ra1028 · rafaelnobrekz · Apr 11, 2023
diff --git a/DiffableDataSources.xcodeproj/xcshareddata/xcschemes/DiffableDataSources.xcscheme b/DiffableDataSources.xcodeproj/xcshareddata/xcschemes/DiffableDataSources.xcscheme
@@ -27,6 +27,15 @@
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       shouldUseLaunchSchemeArgsEnv = "YES">
+      <MacroExpansion>
+         <BuildableReference
+            BuildableIdentifier = "primary"
+            BlueprintIdentifier = "6BB762CB22B455170050DC03"
+            BuildableName = "DiffableDataSources.framework"
+            BlueprintName = "DiffableDataSources"
+            ReferencedContainer = "container:DiffableDataSources.xcodeproj">
+         </BuildableReference>
+      </MacroExpansion>
       <Testables>
          <TestableReference
             skipped = "NO">
@@ -39,17 +48,6 @@
             </BuildableReference>
          </TestableReference>
       </Testables>
-      <MacroExpansion>
-         <BuildableReference
-            BuildableIdentifier = "primary"
-            BlueprintIdentifier = "6BB762CB22B455170050DC03"
-            BuildableName = "DiffableDataSources.framework"
-            BlueprintName = "DiffableDataSources"
-            ReferencedContainer = "container:DiffableDataSources.xcodeproj">
-         </BuildableReference>
-      </MacroExpansion>
-      <AdditionalOptions>
-      </AdditionalOptions>
    </TestAction>
    <LaunchAction
       buildConfiguration = "Debug"
@@ -70,8 +68,6 @@
             ReferencedContainer = "container:DiffableDataSources.xcodeproj">
          </BuildableReference>
       </MacroExpansion>
-      <AdditionalOptions>
-      </AdditionalOptions>
    </LaunchAction>
    <ProfileAction
       buildConfiguration = "Release"

diff --git a/Sources/DiffableDataSourceSnapshot.swift b/Sources/DiffableDataSourceSnapshot.swift
@@ -1,28 +1,71 @@
+import UIKit
+
 /// A class for backporting `NSDiffableDataSourceSnapshot` introduced in iOS 13.0+, macOS 10.15+, tvOS 13.0+.
 /// Represents the mutable state of diffable data source of UI.
 public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemIdentifierType: Hashable> {
     internal var structure = SnapshotStructure<SectionIdentifierType, ItemIdentifierType>()
 
+    private let forceFallback: Bool
+    private var _nativeSnapshot: Any?
+    @available(iOS 13.0, *)
+    internal var nativeSnapshot: NSDiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType> {
+        get {
+            return _nativeSnapshot as! NSDiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType>
+        }
+        set {
+            _nativeSnapshot = newValue
+        }
+    }
+
     /// Creates a new empty snapshot object.
-    public init() {}
+    public init() {
+        self.init(forceFallback: false)
+    }
+
+    internal init(forceFallback: Bool) {
+        self.forceFallback = forceFallback
+        if #available(iOS 13.0, *), !forceFallback {
+            nativeSnapshot = .init()
+            return
+        }
+    }
+
+    @available(iOS 13.0, *)
+    static func from(nativeSnapshot: NSDiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType>) -> Self {
+        var snapshot = DiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType>()
+        snapshot.nativeSnapshot = nativeSnapshot
+        return snapshot
+    }
 
     /// The number of item identifiers in the snapshot.
     public var numberOfItems: Int {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.numberOfItems
+        }
         return itemIdentifiers.count
     }
 
     /// The number of section identifiers in the snapshot.
     public var numberOfSections: Int {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.numberOfSections
+        }
         return sectionIdentifiers.count
     }
 
     /// All section identifiers in the snapshot.
     public var sectionIdentifiers: [SectionIdentifierType] {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.sectionIdentifiers
+        }
         return structure.allSectionIDs
     }
 
     /// All item identifiers in the snapshot.
     public var itemIdentifiers: [ItemIdentifierType] {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.itemIdentifiers
+        }
         return structure.allItemIDs
     }
 
@@ -33,6 +76,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///
     /// - Returns: The number of item identifiers in the specified section.
     public func numberOfItems(inSection identifier: SectionIdentifierType) -> Int {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.numberOfItems(inSection: identifier)
+        }
         return itemIdentifiers(inSection: identifier).count
     }
 
@@ -43,6 +89,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///
     /// - Returns: The item identifiers in the specified section.
     public func itemIdentifiers(inSection identifier: SectionIdentifierType) -> [ItemIdentifierType] {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.itemIdentifiers(inSection: identifier)
+        }
         return structure.items(in: identifier)
     }
 
@@ -53,6 +102,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///
     /// - Returns: A section identifier containing the specified item.
     public func sectionIdentifier(containingItem identifier: ItemIdentifierType) -> SectionIdentifierType? {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.sectionIdentifier(containingItem: identifier)
+        }
         return structure.section(containing: identifier)
     }
 
@@ -63,6 +115,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///
     /// - Returns: An index of the specified item.
     public func indexOfItem(_ identifier: ItemIdentifierType) -> Int? {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.indexOfItem(identifier)
+        }
         return itemIdentifiers.firstIndex { $0.isEqualHash(to: identifier) }
     }
 
@@ -73,6 +128,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///
     /// - Returns: An index of the specified section.
     public func indexOfSection(_ identifier: SectionIdentifierType) -> Int? {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.indexOfSection(identifier)
+        }
         return sectionIdentifiers.firstIndex { $0.isEqualHash(to: identifier) }
     }
 
@@ -82,6 +140,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///   - identifiers: The item identifiers to be appended.
     ///   - sectionIdentifier: An identifier of section to append the given identiciers.
     public mutating func appendItems(_ identifiers: [ItemIdentifierType], toSection sectionIdentifier: SectionIdentifierType? = nil) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.appendItems(identifiers, toSection: sectionIdentifier)
+        }
         structure.append(itemIDs: identifiers, to: sectionIdentifier)
     }
 
@@ -91,6 +152,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///   - identifiers: The item identifiers to be inserted.
     ///   - beforeIdentifier: An identifier of item.
     public mutating func insertItems(_ identifiers: [ItemIdentifierType], beforeItem beforeIdentifier: ItemIdentifierType) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.insertItems(identifiers, beforeItem: beforeIdentifier)
+        }
         structure.insert(itemIDs: identifiers, before: beforeIdentifier)
     }
 
@@ -100,6 +164,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///   - identifiers: The item identifiers to be inserted.
     ///   - afterIdentifier: An identifier of item.
     public mutating func insertItems(_ identifiers: [ItemIdentifierType], afterItem afterIdentifier: ItemIdentifierType) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.insertItems(identifiers, afterItem: afterIdentifier)
+        }
         structure.insert(itemIDs: identifiers, after: afterIdentifier)
     }
 
@@ -108,11 +175,17 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     /// - Parameters:
     ///   - identifiers: The item identifiers to be deleted.
     public mutating func deleteItems(_ identifiers: [ItemIdentifierType]) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.deleteItems(identifiers)
+        }
         structure.remove(itemIDs: identifiers)
     }
 
     /// Deletes the all items in the snapshot.
     public mutating func deleteAllItems() {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.deleteAllItems()
+        }
         structure.removeAllItems()
     }
 
@@ -122,6 +195,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///   - identifier: An item identifier to be moved.
     ///   - toIdentifier: An identifier of item.
     public mutating func moveItem(_ identifier: ItemIdentifierType, beforeItem toIdentifier: ItemIdentifierType) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.moveItem(identifier, beforeItem: toIdentifier)
+        }
         structure.move(itemID: identifier, before: toIdentifier)
     }
 
@@ -131,6 +207,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///   - identifier: An item identifier to be moved.
     ///   - toIdentifier: An identifier of item.
     public mutating func moveItem(_ identifier: ItemIdentifierType, afterItem toIdentifier: ItemIdentifierType) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.moveItem(identifier, afterItem: toIdentifier)
+        }
         structure.move(itemID: identifier, after: toIdentifier)
     }
 
@@ -139,6 +218,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     /// - Parameters:
     ///   - identifiers: The item identifiers to be reloaded.
     public mutating func reloadItems(_ identifiers: [ItemIdentifierType]) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.reloadItems(identifiers)
+        }
         structure.update(itemIDs: identifiers)
     }
 
@@ -147,6 +229,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     /// - Parameters:
     ///   - identifiers: The section identifiers to be appended.
     public mutating func appendSections(_ identifiers: [SectionIdentifierType]) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.appendSections(identifiers)
+        }
         structure.append(sectionIDs: identifiers)
     }
 
@@ -156,6 +241,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///   - identifiers: The section identifiers to be inserted.
     ///   - toIdentifier: An identifier of setion.
     public mutating func insertSections(_ identifiers: [SectionIdentifierType], beforeSection toIdentifier: SectionIdentifierType) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.insertSections(identifiers, beforeSection: toIdentifier)
+        }
         structure.insert(sectionIDs: identifiers, before: toIdentifier)
     }
 
@@ -165,6 +253,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///   - identifiers: The section identifiers to be inserted.
     ///   - toIdentifier: An identifier of setion.
     public mutating func insertSections(_ identifiers: [SectionIdentifierType], afterSection toIdentifier: SectionIdentifierType) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.insertSections(identifiers, afterSection: toIdentifier)
+        }
         structure.insert(sectionIDs: identifiers, after: toIdentifier)
     }
 
@@ -173,6 +264,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     /// - Parameters:
     ///   - identifiers: The section identifiers to be deleted.
     public mutating func deleteSections(_ identifiers: [SectionIdentifierType]) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.deleteSections(identifiers)
+        }
         structure.remove(sectionIDs: identifiers)
     }
 
@@ -182,6 +276,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///   - identifier: A section identifier to be moved.
     ///   - toIdentifier: An identifier of section.
     public mutating func moveSection(_ identifier: SectionIdentifierType, beforeSection toIdentifier: SectionIdentifierType) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.moveSection(identifier, beforeSection: toIdentifier)
+        }
         structure.move(sectionID: identifier, before: toIdentifier)
     }
 
@@ -191,6 +288,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     ///   - identifier: A section identifier to be moved.
     ///   - toIdentifier: An identifier of section.
     public mutating func moveSection(_ identifier: SectionIdentifierType, afterSection toIdentifier: SectionIdentifierType) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.moveSection(identifier, afterSection: toIdentifier)
+        }
         structure.move(sectionID: identifier, after: toIdentifier)
     }
 
@@ -199,6 +299,9 @@ public struct DiffableDataSourceSnapshot<SectionIdentifierType: Hashable, ItemId
     /// - Parameters:
     ///   - identifiers: The section identifiers to be reloaded.
     public mutating func reloadSections(_ identifiers: [SectionIdentifierType]) {
+        if #available(iOS 13.0, *), !forceFallback {
+            return nativeSnapshot.reloadSections(identifiers)
+        }
         structure.update(sectionIDs: identifiers)
     }
 }
diff --git a/Sources/Internal/DiffableDataSourceCore.swift b/Sources/Internal/DiffableDataSourceCore.swift
@@ -51,8 +51,8 @@ final class DiffableDataSourceCore<SectionIdentifierType: Hashable, ItemIdentifi
         }
     }
 
-    func snapshot() -> DiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType> {
-        var snapshot = DiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType>()
+    func snapshot(forceFallback: Bool) -> DiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType> {
+        var snapshot = DiffableDataSourceSnapshot<SectionIdentifierType, ItemIdentifierType>(forceFallback: forceFallback)
         snapshot.structure.sections = currentSnapshot.structure.sections
         return snapshot
     }