feat: Specify caching fields with typePolicy directive

Sources/AnimalKingdomAPI/animalkingdom-graphql/AnimalSchema.graphqls

@@ -41,15 +41,15 @@ input PetSearchFilters {
   measurements: MeasurementsInput
 }
 
-interface Animal {
+interface Animal @typePolicy(keyFields: "id") {
   id: ID!
   species: String!
   height: Height!
   predators: [Animal!]!
   skinCovering: SkinCovering
 }
 
-interface Pet {
+interface Pet @typePolicy(keyFields: "id") {
   id: ID!
   humanName: String
   favoriteToy: String!
@@ -198,5 +198,5 @@ enum SkinCovering {
   FUR
   HAIR
   FEATHERS
-  SCALES  
+  SCALES
 }

Tests/ApolloCodegenInternalTestHelpers/MockGraphQLType.swift

@@ -20,13 +20,15 @@ public extension GraphQLObjectType {
     _ name: String = "",
     interfaces: [GraphQLInterfaceType] = [],
     fields: [String: GraphQLField] = [:],
+    keyFields: [String] = [],
     documentation: String? = nil
   ) -> GraphQLObjectType {
     GraphQLObjectType(
       name: GraphQLName(schemaName: name),
       documentation: documentation,
       fields: fields,
-      interfaces: interfaces
+      interfaces: interfaces,
+      keyFields: keyFields
     )
   }
 }

Tests/ApolloCodegenTests/CodeGeneration/Templates/ObjectTemplateTests.swift

@@ -20,12 +20,14 @@ class ObjectTemplateTests: XCTestCase {
     name: String = "Dog",
     customName: String? = nil,
     interfaces: [GraphQLInterfaceType] = [],
+    keyFields: [String] = [],
     documentation: String? = nil,
     config: ApolloCodegenConfiguration = .mock()
   ) {
     let objectType = GraphQLObjectType.mock(
       name,
       interfaces: interfaces,
+      keyFields: keyFields,
       documentation: documentation
     )
     objectType.name.customName = customName
@@ -82,7 +84,7 @@ class ObjectTemplateTests: XCTestCase {
       implementedInterfaces: [
         TestSchema.Interfaces.Animal.self,
         TestSchema.Interfaces.Pet.self
-      ]
+      ],
     """
 
     // when
@@ -106,7 +108,7 @@ class ObjectTemplateTests: XCTestCase {
       implementedInterfaces: [
         Interfaces.Animal.self,
         Interfaces.Pet.self
-      ]
+      ],
     """
 
     // when
@@ -121,7 +123,7 @@ class ObjectTemplateTests: XCTestCase {
     buildSubject()
 
     let expected = """
-      implementedInterfaces: []
+      implementedInterfaces: [],
     """
 
     // when
@@ -130,6 +132,21 @@ class ObjectTemplateTests: XCTestCase {
     // then
     expect(actual).to(equalLineByLine(expected, atLine: 3, ignoringExtraLines: true))
   }
+
+  func test_render_givenKeyFields_rendersKeyFieldArray() {
+    // given
+    buildSubject(keyFields: ["id"])
+
+    let expected = """
+      keyFields: ["id"]
+    """
+
+    // when
+    let actual = renderSubject()
+
+    // then
+    expect(actual).to(equalLineByLine(expected, atLine: 4, ignoringExtraLines: true))
+  }
 
   // MARK: Documentation Tests
 
@@ -213,7 +230,8 @@ class ObjectTemplateTests: XCTestCase {
     // Renamed from GraphQL schema value: 'MyObject'
     static let MyCustomObject = ApolloAPI.Object(
       typename: "MyObject",
-      implementedInterfaces: [TestSchema.Interfaces.MyCustomInterface.self]
+      implementedInterfaces: [TestSchema.Interfaces.MyCustomInterface.self],
+      keyFields: nil
     )
     """
 

Tests/ApolloCodegenTests/CodeGeneration/Templates/SelectionSet/SelectionSetTemplateTests.swift

@@ -4794,7 +4794,7 @@ class SelectionSetTemplateTests: XCTestCase {
       AllAnimals: [Animal!]
     }
 
-    type Animal {
+    type Animal @typePolicy(keyFields: "id") {
       id: ID!
     }
     """

Tests/ApolloTests/CacheKeyResolutionTests.swift

@@ -209,4 +209,55 @@ class CacheKeyResolutionTests: XCTestCase {
     expect(actual).to(equal("GreekLetters:δ"))
   }
 
+  func test__schemaConfiguration__givenSingleKeyField_shouldReturnKeyFieldValue() {
+    let Delta = Object(typename: "Dog", implementedInterfaces: [], keyFields: ["id"])
+
+    MockSchemaMetadata.stub_objectTypeForTypeName({ _ in Delta })
+
+    let object: JSONObject = [
+      "__typename": "Dog",
+      "id": "10",
+      "name": "Beagle"
+    ]
+
+    let objectDict = NetworkResponseExecutionSource().opaqueObjectDataWrapper(for: object)
+    let actual = MockSchemaMetadata.cacheKey(for: objectDict)
+
+    expect(actual).to(equal("Dog:10"))
+  }
+
+  func test__schemaConfiguration__givenMultipleKeyFields_shouldReturnKeyFieldValues() {
+    let Delta = Object(typename: "Dog", implementedInterfaces: [], keyFields: ["id", "name"])
+
+    MockSchemaMetadata.stub_objectTypeForTypeName({ _ in Delta })
+
+    let object: JSONObject = [
+      "__typename": "Dog",
+      "id": "10",
+      "name": "Beagle",
+      "height": 20,
+    ]
+
+    let objectDict = NetworkResponseExecutionSource().opaqueObjectDataWrapper(for: object)
+    let actual = MockSchemaMetadata.cacheKey(for: objectDict)
+
+    expect(actual).to(equal("Dog:10/Beagle"))
+  }
+
+  func test__schemaConfiguration__givenMissingKeyFields_shouldReturnNil() {
+    let Delta = Object(typename: "Dog", implementedInterfaces: [], keyFields: ["id", "name"])
+
+    MockSchemaMetadata.stub_objectTypeForTypeName({ _ in Delta })
+
+    let object: JSONObject = [
+      "__typename": "Dog",
+      "id": "10",
+    ]
+
+    let objectDict = NetworkResponseExecutionSource().opaqueObjectDataWrapper(for: object)
+    let actual = MockSchemaMetadata.cacheKey(for: objectDict)
+
+    expect(actual).to(beNil())
+  }
+
 }

apollo-ios-codegen/Sources/ApolloCodegenLib/Templates/ObjectTemplate.swift

@@ -20,10 +20,19 @@ struct ObjectTemplate: TemplateRenderer {
     \(graphqlObject.name.typeNameDocumentation)
     static let \(graphqlObject.render(as: .typename)) = \(config.ApolloAPITargetName).Object(
       typename: "\(graphqlObject.name.schemaName)\",
-      implementedInterfaces: \(ImplementedInterfacesTemplate())
+      implementedInterfaces: \(ImplementedInterfacesTemplate()),
+      keyFields: \(KeyFieldsTemplate())
     )
     """
   }
+
+  private func KeyFieldsTemplate() -> TemplateString {
+    guard let fields = graphqlObject.keyFields, !fields.isEmpty else { return "nil" }
+
+    return """
+    [\(list: fields.map { "\"\($0)\"" })]
+    """
+  }
 
   private func ImplementedInterfacesTemplate() -> TemplateString {
     return """

apollo-ios-codegen/Sources/GraphQLCompiler/GraphQLSchema.swift

@@ -239,16 +239,20 @@ public final class GraphQLObjectType: GraphQLCompositeType, GraphQLInterfaceImpl
   public private(set) var fields: [String: GraphQLField]!
 
   public private(set) var interfaces: [GraphQLInterfaceType]!
+
+  public private(set) var keyFields: [String]!
 
   /// Initializer to be used for creating mock objects in tests only.
   init(
     name: GraphQLName,
     documentation: String?,
     fields: [String: GraphQLField],
-    interfaces: [GraphQLInterfaceType]
+    interfaces: [GraphQLInterfaceType],
+    keyFields: [String]
   ) {
     self.fields = fields
     self.interfaces = interfaces
+    self.keyFields = keyFields
     super.init(name: name, documentation: documentation)
   }
 
@@ -259,6 +263,7 @@ public final class GraphQLObjectType: GraphQLCompositeType, GraphQLInterfaceImpl
   override func finalize(_ jsValue: JSValue, bridge: isolated JavaScriptBridge) {
     self.fields = try! bridge.invokeMethod("getFields", on: jsValue)
     self.interfaces = try! bridge.invokeMethod("getInterfaces", on: jsValue)
+    self.keyFields = jsValue["_apolloKeyFields"]
   }
 
   public override var debugDescription: String {

apollo-ios-codegen/Sources/GraphQLCompiler/JavaScript/src/compiler/ir.ts

@@ -96,4 +96,4 @@ export type InclusionConditionSkipped = "SKIPPED";
 export interface InclusionConditionVariable {
   variable: string;
   isInverted: Boolean;
-}
+}

apollo-ios-codegen/Sources/GraphQLCompiler/JavaScript/src/index.ts

@@ -17,10 +17,11 @@ import { assertValidSchema, assertValidSDL } from "./utilities/graphql";
 import {
   addApolloCodegenSchemaExtensionToDocument,
 } from "./utilities/apolloCodegenSchemaExtension";
-import { 
+import {
   addExperimentalDeferDirectiveToSDLDocument,
   addExperimentalDeferDirectiveToIntrospectionSchema
 } from "./utilities/experimentalDeferDirective";
+import { addTypePolicyDirectivesToSchema } from "./utilities/typePolicyResolver";
 
 // We need to export all the classes we want to map to native objects,
 // so we have access to the constructor functions for type checks.
@@ -61,6 +62,7 @@ export function loadSchemaFromSources(sources: Source[]): GraphQLSchema {
     assertValidSDL(document)
 
     const schema = buildASTSchema(document, { assumeValid: true, assumeValidSDL: true })
+    addTypePolicyDirectivesToSchema(schema)
     assertValidSchema(schema)
 
     return schema
@@ -69,6 +71,7 @@ export function loadSchemaFromSources(sources: Source[]): GraphQLSchema {
     var schema = loadSchemaFromIntrospectionResult(introspectionJSONResult.body)
     document = addExperimentalDeferDirectiveToIntrospectionSchema(schema, document)
     schema = extendSchema(schema, document, { assumeValid: true, assumeValidSDL: true })
+    addTypePolicyDirectivesToSchema(schema)
 
     assertValidSchema(schema)
 

apollo-ios-codegen/Sources/GraphQLCompiler/JavaScript/src/utilities/apolloCodegenSchemaExtension.ts

@@ -9,6 +9,22 @@ export const directive_apollo_client_ios_localCacheMutation: DirectiveDefinition
   locations: [nameNode("QUERY"), nameNode("MUTATION"), nameNode("SUBSCRIPTION"), nameNode("FRAGMENT_DEFINITION")]
 }
 
+export const directive_typePolicy: DirectiveDefinitionNode = {
+  kind: Kind.DIRECTIVE_DEFINITION,
+  description: stringNode("Attach extra information to a given type."),
+  name: nameNode("typePolicy"),
+  arguments: [
+    {
+      kind: Kind.INPUT_VALUE_DEFINITION,
+      description: stringNode("A selection set containing fields used to compute the cache key of an object. Order is important."),
+      name: nameNode("keyFields"),
+      type: nonNullNode(typeNode(GraphQLString))
+    }
+  ],
+  repeatable: false,
+  locations: [nameNode("OBJECT"), nameNode("INTERFACE")]
+}
+
 export const directive_import_statement: DirectiveDefinitionNode = {
   kind: Kind.DIRECTIVE_DEFINITION,
   description: stringNode("A directive used by the Apollo iOS code generation engine to generate custom import statements in operation or fragment definition files. An import statement to import a module with the name provided in the `module` argument will be added to the generated definition file."),
@@ -29,7 +45,8 @@ export const apolloCodegenSchemaExtension: DocumentNode = {
   kind: Kind.DOCUMENT,
   definitions: [
     directive_apollo_client_ios_localCacheMutation,
-    directive_import_statement
+    directive_import_statement,
+    directive_typePolicy,
   ]
 }
 

apollo-ios-codegen/Sources/GraphQLCompiler/JavaScript/src/utilities/graphql.ts

@@ -22,7 +22,7 @@ import {
 } from "graphql";
 import { isNode } from "graphql/language/ast";
 import { validateSDL } from "graphql/validation/validate";
-import { directive_apollo_client_ios_localCacheMutation, directive_import_statement } from "./apolloCodegenSchemaExtension";
+import { directive_apollo_client_ios_localCacheMutation, directive_import_statement, directive_typePolicy } from "./apolloCodegenSchemaExtension";
 import { addTypeNameFieldForLegacySafelisting } from "./legacySafelistingTransform";
 
 export class GraphQLSchemaValidationError extends Error {
@@ -124,7 +124,8 @@ function transformTypenameFieldIfNeeded(node: FieldNode): FieldNode {
 function stripApolloClientSpecificDirectives(node: DirectiveNode): DirectiveNode | null {
   const apolloClientSpecificDirectives: DirectiveDefinitionNode[] = [
     directive_apollo_client_ios_localCacheMutation,
-    directive_import_statement
+    directive_import_statement,
+    directive_typePolicy,
   ]
 
   for (const directive of apolloClientSpecificDirectives) {