Update background activity invoker to only transport workflow-stored variables

src/modules/Elsa.Http/Activities/SendHttpRequest.cs

@@ -112,7 +112,7 @@ public class HttpStatusCodeCase
 /// <summary>
 /// Base class for activities that send HTTP requests.
 /// </summary>
-public abstract class SendHttpRequestBase : Activity<HttpResponse>
+public abstract class SendHttpRequestBase : Activity<HttpResponseMessage>
 {
     /// <summary>
     /// The URL to send the request to.

src/modules/Elsa.Http/Features/HttpFeature.cs

@@ -69,6 +69,7 @@ public class HttpFeature : FeatureBase
                 typeof(RouteData),
                 typeof(HttpRequest),
                 typeof(HttpResponse),
+                typeof(HttpResponseMessage),
                 typeof(HttpRequestHeaders)
             }, "HTTP");
 

src/modules/Elsa.Workflows.Runtime/Services/AmbientActivityContext.cs

@@ -1,18 +0,0 @@
-namespace Elsa.Workflows.Runtime.Services;
-
-/// <summary>
-/// Provides ambient context for activities.
-/// </summary>
-internal static class AmbientActivityContext
-{
-    private static readonly AsyncLocal<bool> IsDetachedState = new();
-
-    /// <summary>
-    /// Gets or sets a value indicating whether the current activity is detached.
-    /// </summary>
-    public static bool IsDetached
-    {
-        get => IsDetachedState.Value;
-        set => IsDetachedState.Value = value;
-    }
-}

src/modules/Elsa.Workflows.Runtime/Services/DefaultBackgroundActivityInvoker.cs

@@ -1,6 +1,7 @@
 using Elsa.Common.Models;
 using Elsa.Workflows.Core.Contracts;
 using Elsa.Workflows.Core.Models;
+using Elsa.Workflows.Core.Services;
 using Elsa.Workflows.Runtime.Contracts;
 using Elsa.Workflows.Runtime.Middleware.Activities;
 using Elsa.Workflows.Runtime.Models;
@@ -73,19 +74,38 @@ public class DefaultBackgroundActivityInvoker : IBackgroundActivityInvoker
         // Invoke the activity.
         await _activityInvoker.InvokeAsync(activityExecutionContext);
 
-        // Capture any activity output produced by the activity.
+        // Capture any activity output produced by the activity (but only if the associated memory block is stored in the workflow itself).
         var outputDescriptors = activityExecutionContext.ActivityDescriptor.Outputs;
         var outputValues = new Dictionary<string, object>();
 
         foreach (var outputDescriptor in outputDescriptors)
         {
             var output = (Output?)outputDescriptor.ValueGetter(activityExecutionContext.Activity);
-            var outputValue = output != null ? activityExecutionContext.Get(output.MemoryBlockReference()) : default!;
+            
+            if(output == null)
+                continue;
+
+            var memoryBlockReference = output.MemoryBlockReference();
+            
+            if(!activityExecutionContext.ExpressionExecutionContext.TryGetBlock(memoryBlockReference, out var memoryBlock))
+                continue;
+            
+            var variableMetadata = memoryBlock.Metadata as VariableBlockMetadata;
+            var driver = variableMetadata?.StorageDriverType;
+            
+            // We only capture output written to the workflow itself. Other drivers like blob storage, etc. will be ignored since the foreground context will be loading those.
+            if(driver != typeof(WorkflowStorageDriver))
+                continue;
+            
+            var outputValue = activityExecutionContext.Get(memoryBlockReference);
 
             if (outputValue != null)
                 outputValues[outputDescriptor.Name] = outputValue;
         }
 
+        // Persist any variables that were written to by the activity.
+        await _variablePersistenceManager.SaveVariablesAsync(workflowExecutionContext);
+        
         // Resume the workflow, passing along the activity output.
         // TODO: This approach will fail if the output is non-serializable. We need to find a way to pass the output to the workflow without serializing it.
         var bookmarkId = scheduledBackgroundActivity.BookmarkId;