Add option to fetch lightweight objects to reduce app hangs (#15774)

Author: itsmeichigo

Modules/Sources/Yosemite/Model/Storage/Order+ReadOnlyConvertible.swift

@@ -123,6 +123,51 @@ extension Storage.Order: ReadOnlyConvertible {
 
     }
 
+    /// Returns a lightweight ReadOnly version of the receiver without any relationships populated.
+    ///
+    public func toLightweightReadOnly() -> Yosemite.Order {
+        Order(siteID: siteID,
+              orderID: orderID,
+              parentID: parentID,
+              customerID: customerID,
+              orderKey: orderKey,
+              isEditable: isEditable,
+              needsPayment: needsPayment,
+              needsProcessing: needsPayment,
+              number: number ?? "",
+              status: OrderStatusEnum(rawValue: statusKey),
+              currency: currency ?? "",
+              currencySymbol: "", // Not stored in the Storage Layer, only used in the notifications extension.
+              customerNote: customerNote ?? "",
+              dateCreated: dateCreated ?? Date(),
+              dateModified: dateModified ?? Date(),
+              datePaid: datePaid,
+              discountTotal: discountTotal ?? "",
+              discountTax: discountTax ?? "",
+              shippingTotal: shippingTotal ?? "",
+              shippingTax: shippingTax ?? "",
+              total: total ?? "",
+              totalTax: totalTax ?? "",
+              paymentMethodID: paymentMethodID ?? "",
+              paymentMethodTitle: paymentMethodTitle ?? "",
+              paymentURL: paymentURL as URL?,
+              chargeID: chargeID,
+              items: [],
+              billingAddress: createReadOnlyBillingAddress(),
+              shippingAddress: createReadOnlyShippingAddress(),
+              shippingLines: [],
+              coupons: [],
+              refunds: [],
+              fees: [],
+              taxes: [],
+              customFields: [],
+              renewalSubscriptionID: renewalSubscriptionID,
+              appliedGiftCards: [],
+              attributionInfo: attributionInfo?.toReadOnly(),
+              shippingLabels: [])
+
+    }
+
 
     // MARK: - Private Helpers
 

Modules/Sources/Yosemite/Model/Storage/Product+ReadOnlyConvertible.swift

@@ -200,6 +200,93 @@ extension Storage.Product: ReadOnlyConvertible {
                        customFields: productCustomFields.sorted { $0.metadataID < $1.metadataID })
     }
 
+    /// Returns a lightweight ReadOnly version of the receiver.
+    /// No relationships are populated except for images.
+    ///
+    public func toLightweightReadOnly() -> Yosemite.Product {
+
+        let productImages = imagesArray.map { $0.toReadOnly() }
+
+        return Product(siteID: siteID,
+                       productID: productID,
+                       name: name,
+                       slug: slug,
+                       permalink: permalink,
+                       date: date ?? Date(timeIntervalSince1970: 0),
+                       dateCreated: dateCreated ?? Date(timeIntervalSince1970: 0),
+                       dateModified: dateModified,
+                       dateOnSaleStart: dateOnSaleStart,
+                       dateOnSaleEnd: dateOnSaleEnd,
+                       productTypeKey: productTypeKey,
+                       statusKey: statusKey,
+                       featured: featured,
+                       catalogVisibilityKey: catalogVisibilityKey,
+                       fullDescription: fullDescription,
+                       shortDescription: briefDescription,
+                       sku: sku,
+                       globalUniqueID: globalUniqueID,
+                       price: price,
+                       regularPrice: regularPrice,
+                       salePrice: salePrice,
+                       onSale: onSale,
+                       purchasable: purchasable,
+                       totalSales: Int(totalSales),
+                       virtual: virtual,
+                       downloadable: downloadable,
+                       downloads: [],
+                       downloadLimit: downloadLimit,
+                       downloadExpiry: downloadExpiry,
+                       buttonText: buttonText,
+                       externalURL: externalURL,
+                       taxStatusKey: taxStatusKey,
+                       taxClass: taxClass,
+                       manageStock: manageStock,
+                       stockQuantity: nil,
+                       stockStatusKey: stockStatusKey,
+                       backordersKey: backordersKey,
+                       backordersAllowed: backordersAllowed,
+                       backordered: backordered,
+                       soldIndividually: soldIndividually,
+                       weight: weight,
+                       dimensions: createReadOnlyDimensions(),
+                       shippingRequired: shippingRequired,
+                       shippingTaxable: shippingTaxable,
+                       shippingClass: shippingClass,
+                       shippingClassID: shippingClassID,
+                       productShippingClass: nil,
+                       reviewsAllowed: reviewsAllowed,
+                       averageRating: averageRating,
+                       ratingCount: Int(ratingCount),
+                       relatedIDs: convertIDArray(relatedIDs),
+                       upsellIDs: convertIDArray(upsellIDs),
+                       crossSellIDs: convertIDArray(crossSellIDs),
+                       parentID: parentID,
+                       purchaseNote: purchaseNote,
+                       categories: [],
+                       tags: [],
+                       images: productImages,
+                       attributes: [],
+                       defaultAttributes: [],
+                       variations: variations ?? [],
+                       groupedProducts: groupedProducts ?? [],
+                       menuOrder: Int(menuOrder),
+                       addOns: [],
+                       isSampleItem: isSampleItem,
+                       bundleStockStatus: nil,
+                       bundleStockQuantity: bundleStockQuantity as? Int64,
+                       bundleMinSize: bundleMinSize?.decimalValue,
+                       bundleMaxSize: bundleMaxSize?.decimalValue,
+                       bundledItems: [],
+                       password: password,
+                       compositeComponents: [],
+                       subscription: subscription?.toReadOnly(),
+                       minAllowedQuantity: minAllowedQuantity,
+                       maxAllowedQuantity: maxAllowedQuantity,
+                       groupOfQuantity: groupOfQuantity,
+                       combineVariationQuantities: combineVariationQuantities?.boolValue,
+                       customFields: [])
+    }
+
     // MARK: - Private Helpers
 
     private func createReadOnlyDimensions() -> Yosemite.ProductDimensions {

Modules/Sources/Yosemite/SnapshotsProvider/FetchResultSnapshotsProvider.swift

@@ -179,6 +179,16 @@ public final class FetchResultSnapshotsProvider<MutableType: FetchResultSnapshot
             return nil
         }
     }
+
+    /// The lightweight version of `object(withID:)` method. Returns readonly objects without relationships.
+    ///
+    public func lightweightObject(withID objectID: FetchResultSnapshotObjectID) -> MutableType.ReadOnlyType? {
+        if let storageOrder = storage.loadObject(ofType: MutableType.self, with: objectID) {
+            return storageOrder.toLightweightReadOnly()
+        } else {
+            return nil
+        }
+    }
 }
 
 // MARK: - FetchedResultsController Activation

Modules/Sources/Yosemite/Tools/ReadOnlyConvertible.swift

@@ -17,6 +17,10 @@ public protocol ReadOnlyConvertible: TypeErasedReadOnlyConvertible {
     /// Returns a ReadOnly version of the receiver.
     ///
     func toReadOnly() -> ReadOnlyType
+
+    /// Returns a lightweight ReadOnly version of the receiver.
+    ///
+    func toLightweightReadOnly() -> ReadOnlyType
 }
 
 
@@ -40,4 +44,10 @@ extension ReadOnlyConvertible {
     public func toTypeErasedReadOnly() -> Any {
         return toReadOnly()
     }
+
+    /// Default implementation is the same result with `toReadOnly()`
+    ///
+    public func toLightweightReadOnly() -> ReadOnlyType {
+        toReadOnly()
+    }
 }

Modules/Sources/Yosemite/Tools/ResultsController.swift

@@ -143,6 +143,12 @@ public class ResultsController<T: ResultsControllerMutableType> {
         return controller.object(at: indexPath).toReadOnly()
     }
 
+    /// Returns the lightweight fetched object at a given indexPath.
+    ///
+    public func lightweightObject(at indexPath: IndexPath) -> T.ReadOnlyType {
+        return controller.object(at: indexPath).toLightweightReadOnly()
+    }
+
     /// Returns the fetched object at the given `indexPath`. Returns `nil` if the `indexPath`
     /// does not exist.
     ///
@@ -203,6 +209,17 @@ public class ResultsController<T: ResultsControllerMutableType> {
         return readOnlyObjects ?? []
     }
 
+    /// Returns an array of all of the (ReadOnly) Fetched Objects with no relationships populated.
+    /// Suitable for list views.
+    ///
+    public var lightweightFetchedObjects: [T.ReadOnlyType] {
+        let readOnlyObjects = controller.fetchedObjects?.compactMap { mutableObject in
+            mutableObject.toLightweightReadOnly()
+        }
+
+        return readOnlyObjects ?? []
+    }
+
     /// Returns an array of SectionInfo Entitites.
     ///
     public var sections: [SectionInfo] {

RELEASE-NOTES.txt

@@ -5,6 +5,7 @@
 -----
 - [*] Order Details: Fix crash when reloading data [https://github.com/woocommerce/woocommerce-ios/pull/15764]
 - [*] Shipping Labels: Improved shipment management UI by hiding remove/merge options instead of disabling them, hiding merge option for orders with 2 or fewer unfulfilled shipments, and hiding the ellipsis menu when no remove/merge actions are available [https://github.com/woocommerce/woocommerce-ios/pull/15760]
+- [*] Improve app performance by fetching lightweight objects when necessary [https://github.com/woocommerce/woocommerce-ios/pull/15774]
 - [**] POS: a POS tab in the tab bar is now available in the app for stores eligible for Point of Sale, instead of the previous entry point in the Menu tab. [https://github.com/woocommerce/woocommerce-ios/pull/15766]
 - [***] POS: Barcode scanning using Bluetooth scanners in Point of Sale (HID-based scanners are supported) [https://github.com/woocommerce/woocommerce-ios/pull/15776]
 - [*] POS: Support refreshing product list when it's empty [https://github.com/woocommerce/woocommerce-ios/pull/15782]

WooCommerce/Classes/ViewModels/Order Details/OrderDetailsResultsControllers.swift

@@ -90,7 +90,7 @@ final class OrderDetailsResultsControllers {
     /// Products from an Order
     ///
     var products: [Product] {
-        return productResultsController.fetchedObjects
+        return productResultsController.lightweightFetchedObjects
     }
 
     /// ProductVariations from an Order

WooCommerce/Classes/ViewRelated/Blaze/CampaignCreation/BlazeCampaignCreationFormViewModel.swift

@@ -204,7 +204,7 @@ final class BlazeCampaignCreationFormViewModel: ObservableObject {
 
     private let storage: StorageManagerType
     private var product: Product? {
-        guard let product = productsResultsController.fetchedObjects.first else {
+        guard let product = productsResultsController.lightweightFetchedObjects.first else {
             assertionFailure("Unable to fetch product with ID: \(productID)")
             return nil
         }

WooCommerce/Classes/ViewRelated/Dashboard/DashboardViewModel.swift

@@ -540,7 +540,7 @@ private extension DashboardViewModel {
                 return
             }
 
-            guard ordersResultsController.fetchedObjects.isEmpty else {
+            guard ordersResultsController.lightweightFetchedObjects.isEmpty else {
                 hasOrders = true
                 return
             }

WooCommerce/Classes/ViewRelated/Orders/Order Details/Shipping Labels/WooShipping Create Shipping Labels/WooShipping Items Section/WooShippingItemsDataSource.swift

@@ -32,7 +32,7 @@ final class DefaultWooShippingItemsDataSource: WooShippingItemsDataSource {
     ///
     private var products: [Product] {
         try? productResultsController.performFetch()
-        return productResultsController.fetchedObjects
+        return productResultsController.lightweightFetchedObjects
     }
 
     /// Stored product variations that match the items in the order.