Add version to TaskName

This commit adds an explict set for Version in TaskName. It also
includes a flag that is set so other code can determine if the
TaskName is intended to be versioned. Finally, it updates the
Version property in the TaskOrchestrationContext as that was always
set to empty instead of being able to be used.

Signed-off-by: halspang <[email protected]>

Author: halspang

src/Abstractions/TaskName.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
+using System;
+
 namespace Microsoft.DurableTask;
 
 /// <summary>
@@ -25,7 +27,31 @@ public TaskName(string name)
         else
         {
             this.Name = name;
-            this.Version = string.Empty; // expose setting Version only when we actually consume it.
+            this.Version = string.Empty;
+        }
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="TaskName"/> struct.
+    /// </summary>
+    /// <remarks>
+    /// This <c>TaskName</c> is explicitly versioned, as compared to the default value.
+    /// </remarks>
+    /// <param name="name">The name of the task. Providing <c>null</c> will yield the default struct, ignoring the version.</param>
+    /// <param name="version">Optional. The version of the task. Providing <c>null</c> will yield the default value.</param>
+    public TaskName(string name, string version)
+    {
+        if (name is null)
+        {
+            // Force the default struct when null is passed in.
+            this.Name = null!;
+            this.Version = null!;
+        }
+        else
+        {
+            this.IsVersioned = true;
+            this.Name = name;
+            this.Version = version == null ? null! : version;
         }
     }
 
@@ -46,6 +72,14 @@ public TaskName(string name)
     /// </remarks>
     public string Version { get; }
 
+    /// <summary>
+    /// Gets the flag denoting if this TaskName is versioned.
+    /// </summary>
+    /// <remarks>
+    /// This flag is used to distinguish between the default (empty version) and a Task with an explicit empty version.
+    /// </remarks>
+    public bool IsVersioned { get; } = false;
+
     /// <summary>
     /// Implicitly converts a <see cref="TaskName"/> into a <see cref="string"/> of the <see cref="Name"/> property value.
     /// </summary>

src/Abstractions/TaskOrchestrationContext.cs

@@ -61,9 +61,9 @@ public abstract class TaskOrchestrationContext
     public abstract bool IsReplaying { get; }
 
     /// <summary>
-    /// Gets the version of the current orchestration instance, which was set when the instance was created.
+    /// Gets or sets the version of the current orchestration instance, which was set when the instance was created.
     /// </summary>
-    public virtual string Version => string.Empty;
+    public virtual string Version { get; protected internal set; } = string.Empty;
 
     /// <summary>
     /// Gets the entity feature, for interacting with entities.