Remove stripping of null values from Selection Set models

Tests/ApolloInternalTestHelpers/SelectionSet+TestHelpers.swift

@@ -0,0 +1,15 @@
+@testable import ApolloAPI
+@testable import Apollo
+
+public extension SelectionSet {
+
+  var _rawData: [String: AnyHashable] { self.__data._data }
+
+  func hasNullValue(forKey key: String) -> Bool {
+    guard let value = self.__data._data[key] else {
+      return false
+    }
+    return value == DataDict.NullValue
+  }
+
+}

Tests/ApolloTests/Cache/ReadWriteFromStoreTests.swift

@@ -503,7 +503,8 @@ class ReadWriteFromStoreTests: XCTestCase, CacheDependentTesting, StoreLoading {
 
         let data = try XCTUnwrap(graphQLResult.data)
         XCTAssertEqual(data.hero.name, "Artoo")
-        XCTAssertNil(data.hero.nickname)
+        expect(data.hero.nickname).to(beNil())
+        expect(data.hero.hasNullValue(forKey: "nickname")).to(beTrue())
       }
     }
   }
@@ -1696,6 +1697,73 @@ class ReadWriteFromStoreTests: XCTestCase, CacheDependentTesting, StoreLoading {
     }
   }
 
+  // MARK: - Write w/Selection Set Initializers
+
+  func test_writeDataForOperation_givenSelectionSetManuallyInitialized_withNullValueForField_fieldHasNullValue() throws {
+    // given
+    struct Types {
+      static let Query = Object(typename: "Query", implementedInterfaces: [])
+    }
+
+    MockSchemaMetadata.stub_objectTypeForTypeName = {
+      switch $0 {
+      case "Query": return Types.Query
+      default: XCTFail(); return nil
+      }
+    }
+
+    class Data: MockSelectionSet {
+      typealias Schema = MockSchemaMetadata
+
+      override class var __parentType: ParentType { Types.Query }
+      override class var __selections: [Selection] {[
+        .field("name", String?.self)
+      ]}
+
+      public var name: String? { __data["name"] }
+
+      convenience init(
+        name: String? = nil
+      ) {
+        self.init(_dataDict: DataDict(data: [
+          "__typename": Types.Query.typename,
+          "name": name
+        ], fulfilledFragments: [ObjectIdentifier(Self.self)]))
+      }
+    }
+
+    // when
+    let writeCompletedExpectation = expectation(description: "Write completed")
+
+    store.withinReadWriteTransaction({ transaction in
+      let data = Data(name: nil)
+      let query = MockQuery<Data>()
+      try transaction.write(data: data, for: query)
+
+    }, completion: { result in
+      defer { writeCompletedExpectation.fulfill() }
+      XCTAssertSuccessResult(result)
+    })
+
+    self.wait(for: [writeCompletedExpectation], timeout: Self.defaultWaitTimeout)
+
+    let readCompletedExpectation = expectation(description: "Read completed")
+
+    store.withinReadTransaction({ transaction in
+      let query = MockQuery<Data>()
+      let resultData = try transaction.read(query: query)
+
+      expect(resultData.name).to(beNil())
+      expect(resultData.hasNullValue(forKey: "name")).to(beTrue())
+
+    }, completion: { result in
+      defer { readCompletedExpectation.fulfill() }
+      XCTAssertSuccessResult(result)
+    })
+
+    self.wait(for: [readCompletedExpectation], timeout: Self.defaultWaitTimeout)
+  }
+
   func test_writeDataForOperation_givenSelectionSetManuallyInitializedWithInclusionConditions_writesFieldsForInclusionConditions() throws {
     // given
     struct Types {

Tests/ApolloTests/GraphQLExecutor_SelectionSetMapper_FromResponse_Tests.swift

@@ -23,7 +23,7 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
       selectionSet: selectionSet,
       on: object,      
       variables: variables,
-      accumulator: GraphQLSelectionSetMapper<T>(stripNullValues: true)
+      accumulator: GraphQLSelectionSetMapper<T>()
     )
   }
 
@@ -238,7 +238,8 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     let data = try readValues(GivenSelectionSet.self, from: object)
 
     // then
-    XCTAssertNil(data.name)
+    expect(data.name).to(beNil())
+    expect(data.hasNullValue(forKey: "name")).to(beTrue())
   }
 
   func test__optional_scalar__givenDataWithTypeConvertibleToFieldType_getsConvertedValue() throws {
@@ -689,7 +690,8 @@ class GraphQLExecutor_SelectionSetMapper_FromResponse_Tests: XCTestCase {
     let data = try readValues(GivenSelectionSet.self, from: object)
 
     // then
-    XCTAssertEqual(data.favorites! as [String?], ["Red", nil, "Bird"])
+    expect(data.favorites! as [String?]).to(equal(["Red", nil, "Bird"]))
+    expect((data._rawData["favorites"] as? [AnyHashable])?[1]).to(equal(DataDict.NullValue))
   }
 
   // MARK: Optional List Of Optional Scalar

apollo-ios/Sources/Apollo/ApolloStore.swift

@@ -278,7 +278,6 @@ public class ApolloStore {
         withKey: key,
         variables: variables,
         accumulator: GraphQLSelectionSetMapper<SelectionSet>(
-          stripNullValues: false,
           handleMissingValues: .allowForOptionalFields
         )
       )

apollo-ios/Sources/Apollo/GraphQLSelectionSetMapper.swift

@@ -7,7 +7,6 @@ final class GraphQLSelectionSetMapper<T: SelectionSet>: GraphQLResultAccumulator
 
   let requiresCacheKeyComputation: Bool = false
 
-  let stripNullValues: Bool
   let handleMissingValues: HandleMissingValues
 
   enum HandleMissingValues {
@@ -19,10 +18,8 @@ final class GraphQLSelectionSetMapper<T: SelectionSet>: GraphQLResultAccumulator
   }
 
   init(
-    stripNullValues: Bool = true,
     handleMissingValues: HandleMissingValues = .disallow
   ) {
-    self.stripNullValues = stripNullValues
     self.handleMissingValues = handleMissingValues
   }
 
@@ -48,7 +45,7 @@ final class GraphQLSelectionSetMapper<T: SelectionSet>: GraphQLResultAccumulator
   }
 
   func acceptNullValue(info: FieldExecutionInfo) -> AnyHashable? {
-    return stripNullValues ? nil : Optional<AnyHashable>.none
+    return DataDict.NullValue
   }
 
   func acceptMissingValue(info: FieldExecutionInfo) throws -> AnyHashable? {
@@ -89,3 +86,11 @@ 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

@@ -126,9 +126,7 @@ public struct DataDict: Hashable {
   }
 }
 
-
-
-// MARK: Value Conversion Helpers
+// MARK: - Value Conversion Helpers
 
 public protocol SelectionSetEntityValue {
   /// - Warning: This function is not supported for external use.