NodeJS rules for Bazel

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This is a beta-quality release. Breaking changes are likely.

The nodejs rules integrate NodeJS development toolchain and runtime with Bazel.

This toolchain can be used to build applications that target a browser runtime, so this repo can be thought of as "JavaScript rules for Bazel" as well.

API Docs

Generated documentation for using each rule is at: https://bazelbuild.github.io/rules_nodejs/

Installation

First, install a current bazel distribution, following the bazel instructions.

Next, create a WORKSPACE file in your project root (or edit the existing one) containing:

git_repository(
    name = "build_bazel_rules_nodejs",
    remote = "https://github.com/bazelbuild/rules_nodejs.git",
    tag = "0.10.0", # check for the latest tag when you install
)

load("@build_bazel_rules_nodejs//:defs.bzl", "node_repositories")

Now you can choose from a few options to finish installation.

To choose a version of Node.js:

1. (Simplest) use the version of Node.js that comes with these rules by default
2. Choose from one of the versions we support natively
3. Tell Bazel where to download a specific version you require
4. Check Node.js into your repository and don't download anything

These are described in more detail in the following sections.

Simple usage

Add this to your WORKSPACE file. It only tells Bazel how to find your package.json file. It will use default versions of Node.js and npm.

# NOTE: this rule installs nodejs, npm, and yarn, but does NOT install
# your npm dependencies into your node_modules folder.
# You must still run the package manager to do this.
node_repositories(package_json = ["//:package.json"])

Installation with a specific supported version of Node.js and Yarn

You can choose a specific version of Node.js that's built into these rules. Currently these versions are:

• 9.11.1
• 8.11.1
• 8.9.1

You can also choose a specific version of Yarn. Currently these versions are:

• 1.6.0
• 1.5.1
• 1.3.2

Add to WORKSPACE:

# NOTE: this rule installs nodejs, npm, and yarn, but does NOT install
# your npm dependencies into your node_modules folder.
# You must still run the package manager to do this.
node_repositories(
    package_json = ["//:package.json"],
    node_version = "8.11.1",
    yarn_version = "1.5.1",
)

Installation with a manually specified version of NodeJS and Yarn

If you'd like to use a version of NodeJS and/or Yarn that are not currently supported here, you can manually specify those in your WORKSPACE:

load("@build_bazel_rules_nodejs//:defs.bzl", "node_repositories")

# NOTE: this rule does NOT install your npm dependencies into your node_modules folder.
# You must still run the package manager to do this.
node_repositories(
  node_version = "8.10.0",
  yarn_version = "1.5.1",
  node_repositories = {
    "8.10.0-darwin_amd64": ("node-v8.10.0-darwin-x64.tar.gz", "node-v8.10.0-darwin-x64", "7d77bd35bc781f02ba7383779da30bd529f21849b86f14d87e097497671b0271"),
    "8.10.0-linux_amd64": ("node-v8.10.0-linux-x64.tar.xz", "node-v8.10.0-linux-x64", "92220638d661a43bd0fee2bf478cb283ead6524f231aabccf14c549ebc2bc338"),
    "8.10.0-windows_amd64": ("node-v8.10.0-win-x64.zip", "node-v8.10.0-win-x64", "936ada36cb6f09a5565571e15eb8006e45c5a513529c19e21d070acf0e50321b"),
  },
  yarn_repositories = {
    "1.5.1": ("yarn-v1.5.1.tar.gz", "yarn-v1.5.1", "cd31657232cf48d57fdbff55f38bfa058d2fb4950450bd34af72dac796af4de1"),
  },
  node_urls = ["https://nodejs.org/dist/v{version}/{filename}"],
  yarn_urls = ["https://github.com/yarnpkg/yarn/releases/download/v{version}/{filename}"],
  package_json = ["//:package.json"])

Specifying node_urls and yarn_urls is optional. If omitted, the default values will be used. You may also use a custom NodeJS version and the default Yarn version or vice-versa.

Installation with local vendored versions of NodeJS and Yarn

Finally, you could check Node.js and Yarn into your repository, and not fetch them from the internet. This is what we do internally at Google.

load("@build_bazel_rules_nodejs//:defs.bzl", "node_repositories")

# NOTE: this rule does NOT install your npm dependencies into your node_modules folder.
# You must still run the package manager to do this.
node_repositories(
  node_path = "path/to/node/base",
  yarn_path = "path/to/yarn/base",
  package_json = ["//:package.json"])

Dependencies

You have two options for managing your node_modules dependencies.

Using self-managed dependencies

If you'd like to have Bazel use the node_modules directory you are managing, then next you will create a BUILD.bazel file in your project root containing:

package(default_visibility = ["//visibility:public"])

# NOTE: this may move to node_modules/BUILD in a later release
filegroup(name = "node_modules", srcs = glob(["node_modules/**/*"]))

We recommend using the version of the package management tools installed by Bazel to ensure everything is compatible.

To use the Yarn package manager, which we recommend for its built-in verification command, you can run:

$ bazel run @nodejs//:yarn

If you use npm instead, run:

$ bazel run @nodejs//:npm install

Using Bazel-managed dependencies

To have Bazel manage its own copy of node_modules, which is useful to avoid juggling multiple toolchains, you can add one of the following to your WORKSPACE file:

Using Yarn (preferred):

load("@build_bazel_rules_nodejs//:defs.bzl", "yarn_install")

yarn_install(
    name = "foo",
    package_json = "//:package.json",
    yarn_lock = "//:yarn.lock",
)

Using NPM:

load("@build_bazel_rules_nodejs//:defs.bzl", "npm_install")

npm_install(
    name = "foo",
    package_json = "//:package.json",
    package_lock_json = "//:package-lock.json",
)

You can then reference this version of node_modules in your BUILD rules via:

load("@build_bazel_rules_nodejs//:defs.bzl", "nodejs_binary")

nodejs_binary(
    name = "bar",
    # Ordinarily this defaults to //:node_modules
    node_modules = "@foo//:node_modules",
    ...
)

With this approach, Bazel is responsible for making sure that node_modules is up to date with package[-lock].json or yarn.lock. This means Bazel will set it up when the repo is first cloned, and rebuild it whenever it changes.

For Bazel to provide the strongest guarantees about reproducibility and the fidelity of your build, it is recommended that you let Bazel take responsibility for this.

However, this approach manages a second copy of node_modules, so if you are juggling Bazel and other tooling, or sensitive to the additional network traffic this might incur, consider self-managing.

Usage

The complete API documentation is at https://bazelbuild.github.io/rules_nodejs/

A few example rules contained in this repo:

The nodejs_binary rule allows you to run an application by giving the entry point. The entry point can come from an external dependency installed by the package manager, or it can be a .js file from a package built by Bazel.

nodejs_test is the same as nodejs_binary, but instead of calling it with bazel run, you call it with bazel test. The test passes if the program exits with a zero exit code.

The jasmine_node_test rule allows you to write a test that executes in NodeJS.

rollup_bundle runs the Rollup and Uglify toolchain to produce a single JavaScript bundle.

npm_package packages up a library to publish to npm.

Running a program from npm

The nodejs_binary rule lets you run a program with Node.js. See https://bazelbuild.github.io/rules_nodejs/node/node.html

If you have installed the rollup package, you could write this rule:

load("@build_bazel_rules_nodejs//:defs.bzl", "nodejs_binary")

nodejs_binary(
    name = "rollup",
    entry_point = "rollup/bin/rollup",
)

and run it with

$ bazel run :rollup -- --help

See the examples/rollup directory in this repository.

Running a program from local sources

We can reference a path in the local workspace to run a program we write.

load("@build_bazel_rules_nodejs//:defs.bzl", "nodejs_binary")

nodejs_binary(
    name = "example",
    data = [
        "@//:node_modules",
        "main.js",
    ],
    entry_point = "workspace_name/main.js",
    args = ["--node_options=--expose-gc"],
)

This example illustrates how to pass arguments to nodejs (as opposed to passing arguments to the program).

The data attribute is optional, by default it includes the node_modules directory. To include your own sources, include a file or target that produces JavaScript.

See the examples/program directory in this repository.

Testing

The jasmine_node_test rule can be used to run unit tests in NodeJS, using the Jasmine framework. Targets declared with this rule can be run with bazel test. See https://bazelbuild.github.io/rules_nodejs/jasmine_node_test/jasmine_node_test.html

The examples/program/index.spec.js file illustrates this. Another usage is in https://github.com/angular/tsickle/blob/master/test/BUILD

Stamping

Bazel is generally only a build tool, and is unaware of your version control system. However, when publishing releases, you typically want to embed version information in the resulting distribution. Bazel supports this natively, using the following approach:

1. Your tools/bazel.rc should pass the workspace_status_command argument to bazel build. This tells Bazel how to interact with the version control system when needed.

   build --workspace_status_command=./tools/bazel_stamp_vars.sh
   

2. Create tools/bazel_stamp_vars.sh. This is a script that prints variable/value pairs. Make sure you set the executable bit, eg. chmod 755 tools/bazel_stamp_vars.sh. For example, we could run git describe to get the current tag:

   #!/usr/bin/env bash
   echo BUILD_SCM_VERSION $(git describe --abbrev=7 --tags HEAD)

   For a more full-featured script, take a look at the bazel_stamp_vars in Angular

Ideally, rollup_bundle and npm_package should honor the --stamp argument to bazel build. However this is not currently possible, see bazelbuild/bazel#1054

WARNING: Bazel doesn't rebuild a target if only the result of the workspace_status_command has changed. That means changes to the version information may not be reflected if you re-build the package or bundle, and nothing in the package or bundle has changed.

See https://www.kchodorow.com/blog/2017/03/27/stamping-your-builds/ for more background.

Bundling/optimizing

A rollup_bundle rule produces several bundle files. See https://bazelbuild.github.io/rules_nodejs/rollup/rollup_bundle.html

Note: we expect other bundling rules will follow later, such as Closure compiler and Webpack.

Publishing to npm

The npm_package rule is used to create a package to publish to external users who do not use Bazel. See https://bazelbuild.github.io/rules_nodejs/npm_package/npm_package.html

For those downstream dependencies that use Bazel, they can simply write BUILD files to consume your library.

Design

Most bazel rules include package management. That is, the WORKSPACE file installs your dependencies as well as the toolchain. In some environments, this is the normal workflow, for example in Java, Gradle and Maven are each both a build tool and a package manager.

In nodejs, there are a variety of package managers and build tools which can interoperate. Also, there is a well-known package installation location (node_modules directory in your project). Command-line and other tools look in this directory to find packages. So we must either download packages twice (risking version skew between them) or point all tools to Bazel's external directory with NODE_PATH which would be very inconvenient.

Instead, our philosophy is: in the NodeJS ecosystem, Bazel is only a build tool. It is up to the user to install packages into their node_modules directory, though the build tool can verify the contents.

Hermeticity and reproducibility

Bazel generally guarantees builds are correct with respect to their inputs. For example, this means that given the same source tree, you can re-build the same artifacts as an earlier release of your program. In the nodejs rules, Bazel is not the package manager, so some reponsibility falls to the developer to avoid builds that use the wrong dependencies. This problem exists with any build system in the JavaScript ecosystem.

Both NPM and Yarn have a lockfile, which ensures that dependencies only change when the lockfile changes. Users are strongly encouraged to use the locking mechanism in their package manager.

References:

• npm: https://docs.npmjs.com/files/package-lock.json
• yarn: https://yarnpkg.com/lang/en/docs/yarn-lock/

Note that bazel-contrib#1 will take the guarantee further: by using the lockfile as an input to Bazel, the nodejs rules can verify the integrity of the dependencies. This would make it impossible for a build to be non-reproducible, so long as you have the same lockfile.

For Developers

Releasing

Start from a clean checkout at master/HEAD. Check if there are any breaking changes since the last tag - if so, this will be a minor, if not it's a patch. (This may not sound like semver, but since our major version is a zero, the rule is that minors are breaking changes and patches are new features.)

1. Re-generate the API docs: yarn skydoc
2. git commit -a -m 'Update docs for release'
3. Write some brief release notes (manual for now): git tag -a 0.x.y
4. git push && git push --tags