Merge pull request #283 from expo/@evanbacon/with-workbox/create-example

feat: added workbox example

with-workbox/App.js

@@ -0,0 +1,23 @@
+import * as React from "react";
+import { View, Text } from "react-native";
+
+import * as serviceWorkerRegistration from "./src/serviceWorkerRegistration";
+
+export default function App() {
+  return (
+    <View
+      style={{
+        flex: 1,
+        justifyContent: "center",
+        alignItems: "center",
+      }}
+    >
+      <Text>Universal (offline) React with Expo</Text>
+    </View>
+  );
+}
+
+// If you want your app to work offline and load faster, you can change
+// unregister() to register() below. Note this comes with some pitfalls.
+// Learn more about service workers: https://cra.link/PWA
+serviceWorkerRegistration.register();

with-workbox/README.md

@@ -0,0 +1,52 @@
+# Workbox Example
+
+<p>
+  <!-- iOS -->
+  <img alt="Supports Expo iOS" longdesc="Supports Expo iOS" src="https://img.shields.io/badge/iOS-4630EB.svg?style=flat-square&logo=APPLE&labelColor=999999&logoColor=fff" />
+  <!-- Android -->
+  <img alt="Supports Expo Android" longdesc="Supports Expo Android" src="https://img.shields.io/badge/Android-4630EB.svg?style=flat-square&logo=ANDROID&labelColor=A4C639&logoColor=fff" />
+  <!-- Web -->
+  <img alt="Supports Expo Web" longdesc="Supports Expo Web" src="https://img.shields.io/badge/web-4630EB.svg?style=flat-square&logo=GOOGLE-CHROME&labelColor=4285F4&logoColor=fff" />
+</p>
+
+```sh
+npx create-react-native-app -t with-workbox
+```
+
+[Workbox](https://developers.google.com/web/tools/workbox) is a collection of libraries for creating and managing powerful web service workers. Service workers can be used to add offline support to websites.
+
+This example is based on the [create-react-app](https://create-react-app.dev/docs/making-a-progressive-web-app/) PWA guide, with native escape hatches added.
+
+## 🚀 How to use
+
+#### Creating a new project
+
+- Install the CLI: `npm i -g expo-cli`
+- Create a project: `npx create-react-native-app -t with-workbox`
+- `cd` into the project
+
+### Testing the service worker
+
+The service worker is disabled in development and requires that you build the app for production and host locally to test.
+
+- Check to make sure you are invoking `serviceWorkerRegistration.register();` and not `serviceWorkerRegistration.unregister();` in your `./App.js`.
+
+- `expo build:web`
+- Host the files locally with `yarn serve`
+  - This uses serve CLI to host your `/web-build` folder.
+- Open: http://localhost:5000/
+- In chrome, you can hard reset the service workers with <kbd>⌘+shift+R</kbd>
+
+Service workers are disabled in development in three places:
+
+- The custom Webpack dev server adds a noop service worker on `/service-worker.js` to prevent collisions from other projects on your computer.
+- The `webpack.config.js` skips adding the injection plugin unless the environment is production (`expo build:web`)
+- The `src/serviceWorkerRegistration.js` `register` method checks to ensure the app is running in production.
+
+You may find that your website doesn't update by default when refreshing the page. You might need to ensure that no other tabs on your computer are open to the website. This is just one of [many pitfalls](https://create-react-app.dev/docs/making-a-progressive-web-app/#offline-first-considerations) that you need to consider when using service workers.
+
+## 📝 Notes
+
+- [create-react-app PWA guide](https://create-react-app.dev/docs/making-a-progressive-web-app/#offline-first-considerations)
+- [workbox docs](https://developers.google.com/web/tools/workbox)
+- [Enabling service workers in Expo web](https://expo.fyi/enabling-web-service-workers)

with-workbox/babel.config.js

@@ -0,0 +1,6 @@
+module.exports = function(api) {
+  api.cache(true);
+  return {
+    presets: ['babel-preset-expo'],
+  };
+};

with-workbox/package.json

@@ -0,0 +1,30 @@
+{
+  "scripts": {
+    "serve": "serve web-build"
+  },
+  "dependencies": {
+    "expo": "~42.0.0",
+    "react": "16.13.1",
+    "react-dom": "16.13.1",
+    "react-native": "https://github.com/expo/react-native/archive/sdk-42.0.0.tar.gz",
+    "react-native-web": "~0.13.12"
+  },
+  "devDependencies": {
+    "@babel/core": "^7.9.0",
+    "@expo/webpack-config": "^0.13.3",
+    "serve": "^12.0.0",
+    "workbox-webpack-plugin": "^6.1.5",
+    "workbox-background-sync": "^6.1.5",
+    "workbox-broadcast-update": "^6.1.5",
+    "workbox-cacheable-response": "^6.1.5",
+    "workbox-core": "^6.1.5",
+    "workbox-expiration": "^6.1.5",
+    "workbox-google-analytics": "^6.1.5",
+    "workbox-navigation-preload": "^6.1.5",
+    "workbox-precaching": "^6.1.5",
+    "workbox-range-requests": "^6.1.5",
+    "workbox-routing": "^6.1.5",
+    "workbox-strategies": "^6.1.5",
+    "workbox-streams": "^6.1.5"
+  }
+}

with-workbox/src/service-worker.js

@@ -0,0 +1,73 @@
+/* eslint-disable no-restricted-globals */
+
+// This service worker can be customized!
+// See https://developers.google.com/web/tools/workbox/modules
+// for the list of available Workbox modules, or add any other
+// code you'd like.
+// You can also remove this file if you'd prefer not to use a
+// service worker, and the Workbox build step will be skipped.
+
+import { clientsClaim } from "workbox-core";
+import { ExpirationPlugin } from "workbox-expiration";
+import { precacheAndRoute, createHandlerBoundToURL } from "workbox-precaching";
+import { registerRoute } from "workbox-routing";
+import { StaleWhileRevalidate } from "workbox-strategies";
+
+clientsClaim();
+
+// Precache all of the assets generated by your build process.
+// Their URLs are injected into the manifest variable below.
+// This variable must be present somewhere in your service worker file,
+// even if you decide not to use precaching. See https://cra.link/PWA
+precacheAndRoute(self.__WB_MANIFEST);
+
+// Set up App Shell-style routing, so that all navigation requests
+// are fulfilled with your index.html shell. Learn more at
+// https://developers.google.com/web/fundamentals/architecture/app-shell
+const fileExtensionRegexp = new RegExp("/[^/?]+\\.[^/]+$");
+registerRoute(
+  // Return false to exempt requests from being fulfilled by index.html.
+  ({ request, url }) => {
+    // If this isn't a navigation, skip.
+    if (request.mode !== "navigate") {
+      return false;
+    } // If this is a URL that starts with /_, skip.
+
+    if (url.pathname.startsWith("/_")) {
+      return false;
+    } // If this looks like a URL for a resource, because it contains // a file extension, skip.
+
+    if (url.pathname.match(fileExtensionRegexp)) {
+      return false;
+    } // Return true to signal that we want to use the handler.
+
+    return true;
+  },
+  createHandlerBoundToURL(process.env.PUBLIC_URL + "/index.html")
+);
+
+// An example runtime caching route for requests that aren't handled by the
+// precache, in this case same-origin .png requests like those from in public/
+registerRoute(
+  // Add in any other file extensions or routing criteria as needed.
+  ({ url }) =>
+    url.origin === self.location.origin && url.pathname.endsWith(".png"), // Customize this strategy as needed, e.g., by changing to CacheFirst.
+  new StaleWhileRevalidate({
+    cacheName: "images",
+    plugins: [
+      // Ensure that once this runtime cache reaches a maximum size the
+      // least-recently used images are removed.
+      new ExpirationPlugin({ maxEntries: 50 }),
+    ],
+  })
+);
+
+// This allows the web app to trigger skipWaiting via
+// registration.waiting.postMessage({type: 'SKIP_WAITING'})
+self.addEventListener("message", (event) => {
+  if (event.data && event.data.type === "SKIP_WAITING") {
+    self.skipWaiting();
+  }
+});
+
+// Any other custom service worker logic can go here.

with-workbox/src/serviceWorkerRegistration.js

@@ -0,0 +1,142 @@
+// This optional code is used to register a service worker.
+// register() is not called by default.
+
+// This lets the app load faster on subsequent visits in production, and gives
+// it offline capabilities. However, it also means that developers (and users)
+// will only see deployed updates on subsequent visits to a page, after all the
+// existing tabs open on the page have been closed, since previously cached
+// resources are updated in the background.
+
+// To learn more about the benefits of this model and instructions on how to
+// opt-in, read https://cra.link/PWA
+
+const isLocalhost = Boolean(
+  window.location.hostname === "localhost" ||
+    // [::1] is the IPv6 localhost address.
+    window.location.hostname === "[::1]" ||
+    // 127.0.0.0/8 are considered localhost for IPv4.
+    window.location.hostname.match(
+      /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/
+    )
+);
+
+export function register(config) {
+  const isEnvProduction = process.env.NODE_ENV === "production";
+  if (isEnvProduction && "serviceWorker" in navigator) {
+    // The URL constructor is available in all browsers that support SW.
+    const publicUrl = new URL(process.env.PUBLIC_URL, window.location.href);
+    if (publicUrl.origin !== window.location.origin) {
+      // Our service worker won't work if PUBLIC_URL is on a different origin
+      // from what our page is served on. This might happen if a CDN is used to
+      // serve assets; see https://github.com/facebook/create-react-app/issues/2374
+      return;
+    }
+
+    window.addEventListener("load", () => {
+      const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`;
+
+      if (isLocalhost) {
+        // This is running on localhost. Let's check if a service worker still exists or not.
+        checkValidServiceWorker(swUrl, config);
+
+        // Add some additional logging to localhost, pointing developers to the
+        // service worker/PWA documentation.
+        navigator.serviceWorker.ready.then(() => {
+          console.log(
+            "This web app is being served cache-first by a service " +
+              "worker. To learn more, visit https://cra.link/PWA"
+          );
+        });
+      } else {
+        // Is not localhost. Just register service worker
+        registerValidSW(swUrl, config);
+      }
+    });
+  }
+}
+
+function registerValidSW(swUrl, config) {
+  navigator.serviceWorker
+    .register(swUrl)
+    .then((registration) => {
+      registration.onupdatefound = () => {
+        const installingWorker = registration.installing;
+        if (installingWorker == null) {
+          return;
+        }
+        installingWorker.onstatechange = () => {
+          if (installingWorker.state === "installed") {
+            if (navigator.serviceWorker.controller) {
+              // At this point, the updated precached content has been fetched,
+              // but the previous service worker will still serve the older
+              // content until all client tabs are closed.
+              console.log(
+                "New content is available and will be used when all " +
+                  "tabs for this page are closed. See https://cra.link/PWA."
+              );
+
+              // Execute callback
+              if (config && config.onUpdate) {
+                config.onUpdate(registration);
+              }
+            } else {
+              // At this point, everything has been precached.
+              // It's the perfect time to display a
+              // "Content is cached for offline use." message.
+              console.log("Content is cached for offline use.");
+
+              // Execute callback
+              if (config && config.onSuccess) {
+                config.onSuccess(registration);
+              }
+            }
+          }
+        };
+      };
+    })
+    .catch((error) => {
+      console.error("Error during service worker registration:", error);
+    });
+}
+
+function checkValidServiceWorker(swUrl, config) {
+  // Check if the service worker can be found. If it can't reload the page.
+  fetch(swUrl, {
+    headers: { "Service-Worker": "script" },
+  })
+    .then((response) => {
+      // Ensure service worker exists, and that we really are getting a JS file.
+      const contentType = response.headers.get("content-type");
+      if (
+        response.status === 404 ||
+        (contentType != null && contentType.indexOf("javascript") === -1)
+      ) {
+        // No service worker found. Probably a different app. Reload the page.
+        navigator.serviceWorker.ready.then((registration) => {
+          registration.unregister().then(() => {
+            window.location.reload();
+          });
+        });
+      } else {
+        // Service worker found. Proceed as normal.
+        registerValidSW(swUrl, config);
+      }
+    })
+    .catch(() => {
+      console.log(
+        "No internet connection found. App is running in offline mode."
+      );
+    });
+}
+
+export function unregister() {
+  if ("serviceWorker" in navigator) {
+    navigator.serviceWorker.ready
+      .then((registration) => {
+        registration.unregister();
+      })
+      .catch((error) => {
+        console.error(error.message);
+      });
+  }
+}

with-workbox/src/serviceWorkerRegistration.native.js

@@ -0,0 +1,5 @@
+// No-op on native. For offline support in native apps, check out expo-updates.
+
+export function register(config) {}
+
+export function unregister() {}

with-workbox/webpack.config.js

@@ -0,0 +1,36 @@
+const createExpoWebpackConfigAsync = require("@expo/webpack-config");
+const path = require("path");
+const WorkboxWebpackPlugin = require("workbox-webpack-plugin");
+
+module.exports = async function (env, argv) {
+  // Set by expo-cli during `expo build:web`
+  const isEnvProduction = env.mode === "production";
+
+  // Create the default config
+  const config = await createExpoWebpackConfigAsync(env, argv);
+
+  if (isEnvProduction) {
+    config.plugins.push(
+      // Generate a service worker script that will precache, and keep up to date,
+      // the HTML & assets that are part of the webpack build.
+      new WorkboxWebpackPlugin.InjectManifest({
+        swSrc: path.resolve(__dirname, "src/service-worker.js"),
+        dontCacheBustURLsMatching: /\.[0-9a-f]{8}\./,
+        exclude: [
+          /\.map$/,
+          /asset-manifest\.json$/,
+          /LICENSE/,
+          /\.js\.gz$/,
+          // Exclude all apple touch and chrome images because they're cached locally after the PWA is added.
+          /(apple-touch-startup-image|chrome-icon|apple-touch-icon).*\.png$/,
+        ],
+        // Bump up the default maximum size (2mb) that's precached,
+        // to make lazy-loading failure scenarios less likely.
+        // See https://github.com/cra-template/pwa/issues/13#issuecomment-722667270
+        maximumFileSizeToCacheInBytes: 5 * 1024 * 1024,
+      })
+    );
+  }
+
+  return config;
+};