fix: ClientTrace nil pointer panic

CHANGELOG.md

@@ -74,6 +74,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 ### Fixed
 
 - Fix data race when writing log entries with `context.Context` fields in `go.opentelemetry.io/contrib/bridges/otelzap`. (#7368)
+- Fix nil pointer dereference when `ClientTracer` did not have a span in `go.opentelemetry.io/contrib/instrumentation/net/http/httptrace/otelhttptrace`. (#7464)
 
 <!-- Released section -->
 <!-- Don't change this section unless doing release -->

instrumentation/net/http/httptrace/otelhttptrace/clienttrace.go

@@ -11,11 +11,12 @@
 	"strings"
 	"sync"
 
-	"go.opentelemetry.io/contrib/instrumentation/net/http/httptrace/otelhttptrace/internal/semconv"
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/codes"
 	"go.opentelemetry.io/otel/trace"
+
+	"go.opentelemetry.io/contrib/instrumentation/net/http/httptrace/otelhttptrace/internal/semconv"
 )
 
 // ScopeName is the instrumentation scope name.
@@ -360,26 +361,35 @@
 	if ct.useSpans {
 		span = ct.span("http.receive")
 	}
-	span.AddEvent("GOT 100 - Continue")
+	// It's possible that Got100Continue is called before GotFirstResponseByte at which point span can be `nil`.
+	if span != nil {
+		span.AddEvent("GOT 100 - Continue")
+	}
 }
 
 func (ct *clientTracer) wait100Continue() {
 	span := ct.root
 	if ct.useSpans {
 		span = ct.span("http.send")
 	}
-	span.AddEvent("GOT 100 - Wait")
+	// It's possible that Wait100Continue is called before GotFirstResponseByte at which point span can be `nil`.
+	if span != nil {
+		span.AddEvent("GOT 100 - Wait")
+	}
 }
 
 func (ct *clientTracer) got1xxResponse(code int, header textproto.MIMEHeader) error {
 	span := ct.root
 	if ct.useSpans {
 		span = ct.span("http.receive")
 	}
-	span.AddEvent("GOT 1xx", trace.WithAttributes(
-		HTTPStatus.Int(code),
-		HTTPHeaderMIME.String(sm2s(header)),
-	))
+	// It's possible that Got1xxResponse is called before GotFirstResponseByte at which point span can be `nil`.
+	if span != nil {
+		span.AddEvent("GOT 1xx", trace.WithAttributes(
+			HTTPStatus.Int(code),
+			HTTPHeaderMIME.String(sm2s(header)),
+		))
+	}
 	return nil
 }
 

instrumentation/net/http/httptrace/otelhttptrace/clienttracetest_test.go

@@ -15,11 +15,12 @@ import (
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
-	"go.opentelemetry.io/contrib/instrumentation/net/http/httptrace/otelhttptrace"
 	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/sdk/trace"
 	"go.opentelemetry.io/otel/sdk/trace/tracetest"
+
+	"go.opentelemetry.io/contrib/instrumentation/net/http/httptrace/otelhttptrace"
 )
 
 func getSpanFromRecorder(sr *tracetest.SpanRecorder, name string) (trace.ReadOnlySpan, bool) {
@@ -266,6 +267,29 @@ func TestEndBeforeStartWithoutSubSpansDoesNotPanic(t *testing.T) {
 	require.Empty(t, sr.Ended())
 }
 
+func TestNoClientTraceCallGuarantee(t *testing.T) {
+	t.Run("Got100Continue", func(t *testing.T) {
+		// It is possible that Got100Continue is called before GotFirstResponseByte.
+		// Also as there is no guarantee provided in the ClientTrace docs that GotFirstResponseByte should be called before
+		// Got100Continue this edge case should be covered.
+		assert.NotPanics(t, func() {
+			clientTrace := otelhttptrace.NewClientTrace(context.Background())
+			clientTrace.Got100Continue()
+		})
+	})
+	t.Run("Got1xxResponse", func(t *testing.T) {
+		clientTrace := otelhttptrace.NewClientTrace(context.Background())
+		err := clientTrace.Got1xxResponse(http.StatusNoContent, nil)
+		assert.NoError(t, err)
+	})
+	t.Run("Wait100Continue", func(t *testing.T) {
+		assert.NotPanics(t, func() {
+			clientTrace := otelhttptrace.NewClientTrace(context.Background())
+			clientTrace.Wait100Continue()
+		})
+	})
+}
+
 type clientTraceTestFixture struct {
 	Address      string
 	URL          string