fix: reject request promise if remove server is unavailable

src/RESTController.js

@@ -109,6 +109,7 @@ const RESTController = {
       const xhr = new XHR();
       xhr.onreadystatechange = function () {
         if (xhr.readyState !== 4 || handled || xhr._aborted) {
+          promise.reject(xhr);
           return;
         }
         handled = true;

src/__tests__/RESTController-test.js

@@ -67,6 +67,15 @@ describe('RESTController', () => {
     });
   });
 
+  it('reject response if server is unavailable', done => {
+    RESTController._setXHR(mockXHR([{ status: 0 }], { readyState: 1 }));
+    RESTController.ajax('POST', 'users', {}).then(null, err => {
+      expect(err.readyState).toBe(1);
+      done();
+    });
+    jest.runAllTimers();
+  });
+
   it('retries on 5XX errors', done => {
     RESTController._setXHR(
       mockXHR([{ status: 500 }, { status: 500 }, { status: 200, response: { success: true } }])
@@ -462,7 +471,6 @@ describe('RESTController', () => {
     });
     RESTController.request('GET', 'classes/MyObject', {}, {});
     await flushPromises();
-    xhr.onreadystatechange();
     expect(JSON.parse(xhr.send.mock.calls[0][0])).toEqual({
       _method: 'GET',
       _ApplicationId: 'A',

src/__tests__/test_helpers/mockXHR.js

@@ -32,7 +32,7 @@ function mockXHR(results, options = {}) {
     send: function () {
       this.status = results[attempts].status;
       this.responseText = JSON.stringify(results[attempts].response || {});
-      this.readyState = 4;
+      this.readyState = options.readyState || 4;
       attempts++;
       this.onreadystatechange();
       this.onprogress(options.progress);