fix(dynamic-sampling): Do not crash in Span.Finish() when Client is empty

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Changelog
 
+## Unreleased
+
+### Bug Fixes
+
+- fix(dynamic-sampling): Do not crash in Span.Finish() when Client is empty [#520](https://github.com/getsentry/sentry-go/pull/520)
+  - Fixes [#518](https://github.com/getsentry/sentry-go/issues/518)
+
 ## 0.16.0
 
 The Sentry SDK team is happy to announce the immediate availability of Sentry Go SDK v0.16.0.

dynamic_sampling_context.go

@@ -43,6 +43,14 @@ func DynamicSamplingContextFromTransaction(span *Span) DynamicSamplingContext {
 	hub := hubFromContext(span.Context())
 	scope := hub.Scope()
 	client := hub.Client()
+
+	if client == nil || scope == nil {
+		return DynamicSamplingContext{
+			Entries: map[string]string{},
+			Frozen:  false,
+		}
+	}
+
 	options := client.Options()
 
 	if traceID := span.TraceID.String(); traceID != "" {

dynamic_sampling_context_test.go

@@ -1,6 +1,7 @@
 package sentry
 
 import (
+	"context"
 	"strings"
 	"testing"
 )
@@ -108,6 +109,18 @@ func TestDynamicSamplingContextFromTransaction(t *testing.T) {
 				},
 			},
 		},
+		// Empty context without a valid Client
+		{
+			input: func() *Span {
+				ctx := context.Background()
+				tx := StartTransaction(ctx, "op")
+				return tx
+			}(),
+			want: DynamicSamplingContext{
+				Frozen:  false,
+				Entries: map[string]string{},
+			},
+		},
 	}
 
 	for _, tc := range tests {

tracing_test.go

@@ -567,3 +567,12 @@ func TestSample(t *testing.T) {
 		t.Fatalf("got %s, want %s", got, SampledTrue)
 	}
 }
+
+func TestDoesNotCrashWithEmptyContext(t *testing.T) {
+	// This test makes sure that we can still start and finish transactions
+	// with empty context (for example, when Sentry SDK is not initialized)
+	ctx := context.Background()
+	tx := StartTransaction(ctx, "op")
+	tx.Sampled = SampledTrue
+	tx.Finish()
+}