Merge pull request #7 from mercadolibre/feature/skip-unexpected-tlv-tags

Feature/skip unexpected tlv tags

field/composite.go

@@ -4,6 +4,8 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"github.com/mercadolibre/iso8583/encoding"
+	"github.com/mercadolibre/iso8583/prefix"
 	"reflect"
 	"regexp"
 	"strconv"
@@ -342,7 +344,7 @@ func (f *Composite) UnmarshalJSON(b []byte) error {
 	}
 
 	for tag, rawMsg := range data {
-		if _, ok := f.spec.Subfields[tag]; !ok {
+		if _, ok := f.spec.Subfields[tag]; !ok && !f.spec.Tag.SkipUnknownTLVTags {
 			return fmt.Errorf("failed to unmarshal subfield %v: received subfield not defined in spec", tag)
 		}
 
@@ -491,12 +493,20 @@ func (f *Composite) unpackSubfieldsByTag(data []byte) (int, error) {
 			tagBytes = f.spec.Tag.Pad.Unpad(tagBytes)
 		}
 		tag := string(tagBytes)
-		if _, ok := f.spec.Subfields[tag]; !ok {
+		if _, ok := f.spec.Subfields[tag]; !ok && !f.spec.Tag.SkipUnknownTLVTags {
 			return 0, fmt.Errorf("failed to unpack subfield %v: field not defined in Spec", tag)
 		}
 
 		field, ok := f.subfields[tag]
 		if !ok {
+			// Obtain the length of the unknown tag and add it to the offset.
+			if f.spec.Tag.SkipUnknownTLVTags && f.spec.Tag.Enc == encoding.BerTLVTag {
+				fieldLength, readed, err := prefix.BerTLV.DecodeLength(999, data[offset:])
+				if err != nil {
+					return 0, err
+				}
+				offset += fieldLength + readed
+			}
 			continue
 		}
 

field/composite_test.go

@@ -335,6 +335,24 @@ func TestTLVPacking(t *testing.T) {
 		require.Equal(t, "000000000501", data.F9F02.Value())
 	})
 
+	t.Run("Unpack correctly deserialises bytes to the data struct skipping unexpected tags", func(t *testing.T) {
+		spec := *tlvTestSpec
+		spec.Tag.SkipUnknownTLVTags = true
+		composite := NewComposite(tlvTestSpec)
+
+		// Data contains tags 9F36, 9A, 9F02 and 9F37
+		read, err := composite.Unpack([]byte{0x30, 0x32, 0x36, 0x9f, 0x36, 0x2, 0x1, 0x57, 0x9a, 0x3, 0x21, 0x7, 0x20,
+			0x9f, 0x2, 0x6, 0x0, 0x0, 0x0, 0x0, 0x5, 0x1, 0x9f, 0x37, 0x4, 0x9b, 0xad, 0xbc, 0xab})
+		require.NoError(t, err)
+		require.Equal(t, 29, read)
+
+		data := &TLVTestData{}
+		require.NoError(t, composite.Unmarshal(data))
+
+		require.Equal(t, "210720", data.F9A.Value())
+		require.Equal(t, "000000000501", data.F9F02.Value())
+	})
+
 	t.Run("Pack correctly serializes data to bytes (constructed ber-tlv)", func(t *testing.T) {
 		data := &ConstructedTLVTestData{
 			F82:   NewStringValue("017f"),
@@ -399,6 +417,16 @@ func TestTLVPacking(t *testing.T) {
 		require.Equal(t, "027F", data.F9F36.Value())
 		require.Equal(t, "047F", data.F9F3B.F9F45.Value())
 	})
+
+	t.Run("Unpack throws an error due unexpected tags", func(t *testing.T) {
+		spec := *tlvTestSpec
+		spec.Tag.SkipUnknownTLVTags = false
+		composite := NewComposite(tlvTestSpec)
+
+		_, err := composite.Unpack([]byte{0x30, 0x32, 0x36, 0x9f, 0x36, 0x2, 0x1, 0x57, 0x9a, 0x3, 0x21, 0x7, 0x20,
+			0x9f, 0x2, 0x6, 0x0, 0x0, 0x0, 0x0, 0x5, 0x1, 0x9f, 0x37, 0x4, 0x9b, 0xad, 0xbc, 0xab})
+		require.EqualError(t, err, "failed to unpack subfield 9F36: field not defined in Spec")
+	})
 }
 
 func TestCompositePacking(t *testing.T) {

field/spec.go

@@ -31,6 +31,10 @@ type TagSpec struct {
 	// spec must be packed. This ordering may also be used for unpacking
 	// if Spec.Tag.Enc == nil.
 	Sort sort.StringSlice
+	// SkipUnknownTLVTags is a flag which indicates whether TLV tags that are not found in
+	// the spec should be skipped or throw an error.
+	// This flag is only meant to be used in Composite fields with TLV encoding.
+	SkipUnknownTLVTags bool
 }
 
 // Spec defines the structure of a field.