npm_import.md

Repository rules to fetch third-party npm packages

These use Bazel's downloader to fetch the packages. You can use this to redirect all fetches through a store like Artifactory.

See https://blog.aspect.dev/configuring-bazels-downloader for more info about how it works and how to configure it.

translate_pnpm_lock is the primary user-facing API. It uses the lockfile format from pnpm because it gives us reliable semantics for how to dynamically lay out node_modules trees on disk in bazel-out.

To create pnpm-lock.yaml, consider using pnpm import to preserve the versions pinned by your existing package-lock.json or yarn.lock file.

If you don't have an existing lock file, you can run npx pnpm install --lockfile-only.

Advanced users may want to directly fetch a package from npm rather than start from a lockfile. npm_import does this.

translate_pnpm_lock

translate_pnpm_lock(name, custom_postinstalls, dev, lifecycle_hooks_exclude, no_optional,
                    patch_args, patches, pnpm_lock, prod, repo_mapping, run_lifecycle_hooks)

Repository rule to generate npm_import rules from pnpm lock file.

The pnpm lockfile format includes all the information needed to define npm_import rules, including the integrity hash, as calculated by the package manager.

For more details see, https://github.com/pnpm/pnpm/blob/main/packages/lockfile-types/src/index.ts.

Instead of manually declaring the npm_imports, this helper generates an external repository containing a helper starlark module repositories.bzl, which supplies a loadable macro npm_repositories. This macro creates an npm_import for each package.

The generated repository also contains BUILD files declaring targets for the packages listed as dependencies or devDependencies in package.json, so you can declare dependencies on those packages without having to repeat version information.

Bazel will only fetch the packages which are required for the requested targets to be analyzed. Thus it is performant to convert a very large pnpm-lock.yaml file without concern for users needing to fetch many unnecessary packages.

Setup

In WORKSPACE, call the repository rule pointing to your pnpm-lock.yaml file:

load("@aspect_rules_js//js:npm_import.bzl", "translate_pnpm_lock")

# Read the pnpm-lock.yaml file to automate creation of remaining npm_import rules
translate_pnpm_lock(
    # Creates a new repository named "@npm_deps"
    name = "npm_deps",
    pnpm_lock = "//:pnpm-lock.yaml",
)

Next, there are two choices, either load from the generated repo or check in the generated file. The tradeoffs are similar to this rules_python thread.

1. Immediately load from the generated repositories.bzl file in WORKSPACE. This is similar to the pip_parse rule in rules_python for example. It has the advantage of also creating aliases for simpler dependencies that don't require spelling out the version of the packages. However it causes Bazel to eagerly evaluate the translate_pnpm_lock rule for every build, even if the user didn't ask for anything JavaScript-related.

load("@npm_deps//:repositories.bzl", "npm_repositories")

npm_repositories()

In BUILD files, declare dependencies on the packages using the same external repository.

Following the same example, this might look like:

js_test(
    name = "test_test",
    data = ["@npm_deps//@types/node"],
    entry_point = "test.js",
)

2. Check in the repositories.bzl file to version control, and load that instead. This makes it easier to ship a ruleset that has its own npm dependencies, as users don't have to install those dependencies. It also avoids eager-evaluation of translate_pnpm_lock for builds that don't need it. This is similar to the update-repos approach from bazel-gazelle.

In a BUILD file, use a rule like write_source_files to copy the generated file to the repo and test that it stays updated:

write_source_files(
    name = "update_repos",
    files = {
        "repositories.bzl": "@npm_deps//:repositories.bzl",
    },
)

Then in WORKSPACE, load from that checked-in copy or instruct your users to do so. In this case, the aliases are not created, so you get only the npm_import behavior and must depend on packages with their versioned label like @npm__types_node-15.12.2.

ATTRIBUTES

Name	Description	Type	Mandatory	Default
name	A unique name for this repository.	Name	required
custom_postinstalls	A map of package names or package names with their version (e.g., "my-package" or "[email protected]") to a custom postinstall script to apply to the downloaded npm package after its lifecycle scripts runs. If the version is left out of the package name, the script will run on every version of the npm package. If a custom postinstall scripts exists for a package as well as for a specific version, the script for the versioned package will be appended with && to the non-versioned package script.	Dictionary: String -> String	optional	{}
dev	If true, only install devDependencies	Boolean	optional	False
lifecycle_hooks_exclude	A list of package names or package names with their version (e.g., "my-package" or "[email protected]") to not run lifecycle hooks on	List of strings	optional	[]
no_optional	If true, optionalDependencies are not installed	Boolean	optional	False
patch_args	A map of package names or package names with their version (e.g., "my-package" or "[email protected]") to a label list arguments to pass to the patch tool. Defaults to -p0, but -p1 will usually be needed for patches generated by git. If patch args exists for a package as well as a package version, then the version-specific args will be appended to the args for the package.	Dictionary: String -> List of strings	optional	{}
patches	A map of package names or package names with their version (e.g., "my-package" or "[email protected]") to a label list of patches to apply to the downloaded npm package. Paths in the patch file must start with extract_tmp/package where package is the top-level folder in the archive on npm. If the version is left out of the package name, the patch will be applied to every version of the npm package.	Dictionary: String -> List of strings	optional	{}
pnpm_lock	The pnpm-lock.yaml file.	Label	required
prod	If true, only install dependencies	Boolean	optional	False
repo_mapping	A dictionary from local repository name to global repository name. This allows controls over workspace dependency resolution for dependencies of this repository.<p>For example, an entry "@foo": "@bar" declares that, for any time this repository depends on @foo (such as a dependency on @foo//some:target, it should actually resolve that dependency within globally-declared @bar (@bar//some:target).	Dictionary: String -> String	required
run_lifecycle_hooks	If true, runs preinstall, install and postinstall lifecycle hooks on npm packages if they exist	Boolean	optional	True

npm_import

npm_import(name, package, version, deps, transitive_closure, root_path, link_paths,
           run_lifecycle_hooks, integrity, patch_args, patches, custom_postinstall)

Import a single npm package into Bazel.

Normally you'd want to use translate_pnpm_lock to import all your packages at once. It generates npm_import rules. You can create these manually if you want to have exact control.

Bazel will only fetch the given package from an external registry if the package is required for the user-requested targets to be build/tested.

This is a repository rule, which should be called from your WORKSPACE file or some .bzl file loaded from it. For example, with this code in WORKSPACE:

npm_import(
    name = "npm__at_types_node_15.12.2",
    package = "@types/node",
    version = "15.12.2",
    integrity = "sha512-zjQ69G564OCIWIOHSXyQEEDpdpGl+G348RAKY0XXy9Z5kU9Vzv1GMNnkar/ZJ8dzXB3COzD9Mo9NtRZ4xfgUww==",
)

This is similar to Bazel rules in other ecosystems named "_import" like apple_bundle_import, scala_import, java_import, and py_import. go_repository is also a model for this rule.

The name of this repository should contain the version number, so that multiple versions of the same package don't collide. (Note that the npm ecosystem always supports multiple versions of a library depending on where it is required, unlike other languages like Go or Python.)

To consume the downloaded package in rules, it must be "linked" into the link package in the package's BUILD.bazel file:

load("@npm__at_types_node__15.12.2__links//:link_js_package.bzl", link_types_node = "link_js_package")

link_types_node()

This instantiates a link_js_package target for this package that can be referenced by the alias @//link/package:npm__name and @//link/package:npm__@scope+name for scoped packages. The npm prefix of these alias is configurable via the namespace attribute.

When using translate_pnpm_lock, you can link all the npm dependencies in the lock file with:

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

link_js_packages()

translate_pnpm_lock also creates convienence aliases in the external repository that reference the link_js_package targets. For example, @npm//name and @npm//@scope/name.

To change the proxy URL we use to fetch, configure the Bazel downloader:

1. Make a file containing a rewrite rule like

   rewrite (registry.nodejs.org)/(.*) artifactory.build.internal.net/artifactory/$1/$2

2. To understand the rewrites, see UrlRewriterConfig in Bazel sources.

3. Point bazel to the config with a line in .bazelrc like common --experimental_downloader_config=.bazel_downloader_config

PARAMETERS

Name	Description	Default Value
name	Name for this repository rule	none
package	Name of the npm package, such as acorn or @types/node	none
version	Version of the npm package, such as 8.4.0	none
deps	A dict other npm packages this one depends on where the key is the package name and value is the version	{}
transitive_closure	A dict all npm packages this one depends on directly or transitively where the key is the package name and value is a list of version(s) depended on in the closure.	{}
root_path	The root package where the node_modules virtual store is linked to. Typically this is the package that the pnpm-lock.yaml file is located when using translate_pnpm_lock.	""
link_paths	List of paths where direct links will be created at for this package. These paths are relative to the root package with "." being the node_modules at the root package.	["."]
run_lifecycle_hooks	If true, runs preinstall, install and postinstall lifecycle hooks declared in this package.	False
integrity	Expected checksum of the file downloaded, in Subresource Integrity format. This must match the checksum of the file downloaded. This is the same as appears in the pnpm-lock.yaml, yarn.lock or package-lock.json file. It is a security risk to omit the checksum as remote files can change. At best omitting this field will make your build non-hermetic. It is optional to make development easier but should be set before shipping.	""
patch_args	Arguments to pass to the patch tool. -p1 will usually be needed for patches generated by git.	["-p0"]
patches	Patch files to apply onto the downloaded npm package.	[]
custom_postinstall	Custom string postinstall script to run on the installed npm package. Runs after any existing lifecycle hooks if run_lifecycle_hooks is True.	""