Fix SmtpClientTest.SendAsync_CanBeCanceled_SendAsyncCancel test failure (#116042)

* Initial plan for issue

* Fix SmtpClientTest.SendAsync_CanBeCanceled_SendAsyncCancel test by using IsAssignableFrom

Co-authored-by: stephentoub <[email protected]>

* Fix ThrowsAsync to ThrowsAnyAsync for TaskCanceledException check

Co-authored-by: stephentoub <[email protected]>

* Fix ThrowsAnyAsync<TaskCanceledException> to handle both direct and wrapped exceptions

Co-authored-by: stephentoub <[email protected]>

* Fix assertion and implementation for SmtpClient cancellation

Co-authored-by: rzikm <[email protected]>

* Move Abort() call and fix nullability annotations for ProcessException

Co-authored-by: rzikm <[email protected]>

* Fix cancellation handling for SmtpClient: prevent wrapping OperationCanceledException and fix test race condition

Co-authored-by: rzikm <[email protected]>

* Remove unused serverMre variable and wrap SendMailAsync in Task.Run

Co-authored-by: rzikm <[email protected]>

* Apply suggestions from code review

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: stephentoub <[email protected]>
Co-authored-by: rzikm <[email protected]>
Co-authored-by: Stephen Toub <[email protected]>

Author: 3 people

src/libraries/System.Net.Mail/src/System/Net/Mail/SmtpClient.cs

@@ -556,9 +556,9 @@ Exception ProcessException(Exception e, ref bool canceled, bool forceWrapExcepti
 
                     if (!forceWrapExceptions ||
                         // for compatibility reasons, don't wrap these exceptions during sync executions
-                        (typeof(TIOAdapter) == typeof(SyncReadWriteAdapter) &&
-                            (e is SecurityException || e is AuthenticationException)) ||
-                        e is SmtpException)
+                        (typeof(TIOAdapter) == typeof(SyncReadWriteAdapter) && (e is SecurityException or AuthenticationException)) ||
+                        e is SmtpException ||
+                        e is OperationCanceledException)
                     {
                         return e;
                     }
@@ -574,7 +574,7 @@ Exception ProcessException(Exception e, ref bool canceled, bool forceWrapExcepti
                 // SendCompleted event should ever be invoked only for asynchronous send completions.
                 if (invokeSendCompleted && !synchronous)
                 {
-                    AsyncCompletedEventArgs eventArgs = new AsyncCompletedEventArgs(exception, canceled, userToken);
+                    AsyncCompletedEventArgs eventArgs = new(canceled ? null : exception, canceled, userToken);
                     OnSendCompleted(eventArgs);
                 }
             }

src/libraries/System.Net.Mail/tests/Functional/SmtpClientTest.cs

@@ -314,20 +314,15 @@ public async Task SendMailAsync_CanBeCanceled_CancellationToken()
             server.ReceiveMultipleConnections = true;
 
             // The server will introduce some fake latency so that the operation can be canceled before the request completes
-            ManualResetEvent serverMre = new ManualResetEvent(false);
-            server.OnConnected += _ => serverMre.WaitOne();
-
             CancellationTokenSource cts = new CancellationTokenSource();
+            
+            server.OnConnected += _ => cts.Cancel();
 
             var message = new MailMessage("[email protected]", "[email protected]", "Foo", "Bar");
 
             Task sendTask = Task.Run(() => client.SendMailAsync(message, cts.Token));
 
-            cts.Cancel();
-            await Task.Delay(500);
-            serverMre.Set();
-
-            await Assert.ThrowsAsync<TaskCanceledException>(async () => await sendTask).WaitAsync(TestHelper.PassingTestTimeout);
+            await Assert.ThrowsAnyAsync<OperationCanceledException>(async () => await sendTask).WaitAsync(TestHelper.PassingTestTimeout);
 
             // We should still be able to send mail on the SmtpClient instance
             await Task.Run(() => client.SendMailAsync(message)).WaitAsync(TestHelper.PassingTestTimeout);
@@ -369,8 +364,7 @@ public async Task SendAsync_CanBeCanceled_SendAsyncCancel()
             client.SendAsync(message, null);
             AsyncCompletedEventArgs e = await tcs.Task.WaitAsync(TestHelper.PassingTestTimeout);
             Assert.True(e.Cancelled, "SendAsync should have been canceled");
-            _output.WriteLine(e.Error?.ToString() ?? "No error");
-            Assert.IsType<OperationCanceledException>(e.Error.InnerException);
+            Assert.Null(e.Error);
 
             // We should still be able to send mail on the SmtpClient instance
             await client.SendMailAsync(message).WaitAsync(TestHelper.PassingTestTimeout);