I'm compiling my Stylus .styl stylesheets with its JavaScript API: http://learnboost.github.io/stylus/docs/js.html
var stylus = require('../')
, str = require('fs').readFileSync(__dirname + '/test.styl', 'utf8');
stylus(str)
.set('filename', __dirname + '/test.styl')
.import('mixins/vendor')
.render(function(err, css){
if (err) throw err;
console.log(css);
});
It doesn't mention whether the callback it's using is Synchronous or Asynchronous. Although in my experience it seems to be Synchronous but I'm not sure. Is it?
The render function is pseudo-asynchronous because it accepts a callback, but all calls inside the function are actually synchronous. There is also a fully synchronous version of this function (if you don't provide the callback):
var styl = stylus(str)
.set('filename', __dirname + '/test.styl')
.import('mixins/vendor');
console.log(styl.render()); // outputs compiled css
Related
I'm attempting to test that a value is changed to true after a promise is resolved inside $onInit. I'm following, as best I can, the example in this Stack Overflow question/answer. Here is my code:
class TestCtrl {
constructor(SearchService) {
this.testValue = false;
this.SearchService = SearchService;
}
$onInit() {
this.SearchService.getResults()
.then(function () {
this.testValue = true;
});
}
}
TestCtrl.$inject = ['SearchService'];
And here's the test I'm attempting to run (using mocha, chai, sinon):
it('should work', function() {
ctrl = $componentController('test', {
SearchService: SearchService
}, {});
sinon.stub(SearchService, 'getResults').resolves({response:{data: 'data'}});
ctrl.$onInit();
$rootScope.$apply();
ctrl.testValue.should.equal(true);
});
Should I be testing ctrl.testValue inside a then? Also, is using this example a bad idea because that example doesn't use a component with an $onInit lifecycle hook?
From what I've read, no, "don't use expect inside then in tests." But I'm not so sure based on what I've read elsewhere.
I wouldn't be surprised if I'm missing something obvious in how to test promises (maybe a stub wasn't the way to go?) and/or how to test what happens in the $onInit lifecycle hook.
If the question needs more details, please ask and I'll do my best to add them.
Edit: Checkout you $onInit method:
$onInit() {
this.SearchService.getResults()
.then(function () {
// `this` in anonymous function is reffering to window not the controller instance
this.testValue = true;
});
}
$onInit() {
var self = this;
self.SearchService.getResults()
.then(function () {
self.testValue = true;
});
}
Your example is correct
This is the way to test async code in angularjs - it is tested like synchronous code. Stubs' returning promises are resolved when you execute $rootScope.$apply().
Why it doesn't work
The promise returned from stub.resolves() is not an angular promise. It cannot be triggered to resolve using $rootScope, because it's not a part of angular's world. It's promise resolution queue is tied to something else and hence the need to test like you usually test async code.
Angular doesn't depend on JavaScript's native Promise implementation - it uses a light implementation of Q's promise library that is wrapped in a service called $q
The answer you have quoted uses the same service to create and return a promise from a stub
In order for your code to work - to test like you test synchronous code - you should return a $q promise (By wrapping a value in $q.when(value)) calling $rootScope.$apply() will execute the code in the then block, then proceed with the code below $rootScope.$apply() line.
Here is an example:
it('Sinon should work with angular promises', function () {
var resolved = 'resolved';
var promise = $q.when(resolved);
// Our async function
var stub = sinon.stub().returns(promise);
// Callback to be executed after the promise resolves
var handler = sinon.stub();
stub().then(handler); // async code
// The handler will be called only after $rootScope.$apply()
handler.callCount.should.equal(0);
// triggers digest which will resolve `ready` promises
// like those created with $q.when(), $q.resolve() or those created
// using the $q.defer() and deferred.resolve() was called
// this will execute the code inside the appropriate callback for
// `then/catch/finally` for all promises and then continue
// with the code bellow -> this is why the test is considered `synchronous`
$rootScope.$apply();
// Verify the handler was called and with the expected value
handler.callCount.should.equal(1);
handler.should.have.been.calledWith(resolved);
})
Here it is in action test promise synchronously in angular
For starters, you should read up on how Mocha expects you to test async code.
To start out with the quick bits:
You are on the right path - there are just some bits missing.
Yes you should do your test inside a then.
The example you linked to is fine. Just understand it.
There is absolutely no reason to avoid asserting a test inside a then. In fact, it is usually the only way to assert the resolved value of a promise.
The main problem with your test code is it tries to assert the result before it is available (as promises resolve in a later tick, they are asynchronous).
The main problem with the code you are trying to test is that there is no way of knowing when the init function has resolved.
We can deal with #2 by waiting for the stubbed SearchService.getResults to resolve (as we control the stub in the test), but that assumes too much knowledge of the implementation of onInit, so that is a bad hack.
Instead, we fix the code in TestCtrl, simply by returning the promise in onInit:
//main code / TestCtrl
$onInit() {
return this.SearchService.getResults()
.then(function () {
this.testValue = true;
});
}
Now we can simply wait for any call to onInit to resolve before we test what has happened during its execution!
To fix your test we first add a parameter to the wrapping test function. Mocha will see this and pass in a function that you can call when your test finishes.
it('should work', function(done) {
That makes it an async test. Now lets fix the test part:
ctrl.$onInit().then( () => {
ctrl.testValue.should.equal(true);
done(); // signals to mocha that the test is finished ok
}).catch(done); // pass any errors to the callback
You might find also find this answer enlightening (upvote if it helps you out). After reading it you might also understand why Mocha also supports dropping the done callback by returning a promise from the test instead. Makes for shorter tests:
return ctrl.$onInit().then( () => {
ctrl.testValue.should.equal(true);
});
sinon.stub(SearchService, 'getResults').resolves({response:{data: 'data'}}); is not returning a promise. Use $q.
I would suggest doing this:
ctrl = $componentController('test', {
SearchService: SearchService
}, {});
let deferred =$q.defer();
deferred.resolve({response:{data: 'data'}});
sinon.stub(SearchService, 'getResults').resolves(deferred.promise);
ctrl.$onInit();
$rootScope.$apply();
ctrl.testValue.should.equal(true);
You don't need to test ctrl.testValue inside a then. And generally, I would recommend not assert inside .then() in your specs. The specs will not fail if the promise never gets resolved. That can give you a false sense of security when in reality, your tests are not doing anything. But that's just my opinion.
Your test will pass once the stub returns a promise. Ideally, I would recommend using $httpBackend if the service is making an http call.
Cheers.
I'm using Typescript 2.1(developer version) to transpile async/await to ES5.
I've noticed that after I change any property which is bound to view in my async function the view isn't updated with current value, so each time I have to call $scope.$apply() at the end of function.
Example async code:
async testAsync() {
await this.$timeout(2000);
this.text = "Changed";
//$scope.$apply(); <-- would like to omit this
}
And new text value isn't shown in view after this.
Is there any workaround so I don't have to manually call $scope.$apply() every time?
The answers here are correct in that AngularJS does not know about the method so you need to 'tell' Angular about any values that have been updated.
Personally I'd use $q for asynchronous behaviour instead of using await as its "The Angular way".
You can wrap non Angular methods with $q quite easily i.e. [Note this is how I wrap all Google Maps functions as they all follow this pattern of passing in a callback to be notified of completion]
function doAThing()
{
var defer = $q.defer();
// Note that this method takes a `parameter` and a callback function
someMethod(parameter, (someValue) => {
$q.resolve(someValue)
});
return defer.promise;
}
You can then use it like so
this.doAThing().then(someValue => {
this.memberValue = someValue;
});
However if you do wish to continue with await there is a better way than using $apply, in this case, and that it to use $digest. Like so
async testAsync() {
await this.$timeout(2000);
this.text = "Changed";
$scope.$digest(); <-- This is now much faster :)
}
$scope.$digest is better in this case because $scope.$apply will perform dirty checking (Angulars method for change detection) for all bound values on all scopes, this can be expensive performance wise - especially if you have many bindings. $scope.$digest will, however, only perform checking on bound values within the current $scope making it much more performant.
This can be conveniently done with angular-async-await extension:
class SomeController {
constructor($async) {
this.testAsync = $async(this.testAsync.bind(this));
}
async testAsync() { ... }
}
As it can be seen, all it does is wrapping promise-returning function with a wrapper that calls $rootScope.$apply() afterwards.
There is no reliable way to trigger digest automatically on async function, doing this would result in hacking both the framework and Promise implementation. There is no way to do this for native async function (TypeScript es2017 target), because it relies on internal promise implementation and not Promise global. More importantly, this way would be unacceptable because this is not a behaviour that is expected by default. A developer should have full control over it and assign this behaviour explicitly.
Given that testAsync is being called multiple times, and the only place where it is called is testsAsync, automatic digest in testAsync end would result in digest spam. While a proper way would be to trigger a digest once, after testsAsync.
In this case $async would be applied only to testsAsync and not to testAsync itself:
class SomeController {
constructor($async) {
this.testsAsync = $async(this.testsAsync.bind(this));
}
private async testAsync() { ... }
async testsAsync() {
await Promise.all([this.testAsync(1), this.testAsync(2), ...]);
...
}
}
I have examined the code of angular-async-await and It seems like they are using $rootScope.$apply() to digest the expression after the async promise is resolved.
This is not a good method. You can use AngularJS original $q and with a little trick, you can achieve the best performance.
First, create a function ( e.g., factory, method)
// inject $q ...
const resolver=(asyncFunc)=>{
const deferred = $q.defer();
asyncFunc()
.then(deferred.resolve)
.catch(deferred.reject);
return deferred.promise;
}
Now, you can use it in your for instance services.
getUserInfo=()=>{
return resolver(async()=>{
const userInfo=await fetch(...);
const userAddress= await fetch (...);
return {userInfo,userAddress};
});
};
This is as efficient as using AngularJS $q and with minimal code.
As #basarat said the native ES6 Promise doesn't know about the digest cycle.
What you could do is let Typescript use $q service promise instead of the native ES6 promise.
That way you won't need to invoke $scope.$apply()
angular.module('myApp')
.run(['$window', '$q', ($window, $q) => {
$window.Promise = $q;
}]);
I've set up a fiddle showcasing the desired behavior. It can be seen here: Promises with AngularJS.
Please note that it's using a bunch of Promises which resolve after 1000ms, an async function, and a Promise.race and it still only requires 4 digest cycles (open the console).
I'll reiterate what the desired behavior was:
to allow the usage of async functions just like in native JavaScript; this means no other 3rd party libraries, like $async
to automatically trigger the minimum number of digest cycles
How was this achieved?
In ES6 we've received an awesome featured called Proxy. This object is used to define custom behavior for fundamental operations (e.g. property lookup, assignment, enumeration, function invocation, etc).
This means that we can wrap the Promise into a Proxy which, when the promise gets resolved or rejected, triggers a digest cycle, only if needed. Since we need a way to trigger the digest cycle, this change is added at AngularJS run time.
function($rootScope) {
function triggerDigestIfNeeded() {
// $applyAsync acts as a debounced funciton which is exactly what we need in this case
// in order to get the minimum number of digest cycles fired.
$rootScope.$applyAsync();
};
// This principle can be used with other native JS "features" when we want to integrate
// then with AngularJS; for example, fetch.
Promise = new Proxy(Promise, {
// We are interested only in the constructor function
construct(target, argumentsList) {
return (() => {
const promise = new target(...argumentsList);
// The first thing a promise does when it gets resolved or rejected,
// is to trigger a digest cycle if needed
promise.then((value) => {
triggerDigestIfNeeded();
return value;
}, (reason) => {
triggerDigestIfNeeded();
return reason;
});
return promise;
})();
}
});
}
Since async functions rely on Promises to work, the desired behavior was achieved with just a few lines of code. As an additional feature, one can use native Promises into AngularJS!
Later edit: It's not necessary to use Proxy as this behavior can be replicated with plain JS. Here it is:
Promise = ((Promise) => {
const NewPromise = function(fn) {
const promise = new Promise(fn);
promise.then((value) => {
triggerDigestIfNeeded();
return value;
}, (reason) => {
triggerDigestIfNeeded();
return reason;
});
return promise;
};
// Clone the prototype
NewPromise.prototype = Promise.prototype;
// Clone all writable instance properties
for (const propertyName of Object.getOwnPropertyNames(Promise)) {
const propertyDescription = Object.getOwnPropertyDescriptor(Promise, propertyName);
if (propertyDescription.writable) {
NewPromise[propertyName] = Promise[propertyName];
}
}
return NewPromise;
})(Promise) as any;
In case you're upgrading from AngularJS to Angular using ngUpgrade (see https://angular.io/guide/upgrade#upgrading-with-ngupgrade):
As Zone.js patches native Promises you can start rewriting all $q based AngularJS promises to native Promises, because Angular triggers a $digest automatically when the microtask queue is empty (e.g. when a Promise is resolved).
Even if you don't plan to upgrade to Angular, you can still do the same, by including Zone.js in your project and setting up a similar hook like ngUpgrade does.
Is there any workaround so I don't have to manually call $scope.$apply() every time?
This is because TypeScript uses the browser native Promise implementation and that is not what Angular 1.x knows about. To do its dirty checking all async functions that it does not control must trigger a digest cycle.
As #basarat said the native ES6 Promise doesn't know about the digest cycle. You should to promise
async testAsync() {
await this.$timeout(2000).toPromise()
.then(response => this.text = "Changed");
}
As it already has been described, angular does not know when the native Promise is finished. All async functions create a new Promise.
The possible solution can be this:
window.Promise = $q;
This way TypeScript/Babel will use angular promises instead.
Is it safe? Honestly I'm not sure - still testing this solution.
I would write a converter function, in some generic factory (didnt tested this code, but should be work)
function toNgPromise(promise)
{
var defer = $q.defer();
promise.then((data) => {
$q.resolve(data);
}).catch(response)=> {
$q.reject(response);
});
return defer.promise;
}
This is just to get you started, though I assume conversion in the end will not be as simple as this...
Is there a way to specify an "onSuccess" handler when using Angular-modelizer fetch? I looked at the angular-modelizer-0.2.24 source implementation of "fetch"
but the Javascript in there is boggling my mind... Does anyone have sample code?
I would prefer not to use a $future or "promise"; I would like to treat the fetch as synchronous.
After some further research I figured this out; the first callback function is the "success" path, and the second callback is the error path. Code sample included.
Given that the underlying AJAX call is asynchronous, I believe that the prevalent current pattern is to use $q and $promise, so that is what I have done.
var deferred = $q.defer();
var retModel = undefined;
//modelizer fetch
myModelObject.fetch(config).then(
//1st function is the "success" function
function(response) {
console.log ("Fetch success path");
retModel = response;
deferred.resolve(retModel);
},
//2nd function is the error function.
function(errResponse) {
console.log ("Error on fetch");
deferred.reject(errResponse);
//ErrorService.buildErrors(errResponse);
}
);
return deferred.promise;
I recently had a question on how I could load jQuery when I moved to a new page
using AngularJS ui-router. Here's the answer that I accepted:
resolve:{
jquery: function($q){
if (typeof jQuery === 'undefined') {
var deferred = $q.defer();
var script = document.createElement('script');
script.setAttribute("src", "http://code.jquery.com/jquery-2.0.3.min.js");
document.getElementsByTagName("head")[0].appendChild(script);
var wait = setInterval(function(){
if (typeof jQuery === 'function') {
console.log('jQuery:', typeof jQuery)
deferred.resolve();
clearInterval(wait);
}
}, 100);
return deferred.promise;
}
}
}
Can someone tell me how I can extend this so I get the jQuery script and also another
local script from my server. The important thing for me is that the second script would need to download after jQuery as it depends on it.
The second script I need to get is /Scripts/pagedown/markdown.js
Please note I am not looking for a solution that uses an external library like require.js. I have only one time I am doing this so using an external library would be overkill.
Try using http://requirejs.org/ since it's the best solution here.
jquery-deps.js:
define(['jquery-min'], function (dep1) {
// Your local script here. Dependent file will be fetched here if needed
return someObject; //For example, jQuery object
});
You can add this in router resove:
require(['jquery-min'], function(dependency) {
// jquery will be fetched first, then more scripts will be executed.
// Add more scripts
});
Take a look at requireJS docs, it's easy to implement and don't include js files using plain javascript just because it's not safe and not cool enough.
Convert the script loading process into a more generic, standalone function meant for reuse:
var injectJs = function(url, name, deferred) {
var script = document.createElement('script');
script.setAttribute("src", url);
document.getElementsByTagName("head")[0].appendChild(script);
var wait = setInterval(function(){
if (typeof window[name] === 'function') {
deferred.resolve();
clearInterval(wait);
}
}, 100);
}
Create another promise for markdown.js:
var mdDeferred = $q.defer();
Then, instead of returning the jQuery loading promise from the function, add a callback to it:
jqDeferred.promise.then(function(){
... and inside of that callback, use injectJS again to load the markdown promise, resolving its promise once it has.
Note: you need to pass the name (a string) of the object to check for in as the third object. For jQuery, it is 'jQuery'. Find out what object will be found on the window object once the script loads and use that.
Finally, it's the markdown promise that should now be returned from the resolve function:
return mdDeferred.promise;
Review this demo to see a working example, which uses Underscore in place of markdown.js.
I am new to angular and I'm trying to load/create an angular module using requirejs.
For some reason the config block never gets called.
I don't think requirejs is to blame here - it's only for the sake of completeness.
define(['./IdeaListCtrl'], function (IdeaListCtrl) {
var moduleName = 'clap.Idea';
console.log("Loading " + moduleName); // Printed
angular.module(moduleName, []).config(function () {
console.log("Config block accessed"); // NOT PRINTED
});
console.log("Loaded " + moduleName); // Printed
return moduleName;
});
Angular essentially lazy-loads its components so you need to bootstrap the module to the page or reference it elsewhere before it will run the config block.