handle errors caused when JSAPI is loaded by more than one acceptance…

… test

this code is _very_ ugly, but it works

will try to fix this upstream in esri-loader and remove the ugly hacks here

addon/services/esri-loader.js

@@ -32,9 +32,54 @@ export default Ember.Service.extend({
     // otherwise create a promise that will resolve when the JSAPI is loaded
     this._loadPromise = new Ember.RSVP.Promise((resolve, reject) => {
       esriLoader.bootstrap(err => {
+        // need to kick of run loop in case we are in test mode
+        // see: https://discuss.emberjs.com/t/guide-asynchronous-side-effects-in-testing/2905
         Ember.run(() => {
           if (err) {
-            reject(err);
+            const message = err.message || err;
+            // has esriLoader.bootstrap already been called?
+            if (message === 'The ArcGIS API for JavaScript is already loaded.') {
+              // this can happen when there is more than one instance of this service
+              // running on the page at a time, for example, in acceptance tests
+
+              // TODO: this is _much_ better handled upstream
+              // so we want to get rid of all this once this issue is resolved:
+              // https://github.com/Esri/esri-loader/issues/28
+
+              // first check if it's the same script
+              // NOTE: will haev to update this every time it's updated here:
+              // https://github.com/Esri/esri-loader/blob/master/src/esri-loader.ts#L29
+              const defaultUrl = 'https://js.arcgis.com/4.4/';
+              const url = options.url || defaultUrl;
+              const script = document.querySelector('script[data-esri-loader]');
+              if (script.src !== url) {
+                // user tried to load two different versions of the JSAPI
+                reject(err);
+              } else {
+                // check if the script has loaded yet
+                if (script.dataset.esriLoader === 'loaded' || esriLoader.isLoaded()) {
+                  // notify any watchers of isLoaded copmuted property
+                  this.notifyPropertyChange('isLoaded');
+                  // let the caller know that the API has been successfully loaded
+                  // TODO: would there be something more useful to return here?
+                  resolve({ success: true });
+                } else {
+                  // wait for the script to load and then resolve
+                  script.addEventListener('load', () => {
+                    // more fun w/ Ember.run(), tests will fail w/o this
+                    Ember.run(() => {
+                      // notify any watchers of isLoaded copmuted property
+                      this.notifyPropertyChange('isLoaded');
+                      // let the caller know that the API has been successfully loaded
+                      // TODO: would there be something more useful to return here?
+                      resolve({ success: true });
+                    });
+                  }, false);
+                }
+              }
+            } else {
+              reject(err);
+            }
           } else {
             // notify any watchers of isLoaded copmuted property
             this.notifyPropertyChange('isLoaded');
@@ -70,9 +115,7 @@ export default Ember.Service.extend({
   _loadModules (moduleNames) {
     return new Ember.RSVP.Promise(resolve => {
       esriLoader.dojoRequire(moduleNames, (...modules) => {
-        Ember.run(() => {
-          resolve(modules);
-        });
+        resolve(modules);
       });
     });
   }

tests/acceptance/index-test.js

@@ -1,4 +1,4 @@
-import { skip } from 'qunit';
+import { test } from 'qunit';
 import moduleForAcceptance from '../../tests/helpers/module-for-acceptance';
 
 moduleForAcceptance('Acceptance | index');
@@ -8,7 +8,7 @@ moduleForAcceptance('Acceptance | index');
 // b/c it gets called twice and throws "The ArcGIS API for JavaScript is already loaded."
 // and ember in it's infinite wisdom decides to fail the test even though the route does .catch() the error
 // TODO: don't skip this test once we resolve the above issue
-skip('visiting /', function(assert) {
+test('visiting /', function(assert) {
   visit('/');
 
   andThen(function() {