Implemented shadergraph upgrade system using system data

com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/HDSubTarget.cs

@@ -14,7 +14,7 @@
 namespace UnityEditor.Rendering.HighDefinition.ShaderGraph
 {
     abstract class HDSubTarget : SubTarget<HDTarget>, IHasMetadata,
-        IRequiresData<SystemData>
+        IRequiresData<SystemData>, IVersionable<ShaderGraphVersion>
     {
         SystemData m_SystemData;
         protected bool m_MigrateFromOldCrossPipelineSG; // Use only for the migration to shader stack architecture
@@ -60,12 +60,36 @@ public virtual ScriptableObject GetMetadataObject()
             return hdMetadata;
         }
 
+        ShaderGraphVersion IVersionable<ShaderGraphVersion>.version
+        {
+            get => systemData.version;
+            set => systemData.version = value;
+        }
+
+        // Generate migration description steps to migrate HD shader targets
+        internal static MigrationDescription<ShaderGraphVersion, HDSubTarget> migrationSteps => MigrationDescription.New(
+            Enum.GetValues(typeof(ShaderGraphVersion)).Cast<ShaderGraphVersion>().Select(
+                version => MigrationStep.New(version, (HDSubTarget t) => t.MigrateTo(version))
+            ).ToArray()
+        );
+
+        /// <summary>
+        /// Override this method to handle migration in inherited subtargets
+        /// </summary>
+        /// <param name="version">The current version of the migration</param>
+        internal virtual void MigrateTo(ShaderGraphVersion version)
+        {
+        }
+
         public override void Setup(ref TargetSetupContext context)
         {
             context.AddAssetDependencyPath(AssetDatabase.GUIDToAssetPath("c09e6e9062cbd5a48900c48a0c2ed1c2")); // HDSubTarget.cs
             context.AddAssetDependencyPath(AssetDatabase.GUIDToAssetPath(subTargetAssetGuid));
             context.SetDefaultShaderGUI(customInspector);
 
+            if (migrationSteps.Migrate(this))
+                OnBeforeSerialize();
+
             foreach (var subShader in EnumerateSubShaders())
             {
                 // patch render type and render queue from pass declaration:

com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/ShaderGraphVersion.cs

@@ -0,0 +1,13 @@
+using System;
+using UnityEngine;
+using UnityEngine.Rendering;
+using UnityEngine.Rendering.HighDefinition;
+using UnityEngine.Serialization;
+
+namespace UnityEditor.Rendering.HighDefinition.ShaderGraph
+{
+    public enum ShaderGraphVersion
+    {
+        Initial = 0,
+    }
+}

com.unity.render-pipelines.high-definition/Editor/Material/ShaderGraph/TargetData/SystemData.cs

@@ -133,6 +133,14 @@ public bool dotsInstancing
             set => m_DOTSInstancing = value;
         }
 
+        [SerializeField]
+        ShaderGraphVersion m_Version = MigrationDescription.LastVersion<ShaderGraphVersion>();
+        public ShaderGraphVersion version
+        {
+            get => m_Version;
+            set => m_Version = value;
+        }
+
         internal int inspectorFoldoutMask;
     }