attempt at actionListenerMiddleware

src/createAction.ts

@@ -81,7 +81,7 @@ export type _ActionCreatorWithPreparedPayload<
  *
  * @inheritdoc {redux#ActionCreator}
  */
-interface BaseActionCreator<P, T extends string, M = never, E = never> {
+export interface BaseActionCreator<P, T extends string, M = never, E = never> {
   type: T
   match(action: Action<unknown>): action is PayloadAction<P, T, M, E>
 }

src/entities/createActionListenerMiddleware.test.ts

@@ -0,0 +1,236 @@
+import { configureStore } from '../configureStore'
+import {
+  createActionListenerMiddleware,
+  addListenerAction,
+  removeListenerAction
+} from './createActionListenerMiddleware'
+import { createAction } from '../createAction'
+
+const middlewareApi = {
+  getState: expect.any(Function),
+  dispatch: expect.any(Function)
+}
+
+describe('createActionListenerMiddleware', () => {
+  let store = configureStore({
+    reducer: () => ({}),
+    middleware: [createActionListenerMiddleware()] as const
+  })
+  let reducer: jest.Mock
+  let middleware: ReturnType<typeof createActionListenerMiddleware>
+
+  const testAction1 = createAction<string>('testAction1')
+  type TestAction1 = ReturnType<typeof testAction1>
+  const testAction2 = createAction<string>('testAction2')
+
+  beforeEach(() => {
+    middleware = createActionListenerMiddleware()
+    reducer = jest.fn(() => ({}))
+    store = configureStore({
+      reducer,
+      middleware: [middleware] as const
+    })
+  })
+
+  test('directly subscribing', () => {
+    const listener = jest.fn((_: TestAction1) => {})
+
+    middleware.addListener(testAction1, listener)
+
+    store.dispatch(testAction1('a'))
+    store.dispatch(testAction2('b'))
+    store.dispatch(testAction1('c'))
+
+    expect(listener.mock.calls).toEqual([
+      [testAction1('a'), middlewareApi],
+      [testAction1('c'), middlewareApi]
+    ])
+  })
+
+  test('subscribing with the same listener will not make it trigger twice (like EventTarget.addEventListener())', () => {
+    /**
+     * thoughts: allow to use this to override the options for a listener?
+     * right now it's just exiting if the listener is already registered
+     */
+
+    const listener = jest.fn((_: TestAction1) => {})
+
+    middleware.addListener(testAction1, listener)
+    middleware.addListener(testAction1, listener)
+
+    store.dispatch(testAction1('a'))
+    store.dispatch(testAction2('b'))
+    store.dispatch(testAction1('c'))
+
+    expect(listener.mock.calls).toEqual([
+      [testAction1('a'), middlewareApi],
+      [testAction1('c'), middlewareApi]
+    ])
+  })
+
+  test('unsubscribing via callback', () => {
+    const listener = jest.fn((_: TestAction1) => {})
+
+    const unsubscribe = middleware.addListener(testAction1, listener)
+
+    store.dispatch(testAction1('a'))
+    unsubscribe()
+    store.dispatch(testAction2('b'))
+    store.dispatch(testAction1('c'))
+
+    expect(listener.mock.calls).toEqual([[testAction1('a'), middlewareApi]])
+  })
+
+  test('directly unsubscribing', () => {
+    const listener = jest.fn((_: TestAction1) => {})
+
+    middleware.addListener(testAction1, listener)
+
+    store.dispatch(testAction1('a'))
+
+    middleware.removeListener(testAction1, listener)
+    store.dispatch(testAction2('b'))
+    store.dispatch(testAction1('c'))
+
+    expect(listener.mock.calls).toEqual([[testAction1('a'), middlewareApi]])
+  })
+
+  test('subscribing via action', () => {
+    const listener = jest.fn((_: TestAction1) => {})
+
+    store.dispatch(addListenerAction(testAction1, listener))
+
+    store.dispatch(testAction1('a'))
+    store.dispatch(testAction2('b'))
+    store.dispatch(testAction1('c'))
+
+    expect(listener.mock.calls).toEqual([
+      [testAction1('a'), middlewareApi],
+      [testAction1('c'), middlewareApi]
+    ])
+  })
+
+  test('unsubscribing via callback from dispatch', () => {
+    const listener = jest.fn((_: TestAction1) => {})
+
+    const unsubscribe = store.dispatch(addListenerAction(testAction1, listener))
+
+    store.dispatch(testAction1('a'))
+    // @ts-ignore TODO types
+    unsubscribe()
+    store.dispatch(testAction2('b'))
+    store.dispatch(testAction1('c'))
+
+    expect(listener.mock.calls).toEqual([[testAction1('a'), middlewareApi]])
+  })
+
+  test('unsubscribing via action', () => {
+    const listener = jest.fn((_: TestAction1) => {})
+
+    middleware.addListener(testAction1, listener)
+
+    store.dispatch(testAction1('a'))
+
+    store.dispatch(removeListenerAction(testAction1, listener))
+    store.dispatch(testAction2('b'))
+    store.dispatch(testAction1('c'))
+
+    expect(listener.mock.calls).toEqual([[testAction1('a'), middlewareApi]])
+  })
+
+  test('"condition" allows to skip the listener', () => {
+    const listener = jest.fn((_: TestAction1) => {})
+
+    middleware.addListener(testAction1, listener, {
+      condition(action) {
+        return action.payload !== 'b'
+      }
+    })
+
+    store.dispatch(testAction1('a'))
+    store.dispatch(testAction1('b'))
+    store.dispatch(testAction1('c'))
+
+    expect(listener.mock.calls).toEqual([
+      [testAction1('a'), middlewareApi],
+      [testAction1('c'), middlewareApi]
+    ])
+  })
+
+  test('"once" unsubscribes the listener automatically after one use', () => {
+    const listener = jest.fn((_: TestAction1) => {})
+
+    middleware.addListener(testAction1, listener, {
+      once: true
+    })
+
+    store.dispatch(testAction1('a'))
+    store.dispatch(testAction1('b'))
+    store.dispatch(testAction1('c'))
+
+    expect(listener.mock.calls).toEqual([[testAction1('a'), middlewareApi]])
+  })
+
+  test('combining "once" with "condition', () => {
+    const listener = jest.fn((_: TestAction1) => {})
+
+    middleware.addListener(testAction1, listener, {
+      once: true,
+      condition(action) {
+        return action.payload === 'b'
+      }
+    })
+
+    store.dispatch(testAction1('a'))
+    store.dispatch(testAction1('b'))
+    store.dispatch(testAction1('c'))
+
+    expect(listener.mock.calls).toEqual([[testAction1('b'), middlewareApi]])
+  })
+
+  test('by default, actions are forwarded to the store', () => {
+    reducer.mockClear()
+
+    const listener = jest.fn((_: TestAction1) => {})
+
+    middleware.addListener(testAction1, listener)
+
+    store.dispatch(testAction1('a'))
+
+    expect(reducer.mock.calls).toEqual([[{}, testAction1('a')]])
+  })
+
+  test('"preventPropagation" prevents actions from being forwarded to the store', () => {
+    reducer.mockClear()
+
+    const listener = jest.fn((_: TestAction1) => {})
+
+    middleware.addListener(testAction1, listener, { preventPropagation: true })
+
+    store.dispatch(testAction1('a'))
+
+    expect(reducer.mock.calls).toEqual([])
+  })
+
+  test('combining "preventPropagation" and "condition', () => {
+    reducer.mockClear()
+
+    const listener = jest.fn((_: TestAction1) => {})
+
+    middleware.addListener(testAction1, listener, {
+      preventPropagation: true,
+      condition(action) {
+        return action.payload === 'b'
+      }
+    })
+
+    store.dispatch(testAction1('a'))
+    store.dispatch(testAction1('b'))
+    store.dispatch(testAction1('c'))
+
+    expect(reducer.mock.calls).toEqual([
+      [{}, testAction1('a')],
+      [{}, testAction1('c')]
+    ])
+  })
+})