Fix errors & black screen when resetting active URP Asset from UI

Author: arttu-peltonen

Packages/com.unity.render-pipelines.universal/Runtime/Data/UniversalRenderPipelineAsset.cs

@@ -699,6 +699,18 @@ public partial class UniversalRenderPipelineAsset : RenderPipelineAsset<Universa
 #if UNITY_EDITOR
         public static readonly string packagePath = "Packages/com.unity.render-pipelines.universal";
 
+        internal void Reset()
+        {
+            // If the asset path is valid, it means we are explicitly resetting an existing asset, so we will create
+            // a new default renderer asset to avoid errors. If the path is invalid, it means we are creating a new asset
+            // for which the default renderer is provided through UniversalRenderPipelineAsset.Create.
+            string path = AssetDatabase.GetAssetPath(this);
+            if (!string.IsNullOrEmpty(path))
+            {
+                m_RendererDataList[0] = CreateRendererAsset(path, m_RendererType);
+            }
+        }
+
         public static UniversalRenderPipelineAsset Create(ScriptableRendererData rendererData = null)
         {
             // Create Universal RP Asset

Packages/com.unity.render-pipelines.universal/Runtime/UniversalAdditionalCameraData.cs

@@ -671,8 +671,9 @@ public ScriptableRenderer scriptableRenderer
                 if (!UniversalRenderPipeline.asset.ValidateRendererData(m_RendererIndex))
                 {
                     int defaultIndex = UniversalRenderPipeline.asset.m_DefaultRendererIndex;
+                    var defaultRendererData = UniversalRenderPipeline.asset.m_RendererDataList[defaultIndex];
                     Debug.LogWarning(
-                        $"Renderer at <b>index {m_RendererIndex.ToString()}</b> is missing for camera <b>{camera.name}</b>, falling back to Default Renderer. <b>{UniversalRenderPipeline.asset.m_RendererDataList[defaultIndex].name}</b>",
+                        $"Renderer at <b>index {m_RendererIndex.ToString()}</b> is missing for camera <b>{camera.name}</b>, falling back to Default Renderer. <b>{defaultRendererData?.name}</b>",
                         UniversalRenderPipeline.asset);
                     return UniversalRenderPipeline.asset.GetRenderer(defaultIndex);
                 }

Packages/com.unity.render-pipelines.universal/Tests/Editor/EditorTests.cs

@@ -121,6 +121,27 @@ public void ValidateAssetSettings()
         ScriptableObject.DestroyImmediate(data);
     }
 
+    [Test]
+    public void ValidateDefaultRendererAfterReset()
+    {
+        UniversalRendererData data = ScriptableObject.CreateInstance<UniversalRendererData>();
+        UniversalRenderPipelineAsset asset = UniversalRenderPipelineAsset.Create(data);
+        const string kTempDir = "Assets/ValidateDefaultRendererAfterReset";
+        string assetPath = $"{kTempDir}/URPAsset.asset";
+        CoreUtils.EnsureFolderTreeInAssetFilePath(assetPath);
+        AssetDatabase.CreateAsset(asset, assetPath);
+        AssetDatabase.SaveAssets();
+        string path = AssetDatabase.GetAssetPath(asset);
+        Assume.That(!string.IsNullOrEmpty(path));
+
+        Assert.NotNull(asset.m_RendererDataList[asset.m_DefaultRendererIndex]);
+        Unsupported.SmartReset(asset);// will create a new default renderer data
+        Assert.NotNull(asset.m_RendererDataList[asset.m_DefaultRendererIndex]);
+
+        ScriptableObject.DestroyImmediate(data);
+        AssetDatabase.DeleteAsset(kTempDir);
+    }
+
     // When working with SpeedTree v7 assets, UniversalSpeedTree8Upgrader should not throw exception
     [Test]
     public void UniversalSpeedTree8Upgrader_ShouldntThrowExceptionWhenImportingSpeedTree7Assets()