Thanks to @anacrolix, we no longer need to monkey-patch the torrent!

Also added `operations_test.go` to ensure that it works as it's
advertised.

magneticod/bittorrent/operations.go

@@ -235,10 +235,11 @@ func (ms *MetadataSink) awaitMetadata(infoHash metainfo.Hash, peer Peer) {
 		} else if rMessage[1] == 0x01 {
 			// __on_ext_message(message[2:])
 			// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+			// Run TestDecoder() function in operations_test.go in case you have any doubts.
 			rMessageBuf := bytes.NewBuffer(rMessage[2:])
 			rExtDict := new(extDict)
-			// TODO: We monkey-patched anacrolix/torrent!
+			err := bencode.NewDecoder(rMessageBuf).Decode(rExtDict)
-			err := bencode.NewDecoder2(rMessageBuf).Decode(rExtDict)
 			if err != nil {
 				zap.L().Warn("Couldn't decode extension message in the loop!", zap.Error(err))
 				return

magneticod/bittorrent/operations_test.go

@@ -0,0 +1,44 @@
+package bittorrent
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/anacrolix/torrent/bencode"
+)
+
+var operationsTest_instances = []struct{
+	dump    []byte
+	surplus []byte
+}{
+	// No Surplus
+	{
+		dump: []byte("d1:md11:ut_metadatai1ee13:metadata_sizei22528ee"),
+		surplus: []byte(""),
+	},
+	// Surplus is an ASCII string
+	{
+		dump: []byte("d1:md11:ut_metadatai1ee13:metadata_sizei22528eeDENEME"),
+		surplus: []byte("DENEME"),
+	},
+	// Surplus is a bencoded dictionary
+	{
+		dump: []byte("d1:md11:ut_metadatai1ee13:metadata_sizei22528eed3:inti1337ee"),
+		surplus: []byte("d3:inti1337ee"),
+	},
+}
+
+func TestDecoder(t *testing.T) {
+	for i, instance := range operationsTest_instances {
+		buf := bytes.NewBuffer(instance.dump)
+		err := bencode.NewDecoder(buf).Decode(&struct {}{})
+		if err != nil {
+			t.Errorf("Couldn't decode the dump #%d! %s", i + 1, err.Error())
+		}
+
+		bufSurplus := buf.Bytes()
+		if !bytes.Equal(bufSurplus, instance.surplus) {
+			t.Errorf("Surplus #%d is not equal to what we expected! `%s`", i + 1, bufSurplus)
+		}
+	}
+}