Black

Bazel rules for the Python formatter black.

Setup

First ensure rules_venv is setup by referring to rules_venv setup.

Next, the black rules work mostly off of toolchains which are used to provide the necessary python targets (aka black) for the process wrappers. Users will want to make sure they have a way to get the necessary python dependencies. Tools such as req-compile can provide these.

With the appropriate dependencies available, a py_black_toolchain will need to be configured:

load("@rules_venv//python/black:defs.bzl", "py_black_toolchain")

py_black_toolchain(
    name = "toolchain_impl",
    black = "@pip_deps//black",
    visibility = ["//visibility:public"]
)

toolchain(
    name = "toolchain",
    toolchain = ":toolchain_impl",
    toolchain_type = "@rules_venv//python/black:toolchain_type",
    visibility = ["//visibility:public"]
)

This toolchain then needs to be registered in the MODULE.bazel file.

register_toolchains("//tools/python/black:toolchain")

Usage

Python code can be formatted using the following command:

bazel run @rules_venv//python/black

In addition to this formatter, a check can be added to bazel build invocations using the py_black_aspect aspect. Simply add the following to a .bazelrc file to enable this check.

build --aspects=@rules_venv//python/black:py_black_aspect.bzl%py_black_aspect
build --output_groups=+py_black_checks

Aspects

py_black_aspect

py_black_test

load("@rules_venv//python/black:defs.bzl", "py_black_test")

py_black_test(name, config, target)

A rule for running black on a Python target.

ATTRIBUTES

Name	Description	Type	Mandatory	Default
name	A unique name for this target.	Name	required
config	The config file (`pyproject.toml`) containing black settings.	Label	optional	`"@rules_venv//python/black:config"`
target	The target to run `black` on.	Label	required

py_black_toolchain

load("@rules_venv//python/black:defs.bzl", "py_black_toolchain")

py_black_toolchain(name, black)

A toolchain for the black formatter rules.

ATTRIBUTES

Name	Description	Type	Mandatory	Default
name	A unique name for this target.	Name	required
black	The black `py_library` to use with the rules.	Label	required

py_black_aspect

load("@rules_venv//python/black:defs.bzl", "py_black_aspect")

py_black_aspect()

An aspect for running black on targets with Python sources.

ASPECT ATTRIBUTES

ATTRIBUTES