TypeScript rules for Bazel

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WARNING: this is beta-quality software. Breaking changes are likely. Not recommended for production use without expert support.

The TypeScript rules integrate the TypeScript compiler with Bazel.

API Docs

Generated documentation for using each rule is at: http://tsetse.info/api/

Installation

First, install a current Bazel distribution.

Add the @bazel/typescript npm package to your package.json devDependencies. Optionally add the @bazel/karma npm package if you would like to use the ts_web_test_suite rule.

{
  ...
  "devDependencies": {
    "@bazel/typescript": "0.20.3",
    "@bazel/karma": "0.20.3",
    ...
  },
  ...
}

Create a BUILD.bazel file in your project root:

package(default_visibility = ["//visibility:public"])
exports_files(["tsconfig.json"])

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

http_archive(
    name = "build_bazel_rules_typescript",
    url = "https://github.com/bazelbuild/rules_typescript/archive/0.20.3.zip",
    strip_prefix = "rules_typescript-0.20.3",
)

# Fetch transitive Bazel dependencies of build_bazel_rules_typescript
load("@build_bazel_rules_typescript//:package.bzl", "rules_typescript_dependencies")
rules_typescript_dependencies()

# Fetch transitive Bazel dependencies of build_bazel_rules_nodejs
load("@build_bazel_rules_nodejs//:package.bzl", "rules_nodejs_dependencies")
rules_nodejs_dependencies()

# Setup TypeScript toolchain
load("@build_bazel_rules_typescript//:defs.bzl", "ts_setup_workspace")
ts_setup_workspace()

# Setup the NodeJS toolchain
load("@build_bazel_rules_nodejs//:defs.bzl", "node_repositories", "yarn_install")
node_repositories()

# Setup Bazel managed npm dependencies with the `yarn_install` rule.
# The name of this rule should be set to `npm` so that `ts_library` and `ts_web_test_suite`
# can find your npm dependencies by default in the `@npm` workspace. You may
# also use the `npm_install` rule with a `package-lock.json` file if you prefer.
# See https://github.com/bazelbuild/rules_nodejs#dependencies for more info.
yarn_install(
  name = "npm",
  package_json = "//:package.json",
  yarn_lock = "//:yarn.lock",
)

# Setup Go toolchain
load("@io_bazel_rules_go//go:def.bzl", "go_rules_dependencies", "go_register_toolchains")
go_rules_dependencies()
go_register_toolchains()

# Setup web testing, choose browsers we can test on
load("@io_bazel_rules_webtesting//web:repositories.bzl", "browser_repositories", "web_test_repositories")

web_test_repositories()
browser_repositories(
    chromium = True,
)

Self-managed npm dependencies

We recommend you use Bazel managed dependencies but if you would like Bazel to also install a node_modules in your workspace you can also point the node_repositories repository rule in your WORKSPACE file to your package.json.

node_repositories(package_json = ["//:package.json"])

You can then run yarn in your workspace with:

$ bazel run @nodejs//:yarn

To use your workspace node_modules folder as a dependency in ts_library and other rules, add the following to your root BUILD.bazel file:

filegroup(
    name = "node_modules",
    srcs = glob(
        include = [
          "node_modules/**/*.js",
          "node_modules/**/*.d.ts",
          "node_modules/**/*.json",
          "node_modules/.bin/*",
        ],
        exclude = [
          # Files under test & docs may contain file names that
          # are not legal Bazel labels (e.g.,
          # node_modules/ecstatic/test/public/中文/檔案.html)
          "node_modules/**/test/**",
          "node_modules/**/docs/**",
          # Files with spaces in the name are not legal Bazel labels
          "node_modules/**/* */**",
          "node_modules/**/* *",
        ],
    ),
)

# Create a tsc_wrapped compiler rule to use in the ts_library
# compiler attribute when using self-managed dependencies
nodejs_binary(
    name = "@bazel/typescript/tsc_wrapped",
    entry_point = "@bazel/typescript/tsc_wrapped/tsc_wrapped.js",
    # The --expose-gc node option is required for tsc_wrapped
    templated_args = ["--node_options=--expose-gc"],
    # Point bazel to your node_modules to find the entry point
    node_modules = ["//:node_modules"],
)

# Create a karma rule to use in ts_web_test_suite karma
# attribute when using self-managed dependencies
nodejs_binary(
    name = "karma/karma",
    entry_point = "karma/bin/karma",
    # Point bazel to your node_modules to find the entry point
    node_modules = ["//:node_modules"],
)

See https://github.com/bazelbuild/rules_nodejs#dependencies for more information on managing npm dependencies with Bazel.

Usage

Compiling TypeScript: ts_library

The ts_library rule invokes the TypeScript compiler on one compilation unit, or "library" (generally one directory of source files).

Create a BUILD file next to your sources:

package(default_visibility=["//visibility:public"])
load("@build_bazel_rules_typescript//:defs.bzl", "ts_library")

ts_library(
    name = "my_code",
    srcs = glob(["*.ts"]),
    deps = ["//path/to/other:library"],
)

If your ts_library target has npm dependencies you can specify these with fine grained npm dependency targets created by the yarn_install or npm_install rules:

ts_library(
    name = "my_code",
    srcs = glob(["*.ts"]),
    deps = [
      "@npm//@types/node",
      "@npm//@types/foo",
      "@npm//foo",
      "//path/to/other:library",
    ],
)

You can also you the @npm//@types target which will include all packages in the @types scope as dependencies.

If you are using self-managed npm dependencies, you can use the node_modules attribute in ts_library and point it to the //:node_modules filegroup defined in your root BUILD.bazel file. You'll also need to override the compiler attribute if you do this as the Bazel-managed deps and self-managed cannot be used together in the same rule.

ts_library(
    name = "my_code",
    srcs = glob(["*.ts"]),
    deps = ["//path/to/other:library"],
    node_modules = "//:node_modules",
    compiler = "//:@bazel/typescript/tsc_wrapped",
)

To build a ts_library target run:

bazel build //path/to/package:target

The resulting .d.ts file paths will be printed. Additionally, the .js outputs from TypeScript will be written to disk, next to the .d.ts files ¹.

Note that the tsconfig.json file used for compilation should be the same one your editor references, to keep consistent settings for the TypeScript compiler. By default, ts_library uses the tsconfig.json file in the workspace root directory. See the notes about the tsconfig attribute in the ts_library API docs.

¹ The declarationDir compiler option will be silently overwritten if present.

Serving TypeScript for development

There are two choices for development mode:

1. Use the ts_devserver rule to bring up our simple, fast development server. This is intentionally very simple, to help you get started quickly. However, since there are many development servers available, we do not want to mirror their features in yet another server we maintain.
2. Teach your real frontend server to serve files from Bazel's output directory. This is not yet documented. Choose this option if you have an existing server used in development mode, or if your requirements exceed what the ts_devserver supports. Be careful that your development round-trip stays fast (should be under two seconds).

To use ts_devserver, you simply load the rule, and call it with deps that point to your ts_library target(s):

load("@build_bazel_rules_typescript//:defs.bzl", "ts_devserver", "ts_library")

ts_library(
    name = "app",
    srcs = ["app.ts"],
)

ts_devserver(
    name = "devserver",
    # We'll collect all the devmode JS sources from these TypeScript libraries
    deps = [":app"],
    # This is the path we'll request from the browser, see index.html
    serving_path = "/bundle.js",
    # The devserver can serve our static files too
    static_files = ["index.html"],
)

The index.html should be the same one you use for production, and it should load the JavaScript bundle from the path indicated in serving_path.

If you don't have an index.html file, a simple one will be generated by the ts_devserver.

See examples/app in this repository for a working example. To run the devserver, we recommend you use ibazel:

$ ibazel run examples/app:devserver

ibazel will keep the devserver program running, and provides a LiveReload server so the browser refreshes the application automatically when each build finishes.

Writing TypeScript code for Bazel

Bazel's TypeScript compiler has your workspace path mapped, so you can import from an absolute path starting from your workspace.

/WORKSPACE:

workspace(name = "myworkspace")

/some/long/path/to/deeply/nested/subdirectory.ts:

import {thing} from 'myworkspace/place';

will import from /place.ts.

Since this is an extension to the vanillia TypeScript compiler, editors which use the TypeScript language services to provide code completion and inline type checking will not be able to resolve the modules. In the above example, adding

"paths": {
    "myworkspace/*": ["*"]
}

to tsconfig.json will fix the imports for the common case of using absolute paths. See https://www.typescriptlang.org/docs/handbook/module-resolution.html#path-mapping for more details on the paths syntax.

Similarly, you can use path mapping to teach the editor how to resolve imports from ts_library rules which set the module_name attribute.

Notes

If you'd like a "watch mode", try https://github.com/bazelbuild/bazel-watcher (note, it's also quite new).

At some point, we plan to release a tool similar to gazelle to generate the BUILD files from your source code.

In the meantime, we suggest associating the .bazel extension with Python in your editor, so that you get useful syntax highlighting.