Add support for TSLint

packages/react-scripts/config/tslint.json

@@ -0,0 +1,42 @@
+{
+  "defaultSeverity": "warning",
+  "rulesDirectory": "tslint-microsoft-contrib",
+  "rules": {
+    // https://palantir.github.io/tslint/rules/
+    "await-promise": true,
+    "new-parens": true,
+    "no-angle-bracket-type-assertion": true,
+    "no-conditional-assignment": true,
+    "no-debugger": true,
+    "no-duplicate-super": true,
+    "no-duplicate-switch-case": true,
+    "no-duplicate-variable": true,
+    "no-eval": true,
+    "no-floating-promises": true,
+    "no-for-in-array": true,
+    "no-implicit-dependencies": [true, "dev"],
+    "no-invalid-template-strings": true,
+    "no-invalid-this": true,
+    "no-namespace": true,
+    "no-sparse-arrays": true,
+    "no-string-throw": true,
+    "no-switch-case-fall-through": true,
+    "no-unused-expression": [true, "allow-fast-null-checks"],
+    // DEPRECATED. Recommended to use TS 'noUnusedLocals' for now
+    // "no-unused-variable": true,
+    "triple-equals": true,
+    "use-isnan": true,
+
+    // https://github.com/Microsoft/tslint-microsoft-contrib
+    "react-a11y-anchors": true,
+    "react-a11y-aria-unsupported-elements": true,
+    "react-a11y-event-has-role": true,
+    "react-a11y-image-button-has-alt": true,
+    "react-a11y-img-has-alt": true,
+    "react-a11y-props": true,
+    "react-a11y-proptypes": true,
+    "react-a11y-role": true,
+    "react-a11y-role-has-required-aria-props": true,
+    "react-a11y-role-supports-aria-props": true
+  }
+}

packages/react-scripts/config/webpack.config.dev.js

@@ -424,6 +424,7 @@ module.exports = {
         async: false,
         checkSyntacticErrors: true,
         tsconfig: paths.appTsConfig,
+        tslint: path.resolve(__dirname, 'tslint.json'),
         compilerOptions: {
           module: 'esnext',
           moduleResolution: 'node',

packages/react-scripts/config/webpack.config.prod.js

@@ -544,6 +544,7 @@ module.exports = {
         async: false,
         checkSyntacticErrors: true,
         tsconfig: paths.appTsConfig,
+        tslint: path.resolve(__dirname, 'tslint.json'),
         compilerOptions: {
           module: 'esnext',
           moduleResolution: 'node',

packages/react-scripts/package.json

@@ -66,6 +66,8 @@
     "sass-loader": "7.1.0",
     "style-loader": "0.23.0",
     "terser-webpack-plugin": "1.1.0",
+    "tslint": "5.11.0",
+    "tslint-microsoft-contrib": "5.2.1",
     "url-loader": "1.1.1",
     "webpack": "4.19.1",
     "webpack-dev-server": "3.1.9",

packages/react-scripts/template-typescript/src/index.tsx

@@ -9,4 +9,5 @@ ReactDOM.render(<App />, document.getElementById('root'));
 // 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: http://bit.ly/CRA-PWA
+// tslint:disable-next-line:no-floating-promises
 serviceWorker.unregister();

packages/react-scripts/template-typescript/src/serviceWorker.ts

@@ -39,105 +39,100 @@ export function register(config?: Config) {
       return;
     }
 
-    window.addEventListener('load', () => {
+    window.addEventListener('load', async () => {
       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);
+        await 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 http://bit.ly/CRA-PWA'
-          );
-        });
+        await navigator.serviceWorker.ready;
+
+        console.log(
+          'This web app is being served cache-first by a service ' +
+            'worker. To learn more, visit http://bit.ly/CRA-PWA'
+        );
       } else {
         // Is not localhost. Just register service worker
-        registerValidSW(swUrl, config);
+        await registerValidSW(swUrl, config);
       }
     });
   }
 }
 
-function registerValidSW(swUrl: string, config?: 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 http://bit.ly/CRA-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);
-              }
+async function registerValidSW(swUrl: string, config?: Config) {
+  try {
+    const registration = await navigator.serviceWorker.register(swUrl);
+
+    registration.onupdatefound = () => {
+      const installingWorker = registration.installing;
+      if (!installingWorker) {
+        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 http://bit.ly/CRA-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);
-    });
+    };
+  } catch (error) {
+    console.error('Error during service worker registration:', error);
+  }
 }
 
-function checkValidServiceWorker(swUrl: string, config?: Config) {
+async function checkValidServiceWorker(swUrl: string, config?: Config) {
   // Check if the service worker can be found. If it can't reload the page.
-  fetch(swUrl)
-    .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.'
-      );
-    });
+  try {
+    const response = await fetch(swUrl);
+
+    // 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 && contentType.indexOf('javascript') === -1)
+    ) {
+      // No service worker found. Probably a different app. Reload the page.
+      await unregister();
+      window.location.reload();
+    } else {
+      // Service worker found. Proceed as normal.as
+      await registerValidSW(swUrl, config);
+    }
+  } catch {
+    console.log(
+      'No internet connection found. App is running in offline mode.'
+    );
+  }
 }
 
-export function unregister() {
+export async function unregister() {
   if ('serviceWorker' in navigator) {
-    navigator.serviceWorker.ready.then(registration => {
-      registration.unregister();
-    });
+    const registration = await navigator.serviceWorker.ready;
+    await registration.unregister();
   }
 }