RFC: Expose endpoint types

packages/toolkit/src/query/core/module.ts

@@ -320,15 +320,25 @@ export interface ApiEndpointQuery<
   Definition extends QueryDefinition<any, any, any, any, any>,
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
   Definitions extends EndpointDefinitions
-> {}
+> {
+  /**
+   * All of these are `undefined` at runtime, purely to be used in TypeScript declarations!
+   */
+  Types: NonNullable<Definition['Types']>
+}
 
 // eslint-disable-next-line @typescript-eslint/no-unused-vars
 export interface ApiEndpointMutation<
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
   Definition extends MutationDefinition<any, any, any, any, any>,
   // eslint-disable-next-line @typescript-eslint/no-unused-vars
   Definitions extends EndpointDefinitions
-> {}
+> {
+  /**
+   * All of these are `undefined` at runtime, purely to be used in TypeScript declarations!
+   */
+  Types: NonNullable<Definition['Types']>
+}
 
 export type ListenerActions = {
   /**

packages/toolkit/src/query/endpointDefinitions.ts

@@ -154,6 +154,16 @@ interface EndpointDefinitionWithQueryFn<
   structuralSharing?: boolean
 }
 
+export interface BaseEndpointTypes<
+  QueryArg,
+  BaseQuery extends BaseQueryFn,
+  ResultType
+> {
+  QueryArg: QueryArg
+  BaseQuery: BaseQuery
+  ResultType: ResultType
+}
+
 export type BaseEndpointDefinition<
   QueryArg,
   BaseQuery extends BaseQueryFn,
@@ -221,6 +231,31 @@ export interface QueryApi<ReducerPath extends string, Context extends {}> {
   context: Context
 }
 
+export interface QueryTypes<
+  QueryArg,
+  BaseQuery extends BaseQueryFn,
+  TagTypes extends string,
+  ResultType,
+  ReducerPath extends string = string
+> extends BaseEndpointTypes<QueryArg, BaseQuery, ResultType> {
+  /**
+   * The endpoint definition type. To be used with some internal generic types.
+   * @example
+   * ```ts
+   * const useMyWrappedHook: UseQuery<typeof api.endpoints.query.Types.QueryDefinition> = ...
+   * ```
+   */
+  QueryDefinition: QueryDefinition<
+    QueryArg,
+    BaseQuery,
+    TagTypes,
+    ResultType,
+    ReducerPath
+  >
+  TagTypes: TagTypes
+  ReducerPath: ReducerPath
+}
+
 export interface QueryExtraOptions<
   TagTypes extends string,
   ResultType,
@@ -303,6 +338,11 @@ export interface QueryExtraOptions<
     currentCacheData: ResultType,
     responseData: ResultType
   ): ResultType | void
+
+  /**
+   * All of these are `undefined` at runtime, purely to be used in TypeScript declarations!
+   */
+  Types?: QueryTypes<QueryArg, BaseQuery, TagTypes, ResultType, ReducerPath>
 }
 
 export type QueryDefinition<
@@ -314,6 +354,31 @@ export type QueryDefinition<
 > = BaseEndpointDefinition<QueryArg, BaseQuery, ResultType> &
   QueryExtraOptions<TagTypes, ResultType, QueryArg, BaseQuery, ReducerPath>
 
+export interface MutationTypes<
+  QueryArg,
+  BaseQuery extends BaseQueryFn,
+  TagTypes extends string,
+  ResultType,
+  ReducerPath extends string = string
+> extends BaseEndpointTypes<QueryArg, BaseQuery, ResultType> {
+  /**
+   * The endpoint definition type. To be used with some internal generic types.
+   * @example
+   * ```ts
+   * const useMyWrappedHook: UseMutation<typeof api.endpoints.query.Types.MutationDefinition> = ...
+   * ```
+   */
+  MutationDefinition: MutationDefinition<
+    QueryArg,
+    BaseQuery,
+    TagTypes,
+    ResultType,
+    ReducerPath
+  >
+  TagTypes: TagTypes
+  ReducerPath: ReducerPath
+}
+
 export interface MutationExtraOptions<
   TagTypes extends string,
   ResultType,
@@ -378,6 +443,11 @@ export interface MutationExtraOptions<
    * Not to be used. A mutation should not provide tags to the cache.
    */
   providesTags?: never
+
+  /**
+   * All of these are `undefined` at runtime, purely to be used in TypeScript declarations!
+   */
+  Types?: MutationTypes<QueryArg, BaseQuery, TagTypes, ResultType, ReducerPath>
 }
 
 export type MutationDefinition<

packages/toolkit/src/query/tests/buildHooks.test.tsx

@@ -1,4 +1,8 @@
 import * as React from 'react'
+import type {
+  UseMutation,
+  UseQuery,
+} from '@reduxjs/toolkit/dist/query/react/buildHooks'
 import {
   createApi,
   fetchBaseQuery,
@@ -2363,3 +2367,20 @@ describe('skip behaviour', () => {
     expect(subscriptionCount('getUser(1)')).toBe(0)
   })
 })
+
+// type tests:
+{
+  const ANY = {} as any
+
+  // UseQuery type can be used to recreate the hook type
+  const fakeQuery = ANY as UseQuery<
+    typeof api.endpoints.getUser.Types.QueryDefinition
+  >
+  expectExactType(fakeQuery)(api.endpoints.getUser.useQuery)
+
+  // UseMutation type can be used to recreate the hook type
+  const fakeMutation = ANY as UseMutation<
+    typeof api.endpoints.updateUser.Types.MutationDefinition
+  >
+  expectExactType(fakeMutation)(api.endpoints.updateUser.useMutation)
+}