ember-cli-typescript

Use TypeScript in your Ember 2.x apps!

Installation

Just run:

ember install ember-cli-typescript

All dependencies will be added to your package.json, and you're ready to roll!

In addition to ember-cli-typescript, the following files are installed:

• typescript version 2.0.0 or greater
• @types/ember
• tsconfig

Write your add-ons in TypeScript

To support shipping add-ons with TypeScript, move ember-cli-typescript from devDependencies to dependencies in your package.json.

This is a function of the way Ember CLI add-ons work, not specific to TypeScript or this add-on. Any transpiler support (including this, CoffeeScript, or even Babel) needs to be specified in the dependencies, not devDependencies, to use it for developing the add-on itself: that's how its compiled output can be used in consuming apps or add-ons.

⚠️ Warning: install size

This is a WIP 🚧 part of the add-on, and it will make a dramatic difference in the size of your add-on in terms of installation. (It won't affect the size of the add-on after build, of course!)

We're working on making a solution that lets us ship generated typings and compiled JavaScript instead of shipping the entire TypeScript compiler toolchain for add-ons. If you're using ember-cli-typescript in an add-on, you might add a note to your users about the install size until we get that sorted out!

Configuration file notes

If you make changes to the paths included in your tsconfig.json, you will need to restart the server to take the changes into account.

Quirks with tsconfig.json

Additionally, depending on what you're doing, you may notice that your tweaks to tsconfig.json aren't applied exactly as you might expect.

The Problem

The configuration file is used by both Ember CLI (via broccoli) and the tsc command line compiler (used by e.g. VS Code, JetBrains IDEs, etc.).

Broccoli controls the inputs and the output folder of the various build steps that make the Ember build pipeline. Its expectation are impacted by TypeScript configuration properties like "include", "exclude", "outFile", "outDir".

We want to allow you to change unrelated properties in the tsconfig file.

The Solution

This addon takes the following approach to allow this dual use:

• it starts with the default blueprint.

• the generated tsconfig file does not set "outDir" and sets "noEmit" to true. This allows you to run vscode and tsc without creating .js files throughout your codebase.

• before calling broccoli the addon removes any configured outDir, sets the noEmit option to false (so that the compiler will emit files for consumption by your app!), and removes all values set for include, since we use Broccoli to manage the build pipeline directly.

Customization

You can customize the tsconfig.json file further for your use case. For example to see the output of the compilation in a separate folder you are welcome to set and outDir and set noEmit to false. Then VS Code and tsc will generate files here while the broccoli pipeline will use its own temp folder.

Please see the wiki for additional how to tips from other users or to add your own tips. If an use case is frequent enough we can codify in the plugin.

Incremental adoption

If you are porting an existing app to TypeScript, you can install this addon and migrate your files incrementally by changing their extensions from .js to .ts. A good approach is to start at your leaf files and then work your way up. As TypeScript starts to find errors, make sure to celebrate your (small) wins with your team, specially if some people are not convinced yet. We would also love to hear your stories!

You may also find the blog series "Typing Your Ember" helpful as it walks you through not only how to install but how to most effectively use TypeScript in an Ember app today, and gives some important info on the background and roadmap for the project.

Not (yet) supported

While TS works nicely for many things in Ember, there are a number of corners where it won't help you out. Some of them are just a matter of further work on updating the typings; others are a matter of further support landing in TypeScript itself.

Here is the short list of things which do not work yet.

Type safety when invoking actions

TypeScript won't detect a mismatch between this action and the corresponding call in the template:

actions: {
   turnWheel(degrees: number) {
      ...
   }
}

<button onclick={{action 'turnWheel' 'NOT-A-NUMBER'}}> Click Me </button>

Likewise, it won't notice a problem when you use send:

// TypeScript compiler won't detect this type mismatch
this.send('turnWheel', 'ALSO-NOT-A-NUMBER');

Type safety when invoking KVO compliant accessors or mutators

When you use Ember.get or Ember.set, TypeScript won't (yet!) warn you that you're using the wrong type. So in foo() here, this will pass the compiler but be wrong at runtime:

Ember.Object.extend({
  urls: <string[]> null,
  port: 4200,  // number
  init() {
     this._super(...arguments);
     this.set('urls', []);
  },
  foo() {
    // TypeScript won't detect these type mismatches
    this.get('urls').addObject(51);
    this.set('port', '3000');
  }
});

The type definitions I need to reference are not in node_modules/@types

By default ember-cli-typescript loads up any type defs found in node_modules/@types. If the type defs you need are not found here you can register a custom path in the tsconfig.json file:

// tsconfig.json
{
  "compilerOptions": {
    "paths": {
      "welp/*": ["app/*"],
      "redux": ["node_modules/redux/index.d.ts"]
    }
  }
}