[API] Handle null tracestate values

src/OpenTelemetry.Api/CHANGELOG.md

@@ -6,12 +6,13 @@ Notes](../../RELEASENOTES.md).
 
 ## Unreleased
 
-* The library is now marked as trim and AOT compatible.
-  ([#7441](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7441))
-
 * Fixed `TraceContextPropagator` to normalize empty `tracestate` header values
   to `null` when extracting trace context.
-  ([#7407](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7407))
+  ([#7407](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7407),
+  [#7433](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7433))
+
+* The library is now marked as trim and AOT compatible.
+  ([#7441](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7441))
 
 * **Experimental (pre-release builds only):** Updated `EnvironmentVariableCarrier.Get`
   to read only the normalized environment variable name, following the updated

src/OpenTelemetry.Api/Context/Propagation/TraceContextPropagator.cs

@@ -381,6 +381,11 @@ private static bool TryExtractMultipleTracestate(IEnumerable<string> tracestateC
 
         foreach (var tracestateEntry in tracestateCollection)
         {
+            if (tracestateEntry is not { Length: > 0 })
+            {
+                continue;
+            }
+
             var tracestate = tracestateEntry.AsSpan();
             var begin = 0;
             while (begin < tracestate.Length)
@@ -465,11 +470,11 @@ private static bool TryExtractMultipleTracestate(IEnumerable<string> tracestateC
         return true;
     }
 
-    private static bool TryExtractSingleTracestate(string tracestate, out string tracestateResult)
+    private static bool TryExtractSingleTracestate(string? tracestate, out string tracestateResult)
     {
         tracestateResult = string.Empty;
 
-        if (tracestate.Length == 0)
+        if (tracestate is not { Length: > 0 })
         {
             return true;
         }

test/OpenTelemetry.Tests/Trace/Propagation/TraceContextPropagatorTests.cs

@@ -336,6 +336,48 @@ public void TryExtractTracestate_NullCollectionReturnsEmpty()
         Assert.Empty(actual);
     }
 
+    [Fact]
+    public void Extract_HandlesNullTracestateValue()
+    {
+        var headers = new Dictionary<string, string>
+        {
+            { TraceParent, $"00-{TraceId}-{SpanId}-01" },
+        };
+
+        var propagator = new TraceContextPropagator();
+        var context = propagator.Extract(default, headers, (_, name) => headers.TryGetValue(name, out var value) ? [value] : [null!]);
+
+        Assert.Equal(ActivityTraceId.CreateFromString(TraceId.AsSpan()), context.ActivityContext.TraceId);
+        Assert.Equal(ActivitySpanId.CreateFromString(SpanId.AsSpan()), context.ActivityContext.SpanId);
+
+        Assert.True(context.ActivityContext.IsRemote);
+        Assert.True(context.ActivityContext.IsValid());
+        Assert.NotEqual(0, (int)(context.ActivityContext.TraceFlags & ActivityTraceFlags.Recorded));
+
+        Assert.Null(context.ActivityContext.TraceState);
+    }
+
+    [Fact]
+    public void Extract_HandlesNullTracestateValues()
+    {
+        var headers = new Dictionary<string, string>
+        {
+            { TraceParent, $"00-{TraceId}-{SpanId}-01" },
+        };
+
+        var propagator = new TraceContextPropagator();
+        var context = propagator.Extract(default, headers, (_, name) => headers.TryGetValue(name, out var value) ? [value] : [string.Empty, null!]);
+
+        Assert.Equal(ActivityTraceId.CreateFromString(TraceId.AsSpan()), context.ActivityContext.TraceId);
+        Assert.Equal(ActivitySpanId.CreateFromString(SpanId.AsSpan()), context.ActivityContext.SpanId);
+
+        Assert.True(context.ActivityContext.IsRemote);
+        Assert.True(context.ActivityContext.IsValid());
+        Assert.NotEqual(0, (int)(context.ActivityContext.TraceFlags & ActivityTraceFlags.Recorded));
+
+        Assert.Null(context.ActivityContext.TraceState);
+    }
+
     [Fact]
     public void Inject_NoTracestate()
     {