From b43bdfb2a2b60f27845656dd38bdf85c64f96013 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Piotr=20Kie=C5=82kowicz?= <pkiekowicz@splunk.com>
Date: Wed, 4 Oct 2023 20:11:28 +0200
Subject: [PATCH] Fix test_tracestate_duplicated_keys

---
 src/OpenTelemetry.Api/CHANGELOG.md                     |  3 +++
 .../Context/Propagation/TraceContextPropagator.cs      | 10 +++-------
 .../W3CTraceContextTests.cs                            |  4 ++--
 .../Trace/Propagation/TraceContextPropagatorTest.cs    |  8 ++++----
 4 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/src/OpenTelemetry.Api/CHANGELOG.md b/src/OpenTelemetry.Api/CHANGELOG.md
index 6d47071c7e3..4fdffec74ce 100644
--- a/src/OpenTelemetry.Api/CHANGELOG.md
+++ b/src/OpenTelemetry.Api/CHANGELOG.md
@@ -14,6 +14,9 @@
   `trace-flags` field of the `traceparent` header.
   ([#4893](https://github.com/open-telemetry/opentelemetry-dotnet/pull/4893))
 
+* Fix `TraceContextPropagator` by propagating duplicated `tracestate` entries.
+  ([#4937](https://github.com/open-telemetry/opentelemetry-dotnet/pull/4937))
+
 ## 1.6.0
 
 Released 2023-Sep-05
diff --git a/src/OpenTelemetry.Api/Context/Propagation/TraceContextPropagator.cs b/src/OpenTelemetry.Api/Context/Propagation/TraceContextPropagator.cs
index 16c2456ad4a..3922f5f6fb1 100644
--- a/src/OpenTelemetry.Api/Context/Propagation/TraceContextPropagator.cs
+++ b/src/OpenTelemetry.Api/Context/Propagation/TraceContextPropagator.cs
@@ -235,7 +235,7 @@ internal static bool TryExtractTracestate(string[] tracestateCollection, out str
 
         if (tracestateCollection != null)
         {
-            var keySet = new HashSet<string>();
+            int validEntries = 0;
             var result = new StringBuilder();
             for (int i = 0; i < tracestateCollection.Length; ++i)
             {
@@ -264,7 +264,7 @@ internal static bool TryExtractTracestate(string[] tracestateCollection, out str
                         continue;
                     }
 
-                    if (keySet.Count >= 32)
+                    if (validEntries >= 32)
                     {
                         // https://github.com/w3c/trace-context/blob/master/spec/20-http_request_header_format.md#list
                         // test_tracestate_member_count_limit
@@ -295,11 +295,6 @@ internal static bool TryExtractTracestate(string[] tracestateCollection, out str
                     }
 
                     // ValidateKey() call above has ensured the key does not contain upper case letters.
-                    if (!keySet.Add(key.ToString()))
-                    {
-                        // test_tracestate_duplicated_keys
-                        return false;
-                    }
 
                     if (result.Length > 0)
                     {
@@ -307,6 +302,7 @@ internal static bool TryExtractTracestate(string[] tracestateCollection, out str
                     }
 
                     result.Append(listMember.ToString());
+                    validEntries++;
                 }
             }
 
diff --git a/test/OpenTelemetry.Instrumentation.W3cTraceContext.Tests/W3CTraceContextTests.cs b/test/OpenTelemetry.Instrumentation.W3cTraceContext.Tests/W3CTraceContextTests.cs
index 58ec321d600..1effb256171 100644
--- a/test/OpenTelemetry.Instrumentation.W3cTraceContext.Tests/W3CTraceContextTests.cs
+++ b/test/OpenTelemetry.Instrumentation.W3cTraceContext.Tests/W3CTraceContextTests.cs
@@ -103,11 +103,11 @@ public void W3CTraceContextTestSuiteAsync(string value)
 
         if (AspNetCoreHostingVersion.Major <= 6)
         {
-            Assert.StartsWith("FAILED (failures=5)", lastLine);
+            Assert.StartsWith("FAILED (failures=4)", lastLine);
         }
         else
         {
-            Assert.StartsWith("FAILED (failures=2)", lastLine);
+            Assert.StartsWith("FAILED (failures=1)", lastLine);
         }
     }
 
diff --git a/test/OpenTelemetry.Tests/Trace/Propagation/TraceContextPropagatorTest.cs b/test/OpenTelemetry.Tests/Trace/Propagation/TraceContextPropagatorTest.cs
index f7dae35547f..089aa248517 100644
--- a/test/OpenTelemetry.Tests/Trace/Propagation/TraceContextPropagatorTest.cs
+++ b/test/OpenTelemetry.Tests/Trace/Propagation/TraceContextPropagatorTest.cs
@@ -193,10 +193,10 @@ public void Inject_WithTracestate()
     public void DuplicateKeys()
     {
         // test_tracestate_duplicated_keys
-        Assert.Empty(CallTraceContextPropagator("foo=1,foo=1"));
-        Assert.Empty(CallTraceContextPropagator("foo=1,foo=2"));
-        Assert.Empty(CallTraceContextPropagator(new[] { "foo=1", "foo=1" }));
-        Assert.Empty(CallTraceContextPropagator(new[] { "foo=1", "foo=2" }));
+        Assert.Equal("foo=1,foo=1", CallTraceContextPropagator("foo=1,foo=1"));
+        Assert.Equal("foo=1,foo=2", CallTraceContextPropagator("foo=1,foo=2"));
+        Assert.Equal("foo=1,foo=1", CallTraceContextPropagator(new[] { "foo=1", "foo=1" }));
+        Assert.Equal("foo=1,foo=2", CallTraceContextPropagator(new[] { "foo=1", "foo=2" }));
     }
 
     [Fact]