URGENT Fix error in batch/transaction handling

docs/ReleaseNotes.md

@@ -2,6 +2,7 @@
 
 ## Pending
 
+- URGENT Fix: [#2167](https://github.com/StackExchange/StackExchange.Redis/issues/2167), [#2176](https://github.com/StackExchange/StackExchange.Redis/issues/2176): fix error in batch/transaction handling that can result in out-of-order instructions ([#2177 by MarcGravell](https://github.com/StackExchange/StackExchange.Redis/pull/2177))
 - Fix: [#2164](https://github.com/StackExchange/StackExchange.Redis/issues/2164): fix `LuaScript.Prepare` for scripts that don't have parameters ([#2166 by MarcGravell](https://github.com/StackExchange/StackExchange.Redis/pull/2166))
 
 ## 2.6.45

src/StackExchange.Redis/RedisBatch.cs

@@ -63,6 +63,29 @@ public void Execute()
             }
         }
 
+        internal override Task<T> ExecuteAsync<T>(Message? message, ResultProcessor<T>? processor, T defaultValue, ServerEndPoint? server = null)
+        {
+            if (message == null) return CompletedTask<T>.FromDefault(defaultValue, asyncState);
+            multiplexer.CheckMessage(message);
+
+            // prepare the inner command as a task
+            Task<T> task;
+            if (message.IsFireAndForget)
+            {
+                task = CompletedTask<T>.FromDefault(defaultValue, null); // F+F explicitly does not get async-state
+            }
+            else
+            {
+                var source = TaskResultBox<T>.Create(out var tcs, asyncState);
+                task = tcs.Task;
+                message.SetSource(source, processor);
+            }
+
+            // store it
+            (pending ??= new List<Message>()).Add(message);
+            return task!;
+        }
+
         internal override Task<T?> ExecuteAsync<T>(Message? message, ResultProcessor<T>? processor, ServerEndPoint? server = null) where T : default
         {
             if (message == null) return CompletedTask<T>.Default(asyncState);

src/StackExchange.Redis/RedisTransaction.cs

@@ -56,6 +56,30 @@ public Task<bool> ExecuteAsync(CommandFlags flags)
             return base.ExecuteAsync(msg, proc); // need base to avoid our local wrapping override
         }
 
+        internal override Task<T> ExecuteAsync<T>(Message? message, ResultProcessor<T>? processor, T defaultValue, ServerEndPoint? server = null)
+        {
+            if (message == null) return CompletedTask<T>.FromDefault(defaultValue, asyncState);
+            multiplexer.CheckMessage(message);
+
+            multiplexer.Trace("Wrapping " + message.Command, "Transaction");
+            // prepare the inner command as a task
+            Task<T> task;
+            if (message.IsFireAndForget)
+            {
+                task = CompletedTask<T>.FromDefault(defaultValue, null); // F+F explicitly does not get async-state
+            }
+            else
+            {
+                var source = TaskResultBox<T>.Create(out var tcs, asyncState);
+                message.SetSource(source, processor);
+                task = tcs.Task;
+            }
+
+            QueueMessage(message);
+
+            return task;
+        }
+
         internal override Task<T?> ExecuteAsync<T>(Message? message, ResultProcessor<T>? processor, ServerEndPoint? server = null) where T : default
         {
             if (message == null) return CompletedTask<T>.Default(asyncState);
@@ -75,6 +99,13 @@ public Task<bool> ExecuteAsync(CommandFlags flags)
                 task = tcs.Task;
             }
 
+            QueueMessage(message);
+
+            return task;
+        }
+
+        private void QueueMessage(Message message)
+        {
             // prepare an outer-command that decorates that, but expects QUEUED
             var queued = new QueuedMessage(message);
             var wasQueued = SimpleResultBox<bool>.Create();
@@ -102,7 +133,6 @@ public Task<bool> ExecuteAsync(CommandFlags flags)
                         break;
                 }
             }
-            return task;
         }
 
         internal override T? ExecuteSync<T>(Message? message, ResultProcessor<T>? processor, ServerEndPoint? server = null, T? defaultValue = default) where T : default

tests/StackExchange.Redis.Tests/Issues/Issue2176.cs

@@ -0,0 +1,83 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace StackExchange.Redis.Tests.Issues
+{
+    public class Issue2176 : TestBase
+    {
+        public Issue2176(ITestOutputHelper output) : base(output) { }
+
+        [Fact]
+        public void Execute_Batch()
+        {
+            using var conn = Create();
+            var db = conn.GetDatabase();
+
+            var me = Me();
+            var key = me + ":1";
+            var key2 = me + ":2";
+            var keyIntersect = me + ":result";
+
+            db.KeyDelete(key);
+            db.KeyDelete(key2);
+            db.KeyDelete(keyIntersect);
+            db.SortedSetAdd(key, "a", 1345);
+
+            var tasks = new List<Task>();
+            var batch = db.CreateBatch();
+            tasks.Add(batch.SortedSetAddAsync(key2, "a", 4567));
+            tasks.Add(batch.SortedSetCombineAndStoreAsync(SetOperation.Intersect,
+                keyIntersect, new RedisKey[] { key, key2 }));
+            var rangeByRankTask = batch.SortedSetRangeByRankAsync(keyIntersect);
+            tasks.Add(rangeByRankTask);
+            batch.Execute();
+
+            Task.WhenAll(tasks.ToArray());
+
+            var rangeByRankSortedSetValues = rangeByRankTask.Result;
+
+            int size = rangeByRankSortedSetValues.Length;
+            Assert.Equal(1, size);
+            string firstRedisValue = rangeByRankSortedSetValues.FirstOrDefault().ToString();
+            Assert.Equal("a", firstRedisValue);
+        }
+
+        [Fact]
+        public void Execute_Transaction()
+        {
+            using var conn = Create();
+            var db = conn.GetDatabase();
+
+            var me = Me();
+            var key = me + ":1";
+            var key2 = me + ":2";
+            var keyIntersect = me + ":result";
+
+            db.KeyDelete(key);
+            db.KeyDelete(key2);
+            db.KeyDelete(keyIntersect);
+            db.SortedSetAdd(key, "a", 1345);
+
+            var tasks = new List<Task>();
+            var batch = db.CreateTransaction();
+            tasks.Add(batch.SortedSetAddAsync(key2, "a", 4567));
+            tasks.Add(batch.SortedSetCombineAndStoreAsync(SetOperation.Intersect,
+                keyIntersect, new RedisKey[] { key, key2 }));
+            var rangeByRankTask = batch.SortedSetRangeByRankAsync(keyIntersect);
+            tasks.Add(rangeByRankTask);
+            batch.Execute();
+
+            Task.WhenAll(tasks.ToArray());
+
+            var rangeByRankSortedSetValues = rangeByRankTask.Result;
+
+            int size = rangeByRankSortedSetValues.Length;
+            Assert.Equal(1, size);
+            string firstRedisValue = rangeByRankSortedSetValues.FirstOrDefault().ToString();
+            Assert.Equal("a", firstRedisValue);
+        }
+    }
+}