lnwire: add ExtraOpaqueData helper functions and methods

Introduces a couple of new helper functions for both the ExtraOpaqueData
and CustomRecords types along with new methods on the ExtraOpaqueData.

lnwire/custom_records.go

@@ -3,8 +3,10 @@ package lnwire
 import (
 	"bytes"
 	"fmt"
+	"io"
 	"sort"
 
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/tlv"
 )
 
@@ -44,12 +46,12 @@ func NewCustomRecords(tlvMap tlv.TypeMap) (CustomRecords, error) {
 
 // ParseCustomRecords creates a new CustomRecords instance from a tlv.Blob.
 func ParseCustomRecords(b tlv.Blob) (CustomRecords, error) {
-	stream, err := tlv.NewStream()
+	return ParseCustomRecordsFrom(bytes.NewReader(b))
-	if err != nil {
+}
-		return nil, fmt.Errorf("error creating stream: %w", err)
-	}
 
-	typeMap, err := stream.DecodeWithParsedTypes(bytes.NewReader(b))
+// ParseCustomRecordsFrom creates a new CustomRecords instance from a reader.
+func ParseCustomRecordsFrom(r io.Reader) (CustomRecords, error) {
+	typeMap, err := DecodeRecords(r)
 	if err != nil {
 		return nil, fmt.Errorf("error decoding HTLC record: %w", err)
 	}
@@ -121,21 +123,14 @@ func (c CustomRecords) ExtendRecordProducers(
 
 	// Convert the custom records map to a TLV record producer slice and
 	// append them to the exiting records slice.
-	crRecords := tlv.MapToRecords(c)
+	customRecordProducers := RecordsAsProducers(tlv.MapToRecords(c))
-	for _, record := range crRecords {
+	producers = append(producers, customRecordProducers...)
-		r := recordProducer{record}
-		producers = append(producers, &r)
-	}
 
 	// If the records slice which was given as an argument included TLV
 	// values greater than or equal to the minimum custom records TLV type
 	// we will sort the extended records slice to ensure that it is ordered
 	// correctly.
-	sort.Slice(producers, func(i, j int) bool {
+	SortProducers(producers)
-		recordI := producers[i].Record()
-		recordJ := producers[j].Record()
-		return recordI.Type() < recordJ.Type()
-	})
 
 	return producers, nil
 }
@@ -150,27 +145,119 @@ func (c CustomRecords) RecordProducers() []tlv.RecordProducer {
 	// Convert the custom records map to a TLV record producer slice.
 	records := tlv.MapToRecords(c)
 
-	// Convert the records to record producers.
+	return RecordsAsProducers(records)
-	producers := make([]tlv.RecordProducer, len(records))
-	for i, record := range records {
-		producers[i] = &recordProducer{record}
-	}
-
-	return producers
 }
 
 // Serialize serializes the custom records into a byte slice.
 func (c CustomRecords) Serialize() ([]byte, error) {
 	records := tlv.MapToRecords(c)
-	stream, err := tlv.NewStream(records...)
+	return EncodeRecords(records)
-	if err != nil {
+}
-		return nil, fmt.Errorf("error creating stream: %w", err)
+
-	}
+// SerializeTo serializes the custom records into the given writer.
-
+func (c CustomRecords) SerializeTo(w io.Writer) error {
-	var b bytes.Buffer
+	records := tlv.MapToRecords(c)
-	if err := stream.Encode(&b); err != nil {
+	return EncodeRecordsTo(w, records)
-		return nil, fmt.Errorf("error encoding custom records: %w", err)
+}
-	}
+
-
+// ProduceRecordsSorted converts a slice of record producers into a slice of
-	return b.Bytes(), nil
+// records and then sorts it by type.
+func ProduceRecordsSorted(recordProducers ...tlv.RecordProducer) []tlv.Record {
+	records := fn.Map(func(producer tlv.RecordProducer) tlv.Record {
+		return producer.Record()
+	}, recordProducers)
+
+	// Ensure that the set of records are sorted before we attempt to
+	// decode from the stream, to ensure they're canonical.
+	tlv.SortRecords(records)
+
+	return records
+}
+
+// SortProducers sorts the given record producers by their type.
+func SortProducers(producers []tlv.RecordProducer) {
+	sort.Slice(producers, func(i, j int) bool {
+		recordI := producers[i].Record()
+		recordJ := producers[j].Record()
+		return recordI.Type() < recordJ.Type()
+	})
+}
+
+// TlvMapToRecords converts a TLV map into a slice of records.
+func TlvMapToRecords(tlvMap tlv.TypeMap) []tlv.Record {
+	tlvMapGeneric := make(map[uint64][]byte)
+	for k, v := range tlvMap {
+		tlvMapGeneric[uint64(k)] = v
+	}
+
+	return tlv.MapToRecords(tlvMapGeneric)
+}
+
+// RecordsAsProducers converts a slice of records into a slice of record
+// producers.
+func RecordsAsProducers(records []tlv.Record) []tlv.RecordProducer {
+	return fn.Map(func(record tlv.Record) tlv.RecordProducer {
+		return &record
+	}, records)
+}
+
+// EncodeRecords encodes the given records into a byte slice.
+func EncodeRecords(records []tlv.Record) ([]byte, error) {
+	var buf bytes.Buffer
+	if err := EncodeRecordsTo(&buf, records); err != nil {
+		return nil, err
+	}
+
+	return buf.Bytes(), nil
+}
+
+// EncodeRecordsTo encodes the given records into the given writer.
+func EncodeRecordsTo(w io.Writer, records []tlv.Record) error {
+	tlvStream, err := tlv.NewStream(records...)
+	if err != nil {
+		return err
+	}
+
+	return tlvStream.Encode(w)
+}
+
+// DecodeRecords decodes the given byte slice into the given records and returns
+// the rest as a TLV type map.
+func DecodeRecords(r io.Reader,
+	records ...tlv.Record) (tlv.TypeMap, error) {
+
+	tlvStream, err := tlv.NewStream(records...)
+	if err != nil {
+		return nil, err
+	}
+
+	return tlvStream.DecodeWithParsedTypes(r)
+}
+
+// DecodeRecordsP2P decodes the given byte slice into the given records and
+// returns the rest as a TLV type map. This function is identical to
+// DecodeRecords except that the record size is capped at 65535.
+func DecodeRecordsP2P(r *bytes.Reader,
+	records ...tlv.Record) (tlv.TypeMap, error) {
+
+	tlvStream, err := tlv.NewStream(records...)
+	if err != nil {
+		return nil, err
+	}
+
+	return tlvStream.DecodeWithParsedTypesP2P(r)
+}
+
+// AssertUniqueTypes asserts that the given records have unique types.
+func AssertUniqueTypes(r []tlv.Record) error {
+	seen := make(fn.Set[tlv.Type], len(r))
+	for _, record := range r {
+		t := record.Type()
+		if seen.Contains(t) {
+			return fmt.Errorf("duplicate record type: %d", t)
+		}
+		seen.Add(t)
+	}
+
+	return nil
 }

lnwire/custom_records_test.go

@@ -144,10 +144,8 @@ func TestCustomRecordsExtendRecordProducers(t *testing.T) {
 	for _, tc := range testCases {
 		t.Run(tc.name, func(t *testing.T) {
 			nonCustomRecords := tlv.MapToRecords(tc.existingTypes)
-			nonCustomProducers := fn.Map(
+			nonCustomProducers := RecordsAsProducers(
-				func(r tlv.Record) tlv.RecordProducer {
+				nonCustomRecords,
-					return &recordProducer{r}
-				}, nonCustomRecords,
 			)
 
 			combined, err := tc.customRecords.ExtendRecordProducers(

lnwire/extra_bytes.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/tlv"
 )
 
@@ -15,6 +16,21 @@ import (
 // upgrades to the network in a forwards compatible manner.
 type ExtraOpaqueData []byte
 
+// NewExtraOpaqueData creates a new ExtraOpaqueData instance from a tlv.TypeMap.
+func NewExtraOpaqueData(tlvMap tlv.TypeMap) (ExtraOpaqueData, error) {
+	// If the tlv map is empty, we'll want to mirror the behavior of
+	// decoding an empty extra opaque data field (see Decode method).
+	if len(tlvMap) == 0 {
+		return make([]byte, 0), nil
+	}
+
+	// Convert the TLV map into a slice of records.
+	records := TlvMapToRecords(tlvMap)
+
+	// Encode the records into the extra data byte slice.
+	return EncodeRecords(records)
+}
+
 // Encode attempts to encode the raw extra bytes into the passed io.Writer.
 func (e *ExtraOpaqueData) Encode(w *bytes.Buffer) error {
 	eBytes := []byte((*e)[:])
@@ -25,8 +41,8 @@ func (e *ExtraOpaqueData) Encode(w *bytes.Buffer) error {
 	return nil
 }
 
-// Decode attempts to unpack the raw bytes encoded in the passed io.Reader as a
+// Decode attempts to unpack the raw bytes encoded in the passed-in io.Reader as
-// set of extra opaque data.
+// a set of extra opaque data.
 func (e *ExtraOpaqueData) Decode(r io.Reader) error {
 	// First, we'll attempt to read a set of bytes contained within the
 	// passed io.Reader (if any exist).
@@ -39,7 +55,7 @@ func (e *ExtraOpaqueData) Decode(r io.Reader) error {
 	// This ensures that any struct that embeds this type will properly
 	// store the bytes once this method exits.
 	if len(rawBytes) > 0 {
-		*e = ExtraOpaqueData(rawBytes)
+		*e = rawBytes
 	} else {
 		*e = make([]byte, 0)
 	}
@@ -50,28 +66,17 @@ func (e *ExtraOpaqueData) Decode(r io.Reader) error {
 // PackRecords attempts to encode the set of tlv records into the target
 // ExtraOpaqueData instance. The records will be encoded as a raw TLV stream
 // and stored within the backing slice pointer.
-func (e *ExtraOpaqueData) PackRecords(recordProducers ...tlv.RecordProducer) error {
+func (e *ExtraOpaqueData) PackRecords(
-	// First, assemble all the records passed in in series.
+	recordProducers ...tlv.RecordProducer) error {
-	records := make([]tlv.Record, 0, len(recordProducers))
-	for _, producer := range recordProducers {
-		records = append(records, producer.Record())
-	}
 
-	// Ensure that the set of records are sorted before we encode them into
+	// Assemble all the records passed in series, then encode them.
-	// the stream, to ensure they're canonical.
+	records := ProduceRecordsSorted(recordProducers...)
-	tlv.SortRecords(records)
+	encoded, err := EncodeRecords(records)
-
-	tlvStream, err := tlv.NewStream(records...)
 	if err != nil {
 		return err
 	}
 
-	var extraBytesWriter bytes.Buffer
+	*e = encoded
-	if err := tlvStream.Encode(&extraBytesWriter); err != nil {
-		return err
-	}
-
-	*e = ExtraOpaqueData(extraBytesWriter.Bytes())
 
 	return nil
 }
@@ -80,29 +85,38 @@ func (e *ExtraOpaqueData) PackRecords(recordProducers ...tlv.RecordProducer) err
 // it were a tlv stream. The set of raw parsed types is returned, and any
 // passed records (if found in the stream) will be parsed into the proper
 // tlv.Record.
-func (e *ExtraOpaqueData) ExtractRecords(recordProducers ...tlv.RecordProducer) (
+func (e *ExtraOpaqueData) ExtractRecords(
-	tlv.TypeMap, error) {
+	recordProducers ...tlv.RecordProducer) (tlv.TypeMap, error) {
-
-	// First, assemble all the records passed in in series.
-	records := make([]tlv.Record, 0, len(recordProducers))
-	for _, producer := range recordProducers {
-		records = append(records, producer.Record())
-	}
-
-	// Ensure that the set of records are sorted before we attempt to
-	// decode from the stream, to ensure they're canonical.
-	tlv.SortRecords(records)
 
+	// First, assemble all the records passed in series.
+	records := ProduceRecordsSorted(recordProducers...)
 	extraBytesReader := bytes.NewReader(*e)
 
-	tlvStream, err := tlv.NewStream(records...)
+	// Since ExtraOpaqueData is provided by a potentially malicious peer,
+	// pass it into the P2P decoding variant.
+	return DecodeRecordsP2P(extraBytesReader, records...)
+}
+
+// RecordProducers parses ExtraOpaqueData into a slice of TLV record producers
+// by interpreting it as a TLV map.
+func (e *ExtraOpaqueData) RecordProducers() ([]tlv.RecordProducer, error) {
+	var recordProducers []tlv.RecordProducer
+
+	// If the instance is nil or empty, return an empty slice.
+	if e == nil || len(*e) == 0 {
+		return recordProducers, nil
+	}
+
+	// Parse the extra opaque data as a TLV map.
+	tlvMap, err := e.ExtractRecords()
 	if err != nil {
 		return nil, err
 	}
 
-	// Since ExtraOpaqueData is provided by a potentially malicious peer,
+	// Convert the TLV map into a slice of record producers.
-	// pass it into the P2P decoding variant.
+	records := TlvMapToRecords(tlvMap)
-	return tlvStream.DecodeWithParsedTypesP2P(extraBytesReader)
+
+	return RecordsAsProducers(records), nil
 }
 
 // EncodeMessageExtraData encodes the given recordProducers into the given
@@ -120,3 +134,116 @@ func EncodeMessageExtraData(extraData *ExtraOpaqueData,
 	// are all properly sorted.
 	return extraData.PackRecords(recordProducers...)
 }
+
+// ParseAndExtractCustomRecords parses the given extra data into the passed-in
+// records, then returns any remaining records split into custom records and
+// extra data.
+func ParseAndExtractCustomRecords(allExtraData ExtraOpaqueData,
+	knownRecords ...tlv.RecordProducer) (CustomRecords,
+	fn.Set[tlv.Type], ExtraOpaqueData, error) {
+
+	extraDataTlvMap, err := allExtraData.ExtractRecords(knownRecords...)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	// Remove the known and now extracted records from the leftover extra
+	// data map.
+	parsedKnownRecords := make(fn.Set[tlv.Type], len(knownRecords))
+	for _, producer := range knownRecords {
+		r := producer.Record()
+
+		// Only remove the records if it was parsed (remainder is nil).
+		// We'll just store the type so we can tell the caller which
+		// records were actually parsed fully.
+		val, ok := extraDataTlvMap[r.Type()]
+		if ok && val == nil {
+			parsedKnownRecords.Add(r.Type())
+			delete(extraDataTlvMap, r.Type())
+		}
+	}
+
+	// Any records from the extra data TLV map which are in the custom
+	// records TLV type range will be included in the custom records field
+	// and removed from the extra data field.
+	customRecordsTlvMap := make(tlv.TypeMap, len(extraDataTlvMap))
+	for k, v := range extraDataTlvMap {
+		// Skip records that are not in the custom records TLV type
+		// range.
+		if k < MinCustomRecordsTlvType {
+			continue
+		}
+
+		// Include the record in the custom records map.
+		customRecordsTlvMap[k] = v
+
+		// Now that the record is included in the custom records map,
+		// we can remove it from the extra data TLV map.
+		delete(extraDataTlvMap, k)
+	}
+
+	// Set the custom records field to the custom records specific TLV
+	// record map.
+	customRecords, err := NewCustomRecords(customRecordsTlvMap)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	// Encode the remaining records back into the extra data field. These
+	// records are not in the custom records TLV type range and do not
+	// have associated fields in the struct that produced the records.
+	extraData, err := NewExtraOpaqueData(extraDataTlvMap)
+	if err != nil {
+		return nil, nil, nil, err
+	}
+
+	// Help with unit testing where we might have the empty value (nil) for
+	// the extra data instead of the default that's returned by the
+	// constructor (empty slice).
+	if len(extraData) == 0 {
+		extraData = nil
+	}
+
+	return customRecords, parsedKnownRecords, extraData, nil
+}
+
+// MergeAndEncode merges the known records with the extra data and custom
+// records, then encodes the merged records into raw bytes.
+func MergeAndEncode(knownRecords []tlv.RecordProducer,
+	extraData ExtraOpaqueData, customRecords CustomRecords) ([]byte,
+	error) {
+
+	// Construct a slice of all the records that we should include in the
+	// message extra data field. We will start by including any records from
+	// the extra data field.
+	mergedRecords, err := extraData.RecordProducers()
+	if err != nil {
+		return nil, err
+	}
+
+	// Merge the known and extra data records.
+	mergedRecords = append(mergedRecords, knownRecords...)
+
+	// Include custom records in the extra data wire field if they are
+	// present. Ensure that the custom records are validated before encoding
+	// them.
+	if err := customRecords.Validate(); err != nil {
+		return nil, fmt.Errorf("custom records validation error: %w",
+			err)
+	}
+
+	// Extend the message extra data records slice with TLV records from the
+	// custom records field.
+	mergedRecords = append(
+		mergedRecords, customRecords.RecordProducers()...,
+	)
+
+	// Now we can sort the records and make sure there are no records with
+	// the same type that would collide when encoding.
+	sortedRecords := ProduceRecordsSorted(mergedRecords...)
+	if err := AssertUniqueTypes(sortedRecords); err != nil {
+		return nil, err
+	}
+
+	return EncodeRecords(sortedRecords)
+}

lnwire/extra_bytes_test.go

@@ -11,6 +11,12 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+var (
+	tlvType1 tlv.TlvType1
+	tlvType2 tlv.TlvType2
+	tlvType3 tlv.TlvType3
+)
+
 // TestExtraOpaqueDataEncodeDecode tests that we're able to encode/decode
 // arbitrary payloads.
 func TestExtraOpaqueDataEncodeDecode(t *testing.T) {
@@ -153,21 +159,18 @@ func TestPackRecords(t *testing.T) {
 
 	var (
 		// Record type 1.
-		tlvType1     tlv.TlvType1
 		recordBytes1 = []byte("recordBytes1")
 		tlvRecord1   = tlv.NewPrimitiveRecord[tlv.TlvType1](
 			recordBytes1,
 		)
 
 		// Record type 2.
-		tlvType2     tlv.TlvType2
 		recordBytes2 = []byte("recordBytes2")
 		tlvRecord2   = tlv.NewPrimitiveRecord[tlv.TlvType2](
 			recordBytes2,
 		)
 
 		// Record type 3.
-		tlvType3     tlv.TlvType3
 		recordBytes3 = []byte("recordBytes3")
 		tlvRecord3   = tlv.NewPrimitiveRecord[tlv.TlvType3](
 			recordBytes3,
@@ -203,3 +206,308 @@ func TestPackRecords(t *testing.T) {
 	require.Equal(t, recordBytes2, extractedRecords[tlvType2.TypeVal()])
 	require.Equal(t, recordBytes3, extractedRecords[tlvType3.TypeVal()])
 }
+
+type dummyRecordProducer struct {
+	typ           tlv.Type
+	scratchValue  []byte
+	expectedValue []byte
+}
+
+func (d *dummyRecordProducer) Record() tlv.Record {
+	return tlv.MakePrimitiveRecord(d.typ, &d.scratchValue)
+}
+
+// TestExtraOpaqueData tests that we're able to properly encode/decode an
+// ExtraOpaqueData instance.
+func TestExtraOpaqueData(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name          string
+		types         tlv.TypeMap
+		expectedData  ExtraOpaqueData
+		expectedTypes tlv.TypeMap
+		decoders      []tlv.RecordProducer
+	}{
+		{
+			name:          "empty map",
+			expectedTypes: tlv.TypeMap{},
+			expectedData:  make([]byte, 0),
+		},
+		{
+			name: "single record",
+			types: tlv.TypeMap{
+				tlvType1.TypeVal(): []byte{1, 2, 3},
+			},
+			expectedData: ExtraOpaqueData{
+				0x01, 0x03, 1, 2, 3,
+			},
+			expectedTypes: tlv.TypeMap{
+				tlvType1.TypeVal(): []byte{1, 2, 3},
+			},
+			decoders: []tlv.RecordProducer{
+				&dummyRecordProducer{
+					typ:           tlvType1.TypeVal(),
+					expectedValue: []byte{1, 2, 3},
+				},
+			},
+		},
+		{
+			name: "multiple records",
+			types: tlv.TypeMap{
+				tlvType2.TypeVal(): []byte{4, 5, 6},
+				tlvType1.TypeVal(): []byte{1, 2, 3},
+			},
+			expectedData: ExtraOpaqueData{
+				0x01, 0x03, 1, 2, 3,
+				0x02, 0x03, 4, 5, 6,
+			},
+			expectedTypes: tlv.TypeMap{
+				tlvType1.TypeVal(): []byte{1, 2, 3},
+				tlvType2.TypeVal(): []byte{4, 5, 6},
+			},
+			decoders: []tlv.RecordProducer{
+				&dummyRecordProducer{
+					typ:           tlvType1.TypeVal(),
+					expectedValue: []byte{1, 2, 3},
+				},
+				&dummyRecordProducer{
+					typ:           tlvType2.TypeVal(),
+					expectedValue: []byte{4, 5, 6},
+				},
+			},
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			// First, test the constructor.
+			opaqueData, err := NewExtraOpaqueData(tc.types)
+			require.NoError(t, err)
+
+			require.Equal(t, tc.expectedData, opaqueData)
+
+			// Now encode/decode.
+			var b bytes.Buffer
+			err = opaqueData.Encode(&b)
+			require.NoError(t, err)
+
+			var decoded ExtraOpaqueData
+			err = decoded.Decode(&b)
+			require.NoError(t, err)
+
+			require.Equal(t, opaqueData, decoded)
+
+			// Now RecordProducers/PackRecords.
+			producers, err := opaqueData.RecordProducers()
+			require.NoError(t, err)
+
+			var packed ExtraOpaqueData
+			err = packed.PackRecords(producers...)
+			require.NoError(t, err)
+
+			// PackRecords returns nil vs. an empty slice if there
+			// are no records. We need to handle this case
+			// separately.
+			if len(producers) == 0 {
+				// Make sure the packed data is empty.
+				require.Empty(t, packed)
+
+				// Now change it to an empty slice for the
+				// comparison below.
+				packed = make([]byte, 0)
+			}
+			require.Equal(t, opaqueData, packed)
+
+			// ExtractRecords with an empty set of record producers
+			// should return the original type map.
+			extracted, err := opaqueData.ExtractRecords()
+			require.NoError(t, err)
+
+			require.Equal(t, tc.expectedTypes, extracted)
+
+			if len(tc.decoders) == 0 {
+				return
+			}
+
+			// ExtractRecords with a set of record producers should
+			// only return the types that weren't in the passed-in
+			// set of producers.
+			extracted, err = opaqueData.ExtractRecords(
+				tc.decoders...,
+			)
+			require.NoError(t, err)
+
+			for parsedType := range tc.expectedTypes {
+				remainder, ok := extracted[parsedType]
+				require.True(t, ok)
+				require.Nil(t, remainder)
+			}
+
+			for _, dec := range tc.decoders {
+				//nolint:forcetypeassert
+				dec := dec.(*dummyRecordProducer)
+				require.Equal(
+					t, dec.expectedValue, dec.scratchValue,
+				)
+			}
+		})
+	}
+}
+
+// TestExtractAndMerge tests that the ParseAndExtractCustomRecords and
+// MergeAndEncode functions work as expected.
+func TestExtractAndMerge(t *testing.T) {
+	t.Parallel()
+
+	testCases := []struct {
+		name          string
+		knownRecords  []tlv.RecordProducer
+		extraData     ExtraOpaqueData
+		customRecords CustomRecords
+		expectedErr   string
+		expectEncoded []byte
+	}{
+		{
+			name: "invalid custom record",
+			customRecords: CustomRecords{
+				123: []byte("invalid"),
+			},
+			expectedErr: "custom records validation error",
+		},
+		{
+			name: "empty everything",
+		},
+		{
+			name: "just extra data",
+			extraData: ExtraOpaqueData{
+				0x01, 0x03, 1, 2, 3,
+				0x02, 0x03, 4, 5, 6,
+			},
+			expectEncoded: []byte{
+				0x01, 0x03, 1, 2, 3,
+				0x02, 0x03, 4, 5, 6,
+			},
+		},
+		{
+			name: "extra data with known record",
+			extraData: ExtraOpaqueData{
+				0x04, 0x03, 4, 4, 4,
+				0x05, 0x03, 5, 5, 5,
+			},
+			knownRecords: []tlv.RecordProducer{
+				&dummyRecordProducer{
+					typ:           tlvType1.TypeVal(),
+					scratchValue:  []byte{1, 2, 3},
+					expectedValue: []byte{1, 2, 3},
+				},
+				&dummyRecordProducer{
+					typ:           tlvType2.TypeVal(),
+					scratchValue:  []byte{4, 5, 6},
+					expectedValue: []byte{4, 5, 6},
+				},
+			},
+			expectEncoded: []byte{
+				0x01, 0x03, 1, 2, 3,
+				0x02, 0x03, 4, 5, 6,
+				0x04, 0x03, 4, 4, 4,
+				0x05, 0x03, 5, 5, 5,
+			},
+		},
+		{
+			name: "extra data and custom records with known record",
+			extraData: ExtraOpaqueData{
+				0x04, 0x03, 4, 4, 4,
+				0x05, 0x03, 5, 5, 5,
+			},
+			customRecords: CustomRecords{
+				MinCustomRecordsTlvType + 1: []byte{99, 99, 99},
+			},
+			knownRecords: []tlv.RecordProducer{
+				&dummyRecordProducer{
+					typ:           tlvType1.TypeVal(),
+					scratchValue:  []byte{1, 2, 3},
+					expectedValue: []byte{1, 2, 3},
+				},
+				&dummyRecordProducer{
+					typ:           tlvType2.TypeVal(),
+					scratchValue:  []byte{4, 5, 6},
+					expectedValue: []byte{4, 5, 6},
+				},
+			},
+			expectEncoded: []byte{
+				0x01, 0x03, 1, 2, 3,
+				0x02, 0x03, 4, 5, 6,
+				0x04, 0x03, 4, 4, 4,
+				0x05, 0x03, 5, 5, 5,
+				0xfe, 0x0, 0x1, 0x0, 0x1, 0x3, 0x63, 0x63, 0x63,
+			},
+		},
+		{
+			name: "duplicate records",
+			extraData: ExtraOpaqueData{
+				0x01, 0x03, 4, 4, 4,
+				0x05, 0x03, 5, 5, 5,
+			},
+			customRecords: CustomRecords{
+				MinCustomRecordsTlvType + 1: []byte{99, 99, 99},
+			},
+			knownRecords: []tlv.RecordProducer{
+				&dummyRecordProducer{
+					typ:           tlvType1.TypeVal(),
+					scratchValue:  []byte{1, 2, 3},
+					expectedValue: []byte{1, 2, 3},
+				},
+				&dummyRecordProducer{
+					typ:           tlvType2.TypeVal(),
+					scratchValue:  []byte{4, 5, 6},
+					expectedValue: []byte{4, 5, 6},
+				},
+			},
+			expectedErr: "duplicate record type: 1",
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			encoded, err := MergeAndEncode(
+				tc.knownRecords, tc.extraData, tc.customRecords,
+			)
+
+			if tc.expectedErr != "" {
+				require.ErrorContains(t, err, tc.expectedErr)
+
+				return
+			}
+
+			require.NoError(t, err)
+			require.Equal(t, tc.expectEncoded, encoded)
+
+			// Clear all the scratch values, to make sure they're
+			// decoded from the data again.
+			for _, dec := range tc.knownRecords {
+				//nolint:forcetypeassert
+				dec := dec.(*dummyRecordProducer)
+				dec.scratchValue = nil
+			}
+
+			pCR, pKR, pED, err := ParseAndExtractCustomRecords(
+				encoded, tc.knownRecords...,
+			)
+			require.NoError(t, err)
+
+			require.Equal(t, tc.customRecords, pCR)
+			require.Equal(t, tc.extraData, pED)
+
+			for _, dec := range tc.knownRecords {
+				//nolint:forcetypeassert
+				dec := dec.(*dummyRecordProducer)
+				require.Equal(
+					t, dec.expectedValue, dec.scratchValue,
+				)
+
+				require.Contains(t, pKR, dec.typ)
+			}
+		})
+	}
+}