Don't cache SessionDescription during unmarshal

A user could use these across multiple interactions with the API. This
is confusing behavior because all their subsequent calls will be
ignored.

This reverts 3412dc6d95

README.md

@@ -261,6 +261,7 @@ Check out the **[contributing wiki](https://github.com/pion/webrtc/wiki/Contribu
 * [Dean Eigenmann](https://github.com/decanus)
 * [Cameron Elliott](https://github.com/cameronelliott)
 * [Pascal Benoit](https://github.com/pascal-ace)
+* [Mats](https://github.com/Mindgamesnl)
 
 ### License
 MIT License - see [LICENSE](LICENSE) for full text

sessiondescription.go

@@ -13,12 +13,8 @@ type SessionDescription struct {
 	parsed *sdp.SessionDescription
 }
 
-// Unmarshal is a helper to deserialize the sdp, and re-use it internally
-// if required
+// Unmarshal is a helper to deserialize the sdp
 func (sd *SessionDescription) Unmarshal() (*sdp.SessionDescription, error) {
-	if sd.parsed != nil {
-		return sd.parsed, nil
-	}
 	sd.parsed = &sdp.SessionDescription{}
 	err := sd.parsed.Unmarshal([]byte(sd.SDP))
 	return sd.parsed, err

sessiondescription_test.go

@@ -2,6 +2,7 @@ package webrtc
 
 import (
 	"encoding/json"
+	"reflect"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -68,12 +69,15 @@ func TestSessionDescription_Unmarshal(t *testing.T) {
 		SDP:  offer.SDP,
 	}
 	assert.Nil(t, desc.parsed)
-	parsed, err := desc.Unmarshal()
-	assert.NotNil(t, parsed)
+	parsed1, err := desc.Unmarshal()
+	assert.NotNil(t, parsed1)
 	assert.NotNil(t, desc.parsed)
 	assert.NoError(t, err)
-	parsed, err = desc.Unmarshal()
-	assert.NotNil(t, parsed)
-	assert.NoError(t, err)
+	parsed2, err2 := desc.Unmarshal()
+	assert.NotNil(t, parsed2)
+	assert.NoError(t, err2)
 	assert.NoError(t, pc.Close())
+
+	// check if the two parsed results _really_ match, could be affected by internal caching
+	assert.True(t, reflect.DeepEqual(parsed1, parsed2))
 }