lnwire: add MergedCopy method to CustomRecords

lnwire/custom_records.go

@@ -89,6 +89,22 @@ func (c CustomRecords) Copy() CustomRecords {
 	return customRecords
 }
 
+// MergedCopy creates a copy of the records and merges them with the given
+// records. If the same key is present in both sets, the value from the other
+// records will be used.
+func (c CustomRecords) MergedCopy(other CustomRecords) CustomRecords {
+	copiedRecords := make(CustomRecords, len(c))
+	for k, v := range c {
+		copiedRecords[k] = v
+	}
+
+	for k, v := range other {
+		copiedRecords[k] = v
+	}
+
+	return copiedRecords
+}
+
 // ExtendRecordProducers extends the given records slice with the custom
 // records. The resultant records slice will be sorted if the given records
 // slice contains TLV types greater than or equal to MinCustomRecordsTlvType.

lnwire/custom_records_test.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/tlv"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -194,3 +195,54 @@ func serializeRecordProducers(t *testing.T,
 
 	return b.Bytes()
 }
+
+func TestCustomRecordsMergedCopy(t *testing.T) {
+	tests := []struct {
+		name  string
+		c     CustomRecords
+		other CustomRecords
+		want  CustomRecords
+	}{
+		{
+			name: "nil records",
+			want: make(CustomRecords),
+		},
+		{
+			name:  "empty records",
+			c:     make(CustomRecords),
+			other: make(CustomRecords),
+			want:  make(CustomRecords),
+		},
+		{
+			name: "distinct records",
+			c: CustomRecords{
+				1: {1, 2, 3},
+			},
+			other: CustomRecords{
+				2: {4, 5, 6},
+			},
+			want: CustomRecords{
+				1: {1, 2, 3},
+				2: {4, 5, 6},
+			},
+		},
+		{
+			name: "same records, different values",
+			c: CustomRecords{
+				1: {1, 2, 3},
+			},
+			other: CustomRecords{
+				1: {4, 5, 6},
+			},
+			want: CustomRecords{
+				1: {4, 5, 6},
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := tt.c.MergedCopy(tt.other)
+			assert.Equal(t, tt.want, result)
+		})
+	}
+}