Nanopb: Bazel build

The Bazel build system, is designed to be fast and correct. Nanopb provides a set of plugins for the Bazel build system allowing Nanopb to be integrated into the build.

Getting started

Add the following to your MODULE.bazel file.

# MODULE.bazel
bazel_dep(name = "nanopb", version = "0.4.9")
git_override(
    module_name = "nanopb",
    remote = "https://github.com/nanopb/nanopb.git",
    commit = "<commit>",
)

To use the Nanopb rules with in your build you can use the cc_nanopb_proto_library which works in a similar way to the native cc_proto_library rule.

# BUILD.bazel
load("@nanopb//extra/bazel:nanopb_cc_proto_library.bzl", "cc_nanopb_proto_library")

# Your native proto_library.
proto_library(
    name = "descriptor",
    srcs = [
        "generator/proto/google/protobuf/descriptor.proto",
    ],
)

# Generated library.
cc_nanopb_proto_library(
    name = "descriptor_nanopb",
    protos = [":descriptor"],
    visibility = ["//visibility:private"],
)

# Depend directly on the generated code using a cc_library.
cc_library(
    name = "uses_generated_descriptors",
    deps = [":descriptor_nanopb"],
    hdrs = ["my_header.h"],
)

If you have a custom nanopb options file, use the nanopb_options_files argument shown below.

# Generated library with options.
cc_nanopb_proto_library(
    name = "descriptor_nanopb",
    protos = [":descriptor"],
    nanopb_options_files = ["descriptor.options"],
    visibility = ["//visibility:private"],
)

Bazel Configuration Options

Use a non-default extension

By default, nanopb generates files with extension .pb, which ends up creating names such as my_proto.pb.h and my_proto.pb.c. This naming pattern conflicts with cc_proto_library rules, which generate files with the same names.

To resolve this conflict, we provide a string_flag //:nanopb_extension that currently accepts two options: .pb and .nanopb. (In the future, we could pontentially accept your choice of input, but that was tricky to do, so to start with only these two options are supported.)

To build nanopb files with the .nanopb extension (creating files of my_proto.nanopb.h and my_proto.nanopb.c) you can add the following to your command line:

bazel build --@nanopb//:nanopb_extension=".nanopb"

If you want to apply this to all nanopb files, add the above to your .bazelrc file:

# .bazelrc
build --@nanopb//:nanopb_extension=".nanopb"