Alerting/Chore: Mock API (MSW) in browser (#89223)

Co-authored-by: joshhunt <josh@trtr.co>

.github/CODEOWNERS

@@ -369,6 +369,7 @@
 /package.json @grafana/frontend-ops
 /nx.json @grafana/frontend-ops
 /project.json @grafana/frontend-ops
+/.nxignore @grafana/frontend-ops
 /tsconfig.json @grafana/frontend-ops
 /.editorconfig @grafana/frontend-ops
 /.eslintignore @grafana/frontend-ops
@@ -501,6 +502,7 @@ playwright.config.ts @grafana/plugins-platform-frontend
 /public/lib/ @grafana/grafana-frontend-platform
 /public/lib/monaco-languages/kusto.ts @grafana/partner-datasources
 /public/maps/ @ryantxu
+/public/mockServiceWorker.js @grafana/frontend-ops
 /public/robots.txt @grafana/frontend-ops
 /public/fonts/ @grafana/grafana-frontend-platform
 /public/sass/ @grafana/grafana-frontend-platform

.nxignore

@@ -0,0 +1 @@
+!conf/custom.ini

.prettierignore

@@ -28,5 +28,8 @@ public/api-merged.json
 public/api-enterprise-spec.json
 public/openapi3.json
 
+# Generated mock service worker
+public/mockServiceWorker.js
+
 # Crowdin files
 public/locales/**/*.json

conf/defaults.ini

@@ -1996,3 +1996,6 @@ frontend_poll_interval = 2s
 # Should UI tests fail when console log/warn/erroring?
 # Does not affect the result when running on CI - only for allowing devs to choose this behaviour locally
 fail_tests_on_console = true
+# Whether or not to enable the MSW mock API, which intercepts requests and returns mock data
+# Should only be used for local development or demo purposes
+mock_api = false

package.json

@@ -445,5 +445,10 @@
     "prettier@3.3.3": {
       "unplugged": true
     }
+  },
+  "msw": {
+    "workerDirectory": [
+      "public"
+    ]
   }
 }

pkg/api/http_server.go

@@ -604,6 +604,7 @@ func (hs *HTTPServer) addMiddlewaresAndStaticRoutes() {
 	hs.mapStatic(m, hs.Cfg.StaticRootPath, "build", "public/build")
 	hs.mapStatic(m, hs.Cfg.StaticRootPath, "", "public", "/public/views/swagger.html")
 	hs.mapStatic(m, hs.Cfg.StaticRootPath, "robots.txt", "robots.txt")
+	hs.mapStatic(m, hs.Cfg.StaticRootPath, "mockServiceWorker.js", "mockServiceWorker.js")
 
 	if hs.Cfg.ImageUploadProvider == "local" {
 		hs.mapStatic(m, hs.Cfg.ImagesDir, "", "/public/img/attachments")
@@ -753,6 +754,12 @@ func (hs *HTTPServer) mapStatic(m *web.Mux, rootDir string, dir string, prefix s
 		}
 	}
 
+	if prefix == "mockServiceWorker.js" {
+		headers = func(c *web.Context) {
+			c.Resp.Header().Set("Content-Type", "application/javascript")
+		}
+	}
+
 	m.Use(httpstatic.Static(
 		path.Join(rootDir, dir),
 		httpstatic.StaticOptions{

public/app/index.ts

@@ -19,4 +19,16 @@ if (window.nonce) {
 window.__grafana_app_bundle_loaded = true;
 
 import app from './app';
-app.init();
+
+const prepareInit = async () => {
+  if (process.env.frontend_dev_mock_api) {
+    return import('test/mock-api/worker').then((workerModule) => {
+      workerModule.default.start({ onUnhandledRequest: 'bypass' });
+    });
+  }
+  return Promise.resolve();
+};
+
+prepareInit().then(() => {
+  app.init();
+});

public/mockServiceWorker.js

@@ -0,0 +1,284 @@
+/* eslint-disable */
+/* tslint:disable */
+
+/**
+ * Mock Service Worker.
+ * @see https://github.com/mswjs/msw
+ * - Please do NOT modify this file.
+ * - Please do NOT serve this file on production.
+ */
+
+const PACKAGE_VERSION = '2.3.5'
+const INTEGRITY_CHECKSUM = '26357c79639bfa20d64c0efca2a87423'
+const IS_MOCKED_RESPONSE = Symbol('isMockedResponse')
+const activeClientIds = new Set()
+
+self.addEventListener('install', function () {
+  self.skipWaiting()
+})
+
+self.addEventListener('activate', function (event) {
+  event.waitUntil(self.clients.claim())
+})
+
+self.addEventListener('message', async function (event) {
+  const clientId = event.source.id
+
+  if (!clientId || !self.clients) {
+    return
+  }
+
+  const client = await self.clients.get(clientId)
+
+  if (!client) {
+    return
+  }
+
+  const allClients = await self.clients.matchAll({
+    type: 'window',
+  })
+
+  switch (event.data) {
+    case 'KEEPALIVE_REQUEST': {
+      sendToClient(client, {
+        type: 'KEEPALIVE_RESPONSE',
+      })
+      break
+    }
+
+    case 'INTEGRITY_CHECK_REQUEST': {
+      sendToClient(client, {
+        type: 'INTEGRITY_CHECK_RESPONSE',
+        payload: {
+          packageVersion: PACKAGE_VERSION,
+          checksum: INTEGRITY_CHECKSUM,
+        },
+      })
+      break
+    }
+
+    case 'MOCK_ACTIVATE': {
+      activeClientIds.add(clientId)
+
+      sendToClient(client, {
+        type: 'MOCKING_ENABLED',
+        payload: true,
+      })
+      break
+    }
+
+    case 'MOCK_DEACTIVATE': {
+      activeClientIds.delete(clientId)
+      break
+    }
+
+    case 'CLIENT_CLOSED': {
+      activeClientIds.delete(clientId)
+
+      const remainingClients = allClients.filter((client) => {
+        return client.id !== clientId
+      })
+
+      // Unregister itself when there are no more clients
+      if (remainingClients.length === 0) {
+        self.registration.unregister()
+      }
+
+      break
+    }
+  }
+})
+
+self.addEventListener('fetch', function (event) {
+  const { request } = event
+
+  // Bypass navigation requests.
+  if (request.mode === 'navigate') {
+    return
+  }
+
+  // Opening the DevTools triggers the "only-if-cached" request
+  // that cannot be handled by the worker. Bypass such requests.
+  if (request.cache === 'only-if-cached' && request.mode !== 'same-origin') {
+    return
+  }
+
+  // Bypass all requests when there are no active clients.
+  // Prevents the self-unregistered worked from handling requests
+  // after it's been deleted (still remains active until the next reload).
+  if (activeClientIds.size === 0) {
+    return
+  }
+
+  // Generate unique request ID.
+  const requestId = crypto.randomUUID()
+  event.respondWith(handleRequest(event, requestId))
+})
+
+async function handleRequest(event, requestId) {
+  const client = await resolveMainClient(event)
+  const response = await getResponse(event, client, requestId)
+
+  // Send back the response clone for the "response:*" life-cycle events.
+  // Ensure MSW is active and ready to handle the message, otherwise
+  // this message will pend indefinitely.
+  if (client && activeClientIds.has(client.id)) {
+    ;(async function () {
+      const responseClone = response.clone()
+
+      sendToClient(
+        client,
+        {
+          type: 'RESPONSE',
+          payload: {
+            requestId,
+            isMockedResponse: IS_MOCKED_RESPONSE in response,
+            type: responseClone.type,
+            status: responseClone.status,
+            statusText: responseClone.statusText,
+            body: responseClone.body,
+            headers: Object.fromEntries(responseClone.headers.entries()),
+          },
+        },
+        [responseClone.body],
+      )
+    })()
+  }
+
+  return response
+}
+
+// Resolve the main client for the given event.
+// Client that issues a request doesn't necessarily equal the client
+// that registered the worker. It's with the latter the worker should
+// communicate with during the response resolving phase.
+async function resolveMainClient(event) {
+  const client = await self.clients.get(event.clientId)
+
+  if (client?.frameType === 'top-level') {
+    return client
+  }
+
+  const allClients = await self.clients.matchAll({
+    type: 'window',
+  })
+
+  return allClients
+    .filter((client) => {
+      // Get only those clients that are currently visible.
+      return client.visibilityState === 'visible'
+    })
+    .find((client) => {
+      // Find the client ID that's recorded in the
+      // set of clients that have registered the worker.
+      return activeClientIds.has(client.id)
+    })
+}
+
+async function getResponse(event, client, requestId) {
+  const { request } = event
+
+  // Clone the request because it might've been already used
+  // (i.e. its body has been read and sent to the client).
+  const requestClone = request.clone()
+
+  function passthrough() {
+    const headers = Object.fromEntries(requestClone.headers.entries())
+
+    // Remove internal MSW request header so the passthrough request
+    // complies with any potential CORS preflight checks on the server.
+    // Some servers forbid unknown request headers.
+    delete headers['x-msw-intention']
+
+    return fetch(requestClone, { headers })
+  }
+
+  // Bypass mocking when the client is not active.
+  if (!client) {
+    return passthrough()
+  }
+
+  // Bypass initial page load requests (i.e. static assets).
+  // The absence of the immediate/parent client in the map of the active clients
+  // means that MSW hasn't dispatched the "MOCK_ACTIVATE" event yet
+  // and is not ready to handle requests.
+  if (!activeClientIds.has(client.id)) {
+    return passthrough()
+  }
+
+  // Notify the client that a request has been intercepted.
+  const requestBuffer = await request.arrayBuffer()
+  const clientMessage = await sendToClient(
+    client,
+    {
+      type: 'REQUEST',
+      payload: {
+        id: requestId,
+        url: request.url,
+        mode: request.mode,
+        method: request.method,
+        headers: Object.fromEntries(request.headers.entries()),
+        cache: request.cache,
+        credentials: request.credentials,
+        destination: request.destination,
+        integrity: request.integrity,
+        redirect: request.redirect,
+        referrer: request.referrer,
+        referrerPolicy: request.referrerPolicy,
+        body: requestBuffer,
+        keepalive: request.keepalive,
+      },
+    },
+    [requestBuffer],
+  )
+
+  switch (clientMessage.type) {
+    case 'MOCK_RESPONSE': {
+      return respondWithMock(clientMessage.data)
+    }
+
+    case 'PASSTHROUGH': {
+      return passthrough()
+    }
+  }
+
+  return passthrough()
+}
+
+function sendToClient(client, message, transferrables = []) {
+  return new Promise((resolve, reject) => {
+    const channel = new MessageChannel()
+
+    channel.port1.onmessage = (event) => {
+      if (event.data && event.data.error) {
+        return reject(event.data.error)
+      }
+
+      resolve(event.data)
+    }
+
+    client.postMessage(
+      message,
+      [channel.port2].concat(transferrables.filter(Boolean)),
+    )
+  })
+}
+
+async function respondWithMock(response) {
+  // Setting response status code to 0 is a no-op.
+  // However, when responding with a "Response.error()", the produced Response
+  // instance will have status code set to 0. Since it's not possible to create
+  // a Response instance with status code 0, handle that use-case separately.
+  if (response.status === 0) {
+    return Response.error()
+  }
+
+  const mockedResponse = new Response(response.body, response)
+
+  Reflect.defineProperty(mockedResponse, IS_MOCKED_RESPONSE, {
+    value: true,
+    enumerable: true,
+  })
+
+  return mockedResponse
+}

public/test/mock-api/worker.ts

@@ -0,0 +1,5 @@
+import { setupWorker } from 'msw/browser';
+
+import allAlertingHandlers from 'app/features/alerting/unified/mocks/server/all-handlers';
+
+export default setupWorker(...allAlertingHandlers);