Prevent NullReferenceException in SentryTraceHeader Parsing

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Fixes
 
 - Fixed ArgumentNullException in FormRequestPayloadExtractor when handling invalid form data on ASP.NET ([#3734](https://github.com/getsentry/sentry-dotnet/pull/3734))
+- Fixed NullReferenceException in SentryTraceHeader when parsing null or empty values ([#3745](https://github.com/getsentry/sentry-dotnet/pull/3745))
 
 ### Dependencies
 

src/Sentry/SentryTraceHeader.cs

@@ -40,10 +40,25 @@ public override string ToString() => IsSampled is { } isSampled
         : $"{TraceId}-{SpanId}";
 
     /// <summary>
-    /// Parses <see cref="SentryTraceHeader"/> from string.
+    /// Parses a <see cref="SentryTraceHeader"/> from a string representation of the Sentry trace header.
     /// </summary>
-    public static SentryTraceHeader Parse(string value)
+    /// <param name="value">
+    /// A string containing the Sentry trace header, expected to follow the format "traceId-spanId-sampled",
+    /// where "sampled" is optional.
+    /// </param>
+    /// <returns>
+    /// A <see cref="SentryTraceHeader"/> object if parsing succeeds, or <c>null</c> if the input string is null, empty, or whitespace.
+    /// </returns>
+    /// <exception cref="FormatException">
+    /// Thrown if the input string does not contain a valid trace header format, specifically if it lacks required trace ID and span ID components.
+    /// </exception>
+    public static SentryTraceHeader? Parse(string value)
     {
+        if (string.IsNullOrWhiteSpace(value))
+        {
+            return null;
+        }
+
         var components = value.Split('-', StringSplitOptions.RemoveEmptyEntries);
         if (components.Length < 2)
         {

test/Sentry.Tests/ApiApprovalTests.Run.DotNet6_0.verified.txt

@@ -931,7 +931,7 @@ namespace Sentry
         public Sentry.SpanId SpanId { get; }
         public Sentry.SentryId TraceId { get; }
         public override string ToString() { }
-        public static Sentry.SentryTraceHeader Parse(string value) { }
+        public static Sentry.SentryTraceHeader? Parse(string value) { }
     }
     public class SentryTransaction : Sentry.IEventLike, Sentry.IHasExtra, Sentry.IHasTags, Sentry.ISentryJsonSerializable, Sentry.ISpanData, Sentry.ITransactionContext, Sentry.ITransactionData, Sentry.Protocol.ITraceContext
     {

test/Sentry.Tests/ApiApprovalTests.Run.DotNet7_0.verified.txt

@@ -931,7 +931,7 @@ namespace Sentry
         public Sentry.SpanId SpanId { get; }
         public Sentry.SentryId TraceId { get; }
         public override string ToString() { }
-        public static Sentry.SentryTraceHeader Parse(string value) { }
+        public static Sentry.SentryTraceHeader? Parse(string value) { }
     }
     public class SentryTransaction : Sentry.IEventLike, Sentry.IHasExtra, Sentry.IHasTags, Sentry.ISentryJsonSerializable, Sentry.ISpanData, Sentry.ITransactionContext, Sentry.ITransactionData, Sentry.Protocol.ITraceContext
     {

test/Sentry.Tests/ApiApprovalTests.Run.DotNet8_0.verified.txt

@@ -933,7 +933,7 @@ namespace Sentry
         public Sentry.SpanId SpanId { get; }
         public Sentry.SentryId TraceId { get; }
         public override string ToString() { }
-        public static Sentry.SentryTraceHeader Parse(string value) { }
+        public static Sentry.SentryTraceHeader? Parse(string value) { }
     }
     public class SentryTransaction : Sentry.IEventLike, Sentry.IHasExtra, Sentry.IHasTags, Sentry.ISentryJsonSerializable, Sentry.ISpanData, Sentry.ITransactionContext, Sentry.ITransactionData, Sentry.Protocol.ITraceContext
     {

test/Sentry.Tests/ApiApprovalTests.Run.Net4_8.verified.txt

@@ -928,7 +928,7 @@ namespace Sentry
         public Sentry.SpanId SpanId { get; }
         public Sentry.SentryId TraceId { get; }
         public override string ToString() { }
-        public static Sentry.SentryTraceHeader Parse(string value) { }
+        public static Sentry.SentryTraceHeader? Parse(string value) { }
     }
     public class SentryTransaction : Sentry.IEventLike, Sentry.IHasExtra, Sentry.IHasTags, Sentry.ISentryJsonSerializable, Sentry.ISpanData, Sentry.ITransactionContext, Sentry.ITransactionData, Sentry.Protocol.ITraceContext
     {

test/Sentry.Tests/Protocol/SentryTraceHeaderTests.cs

@@ -46,4 +46,17 @@ public void Parse_WithSampledFalse_Works()
         header.SpanId.Should().Be(SpanId.Parse("1000000000000000"));
         header.IsSampled.Should().BeFalse();
     }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("  ")]
+    public void Parse_WithoutHeaderValue_ReturnsNull(string headerValue)
+    {
+        // Act
+        var header = SentryTraceHeader.Parse(headerValue);
+
+        // Assert
+        header.Should().BeNull();
+    }
 }