Python Rules

Rule	Description
py_proto_repositories	Load workspace dependencies.
py_proto_compile	Generate python protobuf source files.
py_proto_library	Generate and compiles protobuf source files.

py_proto_repositories

1. Enable python support by loading the dependencies in your workspace:

load("@org_pubref_rules_protobuf//python:rules.bzl", "py_proto_repositories")
py_proto_repositories()

py_proto_compile

This is a thin wrapper over the proto_compile rule having language @org_pubref_rules_protobuf//python.

load("@org_pubref_rules_protobuf//python:rules.bzl", "py_proto_compile")

py_proto_compile(
  name = "protos",
  protos = ["message.proto"],
  with_grpc = True, # only one file is generated with or without grpc
)

$ bazel build :protos
Target //:protos up-to-date:
  bazel-genfiles/message_pb2.py

py_proto_library

Pass the set of protobuf source files to the protos attribute.

load("@org_pubref_rules_protobuf//python:rules.bzl", "py_proto_library")

py_proto_library(
  name = "protolib",
  protos = ["message.proto"],
  with_grpc = True,
)

Runtime gRPC support

The instructions above demonstrate how to compile python sources for protocol buffer +/- gRPC support. For runtime grpc support in a py_binary rule, the grpcio pypi package is required. You can have bazel include this as follows using rules_python.

Step 1: Install rules_python and pip requirements in your WORKSPACE

# 1-A. Pull down rules_python
http_archive(
    name = "io_bazel_rules_python",
    rule: "http_archive",
    url: "https://github.com/bazelbuild/rules_python/archive/07fba0f91bb5898d19daeaabf635d08059f7eacd.zip",
    sha256: "53fecb9ddc5d3780006511c9904ed09c15a8aed0644914960db89f56b1e875bd",
    strip_prefix: "rules_python-07fba0f91bb5898d19daeaabf635d08059f7eacd",
)

# 1-B. Load the skylark file containing the needed functions
load("@io_bazel_rules_python//python:pip.bzl", "pip_repositories", "pip_import")

# 1-C. Invoke pip_repositories to load rules_python internal dependencies
pip_repositories()

# 1-D. Invoke pip_import with the necessary python requirements.  You can refer to the
# one in rules_protobuf, or roll your own (make sure it includes 'grpcio==1.6.0' (or later)).
pip_import(
   name = "pip_grpcio",
   requirements = "@org_pubref_rules_protobuf//python:requirements.txt",
)

# 1-E. Load the requirements.bzl file that will be written in this new workspace
# defined in 1-D.
load("@pip_grpcio//:requirements.bzl", pip_grpcio_install = "pip_install")

# 1-F. Invoke this new function to trigger pypi install of 'grpcio' when needed.
pip_grpcio_install()

Step 2: Include the grpcio package the py_binary rule for your gRPC client/server

# Load the 'packages' function from the 'pip_grpcio' workspace
load("@pip_grpcio//:requirements.bzl", "packages")

# Define a py_binary rule and include the grpcio package as a dependency.
py_binary(
    name = "my_grpc_server",
    srcs = [
        "server.py",
    ],
    deps = [
        ":protolib", # a py_proto_library rule
        packages("grpcio"), # grpcio pypi package
    ],
)