This removes TaskSource.CreateDenyExecSync (#798)

After 50547eba, TaskSource.Create and TaskSource.CreateDenyExecSync methods are the same. There was some crud left everywhere that appeared like differences but it's really determined once in the static initializer for TaskSource based on the platform anyway.

I've fixed the tests as well - they were a bit backwards on logic/assumptions so hard to read, and have been failing for some time. Now we'd expect ContinueWithExecSync to *not* be hijacked, and everything else to be...that's how the tests are as well.

Note: the #if DEBUG change is because internals are already visible to tests...just simpler.

StackExchange.Redis.Tests/TaskTests.cs

@@ -33,24 +33,19 @@ private static TaskCompletionSource<T> Create<T>(SourceOrign origin)
             {
                 case SourceOrign.NewTCS: return new TaskCompletionSource<T>();
                 case SourceOrign.Create: return TaskSource.Create<T>(null);
-                case SourceOrign.CreateDenyExec: return TaskSource.CreateDenyExecSync<T>(null);
                 default: throw new ArgumentOutOfRangeException(nameof(origin));
             }
         }
 
         [Theory]
         // regular framework behaviour: 2 out of 3 cause hijack
-        [InlineData(SourceOrign.NewTCS, AttachMode.ContinueWith, false)]
-        [InlineData(SourceOrign.NewTCS, AttachMode.ContinueWithExecSync, true)]
+        [InlineData(SourceOrign.NewTCS, AttachMode.ContinueWith, true)]
+        [InlineData(SourceOrign.NewTCS, AttachMode.ContinueWithExecSync, false)]
         [InlineData(SourceOrign.NewTCS, AttachMode.Await, true)]
         // Create is just a wrapper of ^^^; expect the same
-        [InlineData(SourceOrign.Create, AttachMode.ContinueWith, false)]
-        [InlineData(SourceOrign.Create, AttachMode.ContinueWithExecSync, true)]
+        [InlineData(SourceOrign.Create, AttachMode.ContinueWith, true)]
+        [InlineData(SourceOrign.Create, AttachMode.ContinueWithExecSync, false)]
         [InlineData(SourceOrign.Create, AttachMode.Await, true)]
-        // deny exec-sync: none should cause hijack
-        [InlineData(SourceOrign.CreateDenyExec, AttachMode.ContinueWith, false)]
-        [InlineData(SourceOrign.CreateDenyExec, AttachMode.ContinueWithExecSync, false)]
-        [InlineData(SourceOrign.CreateDenyExec, AttachMode.Await, false)]
         public void TestContinuationHijacking(SourceOrign origin, AttachMode attachMode, bool expectHijack)
         {
             TaskCompletionSource<int> source = Create<int>(origin);
@@ -64,19 +59,18 @@ public void TestContinuationHijacking(SourceOrign origin, AttachMode attachMode,
             Assert.NotEqual(-1, from); // not set
             if (expectHijack)
             {
-                Assert.True(settingThread == from, "expected hijack; didn't happen");
+                Assert.True(settingThread != from, $"expected hijack; didn't happen, Origin={settingThread}, Final={from}");
             }
             else
             {
-                Assert.False(settingThread == from, "setter was hijacked");
+                Assert.True(settingThread == from, $"setter was hijacked, Origin={settingThread}, Final={from}");
             }
         }
 
         public enum SourceOrign
         {
             NewTCS,
-            Create,
-            CreateDenyExec
+            Create
         }
 
         public enum AttachMode

StackExchange.Redis/StackExchange/Redis/ConnectionMultiplexer.cs

@@ -1967,7 +1967,7 @@ internal Task<T> ExecuteAsyncImpl<T>(Message message, ResultProcessor<T> process
             }
             else
             {
-                var tcs = TaskSource.CreateDenyExecSync<T>(state);
+                var tcs = TaskSource.Create<T>(state);
                 var source = ResultBox<T>.Get(tcs);
                 if (!TryPushMessageToBridge(message, processor, source, ref server))
                 {

StackExchange.Redis/StackExchange/Redis/RedisBatch.cs

@@ -78,7 +78,7 @@ internal override Task<T> ExecuteAsync<T>(Message message, ResultProcessor<T> pr
             }
             else
             {
-                var tcs = TaskSource.CreateDenyExecSync<T>(asyncState);
+                var tcs = TaskSource.Create<T>(asyncState);
                 var source = ResultBox<T>.Get(tcs);
                 message.SetSource(source, processor);
                 task = tcs.Task;

StackExchange.Redis/StackExchange/Redis/RedisTransaction.cs

@@ -72,7 +72,7 @@ internal override Task<T> ExecuteAsync<T>(Message message, ResultProcessor<T> pr
             }
             else
             {
-                var tcs = TaskSource.CreateDenyExecSync<T>(asyncState);
+                var tcs = TaskSource.Create<T>(asyncState);
                 var source = ResultBox<T>.Get(tcs);
                 message.SetSource(source, processor);
                 task = tcs.Task;

StackExchange.Redis/StackExchange/Redis/ServerEndPoint.cs

@@ -562,7 +562,7 @@ internal void OnHeartbeat()
 
         internal Task<T> QueueDirectAsync<T>(Message message, ResultProcessor<T> processor, object asyncState = null, PhysicalBridge bridge = null)
         {
-            var tcs = TaskSource.CreateDenyExecSync<T>(asyncState);
+            var tcs = TaskSource.Create<T>(asyncState);
             var source = ResultBox<T>.Get(tcs);
             message.SetSource(processor, source);
             if (bridge == null) bridge = GetBridge(message.Command);

StackExchange.Redis/StackExchange/Redis/TaskSource.cs

@@ -13,10 +13,7 @@ namespace StackExchange.Redis
     /// see https://stackoverflow.com/a/22588431/23354 for more information; a huge
     /// thanks to Eli Arbel for spotting this (even though it is pure evil; it is *my kind of evil*)
     /// </summary>
-#if DEBUG
-    public // for the unit tests in TaskTests.cs
-#endif
-    static class TaskSource
+    internal static class TaskSource
     {
 #if !PLAT_SAFE_CONTINUATIONS
         // on .NET < 4.6, it was possible to have threads hijacked; this is no longer a problem in 4.6 and core-clr 5,
@@ -93,15 +90,5 @@ public static TaskCompletionSource<T> Create<T>(object asyncState)
             return new TaskCompletionSource<T>(asyncState, TaskCreationOptions.None);
 #endif
         }
-
-        /// <summary>
-        /// Create a new TaskCompletionSource that will not allow result-setting threads to be hijacked
-        /// </summary>
-        public static TaskCompletionSource<T> CreateDenyExecSync<T>(object asyncState)
-        {
-            var source = new TaskCompletionSource<T>(asyncState);
-            //DenyExecSync(source.Task);
-            return source;
-        }
     }
 }