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Building and Testing Angular

This document describes how to set up your development environment to build and test Angular. It also explains the basic mechanics of using git, node, and yarn.

See the contribution guidelines if you'd like to contribute to Angular.

Prerequisite Software

Before you can build and test Angular, you must install and configure the following on your development machine:

  • Git and/or the GitHub app (for Mac and Windows); GitHub's Guide to Installing Git is a good source of information.
    Windows Users: Git Bash or an equivalent shell is required
    Windows Powershell and cmd shells are not supported #46780 so some commands might fail

  • Node.js, (version specified in .nvmrc) which is used to run a development web server, run tests, and generate distributable files.
    .nvmrc is read by nvm commands like nvm install and nvm use.

  • Yarn (version specified in the engines field of package.json) which is used to install dependencies.

  • On Windows: MSYS2 which is used by Bazel. Follow the instructions

Getting the Sources

Fork and clone the Angular repository:

  1. Login to your GitHub account or create one by following the instructions given here.
  2. Fork the main Angular repository.
  3. Clone your fork of the Angular repository and define an upstream remote pointing back to the Angular repository that you forked in the first place.
# Clone your GitHub repository:
git clone [email protected]:<github username>/angular.git

# Go to the Angular directory:
cd angular

# Add the main Angular repository as an upstream remote to your repository:
git remote add upstream https://github.com/angular/angular.git

Installing NPM Modules

Next, install the JavaScript modules needed to build and test Angular:

# Install Angular project dependencies (package.json)
yarn install

Building

To build Angular run:

yarn build
  • Results are put in the dist/packages-dist folder.

Running Tests Locally

Bazel is used as the primary tool for building and testing Angular.

To see how to run and debug Angular tests locally please refer to the Bazel Testing Angular section.

Note that you should execute all test suites before submitting a PR to GitHub (yarn test //packages/...).

However, affected tests will be executed on our CI infrastructure. So if you forgot to run some affected tests which would fail, GitHub will indicate the error state and present you the failures.

PRs can only be merged if the code is formatted properly and all tests are passing.

Testing changes against a local library/project

Often for developers the best way to ensure the changes they have made work as expected is to run use changes in another library or project. To do this developers can build Angular locally, and using yarn link build a local project with the created artifacts.

This can be done by running:

yarn ng-dev misc build-and-link <path-to-local-project-root>

Building and serving a project

Cache

When making changes to Angular packages and testing in a local library/project you need to run ng cache disable to disable the Angular CLI disk cache. If you are making changes that are not reflected in your locally served library/project, verify if you have CLI Cache disabled.

Invoking the Angular CLI

The Angular CLI needs to be invoked using Node.js --preserve-symlinks flag. Otherwise the symbolic links will be resolved using their real path which causes node module resolution to fail.

node --preserve-symlinks --preserve-symlinks-main node_modules/@angular/cli/lib/init.js serve

Formatting your source code

Angular uses prettier to format the source code. If the source code is not properly formatted, the CI will fail and the PR cannot be merged.

You can automatically format your code by running:

  • yarn ng-dev format changed [shaOrRef]: format only files changed since the provided sha/ref. shaOrRef defaults to main.
  • yarn ng-dev format all: format all source code
  • yarn ng-dev format files <files..>: format only provided files

Linting/verifying your Source Code

You can check that your code is properly formatted and adheres to coding style by running:

$ yarn lint

Publishing Snapshot Builds

When a build of any branch on the upstream fork angular/angular is green on CI, it automatically publishes build artifacts to repositories in the Angular org. For example, the @angular/core package is published to https://github.com/angular/core-builds.

You may find that your un-merged change needs some validation from external participants. Rather than requiring them to pull your Pull Request and build Angular locally, they can depend on snapshots of the Angular packages created based on the code in the Pull Request.

Publishing to GitHub Repos

You can also manually publish *-builds snapshots just like our CI build does for upstream builds. Before being able to publish the packages, you need to build them locally by running the yarn build command.

First time, you need to create the GitHub repositories:

$ export TOKEN=[get one from https://github.com/settings/tokens]
$ CREATE_REPOS=1 ./scripts/ci/publish-build-artifacts.sh [GitHub username]

For subsequent snapshots, just run:

$ ./scripts/ci/publish-build-artifacts.sh [GitHub username]

The script will publish the build snapshot to a branch with the same name as your current branch, and create it if it doesn't exist.

Bazel Support

IDEs

VS Code

  1. Install Bazel extension for VS Code.

WebStorm / IntelliJ

  1. Install the Bazel plugin
  2. You can find the settings under Preferences->Other Settings->Bazel Settings

It will automatically recognize *.bazel and *.bzl files.

Remote Build Execution and Remote Caching

Bazel builds in the Angular repository use a shared cache. When a build occurs, a hash of the inputs is computed and checked against available outputs in the shared cache. If an output is found, it is used as the output for the build action rather than performing the build locally.

Remote Build Execution requires authentication as a google.com account.

--config=remote flag

The --config=remote flag can be added to enable remote execution of builds.