Session disposal (#6525)

* resolve storage session per call

* only dispose session once

* approve scope change in test

* change registration back to same scope as the referenced type

src/NServiceBus.Core.Tests/Reliability/SynchronizedStorage/CompletableSynchronizedStorageSessionAdapterTests.cs

@@ -0,0 +1,44 @@
+namespace NServiceBus.Core.Tests.Reliability
+{
+    using System.Threading.Tasks;
+    using Extensibility;
+    using NServiceBus.Outbox;
+    using NServiceBus.Persistence;
+    using NUnit.Framework;
+    using Transport;
+
+    [TestFixture]
+    public class CompletableSynchronizedStorageSessionAdapterTests
+    {
+        [Test]
+        public async Task Should_dispose_adapted_session_only_once()
+        {
+            var storageAdapter = new FakeStorageAdapter();
+            var sessionAdapter = new CompletableSynchronizedStorageSessionAdapter(storageAdapter, null);
+            await sessionAdapter.TryOpen(new TransportTransaction(), new ContextBag());
+
+            sessionAdapter.Dispose();
+            sessionAdapter.Dispose();
+
+            Assert.AreEqual(1, storageAdapter.StorageSession.DisposeCounter);
+        }
+    }
+
+    public class FakeStorageAdapter : ISynchronizedStorageAdapter
+    {
+        public FakeStorageSession StorageSession { get; } = new FakeStorageSession();
+
+        public Task<CompletableSynchronizedStorageSession> TryAdapt(OutboxTransaction transaction, ContextBag context) => Task.FromResult<CompletableSynchronizedStorageSession>(StorageSession);
+
+        public Task<CompletableSynchronizedStorageSession> TryAdapt(TransportTransaction transportTransaction, ContextBag context) => Task.FromResult<CompletableSynchronizedStorageSession>(StorageSession);
+    }
+
+    public class FakeStorageSession : CompletableSynchronizedStorageSession
+    {
+        public int DisposeCounter { get; private set; }
+
+        public void Dispose() => DisposeCounter++;
+
+        public Task CompleteAsync() => Task.FromResult(0);
+    }
+}

src/NServiceBus.Core/Reliability/SynchronizedStorage/CompletableSynchronizedStorageSessionAdapter.cs

@@ -17,7 +17,16 @@ public CompletableSynchronizedStorageSessionAdapter(ISynchronizedStorageAdapter
         }
         public CompletableSynchronizedStorageSession AdaptedSession { get; private set; }
 
-        public void Dispose() => AdaptedSession?.Dispose();
+        public void Dispose()
+        {
+            if (disposed)
+            {
+                return;
+            }
+
+            AdaptedSession?.Dispose();
+            disposed = true;
+        }
 
         public Task CompleteAsync() => AdaptedSession.CompleteAsync();
 
@@ -37,6 +46,8 @@ public async Task<bool> TryOpen(TransportTransaction transportTransaction, Conte
 
         public async Task Open(ContextBag contextBag) => AdaptedSession = await synchronizedStorage.OpenSession(contextBag).ConfigureAwait(false);
 
+        bool disposed;
+
         readonly ISynchronizedStorageAdapter synchronizedStorageAdapter;
         readonly ISynchronizedStorage synchronizedStorage;
     }