Fixing a crash when unparenting prefab instance in a new level

Signed-off-by: mnaumov <mnaumov@amazon.com>

Code/Framework/AzToolsFramework/AzToolsFramework/Entity/PrefabEditorEntityOwnershipService.cpp

@@ -202,7 +202,7 @@ namespace AzToolsFramework
         m_rootInstance->SetTemplateId(templateId);
         m_rootInstance->SetTemplateSourcePath(m_loaderInterface->GenerateRelativePath(filename));
         m_rootInstance->SetContainerEntityName("Level");
-        m_prefabSystemComponent->PropagateTemplateChanges(templateId);
+        m_prefabSystemComponent->PropagateTemplateChangesDown(templateId);
 
         return true;
     }

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabPublicHandler.cpp

@@ -482,22 +482,36 @@ namespace AzToolsFramework
             AZStd::unique_ptr<Instance>& sourceInstance, TemplateId targetTemplateId, UndoSystem::URSequencePoint* undoBatch)
         {
             LinkReference nestedInstanceLink = m_prefabSystemComponentInterface->FindLink(sourceInstance->GetLinkId());
-            AZ_Assert(
-                nestedInstanceLink.has_value(),
-                "A valid link was not found for one of the instances provided as input for the CreatePrefab operation.");    
+            if (!nestedInstanceLink)
+            {
+                AZ_Assert(
+                    false,
+                    "A valid link was not found for one of the instances provided as input for the CreatePrefab operation.");
+                return;
+            }
 
             PrefabDomReference nestedInstanceLinkDom = nestedInstanceLink->get().GetLinkDom();
-            AZ_Assert(
-                nestedInstanceLinkDom.has_value(),
-                "A valid DOM was not found for the link corresponding to one of the instances provided as input for the "
-                "CreatePrefab operation.");
+
+            if (!nestedInstanceLinkDom)
+            {
+                AZ_Assert(
+                    false,
+                    "A valid DOM was not found for the link corresponding to one of the instances provided as input for the "
+                    "CreatePrefab operation.");
+                return;
+            }
 
             PrefabDomValueReference nestedInstanceLinkPatches =
                 PrefabDomUtils::FindPrefabDomValue(nestedInstanceLinkDom->get(), PrefabDomUtils::PatchesName);
-            AZ_Assert(
-                nestedInstanceLinkPatches.has_value(),
-                "A valid DOM for patches was not found for the link corresponding to one of the instances provided as input for the "
-                "CreatePrefab operation.");
+
+            if (!nestedInstanceLinkPatches)
+            {
+                AZ_Assert(
+                    false,
+                    "A valid DOM for patches was not found for the link corresponding to one of the instances provided as input for the "
+                    "CreatePrefab operation.");
+                return;
+            }
 
             PrefabDom patchesCopyForUndoSupport;
             patchesCopyForUndoSupport.CopyFrom(nestedInstanceLinkPatches->get(), patchesCopyForUndoSupport.GetAllocator());

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabSystemComponent.cpp

@@ -153,6 +153,24 @@ namespace AzToolsFramework
             }
         }
 
+        void PrefabSystemComponent::PropagateTemplateChangesDown(TemplateId templateId, InstanceOptionalReference instanceToExclude)
+        {
+            PropagateTemplateChanges(templateId, instanceToExclude);
+
+            auto templateIterator = m_templateIdMap.find(templateId);
+            if (templateIterator != m_templateIdMap.end())
+            {
+                for (LinkId linkId : templateIterator->second.GetLinks())
+                {
+                    auto linkIterator = m_linkIdMap.find(linkId);
+                    if (linkIterator != m_linkIdMap.end())
+                    {
+                        PropagateTemplateChangesDown(linkIterator->second.GetSourceTemplateId(), instanceToExclude);
+                    }
+                }
+            }
+        }
+
         void PrefabSystemComponent::UpdatePrefabTemplate(TemplateId templateId, const PrefabDom& updatedDom)
         {
             auto templateToUpdate = FindTemplate(templateId);

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabSystemComponent.h

@@ -213,6 +213,8 @@ namespace AzToolsFramework
 
             void PropagateTemplateChanges(TemplateId templateId, InstanceOptionalReference instanceToExclude = AZStd::nullopt) override;
 
+            void PropagateTemplateChangesDown(TemplateId templateIdd, InstanceOptionalReference instanceToExclude = AZStd::nullopt) override;
+
             /**
              * Updates all Instances owned by a Template.
              *

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabSystemComponentInterface.h

@@ -53,6 +53,8 @@ namespace AzToolsFramework
             virtual PrefabDom& FindTemplateDom(TemplateId templateId) = 0;
             virtual void UpdatePrefabTemplate(TemplateId templateId, const PrefabDom& updatedDom) = 0;
             virtual void PropagateTemplateChanges(TemplateId templateId, InstanceOptionalReference instanceToExclude = AZStd::nullopt) = 0;
+            //! Propagates template changes recursively down to its dependents
+            virtual void PropagateTemplateChangesDown(TemplateId templateIdd, InstanceOptionalReference instanceToExclude = AZStd::nullopt) = 0;
 
             virtual AZStd::unique_ptr<Instance> InstantiatePrefab(AZ::IO::PathView filePath) = 0;
             virtual AZStd::unique_ptr<Instance> InstantiatePrefab(const TemplateId& templateId) = 0;