add DeclaredMiddlewareType helper type to specify middleware signatur…

…e on extended function objects

src/createActionListenerMiddleware.test.ts

@@ -120,7 +120,6 @@ describe('createActionListenerMiddleware', () => {
     const unsubscribe = store.dispatch(addListenerAction(testAction1, listener))
 
     store.dispatch(testAction1('a'))
-    // @ts-ignore TODO types
     unsubscribe()
     store.dispatch(testAction2('b'))
     store.dispatch(testAction1('c'))

src/createActionListenerMiddleware.ts

@@ -1,6 +1,7 @@
 import { Middleware, Dispatch, AnyAction, MiddlewareAPI, Action } from 'redux'
 import { TypedActionCreator } from './mapBuilders'
 import { createAction, BaseActionCreator } from './createAction'
+import { WithMiddlewareType } from './tsHelpers'
 
 export type When = 'before' | 'after' | undefined
 type WhenFromOptions<
@@ -349,5 +350,9 @@ export function createActionListenerMiddleware<
     }
   }
 
-  return Object.assign(middleware, { addListener, removeListener })
+  return Object.assign(
+    middleware,
+    { addListener, removeListener },
+    {} as WithMiddlewareType<typeof middleware>
+  )
 }

src/tsHelpers.ts

@@ -65,14 +65,31 @@ export type IsUnknownOrNonInferrable<T, True, False> = AtLeastTS35<
   IsEmptyObj<T, True, IsUnknown<T, True, False>>
 >
 
+const declaredMiddlewareType: unique symbol = undefined as any
+export type WithMiddlewareType<T extends Middleware<any, any, any>> = {
+  [declaredMiddlewareType]: T
+}
+
 /**
  * Combines all dispatch signatures of all middlewares in the array `M` into
  * one intersected dispatch signature.
  */
 export type DispatchForMiddlewares<M> = M extends ReadonlyArray<any>
   ? UnionToIntersection<
       M[number] extends infer MiddlewareValues
-        ? MiddlewareValues extends Middleware<infer DispatchExt, any, any>
+        ? MiddlewareValues extends WithMiddlewareType<
+            infer DeclaredMiddlewareType
+          >
+          ? DeclaredMiddlewareType extends Middleware<
+              infer DispatchExt,
+              any,
+              any
+            >
+            ? DispatchExt extends Function
+              ? DispatchExt
+              : never
+            : never
+          : MiddlewareValues extends Middleware<infer DispatchExt, any, any>
           ? DispatchExt extends Function
             ? DispatchExt
             : never