Skip links with invalid span context (#2275)

* Skip links with invalid span context

* Add CHANGELOG entry

* Review suggestions

CHANGELOG.md

@@ -8,6 +8,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+## Changed
+
+- Skip links with invalid span context. (#2275)
+
 ### Added
 
 - Adds `otlptracegrpc.WithGRPCConn` and `otlpmetricgrpc.WithGRPCConn` for reusing existing gRPC connection. (#2002)

sdk/trace/span.go

@@ -453,7 +453,7 @@ func (s *recordingSpan) Resource() *resource.Resource {
 }
 
 func (s *recordingSpan) addLink(link trace.Link) {
-	if !s.IsRecording() {
+	if !s.IsRecording() || !link.SpanContext.IsValid() {
 		return
 	}
 	s.mu.Lock()

sdk/trace/trace_test.go

@@ -670,6 +670,15 @@ func TestLinks(t *testing.T) {
 	if diff := cmpDiff(got, want); diff != "" {
 		t.Errorf("Link: -got +want %s", diff)
 	}
+	sc1 = trace.NewSpanContext(trace.SpanContextConfig{TraceID: trace.TraceID([16]byte{1, 1}), SpanID: trace.SpanID{3}})
+
+	span1 := startSpan(tp, "name", trace.WithLinks([]trace.Link{
+		{SpanContext: trace.SpanContext{}},
+		{SpanContext: sc1},
+	}...))
+
+	sdkspan, _ := span1.(*recordingSpan)
+	require.Len(t, sdkspan.Links(), 1)
 }
 
 func TestLinksOverLimit(t *testing.T) {

trace/config.go

@@ -259,7 +259,7 @@ func WithStackTrace(b bool) SpanEndEventOption {
 }
 
 // WithLinks adds links to a Span. The links are added to the existing Span
-// links, i.e. this does not overwrite.
+// links, i.e. this does not overwrite. Links with invalid span context are ignored.
 func WithLinks(links ...Link) SpanStartOption {
 	return spanOptionFunc(func(cfg *SpanConfig) {
 		cfg.links = append(cfg.links, links...)