GODRIVER-1919 Support decoding ObjectIDs from hex strings in BSON (#610)

Author: glossd

bson/bsoncodec/default_value_decoders.go

@@ -718,6 +718,7 @@ func (dvd DefaultValueDecoders) UndefinedDecodeValue(dc DecodeContext, vr bsonrw
 	return nil
 }
 
+// Accept both 12-byte string and pretty-printed 24-byte hex string formats.
 func (dvd DefaultValueDecoders) objectIDDecodeType(dc DecodeContext, vr bsonrw.ValueReader, t reflect.Type) (reflect.Value, error) {
 	if t != tOID {
 		return emptyValue, ValueDecoderError{
@@ -740,6 +741,9 @@ func (dvd DefaultValueDecoders) objectIDDecodeType(dc DecodeContext, vr bsonrw.V
 		if err != nil {
 			return emptyValue, err
 		}
+		if oid, err = primitive.ObjectIDFromHex(str); err == nil {
+			break
+		}
 		if len(str) != 12 {
 			return emptyValue, fmt.Errorf("an ObjectID string must be exactly 12 bytes long (got %v)", len(str))
 		}

bson/bsoncodec/default_value_decoders_test.go

@@ -1118,6 +1118,17 @@ func TestDefaultValueDecoders(t *testing.T) {
 					bsonrwtest.ReadString,
 					nil,
 				},
+				{
+					"success/string-hex",
+					primitive.ObjectID{0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x61, 0x62},
+					nil,
+					&bsonrwtest.ValueReaderWriter{
+						BSONType: bsontype.String,
+						Return:   "303132333435363738396162",
+					},
+					bsonrwtest.ReadString,
+					nil,
+				},
 				{
 					"decode null",
 					primitive.ObjectID{},