Enhance: Add isStart property to determine if current node is a start node. (#5040)

src/clients/Elsa.Api.Client/Resources/ActivityDescriptors/Models/ActivityDescriptor.cs

@@ -82,6 +82,11 @@ public record ActivityDescriptor
     /// </summary>
     public bool IsBrowsable { get; set; }
 
+    /// <summary>
+    /// Whether this activity type is a start activity.
+    /// </summary>
+    public bool IsStart { get; set; }
+    
     /// <summary>
     /// Whether this activity type is a terminal activity.
     /// </summary>

src/modules/Elsa.Workflows.Core/Activities/Start.cs

@@ -1,5 +1,6 @@
 using System.Runtime.CompilerServices;
 using Elsa.Workflows.Attributes;
+using Elsa.Workflows.Contracts;
 using JetBrains.Annotations;
 
 namespace Elsa.Workflows.Activities;
@@ -9,7 +10,7 @@ namespace Elsa.Workflows.Activities;
 /// </summary>
 [Activity("Elsa", "Flow", "A milestone activity that marks the start of a flowchart.", Kind = ActivityKind.Action)]
 [PublicAPI]
-public class Start : CodeActivity
+public class Start : CodeActivity, IStartNode
 {
     /// <inheritdoc />
     public Start([CallerFilePath] string? source = default, [CallerLineNumber] int? line = default) : base(source, line)

src/modules/Elsa.Workflows.Core/Contracts/IStartNode.cs

@@ -0,0 +1,8 @@
+namespace Elsa.Workflows.Contracts;
+
+/// <summary>
+/// Marks an activity as a terminal activity.
+/// </summary>
+public interface IStartNode
+{
+}

src/modules/Elsa.Workflows.Core/Models/ActivityDescriptor.cs

@@ -97,6 +97,11 @@ public class ActivityDescriptor
     /// </summary>
     public bool IsBrowsable { get; set; } = true;
 
+    /// <summary>
+    /// Whether this activity type is a start activity.
+    /// </summary>
+    public bool IsStart { get; set; }
+    
     /// <summary>
     /// Whether this activity type is a terminal activity.
     /// </summary>

src/modules/Elsa.Workflows.Core/Services/ActivityDescriber.cs

@@ -74,6 +74,7 @@ public class ActivityDescriber : IActivityDescriber
         var isTrigger = activityType.IsAssignableTo(typeof(ITrigger));
         var browsableAttr = activityType.GetCustomAttribute<BrowsableAttribute>();
         var isTerminal = activityType.FindInterfaces((type, criteria) => type == typeof(ITerminalNode), null).Any();
+        var isStart = activityType.FindInterfaces((type, criteria) => type == typeof(IStartNode), null).Any();
         var attributes = activityType.GetCustomAttributes(true).Cast<Attribute>().ToList();
         var outputAttribute = attributes.OfType<OutputAttribute>().FirstOrDefault();
 
@@ -92,6 +93,7 @@ public class ActivityDescriber : IActivityDescriber
             Outputs = (await DescribeOutputPropertiesAsync(outputProperties, cancellationToken)).ToList(),
             IsContainer = typeof(IContainer).IsAssignableFrom(activityType),
             IsBrowsable = browsableAttr == null || browsableAttr.Browsable,
+            IsStart = isStart,
             IsTerminal = isTerminal,
             Attributes = attributes,
             Constructor = context =>