Feature json assetloading assethints (#4554)

* capture assets using SerializedAssetTracker in LoadInstanceFromPrefabDom()
assign assets using asset hints where the asset ID is not valid
switch up SerializedAssetTracker to store pointers instead of copies of Asset<>

Signed-off-by: jackalbe <23512001+jackalbe@users.noreply.github.com>

* PoC for the AssetFixUp strategy


Signed-off-by: jackalbe <23512001+jackalbe@users.noreply.github.com>

* clean up of PoC

Signed-off-by: jackalbe <23512001+jackalbe@users.noreply.github.com>

Code/Framework/AzCore/AzCore/Asset/AssetJsonSerializer.cpp

@@ -173,6 +173,7 @@ namespace AZ
 
             if (assetTracker)
             {
+                assetTracker->FixUpAsset(*instance);
                 assetTracker->AddAsset(*instance);
             }
 
@@ -185,7 +186,20 @@ namespace AZ
             return context.Report(result, message);
         }
 
-        void SerializedAssetTracker::AddAsset(Asset<AssetData>& asset)
+        void SerializedAssetTracker::SetAssetFixUp(AssetFixUp assetFixUpCallback)
+        {
+            m_assetFixUpCallback = AZStd::move(assetFixUpCallback);
+        }
+
+        void SerializedAssetTracker::FixUpAsset(Asset<AssetData>& asset)
+        {
+            if (m_assetFixUpCallback)
+            {
+                m_assetFixUpCallback(asset);
+            }
+        }
+
+        void SerializedAssetTracker::AddAsset(Asset<AssetData> asset)
         {
             m_serializedAssets.emplace_back(asset);
         }
@@ -199,5 +213,6 @@ namespace AZ
         {
             return m_serializedAssets;
         }
+
     } // namespace Data
 } // namespace AZ

Code/Framework/AzCore/AzCore/Asset/AssetJsonSerializer.h

@@ -39,13 +39,18 @@ namespace AZ
         {
         public:
             AZ_RTTI(SerializedAssetTracker, "{1E067091-8C0A-44B1-A455-6E97663F6963}");
+            using AssetFixUp = AZStd::function<void(Asset<AssetData>& asset)>;
 
-            void AddAsset(Asset<AssetData>& asset);
+            void SetAssetFixUp(AssetFixUp assetFixUpCallback);
+            void FixUpAsset(Asset<AssetData>& asset);
+
+            void AddAsset(Asset<AssetData> asset);
             AZStd::vector<Asset<AssetData>>& GetTrackedAssets();
             const AZStd::vector<Asset<AssetData>>& GetTrackedAssets() const;
 
         private:
             AZStd::vector<Asset<AssetData>> m_serializedAssets;
+            AssetFixUp m_assetFixUpCallback;
         };
     } // namespace Data
 } // namespace AZ

Code/Framework/AzToolsFramework/AzToolsFramework/Prefab/PrefabDomUtils.cpp

@@ -224,6 +224,7 @@ namespace AzToolsFramework
 
                     return false;
                 }
+
                 AZ::Data::SerializedAssetTracker* assetTracker = settings.m_metadata.Find<AZ::Data::SerializedAssetTracker>();
 
                 referencedAssets = AZStd::move(assetTracker->GetTrackedAssets());
@@ -245,6 +246,30 @@ namespace AzToolsFramework
                     entityIdMapper.SetEntityIdGenerationApproach(InstanceEntityIdMapper::EntityIdGenerationApproach::Random);
                 }
 
+                // some assets may come in from the JSON serialzier with no AssetID, but have an asset hint
+                // this attempts to fix up the assets using the assetHint field
+                auto fixUpInvalidAssets = [](AZ::Data::Asset<AZ::Data::AssetData>& asset)
+                {
+                    if (!asset.GetId().IsValid() && !asset.GetHint().empty())
+                    {
+                        AZ::Data::AssetId assetId;
+                        AZ::Data::AssetCatalogRequestBus::BroadcastResult(
+                            assetId,
+                            &AZ::Data::AssetCatalogRequestBus::Events::GetAssetIdByPath,
+                            asset.GetHint().c_str(),
+                            AZ::Data::s_invalidAssetType,
+                            false);
+
+                        if (assetId.IsValid())
+                        {
+                            asset.Create(assetId, true);
+                        }
+                    }
+                };
+
+                auto tracker = AZ::Data::SerializedAssetTracker{};
+                tracker.SetAssetFixUp(fixUpInvalidAssets);
+
                 AZ::JsonDeserializerSettings settings;
                 // The InstanceEntityIdMapper is registered twice because it's used in several places during deserialization where one is
                 // specific for the InstanceEntityIdMapper and once for the generic JsonEntityIdMapper. Because the Json Serializer's meta
@@ -252,16 +277,17 @@ namespace AzToolsFramework
                 settings.m_metadata.Add(static_cast<AZ::JsonEntityIdSerializer::JsonEntityIdMapper*>(&entityIdMapper));
                 settings.m_metadata.Add(&entityIdMapper);
                 settings.m_metadata.Create<InstanceEntityScrubber>(newlyAddedEntities);
+                settings.m_metadata.Add(tracker);
 
                 AZStd::string scratchBuffer;
                 auto issueReportingCallback = [&scratchBuffer](
-                                                  AZStd::string_view message, AZ::JsonSerializationResult::ResultCode result,
-                                                  AZStd::string_view path) -> AZ::JsonSerializationResult::ResultCode
+                    AZStd::string_view message, AZ::JsonSerializationResult::ResultCode result,
+                    AZStd::string_view path) -> AZ::JsonSerializationResult::ResultCode
                 {
                     return Internal::JsonIssueReporter(scratchBuffer, message, result, path);
                 };
                 settings.m_reporting = AZStd::move(issueReportingCallback);
-                
+
                 AZ::JsonSerializationResult::ResultCode result = AZ::JsonSerialization::Load(instance, prefabDom, settings);
 
                 AZ::Data::AssetManager::Instance().ResumeAssetRelease();