From 3c8662b13463c5dbcca8cc1f83933f126abc1349 Mon Sep 17 00:00:00 2001
From: Anton Ovchinnikov <anton@tonyo.info>
Date: Wed, 11 Jan 2023 10:32:17 +0100
Subject: [PATCH] fix(dynamic-sampling): Do not crash in Span.Finish() when
 Client is empty (#520)

---
 CHANGELOG.md                     |  7 +++++++
 dynamic_sampling_context.go      |  8 ++++++++
 dynamic_sampling_context_test.go | 13 +++++++++++++
 tracing_test.go                  |  9 +++++++++
 4 files changed, 37 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ca66fa510..4442cb5bf 100644
--- a/CHANGELOG.md
+++ b/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.
diff --git a/dynamic_sampling_context.go b/dynamic_sampling_context.go
index 3e54839ba..06feb2195 100644
--- a/dynamic_sampling_context.go
+++ b/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 != "" {
diff --git a/dynamic_sampling_context_test.go b/dynamic_sampling_context_test.go
index 6cca56591..5299bc1ea 100644
--- a/dynamic_sampling_context_test.go
+++ b/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 {
diff --git a/tracing_test.go b/tracing_test.go
index 8902f75d3..3cc13dff7 100644
--- a/tracing_test.go
+++ b/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()
+}