Handle coercion of AnyHashable (#61)

Author: AnthonyMDev

Tests/ApolloInternalTestHelpers/SelectionSet+TestHelpers.swift

@@ -9,7 +9,7 @@ public extension SelectionSet {
     guard let value = self.__data._data[key] else {
       return false
     }
-    return value == DataDict.NullValue
+    return value == DataDict._NullValue
   }
 
 }

Tests/ApolloTests/SelectionSetTests.swift

@@ -1436,12 +1436,20 @@ class SelectionSetTests: XCTestCase {
       return
     }
     expect(nameValue).to(beNil())
-
-    guard let nameValue = nameValue as? String? else {
-      fail("name should be Optional.some(Optional.none).")
-      return
+    
+    if DataDict._AnyHashableCanBeCoerced {
+      guard let nameValue = nameValue as? String? else {
+        fail("name should be Optional.some(Optional.none).")
+        return
+      }
+      expect(nameValue).to(beNil())
+    } else {
+      guard let nameValue = nameValue.base as? String? else {
+        fail("name should be Optional.some(Optional.none).")
+        return
+      }
+      expect(nameValue).to(beNil())
     }
-    expect(nameValue).to(beNil())
   }
 
   func test__selectionInitializer_givenOptionalEntityField__fieldIsPresentWithOptionalNilValue() {
@@ -1510,11 +1518,20 @@ class SelectionSetTests: XCTestCase {
     }
     expect(childValue).to(beNil())
 
-    guard let childValue = childValue as? Hero.Child? else {
-      fail("child should be Optional.some(Optional.none).")
-      return
+    if DataDict._AnyHashableCanBeCoerced {
+      guard let childValue = childValue as? Hero.Child? else {
+        fail("child should be Optional.some(Optional.none).")
+        return
+      }
+      expect(childValue).to(beNil())
+
+    } else {
+      guard let childValue = childValue.base as? Hero.Child? else {
+        fail("child should be Optional.some(Optional.none).")
+        return
+      }
+      expect(childValue).to(beNil())
     }
-    expect(childValue).to(beNil())
   }
 
   func test__selectionInitializer_givenOptionalListOfOptionalEntitiesField__setsFieldDataCorrectly() {

apollo-ios/Sources/Apollo/GraphQLSelectionSetMapper.swift

@@ -45,7 +45,7 @@ final class GraphQLSelectionSetMapper<T: SelectionSet>: GraphQLResultAccumulator
   }
 
   func acceptNullValue(info: FieldExecutionInfo) -> AnyHashable? {
-    return DataDict.NullValue
+    return DataDict._NullValue
   }
 
   func acceptMissingValue(info: FieldExecutionInfo) throws -> AnyHashable? {
@@ -86,11 +86,3 @@ final class GraphQLSelectionSetMapper<T: SelectionSet>: GraphQLResultAccumulator
     return T.init(_dataDict: rootValue)
   }
 }
-
-// MARK: - Null Value Definition
-extension DataDict {
-  /// A common value used to represent a null value in a `DataDict`.
-  ///
-  /// This value can be cast to `NSNull` and will bridge automatically.
-  static let NullValue = AnyHashable(Optional<AnyHashable>.none)
-}

apollo-ios/Sources/ApolloAPI/DataDict.swift

@@ -1,3 +1,5 @@
+import Foundation
+
 /// A structure that wraps the underlying data for a ``SelectionSet``.
 public struct DataDict: Hashable {
   @usableFromInline var _storage: _Storage
@@ -51,11 +53,16 @@ public struct DataDict: Hashable {
 
   @inlinable public subscript<T: AnyScalarType & Hashable>(_ key: String) -> T {
     get {
-#if swift(>=5.4)
-        _data[key] as! T
-#else
-        _data[key]?.base as! T
-#endif
+      if DataDict._AnyHashableCanBeCoerced {
+        return _data[key] as! T
+      } else {        
+        let value = _data[key]
+        if value == DataDict._NullValue {
+          return (Optional<T>.none as Any) as! T
+        } else {
+          return (value?.base as? T) ?? (value._asAnyHashable as! T)
+        }
+      }
     }
     set {
       _data[key] = newValue
@@ -126,6 +133,34 @@ public struct DataDict: Hashable {
   }
 }
 
+// MARK: - Null Value Definition
+extension DataDict {
+  /// A common value used to represent a null value in a `DataDict`.
+  ///
+  /// This value can be cast to `NSNull` and will bridge automatically.
+  public static let _NullValue = {
+    if DataDict._AnyHashableCanBeCoerced {
+      return AnyHashable(Optional<AnyHashable>.none)
+    } else {
+      return NSNull()
+    }
+  }()
+
+  /// Indicates if `AnyHashable` can be coerced via casting into its underlying type.
+  ///
+  /// In iOS versions 14.4 and lower, `AnyHashable` coercion does not work. On these platforms,
+  /// we need to do some additional unwrapping and casting of the values to avoid crashes and other
+  /// run time bugs.
+  public static var _AnyHashableCanBeCoerced: Bool {
+    if #available(iOS 14.5, *) {
+      return true
+    } else {
+      return false
+    }
+  }
+
+}
+
 // MARK: - Value Conversion Helpers
 
 public protocol SelectionSetEntityValue {
@@ -160,11 +195,13 @@ extension Optional: SelectionSetEntityValue where Wrapped: SelectionSetEntityVal
       case .none:
         self = .none
       case .some(let hashable):
-        if let optional = hashable.base as? Optional<AnyHashable>, optional == nil {
-          self = .none
-          return
-        }
+      if DataDict._AnyHashableCanBeCoerced && hashable == DataDict._NullValue {
+        self = .none
+      } else if let optional = hashable.base as? Optional<AnyHashable>, optional == nil {
+        self = .none
+      } else {
         self = .some(Wrapped.init(_fieldData: data))
+      }
     }
   }
 
@@ -179,11 +216,11 @@ extension Array: SelectionSetEntityValue where Element: SelectionSetEntityValue
       fatalError("\(Self.self) expected list of data for entity.")
     }
     self = data.map {
-#if swift(>=5.4)
-        Element.init(_fieldData:$0)
-#else
-        Element.init(_fieldData:$0?.base as? AnyHashable)
-#endif
+      if DataDict._AnyHashableCanBeCoerced {
+        return Element.init(_fieldData:$0)
+      } else {
+        return Element.init(_fieldData:$0?.base as? AnyHashable)
+      }
     }
   }
 

apollo-ios/Sources/ApolloTestSupport/TestMock.swift

@@ -97,7 +97,7 @@ public class Mock<O: MockObject>: AnyMock, Hashable {
 
   public var _selectionSetMockData: JSONObject {
     _data.mapValues {
-      if let mock = $0 as? AnyMock {
+      if let mock = $0.base as? AnyMock {
         return mock._selectionSetMockData
       }
       if let mockArray = $0 as? Array<Any> {
@@ -188,20 +188,27 @@ fileprivate extension Array {
   }
 
   func _unsafelyConvertToSelectionSetData() -> [AnyHashable?] {
-    map { element in
-      switch element {
-      case let element as AnyMock:
-        return element._selectionSetMockData
+    map(_unsafelyConvertToSelectionSetData(element:))
+  }
 
-      case let innerArray as Array<Any>:
-        return innerArray._unsafelyConvertToSelectionSetData()
+  private func _unsafelyConvertToSelectionSetData(element: Any) -> AnyHashable? {
+    switch element {
+    case let element as AnyMock:
+      return element._selectionSetMockData
 
-      case let element as AnyHashable:
+    case let innerArray as Array<Any>:
+      return innerArray._unsafelyConvertToSelectionSetData()
+
+    case let element as AnyHashable:
+      if DataDict._AnyHashableCanBeCoerced {
         return element
 
-      default:
-        return nil
+      } else {
+        return _unsafelyConvertToSelectionSetData(element: element.base)
       }
+
+    default:
+      return nil
     }
   }
 }