From 7e38a5f35cbf99e0fd852bfc276b65cce0716a53 Mon Sep 17 00:00:00 2001
From: AMZN-koppersr <82230785+AMZN-koppersr@users.noreply.github.com>
Date: Wed, 8 Dec 2021 18:32:18 -0800
Subject: [PATCH] Fixed entity registration issue when setting up Spawnable
 Entity Aliases.

In some cases entities created for use as a Spawnable Entity Alias would share an entity id with their original. This is no longer working due to a reverse lookup from an entity id to its PrefabDOM. Upon further investigation this turned out to not matter as instances that are created by the PrefabCatchmentProcessor would create new entity ids any way. This cause unexpected behavior at runtime as entity relations may be broken. This will be addressed in a future fix.
Testing the above also highlighted a possible double delete in the builder when aliases were registered. This has also been fixed.

Signed-off-by: AMZN-koppersr <82230785+AMZN-koppersr@users.noreply.github.com>
---
 .../Prefab/Spawnable/PrefabProcessorContext.cpp       |  5 +++--
 .../Prefab/Spawnable/SpawnableUtils.cpp               | 11 ++++++-----
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/Spawnable/PrefabProcessorContext.cpp b/Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/Spawnable/PrefabProcessorContext.cpp
index ff32ac2ea5..d4fd785118 100644
--- a/Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/Spawnable/PrefabProcessorContext.cpp
+++ b/Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/Spawnable/PrefabProcessorContext.cpp
@@ -246,9 +246,10 @@ namespace AzToolsFramework::Prefab::PrefabConversionUtils
                 it = aliasVisitors.emplace(source->m_spawnable.GetId(), AZStd::move(visitor)).first;
             }
             it->second.AddAlias(
-                AZ::Data::Asset<AzFramework::Spawnable>(&target->m_spawnable, loadBehavior), alias.m_tag, sourceIndex, targetIndex,
+                AZ::Data::Asset<AzFramework::Spawnable>(target->m_spawnable.GetId(), azrtti_typeid<AzFramework::Spawnable>()), alias.m_tag,
+                sourceIndex, targetIndex,
                 alias.m_aliasType, alias.m_loadBehavior == EntityAliasSpawnableLoadBehavior::QueueLoad);
-
+            
             // Register the dependency between the two spawnables.
             RegisterProductAssetDependency(source->m_spawnable.GetId(), target->m_spawnable.GetId(), loadBehavior);
         }
diff --git a/Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/Spawnable/SpawnableUtils.cpp b/Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/Spawnable/SpawnableUtils.cpp
index 5e552aad3f..b51df104fe 100644
--- a/Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/Spawnable/SpawnableUtils.cpp
+++ b/Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/Spawnable/SpawnableUtils.cpp
@@ -86,7 +86,9 @@ namespace AzToolsFramework::Prefab::SpawnableUtils
                 entityData.has_value(), "SpawnbleUtils were unable to locate entity '%.*s' in Instance '%s' for replacing.",
                 AZ_STRING_ARG(alias), source.GetTemplateSourcePath().c_str());
             auto placeholder = AZStd::make_unique<AZ::Entity>(entityData->get().GetId(), entityData->get().GetName());
-            return instance->ReplaceEntity(AZStd::move(placeholder), alias);
+            AZStd::unique_ptr<AZ::Entity> result = instance->ReplaceEntity(AZStd::move(placeholder), alias);
+            result->SetId(AZ::Entity::MakeId());
+            return result;
         }
 
         AZStd::unique_ptr<AZ::Entity> ReplaceEntityWithPlaceholder(AZ::EntityId entityId, AzFramework::Spawnable& source)
@@ -102,7 +104,7 @@ namespace AzToolsFramework::Prefab::SpawnableUtils
                 aznumeric_cast<AZ::u64>(entityId));
 
             source.GetEntities()[index] = AZStd::make_unique<AZ::Entity>(original->GetId(), original->GetName());
-            
+            original->SetId(AZ::Entity::MakeId());
             return original;
         }
 
@@ -123,10 +125,9 @@ namespace AzToolsFramework::Prefab::SpawnableUtils
             case PCU::EntityAliasType::Replace:
                 return ResultPair(ReplaceEntityWithPlaceholder(entityId, source), AzFramework::Spawnable::EntityAliasType::Replace);
             case PCU::EntityAliasType::Additional:
-                ResultPair(AZStd::make_unique<AZ::Entity>(AZ::Entity::MakeId()), AzFramework::Spawnable::EntityAliasType::Additional);
+                ResultPair(AZStd::make_unique<AZ::Entity>(), AzFramework::Spawnable::EntityAliasType::Additional);
             case PCU::EntityAliasType::Merge:
-                // Use the same entity id as the original entity so at runtime the entity ids can be verified to match.
-                ResultPair(AZStd::make_unique<AZ::Entity>(entityId), AzFramework::Spawnable::EntityAliasType::Merge);
+                ResultPair(AZStd::make_unique<AZ::Entity>(), AzFramework::Spawnable::EntityAliasType::Merge);
             default:
                 AZ_Assert(
                     false, "Invalid PrefabProcessorContext::EntityAliasType type (%i) provided.", aznumeric_cast<uint64_t>(aliasType));