Improve wording for the "Typing query and mutation endpoints" section of the docs (#1371)

ivansvlv · web-flow · commit d1f7e8006c10 · 2021-07-31T20:43:33.000+02:00
- added a case when `query` doesn't have parameter
- added a case when `query` has an optional parameter
diff --git a/docs/rtk-query/usage-with-typescript.mdx b/docs/rtk-query/usage-with-typescript.mdx
@@ -202,6 +202,8 @@ const api = createApi({
     }
     ```
 - `QueryArg` - The type of the input that will be passed as the only parameter to the `query` property of the endpoint, or the first parameter of a `queryFn` property if used instead.
+  - If `query` doesn't have a parameter, then `void` type has to be provided explicitly.
+  - If `query` has an optional parameter, then a union type with the type of parameter, and `void` has to be provided, e.g. `number | void`.
 
 ```ts title="Defining endpoints with TypeScript"
 import { createApi, fetchBaseQuery } from '@reduxjs/toolkit/query/react'

Original file line number	Diff line number	Diff line change
`@@ -202,6 +202,8 @@ const api = createApi({`
`202`	`202`	`}`
`203`	`203`	```
`204`	`204`	- `QueryArg` - The type of the input that will be passed as the only parameter to the `query` property of the endpoint, or the first parameter of a `queryFn` property if used instead.
	`205`	+ - If `query` doesn't have a parameter, then `void` type has to be provided explicitly.
	`206`	+ - If `query` has an optional parameter, then a union type with the type of parameter, and `void` has to be provided, e.g. `number \| void`.
`205`	`207`
`206`	`208`	```ts title="Defining endpoints with TypeScript"
`207`	`209`	`import { createApi, fetchBaseQuery } from '@reduxjs/toolkit/query/react'`