Repository: reduxjs/redux-toolkit (ts)

Issue:
`store.dispatch` does not work in 1.2.2
After migrating to 1.2.2 `store.dispatch` stopped working with the following error message:

```
Argument of type 'ThunkAction<void, CombinedState<{ auth: AuthState; }>, null, Action<string>>' is not assignable to parameter of type 'AnyAction'.
  Property 'type' is missing in type 'ThunkAction<void, CombinedState<{ auth: AuthState; }>, null, Action<string>>' but required in type 'AnyAction'.
```

Dispathing through dispatcher from hook works fine though:

```
  const dispatch = useDispatch();
  ...
  dispatch(logOut());  // OK
```

I can't use React Hooks in the axios interceptor, so I was using this:

```
import store from '../../store';

store.dispatch(logOut());
```

Pull request description:
Better generic argument for default Thunk Middleware
This should fix #321 

Patch:
diff --git a/docs/introduction/quick-start.md b/docs/introduction/quick-start.md
index 4f8e2afc..d10e37dd 100644
--- a/docs/introduction/quick-start.md
+++ b/docs/introduction/quick-start.md
@@ -39,7 +39,7 @@ Redux Toolkit is available as a package on NPM for use with a module bundler or
 
 ```bash
 # NPM
-npm install --save @reduxjs/toolkit
+npm install @reduxjs/toolkit
 
 # Yarn
 yarn add @reduxjs/toolkit
diff --git a/docs/tutorials/advanced-tutorial.md b/docs/tutorials/advanced-tutorial.md
index 1651c2f9..e7cfe9bb 100644
--- a/docs/tutorials/advanced-tutorial.md
+++ b/docs/tutorials/advanced-tutorial.md
@@ -261,9 +261,9 @@ The main type you will use when declaring action types in reducers is **`Payload
 Let's look at a specific reducer as an example:
 
 ```ts
-    setCurrentPage(state, action: PayloadAction<number>) {
-      state.page = action.payload
-    },
+setCurrentPage(state, action: PayloadAction<number>) {
+    state.page = action.payload
+},
 ```
 
 We don't have to declare a type for `state`, because `createSlice` already knows that this should be the same type as our `initialState`: the `CurrentDisplayState` type.
@@ -541,7 +541,7 @@ Before we go any further, let's add a type declaration we can reuse instead.
 
 export type AppDispatch = typeof store.dispatch
 
-+export type AppThunk = ThunkAction<void, RootState, null, Action<string>>
++export type AppThunk = ThunkAction<void, RootState, unknown, Action<string>>
 ```
 
 The `AppThunk` type declares that the "action" that we're using is specifically a thunk function. The thunk is customized with some additional type parameters:
diff --git a/docs/tutorials/intermediate-tutorial.md b/docs/tutorials/intermediate-tutorial.md
index 27d199c2..6e652871 100644
--- a/docs/tutorials/intermediate-tutorial.md
+++ b/docs/tutorials/intermediate-tutorial.md
@@ -39,7 +39,7 @@ On the one hand, this is a small example app. It's meant to illustrate the basic
 
 ### Adding Redux Toolkit to the Project
 
-Since the original todos example is in the Redux repo, we start by copying the Redux "todos" source code to a fresh Create-React-App project, and adding Prettier to the project to help make sure the code is formatted consistently. There's also a `jsconfig.json` file to enable us to use "absolute import paths" that start from the `/src` folder.
+Since the original todos example is in the Redux repo, we start by copying the Redux "todos" source code to a fresh Create-React-App project, and adding Prettier to the project to help make sure the code is formatted consistently. There's also a [jsconfig.json](https://code.visualstudio.com/docs/languages/jsconfig) file to enable us to use "absolute import paths" that start from the `/src` folder.
 
 > - [Initial commit](https://github.com/reduxjs/rtk-convert-todos-example/commit/a8e0a9a9d77b9dcd9e881079e7cca449084ca7b1).
 > - [Add jsconfig.json to support absolute imports](https://github.com/reduxjs/rtk-convert-todos-example/commit/b866e205b9ebece84367f11d2faabc557bd08e23)
diff --git a/etc/redux-toolkit.api.md b/etc/redux-toolkit.api.md
index 0dbfed2e..87ba8f41 100644
--- a/etc/redux-toolkit.api.md
+++ b/etc/redux-toolkit.api.md
@@ -81,7 +81,7 @@ export type CaseReducerWithPrepare<State, Action extends PayloadAction> = {
 export type ConfigureEnhancersCallback = (defaultEnhancers: StoreEnhancer[]) => StoreEnhancer[];
 
 // @public
-export function configureStore<S = any, A extends Action = AnyAction, M extends Middlewares<S> = [ThunkMiddleware<S>]>(options: ConfigureStoreOptions<S, A, M>): EnhancedStore<S, A, M>;
+export function configureStore<S = any, A extends Action = AnyAction, M extends Middlewares<S> = [ThunkMiddlewareFor<S>]>(options: ConfigureStoreOptions<S, A, M>): EnhancedStore<S, A, M>;
 
 // @public
 export interface ConfigureStoreOptions<S = any, A extends Action = AnyAction, M extends Middlewares<S> = Middlewares<S>> {
diff --git a/package-lock.json b/package-lock.json
index 3ea9df57..826700d8 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -6036,9 +6036,9 @@
       "dev": true
     },
     "mixin-deep": {
-      "version": "1.3.1",
-      "resolved": "https://registry.npmjs.org/mixin-deep/-/mixin-deep-1.3.1.tgz",
-      "integrity": "sha512-8ZItLHeEgaqEvd5lYBXfm4EZSFCX29Jb9K+lAHhDKzReKBQKj3R+7NOF6tjqYi9t4oI8VUfaWITJQm86wnXGNQ==",
+      "version": "1.3.2",
+      "resolved": "https://registry.npmjs.org/mixin-deep/-/mixin-deep-1.3.2.tgz",
+      "integrity": "sha512-WRoDn//mXBiJ1H40rqa3vH0toePwSsGb45iInWlTySa+Uu4k3tYUSxa2v1KqAiLtvlrSzaExqS1gtk96A9zvEA==",
       "dev": true,
       "requires": {
         "for-in": "^1.0.2",
@@ -7225,16 +7225,16 @@
       }
     },
     "rollup-plugin-terser": {
-      "version": "5.1.2",
-      "resolved": "https://registry.npmjs.org/rollup-plugin-terser/-/rollup-plugin-terser-5.1.2.tgz",
-      "integrity": "sha512-sWKBCOS+vUkRtHtEiJPAf+WnBqk/C402fBD9AVHxSIXMqjsY7MnYWKYEUqGixtr0c8+1DjzUEPlNgOYQPVrS1g==",
+      "version": "5.2.0",
+      "resolved": "https://registry.npmjs.org/rollup-plugin-terser/-/rollup-plugin-terser-5.2.0.tgz",
+      "integrity": "sha512-jQI+nYhtDBc9HFRBz8iGttQg7li9klmzR62RG2W2nN6hJ/FI2K2ItYQ7kJ7/zn+vs+BP1AEccmVRjRN989I+Nw==",
       "dev": true,
       "requires": {
-        "@babel/code-frame": "^7.0.0",
-        "jest-worker": "^24.6.0",
-        "rollup-pluginutils": "^2.8.1",
-        "serialize-javascript": "^1.7.0",
-        "terser": "^4.1.0"
+        "@babel/code-frame": "^7.5.5",
+        "jest-worker": "^24.9.0",
+        "rollup-pluginutils": "^2.8.2",
+        "serialize-javascript": "^2.1.2",
+        "terser": "^4.6.2"
       }
     },
     "rollup-plugin-typescript2": {
@@ -7463,9 +7463,9 @@
       "dev": true
     },
     "serialize-javascript": {
-      "version": "1.9.1",
-      "resolved": "https://registry.npmjs.org/serialize-javascript/-/serialize-javascript-1.9.1.tgz",
-      "integrity": "sha512-0Vb/54WJ6k5v8sSWN09S0ora+Hnr+cX40r9F170nT+mSkaxltoE/7R3OrIdBSUv1OoiobH1QoWQbCnAO+e8J1A==",
+      "version": "2.1.2",
+      "resolved": "https://registry.npmjs.org/serialize-javascript/-/serialize-javascript-2.1.2.tgz",
+      "integrity": "sha512-rs9OggEUF0V4jUSecXazOYsLfu7OGK2qIn3c7IPBiffz32XniEp/TX9Xmc9LQfK2nQ2QKHvZ2oygKUGU0lG4jQ==",
       "dev": true
     },
     "set-blocking": {
@@ -7475,9 +7475,9 @@
       "dev": true
     },
     "set-value": {
-      "version": "2.0.0",
-      "resolved": "https://registry.npmjs.org/set-value/-/set-value-2.0.0.tgz",
-      "integrity": "sha512-hw0yxk9GT/Hr5yJEYnHNKYXkIA8mVJgd9ditYZCe16ZczcaELYYcfvaXesNACk2O8O0nTiPQcQhGUQj8JLzeeg==",
+      "version": "2.0.1",
+      "resolved": "https://registry.npmjs.org/set-value/-/set-value-2.0.1.tgz",
+      "integrity": "sha512-JxHc1weCN68wRY0fhCoXpyK55m/XPHafOmK4UWD7m2CI14GMcFypt4w/0+NV5f/ZMby2F6S2wwA7fgynh9gWSw==",
       "dev": true,
       "requires": {
         "extend-shallow": "^2.0.1",
@@ -8015,9 +8015,9 @@
       }
     },
     "terser": {
-      "version": "4.4.2",
-      "resolved": "https://registry.npmjs.org/terser/-/terser-4.4.2.tgz",
-      "integrity": "sha512-Uufrsvhj9O1ikwgITGsZ5EZS6qPokUOkCegS7fYOdGTv+OA90vndUbU6PEjr5ePqHfNUbGyMO7xyIZv2MhsALQ==",
+      "version": "4.6.3",
+      "resolved": "https://registry.npmjs.org/terser/-/terser-4.6.3.tgz",
+      "integrity": "sha512-Lw+ieAXmY69d09IIc/yqeBqXpEQIpDGZqT34ui1QWXIUpR2RjbqEkT8X7Lgex19hslSqcWM5iMN2kM11eMsESQ==",
       "dev": true,
       "requires": {
         "commander": "^2.20.0",
@@ -8514,38 +8514,15 @@
       "dev": true
     },
     "union-value": {
-      "version": "1.0.0",
-      "resolved": "https://registry.npmjs.org/union-value/-/union-value-1.0.0.tgz",
-      "integrity": "sha1-XHHDTLW61dzr4+oM0IIHulqhrqQ=",
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/union-value/-/union-value-1.0.1.tgz",
+      "integrity": "sha512-tJfXmxMeWYnczCVs7XAEvIV7ieppALdyepWMkHkwciRpZraG/xwT+s2JN8+pr1+8jCRf80FFzvr+MpQeeoF4Xg==",
       "dev": true,
       "requires": {
         "arr-union": "^3.1.0",
         "get-value": "^2.0.6",
         "is-extendable": "^0.1.1",
-        "set-value": "^0.4.3"
-      },
-      "dependencies": {
-        "extend-shallow": {
-          "version": "2.0.1",
-          "resolved": "https://registry.npmjs.org/extend-shallow/-/extend-shallow-2.0.1.tgz",
-          "integrity": "sha1-Ua99YUrZqfYQ6huvu5idaxxWiQ8=",
-          "dev": true,
-          "requires": {
-            "is-extendable": "^0.1.0"
-          }
-        },
-        "set-value": {
-          "version": "0.4.3",
-          "resolved": "https://registry.npmjs.org/set-value/-/set-value-0.4.3.tgz",
-          "integrity": "sha1-fbCPnT0i3H945Trzw79GZuzfzPE=",
-          "dev": true,
-          "requires": {
-            "extend-shallow": "^2.0.1",
-            "is-extendable": "^0.1.1",
-            "is-plain-object": "^2.0.1",
-            "to-object-path": "^0.3.0"
-          }
-        }
+        "set-value": "^2.0.1"
       }
     },
     "universalify": {
diff --git a/src/configureStore.ts b/src/configureStore.ts
index 8a4468d4..f0078f61 100644
--- a/src/configureStore.ts
+++ b/src/configureStore.ts
@@ -17,10 +17,12 @@ import {
   composeWithDevTools,
   EnhancerOptions as DevToolsOptions
 } from 'redux-devtools-extension'
-import { ThunkMiddleware } from 'redux-thunk'
 
 import isPlainObject from './isPlainObject'
-import { getDefaultMiddleware } from './getDefaultMiddleware'
+import {
+  getDefaultMiddleware,
+  ThunkMiddlewareFor
+} from './getDefaultMiddleware'
 import { DispatchForMiddlewares } from './tsHelpers'
 
 const IS_PRODUCTION = process.env.NODE_ENV === 'production'
@@ -120,7 +122,7 @@ export interface EnhancedStore<
 export function configureStore<
   S = any,
   A extends Action = AnyAction,
-  M extends Middlewares<S> = [ThunkMiddleware<S>]
+  M extends Middlewares<S> = [ThunkMiddlewareFor<S>]
 >(options: ConfigureStoreOptions<S, A, M>): EnhancedStore<S, A, M> {
   const {
     reducer = undefined,
diff --git a/src/getDefaultMiddleware.ts b/src/getDefaultMiddleware.ts
index ab395818..c2135063 100644
--- a/src/getDefaultMiddleware.ts
+++ b/src/getDefaultMiddleware.ts
@@ -28,13 +28,18 @@ interface GetDefaultMiddlewareOptions {
   serializableCheck?: boolean | SerializableStateInvariantMiddlewareOptions
 }
 
-type ThunkMiddlewareFor<S, O extends GetDefaultMiddlewareOptions> = O extends {
+export type ThunkMiddlewareFor<
+  S,
+  O extends GetDefaultMiddlewareOptions = {}
+> = O extends {
   thunk: false
 }
   ? never
   : O extends { thunk: { extraArgument: infer E } }
   ? ThunkMiddleware<S, AnyAction, E>
-  : ThunkMiddleware<S>
+  :
+      | ThunkMiddleware<S, AnyAction, null> //The ThunkMiddleware with a `null` ExtraArgument is here to provide backwards-compatibility.
+      | ThunkMiddleware<S, AnyAction>
 
 /**
  * Returns any array containing the default middleware installed by


Test patch:
diff --git a/type-tests/files/configureStore.typetest.ts b/type-tests/files/configureStore.typetest.ts
index 95509a36..957b2432 100644
--- a/type-tests/files/configureStore.typetest.ts
+++ b/type-tests/files/configureStore.typetest.ts
@@ -254,4 +254,20 @@ import thunk, { ThunkMiddleware, ThunkAction, ThunkDispatch } from 'redux-thunk'
     const result2: 'B' = store.dispatch('b')
     const result3: Promise<'A'> = store.dispatch(thunkA())
   }
+  /**
+   * Accepts thunk with `unknown`, `undefined` or `null` ThunkAction extraArgument per default
+   */
+  {
+    const store = configureStore({ reducer: {} })
+    // undefined is the default value for the ThunkMiddleware extraArgument
+    store.dispatch(function() {} as ThunkAction<void, {}, undefined, AnyAction>)
+    // null was previously documented in the redux docs
+    store.dispatch(function() {} as ThunkAction<void, {}, null, AnyAction>)
+    // unknown is the best way to type a ThunkAction if you do not care
+    // about the value of the extraArgument, as it will always work with every
+    // ThunkMiddleware, no matter the actual extraArgument type
+    store.dispatch(function() {} as ThunkAction<void, {}, unknown, AnyAction>)
+    // typings:expect-error
+    store.dispatch(function() {} as ThunkAction<void, {}, boolean, AnyAction>)
+  }
 }