd, ok := fields[int(tag)]
+				if ok {
+					if idx == len(tags)-1 {
+						if len(fd.Fields) > 0 {
+							return true
+						}
+					} else {
+						// Map nested fields.
+						newFields := make(map[int]*datadictionary.FieldDef)
+						for _, ff := range fd.Fields {
+							newFields[ff.Tag()] = ff
+						}
+						fields = newFields
+					}
+				}
+			}
+		}
+	}
+	return false
+}
+
+// getGroupFields gets the relevant fields for parsing a repeating group if this tag is the start of a repeating group.
+// tags slice will contain multiple tags if the tag in question is found while processing a group already.
+func getGroupFields(msg *Message, tags []Tag, appDataDictionary *datadictionary.DataDictionary) (fields []*datadictionary.FieldDef) {
+	if appDataDictionary != nil {
+		msgt, err := msg.MsgType()
+		if err != nil {
+			return
+		}
+		mm, ok := appDataDictionary.Messages[msgt]
+		if ok {
+			fields := mm.Fields
+			for idx, tag := range tags {
+				fd, ok := fields[int(tag)]
+				if ok {
+					if idx == len(tags)-1 {
+						if len(fd.Fields) > 0 {
+							return fd.Fields
+						}
+					} else {
+						// Map nested fields.
+						newFields := make(map[int]*datadictionary.FieldDef)
+						for _, ff := range fd.Fields {
+							newFields[ff.Tag()] = ff
+						}
+						fields = newFields
+					}
+				}
+			}
+		}
+	}
+	return
+}
+
+// isGroupMember evaluates if this tag belongs to a repeating group.
+func isGroupMember(tag Tag, fields []*datadictionary.FieldDef) bool {
+	for _, f := range fields {
+		if f.Tag() == int(tag) {
+			return true
+		}
+	}
+	return false
+}
+
 func isHeaderField(tag Tag, dataDict *datadictionary.DataDictionary) bool {
 	if tag.IsHeader() {
 		return true