Add err wrapping to dialer (#402)

deansheather · web-flow · commit d6730798eee4 · 2021-07-27T07:44:34.000+10:00
diff --git a/wsnet/dial.go b/wsnet/dial.go
@@ -104,6 +104,17 @@ func Dial(ctx context.Context, conn net.Conn, options *DialOptions) (*Dialer, er
 		return nil, fmt.Errorf("create peer connection: %w", err)
 	}
 	log.Debug(ctx, "created peer connection")
+	defer func() {
+		if err != nil {
+			// Wrap our error with some extra details.
+			err = errWrap{
+				err:        err,
+				iceServers: rtc.GetConfiguration().ICEServers,
+				rtc:        rtc.ConnectionState(),
+			}
+		}
+	}()
+
 	rtc.OnConnectionStateChange(func(pcs webrtc.PeerConnectionState) {
 		log.Debug(ctx, "connection state change", slog.F("state", pcs.String()))
 	})
@@ -159,7 +170,9 @@ func Dial(ctx context.Context, conn net.Conn, options *DialOptions) (*Dialer, er
 		connClosers: []io.Closer{ctrl},
 	}
 
-	return dialer, dialer.negotiate(ctx)
+	// This is on a separate line so the defer above catches it.
+	err = dialer.negotiate(ctx)
+	return dialer, err
 }
 
 // Dialer enables arbitrary dialing to any network and address
diff --git a/wsnet/error.go b/wsnet/error.go
@@ -0,0 +1,39 @@
+package wsnet
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/pion/webrtc/v3"
+)
+
+// errWrap wraps the error with some extra details about the state of the
+// connection.
+type errWrap struct {
+	err error
+
+	iceServers []webrtc.ICEServer
+	rtc        webrtc.PeerConnectionState
+}
+
+var _ error = errWrap{}
+var _ interface{ Unwrap() error } = errWrap{}
+
+// Error implements error.
+func (e errWrap) Error() string {
+	return fmt.Sprintf("%v (ice: [%v], rtc: %v)", e.err.Error(), e.ice(), e.rtc.String())
+}
+
+func (e errWrap) ice() string {
+	msgs := []string{}
+	for _, s := range e.iceServers {
+		msgs = append(msgs, strings.Join(s.URLs, ", "))
+	}
+
+	return strings.Join(msgs, ", ")
+}
+
+// Unwrap implements Unwrapper.
+func (e errWrap) Unwrap() error {
+	return e.err
+}
