Redux Toolkit Query: Reduce state from "mutation" response - redux-toolkit

Question

Let's say I have an RESTish API to manage "posts".
GET /posts returns all posts
PATCH /posts:id updates a post and responds with new record data
I can implement this using RTK query via something like this:
const TAG_TYPE = 'POST';
// Define a service using a base URL and expected endpoints
export const postsApi = createApi({
reducerPath: 'postsApi',
tagTypes: [TAG_TYPE],
baseQuery,
endpoints: (builder) => ({
getPosts: builder.query<Form[], string>({
query: () => `/posts`,
providesTags: (result) =>
[
{ type: TAG_TYPE, id: 'LIST' },
],
}),
updatePost: builder.mutation<any, { formId: string; formData: any }>({
// note: an optional `queryFn` may be used in place of `query`
query: (data) => ({
url: `/post/${data.formId}`,
method: 'PATCH',
body: data.formData,
}),
// this causes a full re-query.
// Would be more efficient to update state based on resp.body
invalidatesTags: [{ type: TAG_TYPE, id: 'LIST' }],
}),
}),
});
When updatePost runs, it invalidates the LIST tag which causes getPosts to run again.
However, since the PATCH operation responds with the new data itself, I would like to avoid making an additional server request and instead just update my reducer state for that specific record with the content of response.body.
Seems like a common use case, but I'm struggling to find any documentation on doing something like this.

Answer 1

You can apply the mechanism described in optimistic updates, just a little bit later:
import { createApi, fetchBaseQuery } from '#reduxjs/toolkit/query'
import { Post } from './types'
const api = createApi({
// ...
endpoints: (build) => ({
// ...
updatePost: build.mutation<void, Pick<Post, 'id'> & Partial<Post>>({
query: ({ id, ...patch }) => ({
// ...
}),
async onQueryStarted({ id, ...patch }, { dispatch, queryFulfilled }) {
const { data } = await queryFulfilled
dispatch(
api.util.updateQueryData('getPost', id, (draft) => {
Object.assign(draft, data)
})
)
},
}),
}),
})