csharp debug error string improvements

src/csharp/Grpc.Core.Api/Status.cs

@@ -42,6 +42,8 @@ namespace Grpc.Core
 
         /// <summary>
         /// Creates a new instance of <c>Status</c>.
+        /// Users should not use this constructor, except for creating instances for testing.
+        /// The debug error string should only be populated by gRPC internals.
         /// </summary>
         /// <param name="statusCode">Status code.</param>
         /// <param name="detail">Detail.</param>

src/csharp/Grpc.Core.Tests/ClientServerTest.cs

@@ -139,6 +139,26 @@ namespace Grpc.Core.Tests
             Assert.AreEqual(0, ex2.Trailers.Count);
         }
 
+        [Test]
+        public void UnaryCall_StatusDebugErrorStringNotTransmittedFromServer()
+        {
+            helper.UnaryHandler = new UnaryServerMethod<string, string>((request, context) =>
+            {
+                context.Status = new Status(StatusCode.Unauthenticated, "", "this DebugErrorString value should not be transmitted to the client");
+                return Task.FromResult("");
+            });
+
+            var ex = Assert.Throws<RpcException>(() => Calls.BlockingUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unauthenticated, ex.Status.StatusCode);
+            Assert.IsTrue(ex.Status.DebugErrorString.Contains("Error received from peer"));  // a different debug error string set by grpc client
+            Assert.AreEqual(0, ex.Trailers.Count);
+
+            var ex2 = Assert.ThrowsAsync<RpcException>(async () => await Calls.AsyncUnaryCall(helper.CreateUnaryCall(), "abc"));
+            Assert.AreEqual(StatusCode.Unauthenticated, ex2.Status.StatusCode);
+            Assert.IsTrue(ex2.Status.DebugErrorString.Contains("Error received from peer"));  // a different debug error string set by grpc client
+            Assert.AreEqual(0, ex2.Trailers.Count);
+        }
+
         [Test]
         public void UnaryCall_ServerHandlerSetsStatusAndTrailers()
         {

src/csharp/Grpc.Core/Internal/BatchContextSafeHandle.cs

@@ -92,8 +92,8 @@ namespace Grpc.Core.Internal
             UIntPtr detailsLength;
             IntPtr detailsPtr = Native.grpcsharp_batch_context_recv_status_on_client_details(this, out detailsLength);
             string details = MarshalUtils.PtrToStringUTF8(detailsPtr, (int)detailsLength.ToUInt32());
-            string error = Marshal.PtrToStringAnsi(Native.grpcsharp_batch_context_recv_status_on_client_error_string(this));
-            var status = new Status(Native.grpcsharp_batch_context_recv_status_on_client_status(this), details, error);
+            string debugErrorString = Marshal.PtrToStringAnsi(Native.grpcsharp_batch_context_recv_status_on_client_error_string(this));
+            var status = new Status(Native.grpcsharp_batch_context_recv_status_on_client_status(this), details, debugErrorString);
 
             IntPtr metadataArrayPtr = Native.grpcsharp_batch_context_recv_status_on_client_trailing_metadata(this);
             var metadata = MetadataArraySafeHandle.ReadMetadataFromPtrUnsafe(metadataArrayPtr);