Retry on node-xmlhttprequest connection error, and report useful error message

Author: andrewimm

src/InstallationController.js

@@ -19,7 +19,7 @@ function hexOctet() {
   return Math.floor(
     (1 + Math.random()) * 0x10000
   ).toString(16).substring(1);
-};
+}
 
 function generateId() {
   return (

src/RESTController.js

@@ -100,13 +100,15 @@ var RESTController = {
             promise.reject(e);
           }
           promise.resolve(response, xhr.status, xhr);
-        } else if (xhr.status >= 500) { // retry on 5XX
+        } else if (xhr.status >= 500 || xhr.status === 0) { // retry on 5XX or node-xmlhttprequest error
           if (++attempts < CoreManager.get('REQUEST_ATTEMPT_LIMIT')) {
             // Exponentially-growing random delay
             var delay = Math.round(
               Math.random() * 125 * Math.pow(2, attempts)
             );
             setTimeout(dispatch, delay);
+          } else if (xhr.status === 0) {
+            promise.reject('Unable to connect to the Parse API');
           } else {
             // After the retry limit is reached, fail
             promise.reject(xhr);

src/__tests__/RESTController-test.js

@@ -71,6 +71,37 @@ describe('RESTController', () => {
     jest.runAllTimers();
   }));
 
+  it('retries on connection failure', asyncHelper((done) => {
+    RESTController._setXHR(mockXHR([
+      { status: 0 },
+      { status: 0 },
+      { status: 0 },
+      { status: 0 },
+      { status: 0 },
+    ]));
+    RESTController.ajax('POST', 'users', {}).then(null, (err) => {
+      expect(err).toBe('Unable to connect to the Parse API');
+      done();
+    });
+    jest.runAllTimers();
+  }));
+
+  it('returns a connection error on network failure', asyncHelper((done) => {
+    RESTController._setXHR(mockXHR([
+      { status: 0 },
+      { status: 0 },
+      { status: 0 },
+      { status: 0 },
+      { status: 0 },
+    ]));
+    RESTController.request('GET', 'classes/MyObject', {}, { sessionToken: '1234' }).then(null, (err) => {
+      expect(err.code).toBe(100);
+      expect(err.message).toBe('XMLHttpRequest failed: "Unable to connect to the Parse API"');
+      done();
+    });
+    jest.runAllTimers();
+  }));
+
   it('aborts after too many failures', asyncHelper((done) => {
     RESTController._setXHR(mockXHR([
       { status: 500 },