Migrating to rules_js

There are more migration steps needed, this guide is still a work-in-progress.

Upgrade to Bazel 5.0 or greater

We follow Bazel's LTS policy.

rules_js and the related rules depend on APIs that were introduced in Bazel 5.0.

Upgrade to rules_nodejs 5.0 or greater

As explained in the README, rules_js depends on rules_nodejs. We need at least version 5.0.

This also requires you upgrade build_bazel_rules_nodejs to 5.0, along with @bazel-scoped npm packages like @bazel/typescript.

Install pnpm (optional)

rules_js is based on the pnpm package manager. Our implementation is self-contained, so it doesn't matter if users install pnpm, however it's typically useful to manipulate the lockfile or to install packages for use outside of Bazel.

You can follow the pnpm install docs.

Alternatively, you can skip the install. All commands in this guide will use npx to run the pnpm tool without any installation.

Translate your lockfile to pnpm format

rules_js uses the pnpm lockfile to declare dependency versions as well as a deterministic layout for the node_modules tree.

  1. Most migrations should avoid changing two things at the same time, so we recommend taking care to keep all dependencies the same (including transitive). Run npx pnpm import to translate the existing file. See the pnpm import docs
  2. If you don't care about keeping identical versions, or don't have a lockfile, you could just run npx pnpm install which generates a new lockfile.

The new pnpm-lock.yaml file needs to be updated by engineers on the team as well, so when you're ready to switch over to rules_js, you'll have to train them to run pnpm rather than npm or yarn when changing dependency versions.

If needed, you might have both the pnpm lockfile and your legacy one checked into the repo during a migration window. You'll have to avoid version skew between the two files during that time.

Test whether pnpm is working

A few packages have bugs which rely on "hoisting" behavior in yarn or npm, where undeclared dependencies can be loaded because they happen to be installed in an ancestor folder under node_modules.

In many cases, updating your dependencies will fix issues since maintainers are constantly addressing pnpm bugs.

Another pattern which may break is when a configuration file references an npm package, then a library reads that configuration and tries to require that package. For example, this mocha json config file references the mocha-junit-reporter package, so mocha will try to load that package despite not having a declared dependency on it.

See https://pnpm.io/faq#pnpm-does-not-work-with-your-project-here for how to resolve these issues. In our mocha example, the solution is to declare the missing dependency: https://github.com/aspect-build/rules_js/blob/main/.pnpmfile.cjs using hooks.readPackage.

Note that if pnpm has already resolved the dependency you want to modify, then running pnpm install won't apply the changes from hooks.readPackage. For rules_js to see the added dependency edge, you must ensure it appears in the pnpm-lock.yaml file, either by re-creating it (though this loses your transitive dependency version pinning) or by hand-modifying it.

Another approach is to just give up on pnpm's stricter visibility for npm modules, and use the --shamefully-hoist option. This will write a pnpm-lock.yaml file which provides a hoisted node_modules structure, which rules_js will naturally translate into the bazel-out folder.

As long as you're able to run your build and test under pnpm, we expect the behavior of rules_js should match.

Typically you just add a npm_link_all_packages(name = "node_modules") call to the BUILD file next to each package.json file:

load("@npm//:defs.bzl", "npm_link_all_packages")

npm_link_all_packages(name = "node_modules")

This macro will expand to a rule for each npm package, which creates part of the bazel-bin/[path/to/package]/node_modules tree.


The WORKSPACE file contains Bazel module dependency fetching and installation.

Add install steps from a release of rules_js, along with related rulesets you plan to use.

Account for change to working directory

rules_js spawns all Bazel actions in the bazel-bin folder.

  • If you use a chdir.js workaround for tools like react-scripts, you can just remove this.
  • If you use $(location), $(execpath), or $(rootpath) make variable expansions in an argument to a program, you may need to prefix with ../../../ to avoid duplicated bazel-out/[arch]/bin path segments.
  • If you spawn node programs, you'll need to pass the BAZEL_BINDIR environment variable.
    • In a genrule add BAZEL_BINDIR=$(BINDIR)
    • ctx.actions.run add env = { "BAZEL_BINDIR": ctx.bin_dir.path}

Update usage of npm package generated rules

  • the load point is now a bin symbol from package_json.bzl
  • this now produces different rules, which are explicitly referenced from bin
  • to run as a tool under bazel build you use [package] which is a js_run_binary
    • rename data to srcs
    • rename templated_args to args
  • as a program under bazel run you need to add a _binary suffix, you get a js_binary
  • as a test under bazel test you get a js_test

Example, before:

load("@npm//npm-check:index.bzl", "npm_check")

    name = "check",
    data = [
    templated_args = [

Example, after:

load("@npm//npm-check:package_json.bzl", "bin")


    name = "check",
    srcs = [
    args = [

Completing the migration

Once everything is migrated, we can remove the legacy rules.

In package.json you can remove usage of the following npm packages which contain Bazel rules, as they don't work with rules_js. Instead, look under https://github.com/aspect-build/ for replacement rulesets.

  • @bazel/typescript
  • @bazel/rollup
  • @bazel/esbuild
  • @bazel/create
  • @bazel/cypress
  • @bazel/concatjs
  • @bazel/jasmine
  • @bazel/karma
  • @bazel/terser

Some @bazel-scoped packages are still fine, as they're tools or JS libraries rather than Bazel rules:

  • @bazel/bazelisk
  • @bazel/buildozer
  • @bazel/buildifier
  • @bazel/ibazel (watch mode)
  • @bazel/runfiles

In addition, rules_js and associated rulesets can manage dependencies for tools they run. For example, rules_esbuild downloads its own esbuild packages. So you can remove these tools from package.json if you intend to run them only under Bazel.

In WORKSPACE you can remove declaration of the following bazel modules:

  • build_bazel_rules_nodejs

You'll need to remove build_bazel_rules_nodejs load() statements from BUILD files as well. We suggest using https://docs.aspect.build/ to locate replacements for the rules you use.