Add workflow cancellation notifications (#6075)

Introduced WorkflowCancelled and WorkflowCancelling notification records. Changed cancellation service to return a boolean instead of an integer. Integrated mediator notifications in the workflow canceler service.

src/modules/Elsa.MassTransit/Consumers/DispatchCancelWorkflowsRequestConsumer.cs

@@ -16,7 +16,6 @@ public class DispatchCancelWorkflowsRequestConsumer(IWorkflowRuntime workflowRun
     {
         var cancellationToken = context.CancellationToken;
         var request = context.Message;
-
         var client = await workflowRuntime.CreateClientAsync(request.WorkflowInstanceId, cancellationToken);
         await client.CancelAsync(cancellationToken);
     }

src/modules/Elsa.Workflows.Runtime/Contracts/IWorkflowCancellationService.cs

@@ -11,7 +11,7 @@ public interface IWorkflowCancellationService
     /// Cancels a workflow instance.
     /// </summary>
     /// <remarks>Also cancels all children</remarks>
-    Task<int> CancelWorkflowAsync(string workflowInstanceId, CancellationToken cancellationToken = default);
+    Task<bool> CancelWorkflowAsync(string workflowInstanceId, CancellationToken cancellationToken = default);
 
     /// <summary>
     /// Cancels workflow executions with the specified workflow instance ID.

src/modules/Elsa.Workflows.Runtime/Notifications/WorkflowCancelled.cs

@@ -0,0 +1,5 @@
+using Elsa.Mediator.Contracts;
+
+namespace Elsa.Workflows.Runtime.Notifications;
+
+public record WorkflowCancelled(string WorkflowInstanceId) : INotification;

src/modules/Elsa.Workflows.Runtime/Notifications/WorkflowCancelling.cs

@@ -0,0 +1,5 @@
+using Elsa.Mediator.Contracts;
+
+namespace Elsa.Workflows.Runtime.Notifications;
+
+public record WorkflowCancelling(string WorkflowInstanceId) : INotification;

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

@@ -1,39 +1,36 @@
+using Elsa.Mediator.Contracts;
 using Elsa.Workflows.Models;
 using Elsa.Workflows.Pipelines.WorkflowExecution;
 using Elsa.Workflows.Runtime.Middleware.Workflows;
+using Elsa.Workflows.Runtime.Notifications;
 using Elsa.Workflows.State;
 
 namespace Elsa.Workflows.Runtime;
 
 /// <inheritdoc />
-public class WorkflowCanceler(IWorkflowExecutionPipeline workflowExecutionPipeline, IWorkflowStateExtractor workflowStateExtractor, IServiceProvider serviceProvider) : IWorkflowCanceler
+public class WorkflowCanceler(
+    IWorkflowExecutionPipeline workflowExecutionPipeline, 
+    IWorkflowStateExtractor workflowStateExtractor, 
+    IMediator mediator, 
+    IServiceProvider serviceProvider) : IWorkflowCanceler
 {
     /// <inheritdoc />
     public async Task<WorkflowState> CancelWorkflowAsync(WorkflowGraph workflowGraph, WorkflowState workflowState, CancellationToken cancellationToken = default)
     {
         var workflowExecutionContext = await WorkflowExecutionContext.CreateAsync(serviceProvider, workflowGraph, workflowState, cancellationToken: cancellationToken);
-
-        // Alter the workflow execution context to cancel the workflow.
         await CancelWorkflowAsync(workflowExecutionContext, cancellationToken);
-        
-        // Map the workflow execution context back to a workflow state.
         return workflowStateExtractor.Extract(workflowExecutionContext);
     }
 
     /// <inheritdoc />
     public async Task CancelWorkflowAsync(WorkflowExecutionContext workflowExecutionContext, CancellationToken cancellationToken = default)
     {
-        // Build a new workflow execution pipeline.
+        await mediator.SendAsync(new WorkflowCancelling(workflowExecutionContext.Id), cancellationToken);
         var pipelineBuilder = new WorkflowExecutionPipelineBuilder(serviceProvider);
         workflowExecutionPipeline.ConfigurePipelineBuilder(pipelineBuilder);
-
-        // Replace the terminal DefaultActivitySchedulerMiddleware with the CancelWorkflowMiddleware terminal.
         pipelineBuilder.ReplaceTerminal<CancelWorkflowMiddleware>();
-
-        // Build modified pipeline.
         var pipeline = pipelineBuilder.Build();
-
-        // Execute the pipeline.
         await pipeline(workflowExecutionContext);
+        await mediator.SendAsync(new WorkflowCancelled(workflowExecutionContext.Id), cancellationToken);
     }
 }

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

@@ -15,7 +15,7 @@ public class WorkflowCancellationService(
     : IWorkflowCancellationService
 {
     /// <inheritdoc />
-    public async Task<int> CancelWorkflowAsync(string workflowInstanceId, CancellationToken cancellationToken = default)
+    public async Task<bool> CancelWorkflowAsync(string workflowInstanceId, CancellationToken cancellationToken = default)
     {
         var filter = new WorkflowInstanceFilter
         {
@@ -23,12 +23,11 @@ public class WorkflowCancellationService(
         };
         var instance = await workflowInstanceStore.FindAsync(filter, cancellationToken);
 
-        return instance == null
-            ? 0
-            : await CancelWorkflows(new List<WorkflowInstance>
-            {
-                instance
-            }, cancellationToken);
+        if(instance == null)
+            return false;
+            
+        await CancelWorkflows([instance], cancellationToken);
+        return true;
     }
 
     /// <inheritdoc />