Fix for react adapter

Author: ShacharHarshuv

packages/react-query/src/__tests__/queryOptions.test-d.tsx

@@ -169,4 +169,23 @@ describe('queryOptions', () => {
     const data = queryClient.getQueryData(options.queryKey)
     expectTypeOf(data).toEqualTypeOf<unknown>()
   })
+
+  it('should allow undefined response in initialData', () => {
+    return (id: string | null) =>
+      queryOptions({
+        queryKey: ['todo', id],
+        queryFn: () =>
+          Promise.resolve({
+            id: '1',
+            title: 'Do Laundry',
+          }),
+        initialData: () =>
+          !id
+            ? undefined
+            : {
+                id,
+                title: 'Initial Data',
+              },
+      })
+  })
 })

packages/react-query/src/queryOptions.ts

@@ -1,4 +1,9 @@
-import type { DataTag, DefaultError, QueryKey } from '@tanstack/query-core'
+import type {
+  DataTag,
+  DefaultError,
+  InitialDataFunction,
+  QueryKey,
+} from '@tanstack/query-core'
 import type { UseQueryOptions } from './types'
 
 export type UndefinedInitialDataOptions<
@@ -7,7 +12,7 @@ export type UndefinedInitialDataOptions<
   TData = TQueryFnData,
   TQueryKey extends QueryKey = QueryKey,
 > = UseQueryOptions<TQueryFnData, TError, TData, TQueryKey> & {
-  initialData?: undefined
+  initialData?: undefined | InitialDataFunction<NonUndefinedGuard<TQueryFnData>>
 }
 
 type NonUndefinedGuard<T> = T extends undefined ? never : T