diff --git a/src/TypeScriptGenerator.ts b/src/TypeScriptGenerator.ts
index c5c8dffa..3c28b128 100644
--- a/src/TypeScriptGenerator.ts
+++ b/src/TypeScriptGenerator.ts
@@ -24,15 +24,15 @@ import {
 
 type Selection = {
   key: string;
-  schemaName?: string;
-  value?: any;
-  nodeType?: TypeID;
-  conditional?: boolean;
-  concreteType?: string;
-  ref?: string;
-  nodeSelections?: SelectionMap | null;
-  kind?: string;
-  documentName?: string;
+  schemaName?: string | undefined;
+  value?: any | undefined;
+  nodeType?: TypeID | undefined;
+  conditional?: boolean | undefined;
+  concreteType?: string | undefined;
+  ref?: string | undefined;
+  nodeSelections?: SelectionMap | null | undefined;
+  kind?: string | undefined;
+  documentName?: string | undefined;
 };
 
 type SelectionMap = Map<string, Selection>;
@@ -309,10 +309,31 @@ function exactObjectTypeAnnotation(
 
 const idRegex = /^[$a-zA-Z_][$a-z0-9A-Z_]*$/;
 
+// union optional types with undefined for compat with exactOptionalPropertyTypes
+function createInexactOptionalType(type: ts.TypeNode): ts.TypeNode {
+  if (ts.isUnionTypeNode(type)) {
+    return ts.factory.updateUnionTypeNode(
+      type,
+      ts.factory.createNodeArray([
+        ...type.types,
+        ts.factory.createKeywordTypeNode(ts.SyntaxKind.UndefinedKeyword),
+      ])
+    );
+  } else {
+    return ts.factory.createUnionTypeNode([
+      type,
+      ts.factory.createKeywordTypeNode(ts.SyntaxKind.UndefinedKeyword),
+    ]);
+  }
+}
+
 function objectTypeProperty(
   propertyName: string,
   type: ts.TypeNode,
-  options: { readonly?: boolean; optional?: boolean } = {}
+  options: {
+    readonly?: boolean | undefined;
+    optional?: boolean | undefined;
+  } = {}
 ): ts.PropertySignature {
   const { optional, readonly = true } = options;
   const modifiers = readonly
@@ -325,7 +346,7 @@ function objectTypeProperty(
       ? ts.factory.createIdentifier(propertyName)
       : ts.factory.createStringLiteral(propertyName),
     optional ? ts.factory.createToken(ts.SyntaxKind.QuestionToken) : undefined,
-    type
+    optional ? createInexactOptionalType(type) : type
   );
 }
 
diff --git a/src/TypeScriptTypeTransformers.ts b/src/TypeScriptTypeTransformers.ts
index 248fc90f..595d12f7 100644
--- a/src/TypeScriptTypeTransformers.ts
+++ b/src/TypeScriptTypeTransformers.ts
@@ -9,7 +9,7 @@ export type ScalarTypeMapping = {
 export type State = {
   generatedFragments: Set<string>;
   generatedInputObjectTypes: {
-    [name: string]: ts.TypeNode | "pending";
+    [name: string]: ts.TypeLiteralNode | "pending";
   };
   matchFields: Map<string, ts.TypeNode>;
   runtimeImports: Set<string>;
@@ -37,9 +37,7 @@ export function transformScalarType(
   } else {
     return ts.factory.createUnionTypeNode([
       transformNonNullableScalarType(schema, type, state, objectProps),
-      ts.factory.createLiteralTypeNode(
-        ts.factory.createToken(ts.SyntaxKind.NullKeyword)
-      ),
+      ts.factory.createLiteralTypeNode(ts.factory.createNull()),
     ]);
   }
 }
@@ -115,20 +113,29 @@ function transformGraphQLEnumType(
 export function transformInputType(
   schema: Schema,
   type: TypeID,
-  state: State
+  state: State,
+  options: {
+    inputObjectProperty?: boolean | undefined;
+  } = {}
 ): ts.TypeNode {
+  const { inputObjectProperty } = options;
   if (schema.isNonNull(type)) {
     return transformNonNullableInputType(
       schema,
       schema.getNullableType(type),
       state
     );
+  } else if (inputObjectProperty) {
+    return ts.factory.createUnionTypeNode([
+      transformNonNullableInputType(schema, type, state),
+      ts.factory.createLiteralTypeNode(ts.factory.createNull()),
+      // add undefined to support exactOptionalPropertyTypes
+      ts.factory.createKeywordTypeNode(ts.SyntaxKind.UndefinedKeyword),
+    ]);
   } else {
     return ts.factory.createUnionTypeNode([
       transformNonNullableInputType(schema, type, state),
-      ts.factory.createLiteralTypeNode(
-        ts.factory.createToken(ts.SyntaxKind.NullKeyword)
-      ),
+      ts.factory.createLiteralTypeNode(ts.factory.createNull()),
     ]);
   }
 }
@@ -169,7 +176,9 @@ function transformNonNullableInputType(
           !schema.isNonNull(fieldType)
           ? ts.factory.createToken(ts.SyntaxKind.QuestionToken)
           : undefined,
-        transformInputType(schema, fieldType, state)
+        transformInputType(schema, fieldType, state, {
+          inputObjectProperty: true,
+        })
       );
 
       return property;
diff --git a/test/__snapshots__/TypeScriptGenerator-test.ts.snap b/test/__snapshots__/TypeScriptGenerator-test.ts.snap
index e8fa236a..9470b1dd 100644
--- a/test/__snapshots__/TypeScriptGenerator-test.ts.snap
+++ b/test/__snapshots__/TypeScriptGenerator-test.ts.snap
@@ -16,12 +16,12 @@ fragment NestedCondition on Node {
 // ConditionField.graphql
 import { FragmentRefs } from "relay-runtime";
 export type ConditionField = {
-    readonly id?: string;
+    readonly id?: string | undefined;
     readonly " $refType": "ConditionField";
 };
 export type ConditionField$data = ConditionField;
 export type ConditionField$key = {
-    readonly " $data"?: ConditionField$data;
+    readonly " $data"?: ConditionField$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"ConditionField">;
 };
 
@@ -29,12 +29,12 @@ export type ConditionField$key = {
 // NestedCondition.graphql
 import { FragmentRefs } from "relay-runtime";
 export type NestedCondition = {
-    readonly id?: string;
+    readonly id?: string | undefined;
     readonly " $refType": "NestedCondition";
 };
 export type NestedCondition$data = NestedCondition;
 export type NestedCondition$key = {
-    readonly " $data"?: NestedCondition$data;
+    readonly " $data"?: NestedCondition$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"NestedCondition">;
 };
 
@@ -108,7 +108,7 @@ export type FragmentSpread = {
 };
 export type FragmentSpread$data = FragmentSpread;
 export type FragmentSpread$key = {
-    readonly " $data"?: FragmentSpread$data;
+    readonly " $data"?: FragmentSpread$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FragmentSpread">;
 };
 
@@ -132,7 +132,7 @@ export type ConcreateTypes = {
 };
 export type ConcreateTypes$data = ConcreateTypes;
 export type ConcreateTypes$key = {
-    readonly " $data"?: ConcreateTypes$data;
+    readonly " $data"?: ConcreateTypes$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"ConcreateTypes">;
 };
 
@@ -150,7 +150,7 @@ export type PictureFragment = {
 };
 export type PictureFragment$data = PictureFragment;
 export type PictureFragment$key = {
-    readonly " $data"?: PictureFragment$data;
+    readonly " $data"?: PictureFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PictureFragment">;
 };
 
@@ -163,7 +163,7 @@ export type OtherFragment = {
 };
 export type OtherFragment$data = OtherFragment;
 export type OtherFragment$key = {
-    readonly " $data"?: OtherFragment$data;
+    readonly " $data"?: OtherFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"OtherFragment">;
 };
 
@@ -181,7 +181,7 @@ export type PageFragment = {
 };
 export type PageFragment$data = PageFragment;
 export type PageFragment$key = {
-    readonly " $data"?: PageFragment$data;
+    readonly " $data"?: PageFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PageFragment">;
 };
 
@@ -199,7 +199,7 @@ export type UserFrag1 = {
 };
 export type UserFrag1$data = UserFrag1;
 export type UserFrag1$key = {
-    readonly " $data"?: UserFrag1$data;
+    readonly " $data"?: UserFrag1$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"UserFrag1">;
 };
 
@@ -217,7 +217,7 @@ export type UserFrag2 = {
 };
 export type UserFrag2$data = UserFrag2;
 export type UserFrag2$key = {
-    readonly " $data"?: UserFrag2$data;
+    readonly " $data"?: UserFrag2$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"UserFrag2">;
 };
 
@@ -295,15 +295,15 @@ fragment SomeFragment on User {
 import { FragmentRefs } from "relay-runtime";
 export type InlineFragment = {
     readonly id: string;
-    readonly name?: string | null;
+    readonly name?: string | null | undefined;
     readonly message?: {
         readonly text: string | null;
-    } | null;
+    } | null | undefined;
     readonly " $refType": "InlineFragment";
 };
 export type InlineFragment$data = InlineFragment;
 export type InlineFragment$key = {
-    readonly " $data"?: InlineFragment$data;
+    readonly " $data"?: InlineFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"InlineFragment">;
 };
 
@@ -316,14 +316,14 @@ export type InlineFragmentWithOverlappingFields = {
         readonly name: string | null;
         readonly message?: {
             readonly text: string | null;
-        } | null;
-    } | null;
-    readonly name?: string | null;
+        } | null | undefined;
+    } | null | undefined;
+    readonly name?: string | null | undefined;
     readonly " $refType": "InlineFragmentWithOverlappingFields";
 };
 export type InlineFragmentWithOverlappingFields$data = InlineFragmentWithOverlappingFields;
 export type InlineFragmentWithOverlappingFields$key = {
-    readonly " $data"?: InlineFragmentWithOverlappingFields$data;
+    readonly " $data"?: InlineFragmentWithOverlappingFields$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"InlineFragmentWithOverlappingFields">;
 };
 
@@ -331,13 +331,13 @@ export type InlineFragmentWithOverlappingFields$key = {
 // InlineFragmentConditionalID.graphql
 import { FragmentRefs } from "relay-runtime";
 export type InlineFragmentConditionalID = {
-    readonly id?: string;
-    readonly name?: string | null;
+    readonly id?: string | undefined;
+    readonly name?: string | null | undefined;
     readonly " $refType": "InlineFragmentConditionalID";
 };
 export type InlineFragmentConditionalID$data = InlineFragmentConditionalID;
 export type InlineFragmentConditionalID$key = {
-    readonly " $data"?: InlineFragmentConditionalID$data;
+    readonly " $data"?: InlineFragmentConditionalID$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"InlineFragmentConditionalID">;
 };
 
@@ -349,17 +349,17 @@ export type InlineFragmentKitchenSink = {
         readonly id: string;
         readonly profilePicture: {
             readonly uri: string | null;
-            readonly width?: number | null;
-            readonly height?: number | null;
+            readonly width?: number | null | undefined;
+            readonly height?: number | null | undefined;
         } | null;
-        readonly name?: string | null;
+        readonly name?: string | null | undefined;
         readonly " $fragmentRefs": FragmentRefs<"SomeFragment">;
     } | null;
     readonly " $refType": "InlineFragmentKitchenSink";
 };
 export type InlineFragmentKitchenSink$data = InlineFragmentKitchenSink;
 export type InlineFragmentKitchenSink$key = {
-    readonly " $data"?: InlineFragmentKitchenSink$data;
+    readonly " $data"?: InlineFragmentKitchenSink$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"InlineFragmentKitchenSink">;
 };
 
@@ -377,7 +377,7 @@ export type SomeFragment = {
 };
 export type SomeFragment$data = SomeFragment;
 export type SomeFragment$key = {
-    readonly " $data"?: SomeFragment$data;
+    readonly " $data"?: SomeFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"SomeFragment">;
 };
 
@@ -435,7 +435,7 @@ export type LinkedField = {
 };
 export type LinkedField$data = LinkedField;
 export type LinkedField$key = {
-    readonly " $data"?: LinkedField$data;
+    readonly " $data"?: LinkedField$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"LinkedField">;
 };
 
@@ -490,15 +490,15 @@ import { FragmentRefs } from "relay-runtime";
 export type NameRendererFragment = {
     readonly id: string;
     readonly nameRenderer: {
-        readonly __fragmentPropName?: string | null;
-        readonly __module_component?: string | null;
+        readonly __fragmentPropName?: string | null | undefined;
+        readonly __module_component?: string | null | undefined;
         readonly " $fragmentRefs": FragmentRefs<"PlainUserNameRenderer_name" | "MarkdownUserNameRenderer_name">;
     } | null;
     readonly " $refType": "NameRendererFragment";
 };
 export type NameRendererFragment$data = NameRendererFragment;
 export type NameRendererFragment$key = {
-    readonly " $data"?: NameRendererFragment$data;
+    readonly " $data"?: NameRendererFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"NameRendererFragment">;
 };
 
@@ -514,7 +514,7 @@ export type PlainUserNameRenderer_name = {
 };
 export type PlainUserNameRenderer_name$data = PlainUserNameRenderer_name;
 export type PlainUserNameRenderer_name$key = {
-    readonly " $data"?: PlainUserNameRenderer_name$data;
+    readonly " $data"?: PlainUserNameRenderer_name$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PlainUserNameRenderer_name">;
 };
 
@@ -530,7 +530,7 @@ export type MarkdownUserNameRenderer_name = {
 };
 export type MarkdownUserNameRenderer_name$data = MarkdownUserNameRenderer_name;
 export type MarkdownUserNameRenderer_name$key = {
-    readonly " $data"?: MarkdownUserNameRenderer_name$data;
+    readonly " $data"?: MarkdownUserNameRenderer_name$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"MarkdownUserNameRenderer_name">;
 };
 
@@ -569,8 +569,8 @@ export type NameRendererQueryVariables = {};
 export type NameRendererQueryResponse = {
     readonly me: {
         readonly nameRenderer: {
-            readonly __fragmentPropName?: string | null;
-            readonly __module_component?: string | null;
+            readonly __fragmentPropName?: string | null | undefined;
+            readonly __module_component?: string | null | undefined;
             readonly " $fragmentRefs": FragmentRefs<"PlainUserNameRenderer_name" | "MarkdownUserNameRenderer_name">;
         } | null;
     } | null;
@@ -592,7 +592,7 @@ export type PlainUserNameRenderer_name = {
 };
 export type PlainUserNameRenderer_name$data = PlainUserNameRenderer_name;
 export type PlainUserNameRenderer_name$key = {
-    readonly " $data"?: PlainUserNameRenderer_name$data;
+    readonly " $data"?: PlainUserNameRenderer_name$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PlainUserNameRenderer_name">;
 };
 
@@ -608,182 +608,12 @@ export type MarkdownUserNameRenderer_name = {
 };
 export type MarkdownUserNameRenderer_name$data = MarkdownUserNameRenderer_name;
 export type MarkdownUserNameRenderer_name$key = {
-    readonly " $data"?: MarkdownUserNameRenderer_name$data;
+    readonly " $data"?: MarkdownUserNameRenderer_name$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"MarkdownUserNameRenderer_name">;
 };
 
 `;
 
-exports[`Snapshot tests TypeScriptGenerator with a single artifact directory matches expected output: mutaion-with-client-extension.graphql 1`] = `
-~~~~~~~~~~ INPUT ~~~~~~~~~~
-mutation Test($input: UpdateAllSeenStateInput) @raw_response_type {
-  viewerNotificationsUpdateAllSeenState(input: $input) {
-    stories {
-      foos {
-        bar
-      }
-    }
-  }
-}
-
-extend type Story {
-  foos: [Foo]
-}
-
-type Foo {
-  bar: String
-}
-
-~~~~~~~~~~ OUTPUT ~~~~~~~~~~
-// Test.graphql
-export type UpdateAllSeenStateInput = {
-    clientMutationId?: string | null;
-    storyIds?: Array<string | null> | null;
-};
-export type TestVariables = {
-    input?: UpdateAllSeenStateInput | null;
-};
-export type TestResponse = {
-    readonly viewerNotificationsUpdateAllSeenState: {
-        readonly stories: ReadonlyArray<{
-            readonly foos: ReadonlyArray<{
-                readonly bar: string | null;
-            } | null> | null;
-        } | null> | null;
-    } | null;
-};
-export type TestRawResponse = {
-    readonly viewerNotificationsUpdateAllSeenState: ({
-        readonly stories: ReadonlyArray<({
-            readonly id: string;
-            readonly foos?: ReadonlyArray<({
-                readonly bar: string | null;
-            }) | null> | null;
-        }) | null> | null;
-    }) | null;
-};
-export type Test = {
-    readonly response: TestResponse;
-    readonly variables: TestVariables;
-    readonly rawResponse: TestRawResponse;
-};
-
-`;
-
-exports[`Snapshot tests TypeScriptGenerator with a single artifact directory matches expected output: mutaion-with-response-on-inline-fragments.graphql 1`] = `
-~~~~~~~~~~ INPUT ~~~~~~~~~~
-mutation TestMutation($input: CommentCreateInput!) @raw_response_type {
-  commentCreate(input: $input) {
-    viewer {
-      actor {
-        ...InlineFragmentWithOverlappingFields
-      }
-    }
-  }
-}
-
-fragment InlineFragmentWithOverlappingFields on Actor {
-  ... on User {
-    hometown {
-      id
-      name
-    }
-  }
-  ... on Page {
-    name
-    hometown {
-      id
-      message {
-        text
-      }
-    }
-  }
-}
-
-~~~~~~~~~~ OUTPUT ~~~~~~~~~~
-// TestMutation.graphql
-import { FragmentRefs } from "relay-runtime";
-export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
-};
-export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
-};
-export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
-};
-export type TestMutationVariables = {
-    input: CommentCreateInput;
-};
-export type TestMutationResponse = {
-    readonly commentCreate: {
-        readonly viewer: {
-            readonly actor: {
-                readonly " $fragmentRefs": FragmentRefs<"InlineFragmentWithOverlappingFields">;
-            } | null;
-        } | null;
-    } | null;
-};
-export type TestMutationRawResponse = {
-    readonly commentCreate: ({
-        readonly viewer: ({
-            readonly actor: ({
-                readonly __typename: "User";
-                readonly __isActor: "User";
-                readonly id: string;
-                readonly hometown: ({
-                    readonly id: string;
-                    readonly name: string | null;
-                }) | null;
-            } | {
-                readonly __typename: "Page";
-                readonly __isActor: "Page";
-                readonly id: string;
-                readonly name: string | null;
-                readonly hometown: ({
-                    readonly id: string;
-                    readonly message: ({
-                        readonly text: string | null;
-                    }) | null;
-                }) | null;
-            } | {
-                readonly __typename: string;
-                readonly __isActor: string;
-                readonly id: string;
-            }) | null;
-        }) | null;
-    }) | null;
-};
-export type TestMutation = {
-    readonly response: TestMutationResponse;
-    readonly variables: TestMutationVariables;
-    readonly rawResponse: TestMutationRawResponse;
-};
-
-
-// InlineFragmentWithOverlappingFields.graphql
-import { FragmentRefs } from "relay-runtime";
-export type InlineFragmentWithOverlappingFields = {
-    readonly hometown?: {
-        readonly id: string;
-        readonly name: string | null;
-        readonly message?: {
-            readonly text: string | null;
-        } | null;
-    } | null;
-    readonly name?: string | null;
-    readonly " $refType": "InlineFragmentWithOverlappingFields";
-};
-export type InlineFragmentWithOverlappingFields$data = InlineFragmentWithOverlappingFields;
-export type InlineFragmentWithOverlappingFields$key = {
-    readonly " $data"?: InlineFragmentWithOverlappingFields$data;
-    readonly " $fragmentRefs": FragmentRefs<"InlineFragmentWithOverlappingFields">;
-};
-
-`;
-
 exports[`Snapshot tests TypeScriptGenerator with a single artifact directory matches expected output: mutation.graphql 1`] = `
 ~~~~~~~~~~ INPUT ~~~~~~~~~~
 mutation CommentCreateMutation(
@@ -805,20 +635,20 @@ mutation CommentCreateMutation(
 ~~~~~~~~~~ OUTPUT ~~~~~~~~~~
 // CommentCreateMutation.graphql
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentCreateMutationVariables = {
     input: CommentCreateInput;
-    first?: number | null;
-    orderBy?: Array<string> | null;
+    first?: number | null | undefined;
+    orderBy?: Array<string> | null | undefined;
 };
 export type CommentCreateMutationResponse = {
     readonly commentCreate: {
@@ -851,11 +681,11 @@ mutation InputHasArray($input: UpdateAllSeenStateInput) @raw_response_type {
 ~~~~~~~~~~ OUTPUT ~~~~~~~~~~
 // InputHasArray.graphql
 export type UpdateAllSeenStateInput = {
-    clientMutationId?: string | null;
-    storyIds?: Array<string | null> | null;
+    clientMutationId?: string | null | undefined;
+    storyIds?: Array<string | null> | null | undefined;
 };
 export type InputHasArrayVariables = {
-    input?: UpdateAllSeenStateInput | null;
+    input?: UpdateAllSeenStateInput | null | undefined;
 };
 export type InputHasArrayResponse = {
     readonly viewerNotificationsUpdateAllSeenState: {
@@ -913,15 +743,15 @@ mutation PrependEdgeMutation(
 ~~~~~~~~~~ OUTPUT ~~~~~~~~~~
 // AppendEdgeMutation.graphql
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type AppendEdgeMutationVariables = {
     input: CommentCreateInput;
@@ -945,15 +775,15 @@ export type AppendEdgeMutation = {
 
 // PrependEdgeMutation.graphql
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type PrependEdgeMutationVariables = {
     input: CommentCreateInput;
@@ -998,11 +828,11 @@ type Foo {
 ~~~~~~~~~~ OUTPUT ~~~~~~~~~~
 // Test.graphql
 export type UpdateAllSeenStateInput = {
-    clientMutationId?: string | null;
-    storyIds?: Array<string | null> | null;
+    clientMutationId?: string | null | undefined;
+    storyIds?: Array<string | null> | null | undefined;
 };
 export type TestVariables = {
-    input?: UpdateAllSeenStateInput | null;
+    input?: UpdateAllSeenStateInput | null | undefined;
 };
 export type TestResponse = {
     readonly viewerNotificationsUpdateAllSeenState: {
@@ -1019,7 +849,7 @@ export type TestRawResponse = {
             readonly id: string;
             readonly foos?: ReadonlyArray<({
                 readonly bar: string | null;
-            }) | null> | null;
+            }) | null> | null | undefined;
         }) | null> | null;
     }) | null;
 };
@@ -1043,8 +873,8 @@ mutation DeleteRecordMutation(
 ~~~~~~~~~~ OUTPUT ~~~~~~~~~~
 // DeleteRecordMutation.graphql
 export type CommentDeleteInput = {
-    clientMutationId?: string | null;
-    commentId?: string | null;
+    clientMutationId?: string | null | undefined;
+    commentId?: string | null | undefined;
 };
 export type DeleteRecordMutationVariables = {
     input: CommentDeleteInput;
@@ -1096,20 +926,20 @@ fragment FriendFragment on User {
 import { FragmentRefs } from "relay-runtime";
 export type TestEnums = "mark" | "zuck" | "%future added value";
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentCreateMutationVariables = {
     input: CommentCreateInput;
-    first?: number | null;
-    orderBy?: Array<string> | null;
+    first?: number | null | undefined;
+    orderBy?: Array<string> | null | undefined;
 };
 export type CommentCreateMutationResponse = {
     readonly commentCreate: {
@@ -1166,7 +996,7 @@ export type FriendFragment = {
 };
 export type FriendFragment$data = FriendFragment;
 export type FriendFragment$key = {
-    readonly " $data"?: FriendFragment$data;
+    readonly " $data"?: FriendFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FriendFragment">;
 };
 
@@ -1210,20 +1040,20 @@ fragment FeedbackFragment on Feedback {
 // CommentCreateMutation.graphql
 import { FragmentRefs } from "relay-runtime";
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentCreateMutationVariables = {
     input: CommentCreateInput;
-    first?: number | null;
-    orderBy?: Array<string> | null;
+    first?: number | null | undefined;
+    orderBy?: Array<string> | null | undefined;
 };
 export type CommentCreateMutationResponse = {
     readonly commentCreate: {
@@ -1278,7 +1108,7 @@ export type FriendFragment = {
 };
 export type FriendFragment$data = FriendFragment;
 export type FriendFragment$key = {
-    readonly " $data"?: FriendFragment$data;
+    readonly " $data"?: FriendFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FriendFragment">;
 };
 
@@ -1292,7 +1122,7 @@ export type FeedbackFragment = {
 };
 export type FeedbackFragment$data = FeedbackFragment;
 export type FeedbackFragment$key = {
-    readonly " $data"?: FeedbackFragment$data;
+    readonly " $data"?: FeedbackFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FeedbackFragment">;
 };
 
@@ -1331,15 +1161,15 @@ fragment InlineFragmentWithOverlappingFields on Actor {
 // TestMutation.graphql
 import { FragmentRefs } from "relay-runtime";
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type TestMutationVariables = {
     input: CommentCreateInput;
@@ -1398,14 +1228,14 @@ export type InlineFragmentWithOverlappingFields = {
         readonly name: string | null;
         readonly message?: {
             readonly text: string | null;
-        } | null;
-    } | null;
-    readonly name?: string | null;
+        } | null | undefined;
+    } | null | undefined;
+    readonly name?: string | null | undefined;
     readonly " $refType": "InlineFragmentWithOverlappingFields";
 };
 export type InlineFragmentWithOverlappingFields$data = InlineFragmentWithOverlappingFields;
 export type InlineFragmentWithOverlappingFields$key = {
-    readonly " $data"?: InlineFragmentWithOverlappingFields$data;
+    readonly " $data"?: InlineFragmentWithOverlappingFields$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"InlineFragmentWithOverlappingFields">;
 };
 
@@ -1426,7 +1256,7 @@ export type PluralFragment = ReadonlyArray<{
 }>;
 export type PluralFragment$data = PluralFragment;
 export type PluralFragment$key = ReadonlyArray<{
-    readonly " $data"?: PluralFragment$data;
+    readonly " $data"?: PluralFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PluralFragment">;
 }>;
 
@@ -1456,7 +1286,7 @@ query TestDefer @raw_response_type {
 export type TestDeferVariables = {};
 export type TestDeferResponse = {
     readonly node: {
-        readonly name?: string | null;
+        readonly name?: string | null | undefined;
         readonly friends?: {
             readonly edges: ReadonlyArray<{
                 readonly node: {
@@ -1465,7 +1295,7 @@ export type TestDeferResponse = {
                     } | null;
                 } | null;
             } | null> | null;
-        } | null;
+        } | null | undefined;
     } | null;
 };
 export type TestDeferRawResponse = {
@@ -1533,7 +1363,7 @@ export type LinkedHandleFieldResponse = {
     readonly node: {
         readonly friends?: {
             readonly count: number | null;
-        } | null;
+        } | null | undefined;
     } | null;
 };
 export type LinkedHandleFieldRawResponse = {
@@ -1561,7 +1391,7 @@ export type ScalarHandleFieldVariables = {
 };
 export type ScalarHandleFieldResponse = {
     readonly node: {
-        readonly name?: string | null;
+        readonly name?: string | null | undefined;
     } | null;
 };
 export type ScalarHandleFieldRawResponse = {
@@ -1638,17 +1468,17 @@ export type ExampleQuery = {
 // FriendFragment.graphql
 import { FragmentRefs } from "relay-runtime";
 export type FriendFragment = {
-    readonly name?: string | null;
-    readonly lastName?: string | null;
+    readonly name?: string | null | undefined;
+    readonly lastName?: string | null | undefined;
     readonly feedback?: {
         readonly id: string;
         readonly name: string | null;
-    } | null;
+    } | null | undefined;
     readonly " $refType": "FriendFragment";
 };
 export type FriendFragment$data = FriendFragment;
 export type FriendFragment$key = {
-    readonly " $data"?: FriendFragment$data;
+    readonly " $data"?: FriendFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FriendFragment">;
 };
 
@@ -1690,7 +1520,7 @@ export type ExampleQueryResponse = {
         readonly username: string | null;
         readonly friends?: {
             readonly count: number | null;
-        } | null;
+        } | null | undefined;
         readonly " $fragmentRefs": FragmentRefs<"FriendFragment">;
     } | null;
 };
@@ -1711,17 +1541,17 @@ export type ExampleQuery = {
 // FriendFragment.graphql
 import { FragmentRefs } from "relay-runtime";
 export type FriendFragment = {
-    readonly name?: string | null;
-    readonly lastName?: string | null;
+    readonly name?: string | null | undefined;
+    readonly lastName?: string | null | undefined;
     readonly feedback?: {
         readonly id: string;
         readonly name: string | null;
-    } | null;
+    } | null | undefined;
     readonly " $refType": "FriendFragment";
 };
 export type FriendFragment$data = FriendFragment;
 export type FriendFragment$key = {
-    readonly " $data"?: FriendFragment$data;
+    readonly " $data"?: FriendFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FriendFragment">;
 };
 
@@ -1753,14 +1583,14 @@ query TestStream @raw_response_type {
 export type TestStreamVariables = {};
 export type TestStreamResponse = {
     readonly node: {
-        readonly name?: string | null;
+        readonly name?: string | null | undefined;
         readonly friends?: {
             readonly edges: ReadonlyArray<{
                 readonly node: {
                     readonly id: string;
                 } | null;
             } | null> | null;
-        } | null;
+        } | null | undefined;
     } | null;
 };
 export type TestStreamRawResponse = {
@@ -1819,7 +1649,7 @@ query TestDefer @raw_response_type {
 export type TestDeferVariables = {};
 export type TestDeferResponse = {
     readonly node: {
-        readonly name?: string | null;
+        readonly name?: string | null | undefined;
         readonly friends?: {
             readonly edges: ReadonlyArray<{
                 readonly node: {
@@ -1828,7 +1658,7 @@ export type TestDeferResponse = {
                     } | null;
                 } | null;
             } | null> | null;
-        } | null;
+        } | null | undefined;
     } | null;
 };
 export type TestDeferRawResponse = {
@@ -1886,7 +1716,7 @@ export type FragmentSpread = {
 };
 export type FragmentSpread$data = FragmentSpread;
 export type FragmentSpread$key = {
-    readonly " $data"?: FragmentSpread$data;
+    readonly " $data"?: FragmentSpread$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FragmentSpread">;
 };
 
@@ -1914,7 +1744,7 @@ export type RefetchableFragment = {
 };
 export type RefetchableFragment$data = RefetchableFragment;
 export type RefetchableFragment$key = {
-    readonly " $data"?: RefetchableFragment$data;
+    readonly " $data"?: RefetchableFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"RefetchableFragment">;
 };
 
@@ -1989,8 +1819,8 @@ export type RelayClientIDFieldQueryResponse = {
                 readonly __id: string;
                 readonly __typename: string;
                 readonly text: string | null;
-            } | null;
-        } | null;
+            } | null | undefined;
+        } | null | undefined;
     } | null;
 };
 export type RelayClientIDFieldQuery = {
@@ -2052,22 +1882,22 @@ export type ExampleFragment = {
 };
 export type ExampleFragment$data = ExampleFragment;
 export type ExampleFragment$key = {
-    readonly " $data"?: ExampleFragment$data;
+    readonly " $data"?: ExampleFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"ExampleFragment">;
 };
 
 
 // TestMutation.graphql
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type TestMutationVariables = {
     input: CommentCreateInput;
@@ -2087,11 +1917,11 @@ export type TestMutation = {
 
 // TestSubscription.graphql
 export type FeedbackLikeInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
 };
 export type TestSubscriptionVariables = {
-    input?: FeedbackLikeInput | null;
+    input?: FeedbackLikeInput | null | undefined;
 };
 export type TestSubscriptionResponse = {
     readonly feedbackLikeSubscribe: {
@@ -2143,7 +1973,7 @@ export type ScalarField = {
 };
 export type ScalarField$data = ScalarField;
 export type ScalarField$key = {
-    readonly " $data"?: ScalarField$data;
+    readonly " $data"?: ScalarField$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"ScalarField">;
 };
 
@@ -2192,7 +2022,7 @@ export type TypenameInsideWithOverlappingFields = {
 };
 export type TypenameInsideWithOverlappingFields$data = TypenameInsideWithOverlappingFields;
 export type TypenameInsideWithOverlappingFields$key = {
-    readonly " $data"?: TypenameInsideWithOverlappingFields$data;
+    readonly " $data"?: TypenameInsideWithOverlappingFields$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameInsideWithOverlappingFields">;
 };
 
@@ -2300,7 +2130,7 @@ export type TypenameInside = {
 };
 export type TypenameInside$data = TypenameInside;
 export type TypenameInside$key = {
-    readonly " $data"?: TypenameInside$data;
+    readonly " $data"?: TypenameInside$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameInside">;
 };
 
@@ -2323,7 +2153,7 @@ export type TypenameOutside = {
 };
 export type TypenameOutside$data = TypenameOutside;
 export type TypenameOutside$key = {
-    readonly " $data"?: TypenameOutside$data;
+    readonly " $data"?: TypenameOutside$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameOutside">;
 };
 
@@ -2332,18 +2162,18 @@ export type TypenameOutside$key = {
 import { FragmentRefs } from "relay-runtime";
 export type TypenameOutsideWithAbstractType = {
     readonly __typename: string;
-    readonly username?: string | null;
+    readonly username?: string | null | undefined;
     readonly address?: {
         readonly city: string | null;
         readonly country: string | null;
-        readonly street?: string | null;
-    } | null;
-    readonly firstName?: string | null;
+        readonly street?: string | null | undefined;
+    } | null | undefined;
+    readonly firstName?: string | null | undefined;
     readonly " $refType": "TypenameOutsideWithAbstractType";
 };
 export type TypenameOutsideWithAbstractType$data = TypenameOutsideWithAbstractType;
 export type TypenameOutsideWithAbstractType$key = {
-    readonly " $data"?: TypenameOutsideWithAbstractType$data;
+    readonly " $data"?: TypenameOutsideWithAbstractType$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameOutsideWithAbstractType">;
 };
 
@@ -2357,7 +2187,7 @@ export type TypenameWithoutSpreads = {
 };
 export type TypenameWithoutSpreads$data = TypenameWithoutSpreads;
 export type TypenameWithoutSpreads$key = {
-    readonly " $data"?: TypenameWithoutSpreads$data;
+    readonly " $data"?: TypenameWithoutSpreads$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameWithoutSpreads">;
 };
 
@@ -2371,7 +2201,7 @@ export type TypenameWithoutSpreadsAbstractType = {
 };
 export type TypenameWithoutSpreadsAbstractType$data = TypenameWithoutSpreadsAbstractType;
 export type TypenameWithoutSpreadsAbstractType$key = {
-    readonly " $data"?: TypenameWithoutSpreadsAbstractType$data;
+    readonly " $data"?: TypenameWithoutSpreadsAbstractType$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameWithoutSpreadsAbstractType">;
 };
 
@@ -2381,13 +2211,13 @@ import { FragmentRefs } from "relay-runtime";
 export type TypenameWithCommonSelections = {
     readonly __typename: string;
     readonly name: string | null;
-    readonly firstName?: string | null;
-    readonly username?: string | null;
+    readonly firstName?: string | null | undefined;
+    readonly username?: string | null | undefined;
     readonly " $refType": "TypenameWithCommonSelections";
 };
 export type TypenameWithCommonSelections$data = TypenameWithCommonSelections;
 export type TypenameWithCommonSelections$key = {
-    readonly " $data"?: TypenameWithCommonSelections$data;
+    readonly " $data"?: TypenameWithCommonSelections$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameWithCommonSelections">;
 };
 
@@ -2410,7 +2240,7 @@ export type TypenameAlias = {
 };
 export type TypenameAlias$data = TypenameAlias;
 export type TypenameAlias$key = {
-    readonly " $data"?: TypenameAlias$data;
+    readonly " $data"?: TypenameAlias$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameAlias">;
 };
 
@@ -2438,7 +2268,7 @@ export type TypenameAliases = {
 };
 export type TypenameAliases$data = TypenameAliases;
 export type TypenameAliases$key = {
-    readonly " $data"?: TypenameAliases$data;
+    readonly " $data"?: TypenameAliases$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameAliases">;
 };
 
@@ -2487,7 +2317,7 @@ export type UserProfile = {
 };
 export type UserProfile$data = UserProfile;
 export type UserProfile$key = {
-    readonly " $data"?: UserProfile$data;
+    readonly " $data"?: UserProfile$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"UserProfile">;
 };
 
@@ -2501,7 +2331,7 @@ export type PhotoFragment = {
 };
 export type PhotoFragment$data = PhotoFragment;
 export type PhotoFragment$key = {
-    readonly " $data"?: PhotoFragment$data;
+    readonly " $data"?: PhotoFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PhotoFragment">;
 };
 
@@ -2514,7 +2344,7 @@ export type RecursiveFragment = {
 };
 export type RecursiveFragment$data = RecursiveFragment;
 export type RecursiveFragment$key = {
-    readonly " $data"?: RecursiveFragment$data;
+    readonly " $data"?: RecursiveFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"RecursiveFragment">;
 };
 
@@ -2528,7 +2358,7 @@ export type AnotherRecursiveFragment = {
 };
 export type AnotherRecursiveFragment$data = AnotherRecursiveFragment;
 export type AnotherRecursiveFragment$key = {
-    readonly " $data"?: AnotherRecursiveFragment$data;
+    readonly " $data"?: AnotherRecursiveFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"AnotherRecursiveFragment">;
 };
 
@@ -2550,12 +2380,12 @@ fragment NestedCondition on Node {
 // ConditionField.graphql
 import { FragmentRefs } from "relay-runtime";
 export type ConditionField = {
-    readonly id?: string;
+    readonly id?: string | undefined;
     readonly " $refType": "ConditionField";
 };
 export type ConditionField$data = ConditionField;
 export type ConditionField$key = {
-    readonly " $data"?: ConditionField$data;
+    readonly " $data"?: ConditionField$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"ConditionField">;
 };
 
@@ -2563,12 +2393,12 @@ export type ConditionField$key = {
 // NestedCondition.graphql
 import { FragmentRefs } from "relay-runtime";
 export type NestedCondition = {
-    readonly id?: string;
+    readonly id?: string | undefined;
     readonly " $refType": "NestedCondition";
 };
 export type NestedCondition$data = NestedCondition;
 export type NestedCondition$key = {
-    readonly " $data"?: NestedCondition$data;
+    readonly " $data"?: NestedCondition$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"NestedCondition">;
 };
 
@@ -2642,7 +2472,7 @@ export type FragmentSpread = {
 };
 export type FragmentSpread$data = FragmentSpread;
 export type FragmentSpread$key = {
-    readonly " $data"?: FragmentSpread$data;
+    readonly " $data"?: FragmentSpread$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FragmentSpread">;
 };
 
@@ -2666,7 +2496,7 @@ export type ConcreateTypes = {
 };
 export type ConcreateTypes$data = ConcreateTypes;
 export type ConcreateTypes$key = {
-    readonly " $data"?: ConcreateTypes$data;
+    readonly " $data"?: ConcreateTypes$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"ConcreateTypes">;
 };
 
@@ -2684,7 +2514,7 @@ export type PictureFragment = {
 };
 export type PictureFragment$data = PictureFragment;
 export type PictureFragment$key = {
-    readonly " $data"?: PictureFragment$data;
+    readonly " $data"?: PictureFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PictureFragment">;
 };
 
@@ -2697,7 +2527,7 @@ export type OtherFragment = {
 };
 export type OtherFragment$data = OtherFragment;
 export type OtherFragment$key = {
-    readonly " $data"?: OtherFragment$data;
+    readonly " $data"?: OtherFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"OtherFragment">;
 };
 
@@ -2715,7 +2545,7 @@ export type PageFragment = {
 };
 export type PageFragment$data = PageFragment;
 export type PageFragment$key = {
-    readonly " $data"?: PageFragment$data;
+    readonly " $data"?: PageFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PageFragment">;
 };
 
@@ -2733,7 +2563,7 @@ export type UserFrag1 = {
 };
 export type UserFrag1$data = UserFrag1;
 export type UserFrag1$key = {
-    readonly " $data"?: UserFrag1$data;
+    readonly " $data"?: UserFrag1$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"UserFrag1">;
 };
 
@@ -2751,7 +2581,7 @@ export type UserFrag2 = {
 };
 export type UserFrag2$data = UserFrag2;
 export type UserFrag2$key = {
-    readonly " $data"?: UserFrag2$data;
+    readonly " $data"?: UserFrag2$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"UserFrag2">;
 };
 
@@ -2829,15 +2659,15 @@ fragment SomeFragment on User {
 import { FragmentRefs } from "relay-runtime";
 export type InlineFragment = {
     readonly id: string;
-    readonly name?: string | null;
+    readonly name?: string | null | undefined;
     readonly message?: {
         readonly text: string | null;
-    } | null;
+    } | null | undefined;
     readonly " $refType": "InlineFragment";
 };
 export type InlineFragment$data = InlineFragment;
 export type InlineFragment$key = {
-    readonly " $data"?: InlineFragment$data;
+    readonly " $data"?: InlineFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"InlineFragment">;
 };
 
@@ -2850,14 +2680,14 @@ export type InlineFragmentWithOverlappingFields = {
         readonly name: string | null;
         readonly message?: {
             readonly text: string | null;
-        } | null;
-    } | null;
-    readonly name?: string | null;
+        } | null | undefined;
+    } | null | undefined;
+    readonly name?: string | null | undefined;
     readonly " $refType": "InlineFragmentWithOverlappingFields";
 };
 export type InlineFragmentWithOverlappingFields$data = InlineFragmentWithOverlappingFields;
 export type InlineFragmentWithOverlappingFields$key = {
-    readonly " $data"?: InlineFragmentWithOverlappingFields$data;
+    readonly " $data"?: InlineFragmentWithOverlappingFields$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"InlineFragmentWithOverlappingFields">;
 };
 
@@ -2865,13 +2695,13 @@ export type InlineFragmentWithOverlappingFields$key = {
 // InlineFragmentConditionalID.graphql
 import { FragmentRefs } from "relay-runtime";
 export type InlineFragmentConditionalID = {
-    readonly id?: string;
-    readonly name?: string | null;
+    readonly id?: string | undefined;
+    readonly name?: string | null | undefined;
     readonly " $refType": "InlineFragmentConditionalID";
 };
 export type InlineFragmentConditionalID$data = InlineFragmentConditionalID;
 export type InlineFragmentConditionalID$key = {
-    readonly " $data"?: InlineFragmentConditionalID$data;
+    readonly " $data"?: InlineFragmentConditionalID$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"InlineFragmentConditionalID">;
 };
 
@@ -2883,17 +2713,17 @@ export type InlineFragmentKitchenSink = {
         readonly id: string;
         readonly profilePicture: {
             readonly uri: string | null;
-            readonly width?: number | null;
-            readonly height?: number | null;
+            readonly width?: number | null | undefined;
+            readonly height?: number | null | undefined;
         } | null;
-        readonly name?: string | null;
+        readonly name?: string | null | undefined;
         readonly " $fragmentRefs": FragmentRefs<"SomeFragment">;
     } | null;
     readonly " $refType": "InlineFragmentKitchenSink";
 };
 export type InlineFragmentKitchenSink$data = InlineFragmentKitchenSink;
 export type InlineFragmentKitchenSink$key = {
-    readonly " $data"?: InlineFragmentKitchenSink$data;
+    readonly " $data"?: InlineFragmentKitchenSink$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"InlineFragmentKitchenSink">;
 };
 
@@ -2911,7 +2741,7 @@ export type SomeFragment = {
 };
 export type SomeFragment$data = SomeFragment;
 export type SomeFragment$key = {
-    readonly " $data"?: SomeFragment$data;
+    readonly " $data"?: SomeFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"SomeFragment">;
 };
 
@@ -2969,7 +2799,7 @@ export type LinkedField = {
 };
 export type LinkedField$data = LinkedField;
 export type LinkedField$key = {
-    readonly " $data"?: LinkedField$data;
+    readonly " $data"?: LinkedField$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"LinkedField">;
 };
 
@@ -3024,15 +2854,15 @@ import { FragmentRefs } from "relay-runtime";
 export type NameRendererFragment = {
     readonly id: string;
     readonly nameRenderer: {
-        readonly __fragmentPropName?: string | null;
-        readonly __module_component?: string | null;
+        readonly __fragmentPropName?: string | null | undefined;
+        readonly __module_component?: string | null | undefined;
         readonly " $fragmentRefs": FragmentRefs<"PlainUserNameRenderer_name" | "MarkdownUserNameRenderer_name">;
     } | null;
     readonly " $refType": "NameRendererFragment";
 };
 export type NameRendererFragment$data = NameRendererFragment;
 export type NameRendererFragment$key = {
-    readonly " $data"?: NameRendererFragment$data;
+    readonly " $data"?: NameRendererFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"NameRendererFragment">;
 };
 
@@ -3048,7 +2878,7 @@ export type PlainUserNameRenderer_name = {
 };
 export type PlainUserNameRenderer_name$data = PlainUserNameRenderer_name;
 export type PlainUserNameRenderer_name$key = {
-    readonly " $data"?: PlainUserNameRenderer_name$data;
+    readonly " $data"?: PlainUserNameRenderer_name$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PlainUserNameRenderer_name">;
 };
 
@@ -3064,7 +2894,7 @@ export type MarkdownUserNameRenderer_name = {
 };
 export type MarkdownUserNameRenderer_name$data = MarkdownUserNameRenderer_name;
 export type MarkdownUserNameRenderer_name$key = {
-    readonly " $data"?: MarkdownUserNameRenderer_name$data;
+    readonly " $data"?: MarkdownUserNameRenderer_name$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"MarkdownUserNameRenderer_name">;
 };
 
@@ -3103,8 +2933,8 @@ export type NameRendererQueryVariables = {};
 export type NameRendererQueryResponse = {
     readonly me: {
         readonly nameRenderer: {
-            readonly __fragmentPropName?: string | null;
-            readonly __module_component?: string | null;
+            readonly __fragmentPropName?: string | null | undefined;
+            readonly __module_component?: string | null | undefined;
             readonly " $fragmentRefs": FragmentRefs<"PlainUserNameRenderer_name" | "MarkdownUserNameRenderer_name">;
         } | null;
     } | null;
@@ -3126,7 +2956,7 @@ export type PlainUserNameRenderer_name = {
 };
 export type PlainUserNameRenderer_name$data = PlainUserNameRenderer_name;
 export type PlainUserNameRenderer_name$key = {
-    readonly " $data"?: PlainUserNameRenderer_name$data;
+    readonly " $data"?: PlainUserNameRenderer_name$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PlainUserNameRenderer_name">;
 };
 
@@ -3142,182 +2972,12 @@ export type MarkdownUserNameRenderer_name = {
 };
 export type MarkdownUserNameRenderer_name$data = MarkdownUserNameRenderer_name;
 export type MarkdownUserNameRenderer_name$key = {
-    readonly " $data"?: MarkdownUserNameRenderer_name$data;
+    readonly " $data"?: MarkdownUserNameRenderer_name$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"MarkdownUserNameRenderer_name">;
 };
 
 `;
 
-exports[`Snapshot tests TypeScriptGenerator without a single artifact directory matches expected output: mutaion-with-client-extension.graphql 1`] = `
-~~~~~~~~~~ INPUT ~~~~~~~~~~
-mutation Test($input: UpdateAllSeenStateInput) @raw_response_type {
-  viewerNotificationsUpdateAllSeenState(input: $input) {
-    stories {
-      foos {
-        bar
-      }
-    }
-  }
-}
-
-extend type Story {
-  foos: [Foo]
-}
-
-type Foo {
-  bar: String
-}
-
-~~~~~~~~~~ OUTPUT ~~~~~~~~~~
-// Test.graphql
-export type UpdateAllSeenStateInput = {
-    clientMutationId?: string | null;
-    storyIds?: Array<string | null> | null;
-};
-export type TestVariables = {
-    input?: UpdateAllSeenStateInput | null;
-};
-export type TestResponse = {
-    readonly viewerNotificationsUpdateAllSeenState: {
-        readonly stories: ReadonlyArray<{
-            readonly foos: ReadonlyArray<{
-                readonly bar: string | null;
-            } | null> | null;
-        } | null> | null;
-    } | null;
-};
-export type TestRawResponse = {
-    readonly viewerNotificationsUpdateAllSeenState: ({
-        readonly stories: ReadonlyArray<({
-            readonly id: string;
-            readonly foos?: ReadonlyArray<({
-                readonly bar: string | null;
-            }) | null> | null;
-        }) | null> | null;
-    }) | null;
-};
-export type Test = {
-    readonly response: TestResponse;
-    readonly variables: TestVariables;
-    readonly rawResponse: TestRawResponse;
-};
-
-`;
-
-exports[`Snapshot tests TypeScriptGenerator without a single artifact directory matches expected output: mutaion-with-response-on-inline-fragments.graphql 1`] = `
-~~~~~~~~~~ INPUT ~~~~~~~~~~
-mutation TestMutation($input: CommentCreateInput!) @raw_response_type {
-  commentCreate(input: $input) {
-    viewer {
-      actor {
-        ...InlineFragmentWithOverlappingFields
-      }
-    }
-  }
-}
-
-fragment InlineFragmentWithOverlappingFields on Actor {
-  ... on User {
-    hometown {
-      id
-      name
-    }
-  }
-  ... on Page {
-    name
-    hometown {
-      id
-      message {
-        text
-      }
-    }
-  }
-}
-
-~~~~~~~~~~ OUTPUT ~~~~~~~~~~
-// TestMutation.graphql
-import { FragmentRefs } from "relay-runtime";
-export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
-};
-export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
-};
-export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
-};
-export type TestMutationVariables = {
-    input: CommentCreateInput;
-};
-export type TestMutationResponse = {
-    readonly commentCreate: {
-        readonly viewer: {
-            readonly actor: {
-                readonly " $fragmentRefs": FragmentRefs<"InlineFragmentWithOverlappingFields">;
-            } | null;
-        } | null;
-    } | null;
-};
-export type TestMutationRawResponse = {
-    readonly commentCreate: ({
-        readonly viewer: ({
-            readonly actor: ({
-                readonly __typename: "User";
-                readonly __isActor: "User";
-                readonly id: string;
-                readonly hometown: ({
-                    readonly id: string;
-                    readonly name: string | null;
-                }) | null;
-            } | {
-                readonly __typename: "Page";
-                readonly __isActor: "Page";
-                readonly id: string;
-                readonly name: string | null;
-                readonly hometown: ({
-                    readonly id: string;
-                    readonly message: ({
-                        readonly text: string | null;
-                    }) | null;
-                }) | null;
-            } | {
-                readonly __typename: string;
-                readonly __isActor: string;
-                readonly id: string;
-            }) | null;
-        }) | null;
-    }) | null;
-};
-export type TestMutation = {
-    readonly response: TestMutationResponse;
-    readonly variables: TestMutationVariables;
-    readonly rawResponse: TestMutationRawResponse;
-};
-
-
-// InlineFragmentWithOverlappingFields.graphql
-import { FragmentRefs } from "relay-runtime";
-export type InlineFragmentWithOverlappingFields = {
-    readonly hometown?: {
-        readonly id: string;
-        readonly name: string | null;
-        readonly message?: {
-            readonly text: string | null;
-        } | null;
-    } | null;
-    readonly name?: string | null;
-    readonly " $refType": "InlineFragmentWithOverlappingFields";
-};
-export type InlineFragmentWithOverlappingFields$data = InlineFragmentWithOverlappingFields;
-export type InlineFragmentWithOverlappingFields$key = {
-    readonly " $data"?: InlineFragmentWithOverlappingFields$data;
-    readonly " $fragmentRefs": FragmentRefs<"InlineFragmentWithOverlappingFields">;
-};
-
-`;
-
 exports[`Snapshot tests TypeScriptGenerator without a single artifact directory matches expected output: mutation.graphql 1`] = `
 ~~~~~~~~~~ INPUT ~~~~~~~~~~
 mutation CommentCreateMutation(
@@ -3339,20 +2999,20 @@ mutation CommentCreateMutation(
 ~~~~~~~~~~ OUTPUT ~~~~~~~~~~
 // CommentCreateMutation.graphql
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentCreateMutationVariables = {
     input: CommentCreateInput;
-    first?: number | null;
-    orderBy?: Array<string> | null;
+    first?: number | null | undefined;
+    orderBy?: Array<string> | null | undefined;
 };
 export type CommentCreateMutationResponse = {
     readonly commentCreate: {
@@ -3385,11 +3045,11 @@ mutation InputHasArray($input: UpdateAllSeenStateInput) @raw_response_type {
 ~~~~~~~~~~ OUTPUT ~~~~~~~~~~
 // InputHasArray.graphql
 export type UpdateAllSeenStateInput = {
-    clientMutationId?: string | null;
-    storyIds?: Array<string | null> | null;
+    clientMutationId?: string | null | undefined;
+    storyIds?: Array<string | null> | null | undefined;
 };
 export type InputHasArrayVariables = {
-    input?: UpdateAllSeenStateInput | null;
+    input?: UpdateAllSeenStateInput | null | undefined;
 };
 export type InputHasArrayResponse = {
     readonly viewerNotificationsUpdateAllSeenState: {
@@ -3447,15 +3107,15 @@ mutation PrependEdgeMutation(
 ~~~~~~~~~~ OUTPUT ~~~~~~~~~~
 // AppendEdgeMutation.graphql
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type AppendEdgeMutationVariables = {
     input: CommentCreateInput;
@@ -3479,15 +3139,15 @@ export type AppendEdgeMutation = {
 
 // PrependEdgeMutation.graphql
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type PrependEdgeMutationVariables = {
     input: CommentCreateInput;
@@ -3532,11 +3192,11 @@ type Foo {
 ~~~~~~~~~~ OUTPUT ~~~~~~~~~~
 // Test.graphql
 export type UpdateAllSeenStateInput = {
-    clientMutationId?: string | null;
-    storyIds?: Array<string | null> | null;
+    clientMutationId?: string | null | undefined;
+    storyIds?: Array<string | null> | null | undefined;
 };
 export type TestVariables = {
-    input?: UpdateAllSeenStateInput | null;
+    input?: UpdateAllSeenStateInput | null | undefined;
 };
 export type TestResponse = {
     readonly viewerNotificationsUpdateAllSeenState: {
@@ -3553,7 +3213,7 @@ export type TestRawResponse = {
             readonly id: string;
             readonly foos?: ReadonlyArray<({
                 readonly bar: string | null;
-            }) | null> | null;
+            }) | null> | null | undefined;
         }) | null> | null;
     }) | null;
 };
@@ -3577,8 +3237,8 @@ mutation DeleteRecordMutation(
 ~~~~~~~~~~ OUTPUT ~~~~~~~~~~
 // DeleteRecordMutation.graphql
 export type CommentDeleteInput = {
-    clientMutationId?: string | null;
-    commentId?: string | null;
+    clientMutationId?: string | null | undefined;
+    commentId?: string | null | undefined;
 };
 export type DeleteRecordMutationVariables = {
     input: CommentDeleteInput;
@@ -3630,20 +3290,20 @@ fragment FriendFragment on User {
 import { FragmentRefs } from "relay-runtime";
 export type TestEnums = "mark" | "zuck" | "%future added value";
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentCreateMutationVariables = {
     input: CommentCreateInput;
-    first?: number | null;
-    orderBy?: Array<string> | null;
+    first?: number | null | undefined;
+    orderBy?: Array<string> | null | undefined;
 };
 export type CommentCreateMutationResponse = {
     readonly commentCreate: {
@@ -3700,7 +3360,7 @@ export type FriendFragment = {
 };
 export type FriendFragment$data = FriendFragment;
 export type FriendFragment$key = {
-    readonly " $data"?: FriendFragment$data;
+    readonly " $data"?: FriendFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FriendFragment">;
 };
 
@@ -3744,20 +3404,20 @@ fragment FeedbackFragment on Feedback {
 // CommentCreateMutation.graphql
 import { FragmentRefs } from "relay-runtime";
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentCreateMutationVariables = {
     input: CommentCreateInput;
-    first?: number | null;
-    orderBy?: Array<string> | null;
+    first?: number | null | undefined;
+    orderBy?: Array<string> | null | undefined;
 };
 export type CommentCreateMutationResponse = {
     readonly commentCreate: {
@@ -3812,7 +3472,7 @@ export type FriendFragment = {
 };
 export type FriendFragment$data = FriendFragment;
 export type FriendFragment$key = {
-    readonly " $data"?: FriendFragment$data;
+    readonly " $data"?: FriendFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FriendFragment">;
 };
 
@@ -3826,7 +3486,7 @@ export type FeedbackFragment = {
 };
 export type FeedbackFragment$data = FeedbackFragment;
 export type FeedbackFragment$key = {
-    readonly " $data"?: FeedbackFragment$data;
+    readonly " $data"?: FeedbackFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FeedbackFragment">;
 };
 
@@ -3865,15 +3525,15 @@ fragment InlineFragmentWithOverlappingFields on Actor {
 // TestMutation.graphql
 import { FragmentRefs } from "relay-runtime";
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type TestMutationVariables = {
     input: CommentCreateInput;
@@ -3932,14 +3592,14 @@ export type InlineFragmentWithOverlappingFields = {
         readonly name: string | null;
         readonly message?: {
             readonly text: string | null;
-        } | null;
-    } | null;
-    readonly name?: string | null;
+        } | null | undefined;
+    } | null | undefined;
+    readonly name?: string | null | undefined;
     readonly " $refType": "InlineFragmentWithOverlappingFields";
 };
 export type InlineFragmentWithOverlappingFields$data = InlineFragmentWithOverlappingFields;
 export type InlineFragmentWithOverlappingFields$key = {
-    readonly " $data"?: InlineFragmentWithOverlappingFields$data;
+    readonly " $data"?: InlineFragmentWithOverlappingFields$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"InlineFragmentWithOverlappingFields">;
 };
 
@@ -3960,7 +3620,7 @@ export type PluralFragment = ReadonlyArray<{
 }>;
 export type PluralFragment$data = PluralFragment;
 export type PluralFragment$key = ReadonlyArray<{
-    readonly " $data"?: PluralFragment$data;
+    readonly " $data"?: PluralFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PluralFragment">;
 }>;
 
@@ -3990,7 +3650,7 @@ query TestDefer @raw_response_type {
 export type TestDeferVariables = {};
 export type TestDeferResponse = {
     readonly node: {
-        readonly name?: string | null;
+        readonly name?: string | null | undefined;
         readonly friends?: {
             readonly edges: ReadonlyArray<{
                 readonly node: {
@@ -3999,7 +3659,7 @@ export type TestDeferResponse = {
                     } | null;
                 } | null;
             } | null> | null;
-        } | null;
+        } | null | undefined;
     } | null;
 };
 export type TestDeferRawResponse = {
@@ -4067,7 +3727,7 @@ export type LinkedHandleFieldResponse = {
     readonly node: {
         readonly friends?: {
             readonly count: number | null;
-        } | null;
+        } | null | undefined;
     } | null;
 };
 export type LinkedHandleFieldRawResponse = {
@@ -4095,7 +3755,7 @@ export type ScalarHandleFieldVariables = {
 };
 export type ScalarHandleFieldResponse = {
     readonly node: {
-        readonly name?: string | null;
+        readonly name?: string | null | undefined;
     } | null;
 };
 export type ScalarHandleFieldRawResponse = {
@@ -4172,17 +3832,17 @@ export type ExampleQuery = {
 // FriendFragment.graphql
 import { FragmentRefs } from "relay-runtime";
 export type FriendFragment = {
-    readonly name?: string | null;
-    readonly lastName?: string | null;
+    readonly name?: string | null | undefined;
+    readonly lastName?: string | null | undefined;
     readonly feedback?: {
         readonly id: string;
         readonly name: string | null;
-    } | null;
+    } | null | undefined;
     readonly " $refType": "FriendFragment";
 };
 export type FriendFragment$data = FriendFragment;
 export type FriendFragment$key = {
-    readonly " $data"?: FriendFragment$data;
+    readonly " $data"?: FriendFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FriendFragment">;
 };
 
@@ -4224,7 +3884,7 @@ export type ExampleQueryResponse = {
         readonly username: string | null;
         readonly friends?: {
             readonly count: number | null;
-        } | null;
+        } | null | undefined;
         readonly " $fragmentRefs": FragmentRefs<"FriendFragment">;
     } | null;
 };
@@ -4245,17 +3905,17 @@ export type ExampleQuery = {
 // FriendFragment.graphql
 import { FragmentRefs } from "relay-runtime";
 export type FriendFragment = {
-    readonly name?: string | null;
-    readonly lastName?: string | null;
+    readonly name?: string | null | undefined;
+    readonly lastName?: string | null | undefined;
     readonly feedback?: {
         readonly id: string;
         readonly name: string | null;
-    } | null;
+    } | null | undefined;
     readonly " $refType": "FriendFragment";
 };
 export type FriendFragment$data = FriendFragment;
 export type FriendFragment$key = {
-    readonly " $data"?: FriendFragment$data;
+    readonly " $data"?: FriendFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FriendFragment">;
 };
 
@@ -4287,14 +3947,14 @@ query TestStream @raw_response_type {
 export type TestStreamVariables = {};
 export type TestStreamResponse = {
     readonly node: {
-        readonly name?: string | null;
+        readonly name?: string | null | undefined;
         readonly friends?: {
             readonly edges: ReadonlyArray<{
                 readonly node: {
                     readonly id: string;
                 } | null;
             } | null> | null;
-        } | null;
+        } | null | undefined;
     } | null;
 };
 export type TestStreamRawResponse = {
@@ -4353,7 +4013,7 @@ query TestDefer @raw_response_type {
 export type TestDeferVariables = {};
 export type TestDeferResponse = {
     readonly node: {
-        readonly name?: string | null;
+        readonly name?: string | null | undefined;
         readonly friends?: {
             readonly edges: ReadonlyArray<{
                 readonly node: {
@@ -4362,7 +4022,7 @@ export type TestDeferResponse = {
                     } | null;
                 } | null;
             } | null> | null;
-        } | null;
+        } | null | undefined;
     } | null;
 };
 export type TestDeferRawResponse = {
@@ -4420,7 +4080,7 @@ export type FragmentSpread = {
 };
 export type FragmentSpread$data = FragmentSpread;
 export type FragmentSpread$key = {
-    readonly " $data"?: FragmentSpread$data;
+    readonly " $data"?: FragmentSpread$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"FragmentSpread">;
 };
 
@@ -4448,7 +4108,7 @@ export type RefetchableFragment = {
 };
 export type RefetchableFragment$data = RefetchableFragment;
 export type RefetchableFragment$key = {
-    readonly " $data"?: RefetchableFragment$data;
+    readonly " $data"?: RefetchableFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"RefetchableFragment">;
 };
 
@@ -4523,8 +4183,8 @@ export type RelayClientIDFieldQueryResponse = {
                 readonly __id: string;
                 readonly __typename: string;
                 readonly text: string | null;
-            } | null;
-        } | null;
+            } | null | undefined;
+        } | null | undefined;
     } | null;
 };
 export type RelayClientIDFieldQuery = {
@@ -4586,22 +4246,22 @@ export type ExampleFragment = {
 };
 export type ExampleFragment$data = ExampleFragment;
 export type ExampleFragment$key = {
-    readonly " $data"?: ExampleFragment$data;
+    readonly " $data"?: ExampleFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"ExampleFragment">;
 };
 
 
 // TestMutation.graphql
 export type CommentCreateInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
-    feedback?: CommentfeedbackFeedback | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type CommentfeedbackFeedback = {
-    comment?: FeedbackcommentComment | null;
+    comment?: FeedbackcommentComment | null | undefined;
 };
 export type FeedbackcommentComment = {
-    feedback?: CommentfeedbackFeedback | null;
+    feedback?: CommentfeedbackFeedback | null | undefined;
 };
 export type TestMutationVariables = {
     input: CommentCreateInput;
@@ -4621,11 +4281,11 @@ export type TestMutation = {
 
 // TestSubscription.graphql
 export type FeedbackLikeInput = {
-    clientMutationId?: string | null;
-    feedbackId?: string | null;
+    clientMutationId?: string | null | undefined;
+    feedbackId?: string | null | undefined;
 };
 export type TestSubscriptionVariables = {
-    input?: FeedbackLikeInput | null;
+    input?: FeedbackLikeInput | null | undefined;
 };
 export type TestSubscriptionResponse = {
     readonly feedbackLikeSubscribe: {
@@ -4677,7 +4337,7 @@ export type ScalarField = {
 };
 export type ScalarField$data = ScalarField;
 export type ScalarField$key = {
-    readonly " $data"?: ScalarField$data;
+    readonly " $data"?: ScalarField$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"ScalarField">;
 };
 
@@ -4726,7 +4386,7 @@ export type TypenameInsideWithOverlappingFields = {
 };
 export type TypenameInsideWithOverlappingFields$data = TypenameInsideWithOverlappingFields;
 export type TypenameInsideWithOverlappingFields$key = {
-    readonly " $data"?: TypenameInsideWithOverlappingFields$data;
+    readonly " $data"?: TypenameInsideWithOverlappingFields$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameInsideWithOverlappingFields">;
 };
 
@@ -4834,7 +4494,7 @@ export type TypenameInside = {
 };
 export type TypenameInside$data = TypenameInside;
 export type TypenameInside$key = {
-    readonly " $data"?: TypenameInside$data;
+    readonly " $data"?: TypenameInside$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameInside">;
 };
 
@@ -4857,7 +4517,7 @@ export type TypenameOutside = {
 };
 export type TypenameOutside$data = TypenameOutside;
 export type TypenameOutside$key = {
-    readonly " $data"?: TypenameOutside$data;
+    readonly " $data"?: TypenameOutside$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameOutside">;
 };
 
@@ -4866,18 +4526,18 @@ export type TypenameOutside$key = {
 import { FragmentRefs } from "relay-runtime";
 export type TypenameOutsideWithAbstractType = {
     readonly __typename: string;
-    readonly username?: string | null;
+    readonly username?: string | null | undefined;
     readonly address?: {
         readonly city: string | null;
         readonly country: string | null;
-        readonly street?: string | null;
-    } | null;
-    readonly firstName?: string | null;
+        readonly street?: string | null | undefined;
+    } | null | undefined;
+    readonly firstName?: string | null | undefined;
     readonly " $refType": "TypenameOutsideWithAbstractType";
 };
 export type TypenameOutsideWithAbstractType$data = TypenameOutsideWithAbstractType;
 export type TypenameOutsideWithAbstractType$key = {
-    readonly " $data"?: TypenameOutsideWithAbstractType$data;
+    readonly " $data"?: TypenameOutsideWithAbstractType$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameOutsideWithAbstractType">;
 };
 
@@ -4891,7 +4551,7 @@ export type TypenameWithoutSpreads = {
 };
 export type TypenameWithoutSpreads$data = TypenameWithoutSpreads;
 export type TypenameWithoutSpreads$key = {
-    readonly " $data"?: TypenameWithoutSpreads$data;
+    readonly " $data"?: TypenameWithoutSpreads$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameWithoutSpreads">;
 };
 
@@ -4905,7 +4565,7 @@ export type TypenameWithoutSpreadsAbstractType = {
 };
 export type TypenameWithoutSpreadsAbstractType$data = TypenameWithoutSpreadsAbstractType;
 export type TypenameWithoutSpreadsAbstractType$key = {
-    readonly " $data"?: TypenameWithoutSpreadsAbstractType$data;
+    readonly " $data"?: TypenameWithoutSpreadsAbstractType$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameWithoutSpreadsAbstractType">;
 };
 
@@ -4915,13 +4575,13 @@ import { FragmentRefs } from "relay-runtime";
 export type TypenameWithCommonSelections = {
     readonly __typename: string;
     readonly name: string | null;
-    readonly firstName?: string | null;
-    readonly username?: string | null;
+    readonly firstName?: string | null | undefined;
+    readonly username?: string | null | undefined;
     readonly " $refType": "TypenameWithCommonSelections";
 };
 export type TypenameWithCommonSelections$data = TypenameWithCommonSelections;
 export type TypenameWithCommonSelections$key = {
-    readonly " $data"?: TypenameWithCommonSelections$data;
+    readonly " $data"?: TypenameWithCommonSelections$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameWithCommonSelections">;
 };
 
@@ -4944,7 +4604,7 @@ export type TypenameAlias = {
 };
 export type TypenameAlias$data = TypenameAlias;
 export type TypenameAlias$key = {
-    readonly " $data"?: TypenameAlias$data;
+    readonly " $data"?: TypenameAlias$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameAlias">;
 };
 
@@ -4972,7 +4632,7 @@ export type TypenameAliases = {
 };
 export type TypenameAliases$data = TypenameAliases;
 export type TypenameAliases$key = {
-    readonly " $data"?: TypenameAliases$data;
+    readonly " $data"?: TypenameAliases$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"TypenameAliases">;
 };
 
@@ -5021,7 +4681,7 @@ export type UserProfile = {
 };
 export type UserProfile$data = UserProfile;
 export type UserProfile$key = {
-    readonly " $data"?: UserProfile$data;
+    readonly " $data"?: UserProfile$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"UserProfile">;
 };
 
@@ -5035,7 +4695,7 @@ export type PhotoFragment = {
 };
 export type PhotoFragment$data = PhotoFragment;
 export type PhotoFragment$key = {
-    readonly " $data"?: PhotoFragment$data;
+    readonly " $data"?: PhotoFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"PhotoFragment">;
 };
 
@@ -5048,7 +4708,7 @@ export type RecursiveFragment = {
 };
 export type RecursiveFragment$data = RecursiveFragment;
 export type RecursiveFragment$key = {
-    readonly " $data"?: RecursiveFragment$data;
+    readonly " $data"?: RecursiveFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"RecursiveFragment">;
 };
 
@@ -5062,7 +4722,7 @@ export type AnotherRecursiveFragment = {
 };
 export type AnotherRecursiveFragment$data = AnotherRecursiveFragment;
 export type AnotherRecursiveFragment$key = {
-    readonly " $data"?: AnotherRecursiveFragment$data;
+    readonly " $data"?: AnotherRecursiveFragment$data | undefined;
     readonly " $fragmentRefs": FragmentRefs<"AnotherRecursiveFragment">;
 };
 
diff --git a/test/fixtures/type-generator/mutaion-with-client-extension.graphql b/test/fixtures/type-generator/mutaion-with-client-extension.graphql
deleted file mode 100644
index 51c8910f..00000000
--- a/test/fixtures/type-generator/mutaion-with-client-extension.graphql
+++ /dev/null
@@ -1,17 +0,0 @@
-mutation Test($input: UpdateAllSeenStateInput) @raw_response_type {
-  viewerNotificationsUpdateAllSeenState(input: $input) {
-    stories {
-      foos {
-        bar
-      }
-    }
-  }
-}
-
-extend type Story {
-  foos: [Foo]
-}
-
-type Foo {
-  bar: String
-}
diff --git a/test/fixtures/type-generator/mutaion-with-response-on-inline-fragments.graphql b/test/fixtures/type-generator/mutaion-with-response-on-inline-fragments.graphql
deleted file mode 100644
index 031b989f..00000000
--- a/test/fixtures/type-generator/mutaion-with-response-on-inline-fragments.graphql
+++ /dev/null
@@ -1,27 +0,0 @@
-mutation TestMutation($input: CommentCreateInput!) @raw_response_type {
-  commentCreate(input: $input) {
-    viewer {
-      actor {
-        ...InlineFragmentWithOverlappingFields
-      }
-    }
-  }
-}
-
-fragment InlineFragmentWithOverlappingFields on Actor {
-  ... on User {
-    hometown {
-      id
-      name
-    }
-  }
-  ... on Page {
-    name
-    hometown {
-      id
-      message {
-        text
-      }
-    }
-  }
-}
diff --git a/tsconfig.json b/tsconfig.json
index fffeb892..ce645c5a 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -33,6 +33,7 @@
     // "noUnusedParameters": true,            /* Report errors on unused parameters. */
     // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
     // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */
+    "exactOptionalPropertyTypes": true,
     /* Module Resolution Options */
     // "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
     "baseUrl": "./" /* Base directory to resolve non-absolute module names. */,