Example of building an Angular app with Bazel

This is experimental! There may be breaking changes.

This is part of the ABC project. The overall goal is to make it possible to develop Angular applications the same way we do at Google. See http://g.co/ng/abc for an overview.

You can read the documentation in the wiki of this repository to understand how this works.

Follow angular/angular#19058 for updates.

Installation

You only need to install one build tool, and which one you choose typically depends on what kind of development you do most often.

If you're a frontend developer, you should install NodeJS and yarn. The package.json file has an engines section which indicates the range of NodeJS and yarn versions that you could use. You simply run yarn commands shown below, and don't need to install Bazel or any other dependencies.

If you're a full-stack developer, you might be using Bazel for your backend already. In this case, you should install Bazel following instructions at http://bazel.build. Also install ibazel, which is a watch mode for Bazel not included in the standard distribution. See https://github.com/bazelbuild/bazel-watcher#installation. The WORKSPACE file has a check_bazel_version call which will print an error if your Bazel version is not in the supported range. You simply run bazel commands shown below, and don't need to install NodeJS, yarn, or any other dependencies.

Development

First we'll run the development server:

$ yarn serve
# or
$ ibazel run //src:devserver

This runs in "watch mode", which means it will watch any files that are inputs to the devserver, and when they change it will ask Bazel to re-build them. When the re-build is finished, it will trigger a LiveReload in the browser.

This command prints a URL on the terminal. Open that page to see the demo app running. Now you can edit one of the source files (src/lib/file.ts is an easy one to understand and see the effect). As soon as you save a change, the app should refresh in the browser with the new content. Our intent is that this time is less than two seconds, even for a large application.

Control-C twice to kill the devserver.

Testing

We can also run all the unit tests:

$ yarn test
# or
$ bazel test //src/...

Or run the end-to-end tests:

$ yarn e2e
# or
$ bazel test //e2e/...

In this example, there is a unit test for the hello-world component which uses the ts_web_test_suite rule. There are also protractor e2e tests for both the prodserver and devserver which use the protractor_web_test_suite rule.

Note that Bazel will only re-run the tests whose inputs changed since the last run.

Production

We can run the application in production mode, where the code has been bundled and optimized. This can be slower than the development mode, because any change requires re-optimizing the app. This example uses Rollup and Uglify, but other bundlers can be integrated with Bazel.

$ yarn serve-prod
# or
$ bazel run //src:prodserver

Code splitting

The production bundle is code split and the / and /todos routes are lazy loaded. Code splitting is handled by the rollup_bundle rule which now supports the new code splitting feature in rollup.

Note: code splitting is not supported in development mode yet so the //src:devserver target does not serve a code split bundle. For this reason, development and production use different main entry points (main.dev.ts and main.ts) and different root modules (app.module.dev.ts and app.module.ts). The difference in the entry points and modules is how routes are loaded, with production lazy loading routes and development using a custom NgModuleFactoryLoader loader to disable lazy loading. enableProdMode() is also called in the production entry point.

Npm dependencies

Having a local node_modules folder setup by yarn or npm is not necessary when building this example with Bazel. This example makes use of Bazel managed npm dependencies (https://github.com/bazelbuild/rules_nodejs#using-bazel-managed-dependencies) which means Bazel will setup the npm dependencies in your package.json for you outside of your local workspace for use in the build.

However, you may still want to run yarn or npm to manually setup a local node_modules folder for editor and tooling support.