Added VariableExpression (#217)

* Add VariableExpression

* Workflow Runner bug fixes

src/activities/Elsa.Activities.Console/Activities/ReadLine.cs

@@ -33,7 +33,7 @@ namespace Elsa.Activities.Console.Activities
         protected override async Task<IActivityExecutionResult> OnExecuteAsync(ActivityExecutionContext context, CancellationToken cancellationToken)
         {
             if (input == null)
-                return Halt();
+                return Suspend();
 
             var receivedInput = await input.ReadLineAsync();
             return Execute(receivedInput);

src/activities/Elsa.Activities.Http/Activities/ReceiveHttpRequest.cs

@@ -85,7 +85,7 @@ namespace Elsa.Activities.Http.Activities
 
         protected override IActivityExecutionResult OnExecute(ActivityExecutionContext context)
         {
-            return Halt(true);
+            return Suspend(true);
         }
 
         protected override async Task<IActivityExecutionResult> OnResumeAsync(ActivityExecutionContext context, CancellationToken cancellationToken)

src/activities/Elsa.Activities.MassTransit/Activities/ReceiveMassTransitMessage.cs

@@ -30,7 +30,7 @@ namespace Elsa.Activities.MassTransit.Activities
         }
 
         protected override bool OnCanExecute(ActivityExecutionContext context) => context.Input.Value?.GetType() == MessageType;
-        protected override IActivityExecutionResult OnExecute(ActivityExecutionContext context) => Halt(true);
+        protected override IActivityExecutionResult OnExecute(ActivityExecutionContext context) => Suspend(true);
 
         protected override Task<IActivityExecutionResult> OnResumeAsync(ActivityExecutionContext context, CancellationToken cancellationToken)
         {

src/activities/Elsa.Activities.Timers/Activities/CronEvent.cs

@@ -44,7 +44,7 @@ namespace Elsa.Activities.Timers.Activities
 
         protected override IActivityExecutionResult OnExecute(ActivityExecutionContext workflowContext)
         {
-            return Halt();
+            return Suspend();
         }
 
         protected override async Task<IActivityExecutionResult> OnResumeAsync(ActivityExecutionContext context, CancellationToken cancellationToken)
@@ -55,7 +55,7 @@ namespace Elsa.Activities.Timers.Activities
                 return Done();
             }
 
-            return Halt();
+            return Suspend();
         }
 
         private async Task<bool> IsExpiredAsync(ActivityExecutionContext context, CancellationToken cancellationToken)

src/activities/Elsa.Activities.Timers/Activities/InstantEvent.cs

@@ -38,14 +38,14 @@ namespace Elsa.Activities.Timers.Activities
         {
             var isExpired = await IsExpiredAsync(context, cancellationToken);
 
-            return isExpired ? (IActivityExecutionResult)Done() : Halt();
+            return isExpired ? (IActivityExecutionResult)Done() : Suspend();
         }
 
         protected override async Task<IActivityExecutionResult> OnResumeAsync(ActivityExecutionContext context, CancellationToken cancellationToken)
         {
             var isExpired = await IsExpiredAsync(context, cancellationToken);
 
-            return isExpired ? (IActivityExecutionResult)Done() : Halt();
+            return isExpired ? (IActivityExecutionResult)Done() : Suspend();
         }
 
         private async Task<bool> IsExpiredAsync(ActivityExecutionContext workflowContext, CancellationToken cancellationToken)

src/activities/Elsa.Activities.Timers/Activities/TimerEvent.cs

@@ -42,7 +42,7 @@ namespace Elsa.Activities.Timers.Activities
 
         protected override IActivityExecutionResult OnExecute(ActivityExecutionContext context)
         {
-            return Halt();
+            return Suspend();
         }
 
         protected override async Task<IActivityExecutionResult> OnResumeAsync(ActivityExecutionContext context, CancellationToken cancellationToken)
@@ -53,7 +53,7 @@ namespace Elsa.Activities.Timers.Activities
                 return Done();
             }
             
-            return Halt();
+            return Suspend();
         }
 
         private async Task<bool> IsExpiredAsync(ActivityExecutionContext context, CancellationToken cancellationToken)

src/activities/Elsa.Activities.Timers/HostedServices/TimersHostedService.cs

@@ -35,13 +35,11 @@ namespace Elsa.Activities.Timers.HostedServices
             {
                 try
                 {
-                    using (var scope = serviceProvider.CreateScope())
-                    {
-                        var workflowInvoker = scope.ServiceProvider.GetRequiredService<IWorkflowRunner>(); 
-                        await workflowInvoker.TriggerAsync(nameof(TimerEvent), Variables.Empty, stoppingToken);
-                        await workflowInvoker.TriggerAsync(nameof(CronEvent), Variables.Empty, stoppingToken);
-                        await workflowInvoker.TriggerAsync(nameof(InstantEvent), Variables.Empty, stoppingToken);
-                    }
+                    using var scope = serviceProvider.CreateScope();
+                    var workflowInvoker = scope.ServiceProvider.GetRequiredService<IWorkflowRunner>(); 
+                    await workflowInvoker.TriggerAsync(nameof(TimerEvent), cancellationToken: stoppingToken);
+                    await workflowInvoker.TriggerAsync(nameof(CronEvent), cancellationToken:stoppingToken);
+                    await workflowInvoker.TriggerAsync(nameof(InstantEvent), cancellationToken: stoppingToken);
                 }
                 catch (Exception ex)
                 {

src/activities/Elsa.Activities.UserTask/Activities/UserTask.cs

@@ -35,7 +35,7 @@ namespace Elsa.Activities.UserTask.Activities
 
         protected override IActivityExecutionResult OnExecute(ActivityExecutionContext context)
         {
-            return Halt(true);
+            return Suspend(true);
         }
 
         protected override IActivityExecutionResult OnResume(ActivityExecutionContext context)

src/activities/Elsa.Activities.Workflows/Activities/Correlate.cs

@@ -18,7 +18,7 @@ namespace Elsa.Activities.Workflows.Activities
     public class Correlate : Activity
     {
         [ActivityProperty(Hint = "An expression that evaluates to the value to store as the correlation ID.")]
-        public IWorkflowExpression<string> ValueScriptExpression
+        public IWorkflowExpression<string> Value
         {
             get => GetState<IWorkflowExpression<string>>();
             set => SetState(value);
@@ -26,7 +26,7 @@ namespace Elsa.Activities.Workflows.Activities
 
         protected override async Task<IActivityExecutionResult> OnExecuteAsync(ActivityExecutionContext context, CancellationToken cancellationToken)
         {
-            var value = await context.EvaluateAsync(ValueScriptExpression, cancellationToken);
+            var value = await context.EvaluateAsync(Value, cancellationToken);
             context.WorkflowExecutionContext.Workflow.CorrelationId = value;
             return Done();
         }

src/activities/Elsa.Activities.Workflows/Activities/Signaled.cs

@@ -32,7 +32,7 @@ namespace Elsa.Activities.Workflows.Activities
 
         protected override IActivityExecutionResult OnExecute(ActivityExecutionContext context)
         {
-            return Halt(true);
+            return Suspend(true);
         }
 
         protected override IActivityExecutionResult OnResume(ActivityExecutionContext context)

src/core/Elsa.Abstractions/Services/Extensions/WorkflowInvokerExtensions.cs

@@ -12,7 +12,7 @@ namespace Elsa.Services.Extensions
         public static Task TriggerAsync(
             this IWorkflowRunner workflowRunner,
             string activityType,
-            Variables input,
+            Variable input,
             CancellationToken cancellationToken = default)
         {
             return workflowRunner.TriggerAsync(activityType, input, cancellationToken: cancellationToken);

src/core/Elsa.Abstractions/Services/Models/WorkflowBlueprint.cs

@@ -17,6 +17,8 @@ namespace Elsa.Services.Models
             bool isDisabled = false,
             string? name =  default,
             string? description = default,
+            bool isLatest = false,
+            bool isPublished = false,
             IEnumerable<IActivity>? activities = default, 
             IEnumerable<Connection>? connections = default)
         {
@@ -24,6 +26,8 @@ namespace Elsa.Services.Models
             Version = version;
             IsSingleton = isSingleton;
             IsDisabled = isDisabled;
+            IsLatest = isLatest;
+            IsPublished = isPublished;
             Name = name;
             Description = description;
             Activities = activities?.ToList() ?? new List<IActivity>();

src/core/Elsa.Core/Expressions/VariableExpression.cs

@@ -0,0 +1,24 @@
+using System;
+using Elsa.Services.Models;
+
+namespace Elsa.Expressions
+{
+    public class VariableExpression : WorkflowExpression
+    {
+        public static string ExpressionType => "Variable";
+
+        public VariableExpression(string variableName, Type returnType) : base(ExpressionType, returnType)
+        {
+            VariableName = variableName;
+        }
+
+        public string VariableName { get; }
+    }
+
+    public class VariableExpression<T> : VariableExpression, IWorkflowExpression<T>
+    {
+        public VariableExpression(string variableName) : base(variableName, typeof(T))
+        {
+        }
+    }
+}

src/core/Elsa.Core/Expressions/VariableHandler.cs

@@ -0,0 +1,21 @@
+using System.Threading;
+using System.Threading.Tasks;
+using Elsa.Services.Models;
+
+namespace Elsa.Expressions
+{
+    public class VariableHandler : IWorkflowExpressionHandler
+    {
+        public string Type => VariableExpression.ExpressionType;
+
+        public Task<object> EvaluateAsync(
+            IWorkflowExpression expression,
+            ActivityExecutionContext context,
+            CancellationToken cancellationToken)
+        {
+            var variableExpression = (VariableExpression)expression;
+            var result = context.GetVariable(variableExpression.VariableName);
+            return Task.FromResult(result);
+        }
+    }
+}

src/core/Elsa.Core/Extensions/ElsaServiceCollectionExtensions.cs

@@ -75,6 +75,7 @@ namespace Microsoft.Extensions.DependencyInjection
                 .TryAddProvider<ITokenFormatter, XmlTokenFormatter>(ServiceLifetime.Singleton)
                 .TryAddProvider<IWorkflowExpressionHandler, LiteralHandler>(ServiceLifetime.Singleton)
                 .TryAddProvider<IWorkflowExpressionHandler, CodeHandler>(ServiceLifetime.Singleton)
+                .TryAddProvider<IWorkflowExpressionHandler, VariableHandler>(ServiceLifetime.Singleton)
                 .AddTransient<IWorkflowFactory, WorkflowFactory>()
                 .AddScoped<IActivityInvoker, ActivityInvoker>()
                 .AddScoped<IWorkflowExpressionEvaluator, WorkflowExpressionEvaluator>()

src/core/Elsa.Core/Messages/Handlers/PersistenceWorkflowEventHandler.cs

@@ -40,8 +40,11 @@ namespace Elsa.Messages.Handlers
         
         public async Task Handle(WorkflowCompleted notification, CancellationToken cancellationToken)
         {
-            if (notification.Workflow.Blueprint.DeleteCompletedWorkflows)
-                await workflowInstanceStore.DeleteAsync(notification.Workflow.Id, cancellationToken);
+            var workflow = notification.Workflow;
+            var blueprint = workflow.Blueprint;
+            
+            if (blueprint.DeleteCompletedWorkflows || blueprint.PersistenceBehavior == WorkflowPersistenceBehavior.Suspended)
+                await workflowInstanceStore.DeleteAsync(workflow.Id, cancellationToken);
         }
 
         private async Task SaveWorkflowAsync(Workflow workflow, CancellationToken cancellationToken)

src/core/Elsa.Core/Persistence/Memory/MemoryWorkflowInstanceStore.cs

@@ -51,7 +51,7 @@ namespace Elsa.Persistence.Memory
         {
             var query = workflowInstances.Values.AsQueryable();
 
-            query = query.Where(x => x.Status == WorkflowStatus.Running);
+            query = query.Where(x => x.Status == WorkflowStatus.Suspended);
 
             if (!string.IsNullOrWhiteSpace(correlationId))
                 query = query.Where(x => x.CorrelationId == correlationId);

src/core/Elsa.Core/Services/Activity.cs

@@ -8,7 +8,7 @@ namespace Elsa.Services
 {
     public abstract class Activity : ActivityBase
     {
-        protected SuspendWorkflowResult Halt(bool continueOnFirstPass = false) => new SuspendWorkflowResult(continueOnFirstPass);
+        protected SuspendWorkflowResult Suspend(bool continueOnFirstPass = false) => new SuspendWorkflowResult(continueOnFirstPass);
         protected OutcomeResult Outcomes(IEnumerable<string> names) => new OutcomeResult(names);
         protected OutcomeResult Outcome(string name) => Outcomes(new[] { name });
         protected OutcomeResult Outcome(string name, object output) => Outcome(name, Variable.From(output));

src/core/Elsa.Core/Services/WorkflowFactory.cs

@@ -36,12 +36,22 @@ namespace Elsa.Services
             var workflowDefinition = workflowBuilder().Build<T>();
             return CreateWorkflow(workflowDefinition, input, workflowInstance, correlationId);
         }
-        
+
         public WorkflowBlueprint CreateWorkflowBlueprint(WorkflowDefinitionVersion definition)
         {
             var activities = CreateActivities(definition.Activities).ToList();
             var connections = CreateConnections(definition.Connections, activities).ToList();
-            return new WorkflowBlueprint(definition.DefinitionId, definition.Version, definition.IsSingleton, definition.IsDisabled, definition.Name, definition.Description, activities, connections);
+            return new WorkflowBlueprint(
+                definition.DefinitionId,
+                definition.Version,
+                definition.IsSingleton,
+                definition.IsDisabled,
+                definition.Name,
+                definition.Description,
+                definition.IsLatest,
+                definition.IsPublished,
+                activities,
+                connections);
         }
 
         public Workflow CreateWorkflow(
@@ -52,7 +62,7 @@ namespace Elsa.Services
         {
             if (blueprint.IsDisabled)
                 throw new InvalidOperationException("Cannot instantiate disabled workflow definitions.");
-            
+
             var id = idGenerator.Generate();
             var workflow = new Workflow(
                 id,

src/core/Elsa.Core/Services/WorkflowRunner.cs

@@ -318,15 +318,13 @@ namespace Elsa.Services
                     ? await ExecuteActivityAsync(workflowExecutionContext, scheduledActivity, cancellationToken)
                     : await ResumeActivityAsync(workflowExecutionContext, scheduledActivity, cancellationToken);
 
-                workflowExecutionContext.IsFirstPass = false;
-                start = true;
-
                 await mediator.Publish(new ActivityExecuted(workflow, activity), cancellationToken);
                 
-                if (result == null)
-                    break;
-
-                await result.ExecuteAsync(this, workflowExecutionContext, cancellationToken);
+                if (result != null)
+                    await result.ExecuteAsync(this, workflowExecutionContext, cancellationToken);
+                
+                workflowExecutionContext.IsFirstPass = false;
+                start = true;
             }
             
             // Determine new workflow state.
@@ -470,7 +468,7 @@ namespace Elsa.Services
             {
                 var instances = await workflowInstanceStore.ListByStatusAsync(
                     definition.Item1.DefinitionId,
-                    WorkflowStatus.Running,
+                    WorkflowStatus.Suspended,
                     cancellationToken
                 );
 

src/core/Elsa.Core/WorkflowBuilders/WorkflowBuilder.cs

@@ -135,7 +135,7 @@ namespace Elsa.WorkflowBuilders
             var connections = CreateConnections(connectionDefinitions, activities);
             var definitionId = !string.IsNullOrWhiteSpace(Id) ? Id : idGenerator.Generate();
 
-            return new WorkflowBlueprint(definitionId, Version, IsSingleton, IsDisabled, Name, Description, activities, connections);
+            return new WorkflowBlueprint(definitionId, Version, IsSingleton, IsDisabled, Name, Description, true, true, activities, connections);
         }
         
         private IEnumerable<Connection> CreateConnections(IEnumerable<ConnectionDefinition> connectionDefinitions, IEnumerable<IActivity> activities)

src/samples/Sample02/Program.cs

@@ -25,7 +25,7 @@ namespace Sample02
             var workflowBuilderFactory = services.GetRequiredService<Func<IWorkflowBuilder>>();
             var workflowBuilder = workflowBuilderFactory();
             var workflowBlueprint = workflowBuilder
-                .StartWith<WriteLine>(x => x.Text = new LiteralExpression<string>("Hello world!"))
+                .StartWith<WriteLine>(x => x.Text = new CodeExpression<string>(() => "Hello world!"))
                 .Then(() => Console.WriteLine("Look, custom code!"))
                 .Then<WriteLine>(x => x.Text = new LiteralExpression<string>("Goodbye cruel world..."))
                 .Build();

src/samples/Sample05/RecurringWorkflow.cs

@@ -16,7 +16,7 @@ namespace Sample05
                 .WithId("RecurringWorkflow")
                 .AsSingleton()
                 .StartWith<TimerEvent>(x => x.TimeoutScriptExpression = new LiteralExpression<TimeSpan>("00:00:05"))
-                .Then<WriteLine>(x => x.Text = new JavaScriptExpression<string>("`Trigger received. The time is: ${new Date().toISOString()}`"));
+                .Then<WriteLine>(x => x.Text = new CodeExpression<string>(context => $"Trigger received. The time is: {DateTime.UtcNow.ToLocalTime()}"));
         }
     }
 }

src/samples/Sample08/Workflows/CreateOrderWorkflow.cs

@@ -37,7 +37,7 @@ namespace Sample08.Workflows
                 )
                 // Need to ensure that the correlation ID is the same string format that is used by the WorkflowConsumer<T>
                 // MassTransit will always use Guid values for correlation ID's, so need to ensure the same string format is used.
-                .Then<Correlate>(activity => activity.ValueScriptExpression = new JavaScriptExpression<string>("newGuid()"))
+                .Then<Correlate>(activity => activity.Value = new CodeExpression<string>(() => Guid.NewGuid().ToString()))
                 .Then<SendMassTransitMessage>(activity =>
                     {
                         activity.Message = new JavaScriptExpression<CreateOrder>("return { correlationId: correlationId(), order: order};");

src/samples/Sample13/Program.cs

@@ -8,7 +8,7 @@ using Microsoft.Extensions.DependencyInjection;
 namespace Sample13
 {
     /// <summary>
-    /// A strongly-typed workflows program demonstrating scripting, and branching.
+    /// A strongly-typed workflows program demonstrating scripting and branching.
     /// </summary>
     internal class Program
     {