fix(types): remove non-void constraint from queryFn result

src/core/tests/query.test.tsx

@@ -810,7 +810,6 @@ describe('query', () => {
 
     const observer = new QueryObserver(queryClient, {
       queryKey: key,
-      // @ts-expect-error (queryFn must not return undefined)
       queryFn: () => undefined,
       retry: false,
     })

src/core/types.ts

@@ -11,13 +11,7 @@ export type QueryKey = readonly unknown[]
 export type QueryFunction<
   T = unknown,
   TQueryKey extends QueryKey = QueryKey
-> = (
-  context: QueryFunctionContext<TQueryKey>
-) => [T] extends [undefined]
-  ? never | 'queryFn must not return undefined or void'
-  : [T] extends [void]
-  ? never | 'queryFn must not return undefined or void'
-  : T | Promise<T>
+> = (context: QueryFunctionContext<TQueryKey>) => T | Promise<T>
 
 export interface QueryFunctionContext<
   TQueryKey extends QueryKey = QueryKey,

src/reactjs/tests/useQueries.test.tsx

@@ -607,76 +607,6 @@ describe('useQueries', () => {
     // @ts-expect-error (Page component is not rendered)
     // eslint-disable-next-line
     function Page() {
-      // Rejects queryFn that returns/resolved to undefined or void
-      // @ts-expect-error (queryFn must not return undefined)
-      useQueries({ queries: [{ queryKey: key1, queryFn: () => undefined }] })
-      // @ts-expect-error (queryFn must not return void)
-      // eslint-disable-next-line @typescript-eslint/no-empty-function
-      useQueries({ queries: [{ queryKey: key1, queryFn: () => {} }] })
-
-      useQueries({
-        // @ts-expect-error (queryFn must not return explicitly undefined)
-        queries: [{ queryKey: key1, queryFn: (): undefined => undefined }],
-      })
-
-      useQueries({
-        // @ts-expect-error (queryFn must not return explicitly void)
-        queries: [{ queryKey: key1, queryFn: (): void => undefined }],
-      })
-
-      useQueries({
-        // @ts-expect-error (queryFn must not return explicitly Promise<void>)
-        queries: [{ queryKey: key1, queryFn: (): Promise<void> => undefined }],
-      })
-
-      useQueries({
-        queries: [
-          // @ts-expect-error (queryFn must not return explicitly Promise<undefined>)
-          { queryKey: key1, queryFn: (): Promise<undefined> => undefined },
-        ],
-      })
-      useQueries({
-        queries: [
-          // @ts-expect-error (queryFn must not return Promise<undefined>)
-          { queryKey: key2, queryFn: () => Promise.resolve(undefined) },
-        ],
-      })
-      useQueries({
-        // @ts-expect-error (queryFn must not return Promise<undefined>)
-        queries: Array(50).map((_, i) => ({
-          queryKey: ['key', i] as const,
-          queryFn: () => Promise.resolve(undefined),
-        })),
-      })
-
-      // Rejects queryFn that always throws
-      useQueries({
-        queries: [
-          // @ts-expect-error (queryFn must not return undefined)
-          {
-            queryKey: key3,
-            queryFn: async () => {
-              throw new Error('')
-            },
-          },
-        ],
-      })
-
-      // Accepts queryFn that *sometimes* throws
-      useQueries({
-        queries: [
-          {
-            queryKey: key3,
-            queryFn: async () => {
-              if (Math.random() > 0.1) {
-                throw new Error('')
-              }
-              return 'result'
-            },
-          },
-        ],
-      })
-
       // Array.map preserves TQueryFnData
       const result1 = useQueries({
         queries: Array(50).map((_, i) => ({
@@ -898,6 +828,37 @@ describe('useQueries', () => {
           someInvalidField: '',
         })),
       })
+
+      // field names should be enforced - array literal
+      useQueries({
+        queries: [
+          {
+            queryKey: key1,
+            queryFn: () => 'string',
+            // @ts-expect-error (invalidField)
+            someInvalidField: [],
+          },
+        ],
+      })
+
+      // supports queryFn using fetch() to return Promise<any> - Array.map() result
+      useQueries({
+        queries: Array(50).map((_, i) => ({
+          queryKey: ['key', i] as const,
+          queryFn: () => fetch('return Promise<any>').then(resp => resp.json()),
+        })),
+      })
+
+      // supports queryFn using fetch() to return Promise<any> - array literal
+      useQueries({
+        queries: [
+          {
+            queryKey: key1,
+            queryFn: () =>
+              fetch('return Promise<any>').then(resp => resp.json()),
+          },
+        ],
+      })
     }
   })
 

src/reactjs/tests/useQuery.test.tsx

@@ -18,6 +18,7 @@ import {
   QueryCache,
   QueryFunction,
   QueryFunctionContext,
+  UseQueryOptions,
 } from '../..'
 import { ErrorBoundary } from 'react-error-boundary'
 
@@ -36,22 +37,6 @@ describe('useQuery', () => {
       expectType<unknown>(noQueryFn.data)
       expectType<unknown>(noQueryFn.error)
 
-      // it should not be possible for queryFn to return undefined
-      // @ts-expect-error (queryFn returns undefined)
-      useQuery(key, () => undefined)
-
-      // it should not be possible for queryFn to have explicit void return type
-      // @ts-expect-error (queryFn explicit return type is void)
-      useQuery(key, (): void => undefined)
-
-      // it should not be possible for queryFn to have explicit Promise<void> return type
-      // @ts-expect-error (queryFn explicit return type is Promise<void>)
-      useQuery(key, (): Promise<void> => Promise.resolve())
-
-      // it should not be possible for queryFn to have explicit Promise<undefined> return type
-      // @ts-expect-error (queryFn explicit return type is Promise<undefined>)
-      useQuery(key, (): Promise<undefined> => Promise.resolve(undefined))
-
       // it should infer the result type from the query function
       const fromQueryFn = useQuery(key, () => 'test')
       expectType<string | undefined>(fromQueryFn.data)
@@ -137,6 +122,49 @@ describe('useQuery', () => {
         queryKey: ['1'],
         queryFn: getMyDataStringKey,
       })
+
+      // it should handle query-functions that return Promise<any>
+      useQuery(key, () =>
+        fetch('return Promise<any>').then(resp => resp.json())
+      )
+
+      // handles wrapped queries with custom fetcher passed as inline queryFn
+      const useWrappedQuery = <
+        TQueryKey extends [string, Record<string, unknown>?],
+        TQueryFnData,
+        TError,
+        TData = TQueryFnData
+      >(
+        qk: TQueryKey,
+        fetcher: (
+          obj: TQueryKey[1],
+          token: string
+          // return type must be wrapped with TQueryFnReturn
+        ) => Promise<TQueryFnData>,
+        options?: Omit<
+          UseQueryOptions<TQueryFnData, TError, TData, TQueryKey>,
+          'queryKey' | 'queryFn'
+        >
+      ) => useQuery(qk, () => fetcher(qk[1], 'token'), options)
+      const test = useWrappedQuery([''], async () => '1')
+      expectType<string | undefined>(test.data)
+
+      // handles wrapped queries with custom fetcher passed directly to useQuery
+      const useWrappedFuncStyleQuery = <
+        TQueryKey extends [string, Record<string, unknown>?],
+        TQueryFnData,
+        TError,
+        TData = TQueryFnData
+      >(
+        qk: TQueryKey,
+        fetcher: () => Promise<TQueryFnData>,
+        options?: Omit<
+          UseQueryOptions<TQueryFnData, TError, TData, TQueryKey>,
+          'queryKey' | 'queryFn'
+        >
+      ) => useQuery(qk, fetcher, options)
+      const testFuncStyle = useWrappedFuncStyleQuery([''], async () => true)
+      expectType<boolean | undefined>(testFuncStyle.data)
     }
   })
 

src/reactjs/useQueries.ts

@@ -17,10 +17,6 @@ type UseQueryOptionsForUseQueries<
   TQueryKey extends QueryKey = QueryKey
 > = Omit<UseQueryOptions<TQueryFnData, TError, TData, TQueryKey>, 'context'>
 
-type InvalidQueryFn = QueryFunction<
-  undefined | Promise<undefined> | void | Promise<void>
->
-
 // Avoid TS depth-limit error in case of large array literal
 type MAXIMUM_DEPTH = 20
 
@@ -44,9 +40,7 @@ type GetOptions<T> =
     : T extends [infer TQueryFnData]
     ? UseQueryOptionsForUseQueries<TQueryFnData>
     : // Part 3: responsible for inferring and enforcing type if no explicit parameter was provided
-    T extends { queryFn?: InvalidQueryFn }
-    ? never | 'queryFn must not return undefined or void'
-    : T extends {
+    T extends {
         queryFn?: QueryFunction<infer TQueryFnData, infer TQueryKey>
         select: (data: any) => infer TData
       }
@@ -106,9 +100,7 @@ export type QueriesOptions<
   ? T
   : // If T is *some* array but we couldn't assign unknown[] to it, then it must hold some known/homogenous type!
   // use this to infer the param types in the case of Array.map() argument
-  T extends { queryFn: InvalidQueryFn }[]
-  ? (never | 'queryFn must not return undefined or void')[]
-  : T extends UseQueryOptionsForUseQueries<
+  T extends UseQueryOptionsForUseQueries<
       infer TQueryFnData,
       infer TError,
       infer TData,