Remove forced DispatchConsistency.Isolated for outbox operations

src/NServiceBus.Core.Tests/Reliability/Outbox/TransportReceiveToPhysicalMessageConnectorTests.cs

@@ -174,6 +174,25 @@ public async Task Should_not_add_batch_dispatch_events_when_no_batched_messages(
         }
     }
 
+    [Test]
+    public async Task Should_use_default_dispatch_consistency_when_dispatching_from_outbox()
+    {
+        var messageId = "id";
+        var properties = new DispatchProperties { ["Destination"] = "myEndpoint" };
+
+        fakeOutbox.ExistingMessage = new OutboxMessage(messageId, new[]
+        {
+            new NServiceBus.Outbox.TransportOperation("x", properties, Array.Empty<byte>(), [])
+        });
+
+        var context = CreateContext(fakeBatchPipeline, messageId);
+
+        await Invoke(context);
+
+        var operation = fakeBatchPipeline.TransportOperations.First();
+        Assert.That(operation.RequiredDispatchConsistency, Is.EqualTo(DispatchConsistency.Default));
+    }
+
     static TestableTransportReceiveContext CreateContext(FakeBatchPipeline pipeline, string messageId)
     {
         var context = new TestableTransportReceiveContext

src/NServiceBus.Core/NServiceBus.Core.csproj

@@ -32,7 +32,7 @@
     <TargetsForTfmSpecificContentInPackage>$(TargetsForTfmSpecificContentInPackage);AddPropsFileToPackage</TargetsForTfmSpecificContentInPackage>
   </PropertyGroup>
 
-  <ItemGroup Label="Remove this ItemGroup when FastExpressionCompiler stops included test code in the package">
+  <ItemGroup Label="Remove this ItemGroup when FastExpressionCompiler stops included test code in the package" Condition="'$(PkgFastExpressionCompiler_Internal_src)' != ''">
     <Compile Remove="$(PkgFastExpressionCompiler_Internal_src)\**\TestTools.cs" />
   </ItemGroup>
 

src/NServiceBus.Core/Pipeline/Incoming/TransportReceiveToPhysicalMessageConnector.cs

@@ -92,7 +92,7 @@ static void ConvertToPendingOperations(OutboxMessage deduplicationEntry, Pending
                     message,
                     DeserializeRoutingStrategy(operation.Options),
                     operation.Options,
-                    DispatchConsistency.Isolated
+                    DispatchConsistency.Default
                     ));
         }
     }

src/NServiceBus.Core/Reliability/Outbox/Outbox.cs

@@ -49,22 +49,20 @@ protected override void Setup(FeatureConfigurationContext context)
             return;
         }
 
-        // ForceBatchDispatchToBeIsolatedBehavior set the dispatch consistency to isolated which instructs
-        // the transport to not enlist the outgoing operation in the incoming message transaction. Unfortunately
-        // this is not enough. We cannot allow the transport to operate in SendsWithAtomicReceive because a transport
+        // We cannot allow the transport to operate in SendsWithAtomicReceive because a transport
         // might then only release the outgoing operations when the incoming transport transaction is committed meaning
         // the actual sends would happen after we have set the outbox record as dispatched and not as part of
         // TransportReceiveToPhysicalMessageConnector fork into the batched dispatched phase. Should acknowledging
         // the incoming operation fail and the message be retried we would already have cleared the outbox record's
-        // transport operations leading to outgoing message loss.
+        // transport operations leading to outgoing message loss. ReceiveOnly mode prevents outgoing messages from
+        // being enlisted in the receive transaction, so there's no need to force DispatchConsistency.Isolated.
         if (context.Settings.GetRequiredTransactionModeForReceives() != TransportTransactionMode.ReceiveOnly)
         {
             throw new Exception(
                 $"Outbox requires transport to be running in `{nameof(TransportTransactionMode.ReceiveOnly)}` mode. Use the `{nameof(TransportDefinition.TransportTransactionMode)}` property on the transport definition to specify the transaction mode.");
         }
 
         //note: in the future we should change the persister api to give us a "outbox factory" so that we can register it in DI here instead of relying on the persister to do it
-        context.Pipeline.Register("ForceBatchDispatchToBeIsolated", new ForceBatchDispatchToBeIsolatedBehavior(), "Makes sure that we dispatch straight to the transport so that we can safely set the outbox record to dispatched once the dispatch pipeline returns.");
     }
 
     internal const string TimeToKeepDeduplicationEntries = "Outbox.TimeToKeepDeduplicationEntries";