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Building Angular with Bazel

Note: this doc is for developing Angular, it is not public documentation for building an Angular application with Bazel.

The Bazel build tool (http://bazel.build) provides fast, reliable incremental builds. We plan to migrate Angular's build scripts to Bazel.

Installation

Install Bazel from the distribution, see install instructions. On Mac, just brew install bazel.

Bazel will install a hermetic version of Node, npm, and Yarn when you run the first build.

Configuration

The WORKSPACE file indicates that our root directory is a Bazel project. It contains the version of the Bazel rules we use to execute build steps, from build_bazel_rules_typescript. The sources on GitHub are published from Google's internal repository (google3).

That repository defines dependencies on specific versions of all the tools. You can run the tools Bazel installed, for example rather than yarn install (which depends on whatever version you have installed on your machine), you can bazel run @yarn//:yarn.

Bazel accepts a lot of options. We check in some options in the .bazelrc file. See the bazelrc doc. For example, if you don't want Bazel to create several symlinks in your project directory (bazel-*) you can add the line build --symlink_prefix=/ to your .bazelrc file.

Building Angular

Build a package: bazel build packages/core
Build all packages: bazel build packages/...

You can use ibazel to get a "watch mode" that continuously keeps the outputs up-to-date as you save sources. Note this is new as of May 2017 and not very stable yet.

Testing Angular

Test package in node: bazel test packages/core/test:test
Test package in karma: bazel test packages/core/test:test_web
Test all packages: bazel test packages/...

You can use ibazel to get a "watch mode" that continuously keeps the outputs up-to-date as you save sources.

Debugging a Node Test

Open chrome at: chrome://inspect
Click on Open dedicated DevTools for Node to launch a debugger.
Run test: bazel test packages/core/test:test --config=debug

The process should automatically connect to the debugger.

Debugging a Node Test in VSCode

First time setup:

Go to Debug > Add configuration (in the menu bar) to open launch.json
Add the following to the configurations array:

        {
            "name": "Attach (inspect)",
            "type": "node",
            "request": "attach",
            "port": 9229,
            "address": "localhost",
            "restart": false,
            "sourceMaps": true,
            "localRoot": "${workspaceRoot}",
            "remoteRoot": null
        },
        {
            "name": "Attach (no-sm,inspect)",
            "type": "node",
            "request": "attach",
            "port": 9229,
            "address": "localhost",
            "restart": false,
            "sourceMaps": false,
            "localRoot": "${workspaceRoot}",
            "remoteRoot": null
        },

The easiest way to debug a test for now is to add a debugger statement in the code and launch the bazel corresponding test (bazel test <target> --config=debug).

Bazel will wait on a connection. Go to the debug view (by clicking on the sidebar or Apple+Shift+D on Mac) and click on the green play icon next to the configuration name (ie Attach (inspect)).

Debugging a Karma Test

Run test: bazel run packages/core/test:test_web
Open chrome at: http://localhost:9876/debug.html
Open chrome inspector

Known issues

Xcode

If you see the following error:

$ bazel build packages/...
ERROR: /private/var/tmp/[...]/external/local_config_cc/BUILD:50:5: in apple_cc_toolchain rule @local_config_cc//:cc-compiler-darwin_x86_64: Xcode version must be specified to use an Apple CROSSTOOL
ERROR: Analysis of target '//packages/core/test/render3:render3' failed; build aborted: Analysis of target '@local_config_cc//:cc-compiler-darwin_x86_64' failed; build aborted

It might be linked to an interaction with VSCode. If closing VSCode fixes the issue, you can add the following line to your VSCode configuration:

"files.exclude": {"bazel-*": true}

source: https://github.com/bazelbuild/bazel/issues/4603

If VSCode is not the root cause, you might try:

bazel clean --expunge
sudo xcode-select -s /Applications/Xcode.app/Contents/Developer
sudo xcodebuild -license

Source: https://stackoverflow.com/questions/45276830/xcode-version-must-be-specified-to-use-an-apple-crosstool

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