Fix: Make sure MSW loader is resolved only when mocking is enabled

README.md

@@ -257,11 +257,11 @@ initialize({}, [
 
 #### Using the addon in Node.js with Portable Stories
 
-If you're using [portable stories](https://storybook.js.org/docs/writing-tests/stories-in-unit-tests), you need to make sure the MSW loaders are applied correctly.
+If you're using [portable stories](https://storybook.js.org/docs/api/portable-stories/portable-stories-vitest), you need to make sure the MSW loaders are applied correctly.
 
-### Storybook 8
+### Storybook 8.2 or higher
 
-You do so by calling the `load` function of your story before rendering it:
+If you [set up the project annotations](https://storybook.js.org/docs/api/portable-stories/portable-stories-vitest#setprojectannotations) correctly, by calling the `play` function of your story, the MSW loaders will be applied automatically:
 
 ```ts
 import { composeStories } from '@storybook/react'
@@ -270,13 +270,12 @@ import * as stories from './MyComponent.stories'
 const { Success } = composeStories(stories)
 
 test('<Success />', async() => {
-  // 👇 Crucial step, so that the MSW loaders are applied
-  await Success.load()
-  render(<Success />)
+  // The MSW loaders are applied automatically via the play function
+  await Success.play()
 })
 ```
 
-### Storybook 7
+### Storybook < 8.2
 
 You do so by calling the `applyRequestHandlers`  helper before rendering your story:
 

packages/docs/.storybook/preview.ts

@@ -3,13 +3,15 @@ import { initialize, mswLoader } from 'msw-storybook-addon';
 
 import '../src/styles.css';
 
-initialize();
-
 const preview: Preview = {
+  // beforeAll is available in Storybook 8.2. Else the call would happen outside of the preview object
+  beforeAll: async() => {
+    initialize();
+  },
+  loaders: mswLoader,
   parameters: {
     actions: { argTypesRegex: '^on[A-Z].*' },
   },
-  loaders: [mswLoader],
 };
 
 export default preview;

packages/docs/package.json

@@ -40,31 +40,34 @@
   },
   "devDependencies": {
     "@rollup/plugin-replace": "^5.0.5",
-    "@storybook/addon-a11y": "^8.0.0",
-    "@storybook/addon-actions": "^8.0.0",
-    "@storybook/addon-essentials": "^8.0.0",
-    "@storybook/addon-links": "^8.0.0",
-    "@storybook/addon-mdx-gfm": "^8.0.0",
-    "@storybook/node-logger": "^8.0.0",
-    "@storybook/preset-create-react-app": "^8.0.0",
-    "@storybook/react": "^8.0.0",
-    "@storybook/react-vite": "^8.0.0",
-    "@testing-library/jest-dom": "^6.1.4",
-    "@testing-library/react": "^14.1.2",
-    "@testing-library/user-event": "^14.5.1",
+    "@storybook/addon-a11y": "^8.2.1",
+    "@storybook/addon-actions": "^8.2.1",
+    "@storybook/addon-essentials": "^8.2.1",
+    "@storybook/addon-links": "^8.2.1",
+    "@storybook/addon-mdx-gfm": "^8.2.1",
+    "@storybook/node-logger": "^8.2.1",
+    "@storybook/preset-create-react-app": "^8.2.1",
+    "@storybook/react": "^8.2.1",
+    "@storybook/react-vite": "^8.2.1",
+    "@testing-library/dom": "^10.3.1",
+    "@testing-library/jest-dom": "^6.4.6",
+    "@testing-library/react": "^16.0.0",
+    "@testing-library/user-event": "^14.5.2",
     "@types/react": "^18.0.27",
     "@types/react-dom": "^18.0.10",
     "@types/react-router-dom": "^5.3.3",
     "@vitejs/plugin-react": "^4.2.1",
     "chromatic": "^11.0.3",
     "jsdom": "^23.0.0",
-    "msw": "^2.0.9",
-    "storybook": "^8.0.0",
+    "msw": "^2.3.1",
+    "storybook": "^8.2.1",
     "typescript": "^5.3.2",
     "vite": "^5.2.11",
-    "vitest": "^1.6.0"
+    "vitest": "^2.0.2"
   },
   "msw": {
-    "workerDirectory": "public"
+    "workerDirectory": [
+      "public"
+    ]
   }
 }

packages/docs/public/mockServiceWorker.js

@@ -8,7 +8,7 @@
  * - Please do NOT serve this file on production.
  */
 
-const PACKAGE_VERSION = '2.2.14'
+const PACKAGE_VERSION = '2.3.1'
 const INTEGRITY_CHECKSUM = '26357c79639bfa20d64c0efca2a87423'
 const IS_MOCKED_RESPONSE = Symbol('isMockedResponse')
 const activeClientIds = new Set()

packages/docs/src/demos/fetch/AddonOnNode.test.tsx

@@ -1,20 +1,21 @@
 /**
- * @jest-environment jsdom
+ * @vitest-environment jsdom
  */
 import { render, screen } from '@testing-library/react'
 import { composeStories, setProjectAnnotations } from '@storybook/react'
-import { describe, afterAll, it, expect } from 'vitest'
+import { describe, afterAll, it, expect, beforeAll } from 'vitest'
 
 import { getWorker, applyRequestHandlers } from 'msw-storybook-addon'
 import * as stories from './App.stories'
 import projectAnnotations from '../../../.storybook/preview'
 
-setProjectAnnotations(projectAnnotations)
+const annotations = setProjectAnnotations(projectAnnotations)
 
 const { MockedSuccess, MockedError } = composeStories(stories)
 
 // Useful in scenarios where the addon runs on node, such as with portable stories
 describe('Running msw-addon on node', () => {
+  beforeAll(annotations.beforeAll!)
   afterAll(() => {
     // @ts-expect-error TS(2339): Property 'close' does not exist on type 'SetupWork... Remove this comment to see the full error message
     getWorker().close()

packages/msw-addon/src/applyRequestHandlers.ts

@@ -1,21 +1,21 @@
 import type { RequestHandler } from 'msw'
 import { api } from '@build-time/initialize'
 import type { Context } from './decorator.js'
-import { deprecate } from './util.js';
+import { deprecate } from './util.js'
 
-const deprecateMessage =  deprecate(`
+const deprecateMessage = deprecate(`
 [msw-storybook-addon] You are using parameters.msw as an Array instead of an Object with a property "handlers". This usage is deprecated and will be removed in the next release. Please use the Object syntax instead.
 
 More info: https://github.com/mswjs/msw-storybook-addon/blob/main/MIGRATION.md#parametersmsw-array-notation-deprecated-in-favor-of-object-notation
 `)
 
-// P.S. this is used by Storybook 7 users as a way to help them migrate.
+// P.S. this is publicly exported as it is used by Storybook 7 users as a way to help them migrate.
 // This should be removed from the package exports in a future release.
 export function applyRequestHandlers(
   handlersListOrObject: Context['parameters']['msw']
 ): void {
-  api?.resetHandlers();
-  
+  api?.resetHandlers()
+
   if (handlersListOrObject == null) {
     return
   }

packages/msw-addon/src/augmentInitializeOptions.ts

@@ -1,54 +1,60 @@
-import { InitializeOptions } from "./initialize.js";
+import { InitializeOptions } from './initialize.js'
 
-const fileExtensionPattern = /\.(js|jsx|ts|tsx|mjs|woff|woff2|ttf|otf|eot)$/;
+const fileExtensionPattern = /\.(js|jsx|ts|tsx|mjs|woff|woff2|ttf|otf|eot)$/
 const filteredURLSubstrings = [
-  "sb-common-assets",
-  "node_modules",
-  "node-modules",
-  "hot-update.json",
-  "__webpack_hmr",
-  "sb-vite",
-];
+  'sb-common-assets',
+  'node_modules',
+  'node-modules',
+  'hot-update.json',
+  '__webpack_hmr',
+  'iframe.html',
+  'sb-vite',
+  '@vite',
+  '@react-refresh',
+  '/virtual:',
+  '.stories.',
+  '.mdx',
+]
 
 const shouldFilterUrl = (url: string) => {
   // files which are mostly noise from webpack/vite builders + font files
   if (fileExtensionPattern.test(url)) {
-    return true;
+    return true
   }
 
   const isStorybookRequest = filteredURLSubstrings.some((substring) =>
     url.includes(substring)
-  );
+  )
 
   if (isStorybookRequest) {
-    return true;
+    return true
   }
 
-  return false;
-};
+  return false
+}
 
 export const augmentInitializeOptions = (options: InitializeOptions) => {
-  if (typeof options?.onUnhandledRequest === "string") {
-    return options;
+  if (typeof options?.onUnhandledRequest === 'string') {
+    return options
   }
 
   return {
     ...options,
     // Filter requests that we know are not relevant to the user e.g. HMR, builder requests, statics assets, etc.
     onUnhandledRequest: (...args) => {
-      const [{ url }, print] = args;
+      const [{ url }, print] = args
       if (shouldFilterUrl(url)) {
-        return;
+        return
       }
 
       if (!options?.onUnhandledRequest) {
-        print.warning();
-        return;
+        print.warning()
+        return
       }
 
-      if (typeof options?.onUnhandledRequest === "function") {
-        options.onUnhandledRequest(...args);
+      if (typeof options?.onUnhandledRequest === 'function') {
+        options.onUnhandledRequest(...args)
       }
     },
-  } as InitializeOptions;
-};
+  } as InitializeOptions
+}

packages/msw-addon/src/initialize.browser.ts

@@ -6,18 +6,29 @@ type SetupWorker = ReturnType<typeof setupWorker>
 
 export let api: SetupWorker
 
+type ContextfulWorker = SetupWorker & {
+  context: { isMockingEnabled: boolean; activationPromise?: any }
+}
+
 export type InitializeOptions = Parameters<SetupWorker['start']>[0]
 
 export function initialize(
   options?: InitializeOptions,
   initialHandlers: RequestHandler[] = []
 ): SetupWorker {
-  const worker = setupWorker(...initialHandlers)
-  worker.start(augmentInitializeOptions(options))
+  const worker = setupWorker(...initialHandlers) as ContextfulWorker
+  worker.context.activationPromise = worker.start(
+    augmentInitializeOptions(options)
+  )
   api = worker
   return worker
 }
 
+export async function waitForMswReady() {
+  const msw = getWorker() as ContextfulWorker
+  await msw.context.activationPromise
+}
+
 export function getWorker(): SetupWorker {
   if (api === undefined) {
     throw new Error(

packages/msw-addon/src/initialize.d.ts

@@ -13,4 +13,6 @@ export declare function initialize(
   initialHandlers?: RequestHandler[]
 ): SetupApi<LifeCycleEventsMap>
 
-export declare function getWorker(): typeof api
+export declare function waitForMswReady(): Promise<void>
+
+export declare function getWorker(): typeof api

packages/msw-addon/src/initialize.node.ts

@@ -18,6 +18,11 @@ export function initialize(
   return server
 }
 
+export async function waitForMswReady() {
+  // in Node MSW is activated instantly upon registration. Still we need to check the presence of the worker
+  getWorker()
+}
+
 export function getWorker(): SetupServer {
   if (api === undefined) {
     throw new Error(

packages/msw-addon/src/initialize.react-native.ts

@@ -18,6 +18,11 @@ export function initialize(
   return server
 }
 
+export async function waitForMswReady() {
+  // in Node MSW is activated instantly upon registration. Still we need to check the presence of the worker
+  getWorker()
+}
+
 export function getWorker(): SetupServer {
   if (api === undefined) {
     throw new Error(

packages/msw-addon/src/loader.ts

@@ -1,18 +1,10 @@
+import { waitForMswReady } from '@build-time/initialize'
 import type { Context } from './decorator.js'
 import { applyRequestHandlers } from './applyRequestHandlers.js'
 
 export const mswLoader = async (context: Context) => {
+  await waitForMswReady()
   applyRequestHandlers(context.parameters.msw)
 
-  if (
-    typeof window !== 'undefined' &&
-    'navigator' in window &&
-    navigator.serviceWorker?.controller
-  ) {
-    // No need to rely on the MSW Promise exactly
-    // since only 1 worker can control 1 scope at a time.
-    await navigator.serviceWorker.ready
-  }
-
   return {}
 }