nanobind-bazel: Bazel build rules for C++ Python bindings with nanobind

This repo contains Bazel build defs for Python bindings created with nanobind.

Here's the full list of exported rules:

• nanobind_extension, building a Python extension containing the bindings as a *.so file. These extensions can be used e.g. as a data dependency for a py_library target.
• nanobind_library, a C++ library target that can be used as a dependency of a nanobind_extension. Directly forwards its arguments to the cc_library rule.
• nanobind_test, a C++ test for a nanobind_library. Forwards its argument to a cc_test.

Each target is given nanobind's specific build flags, optimizations and dependencies.

Usage with bzlmod

This repo is published to the Bazel Central Registry (BCR). To use it, specify it as a bazel_dep:

# the major version is equal to the major version of the internally used nanobind.
bazel_dep(name = "nanobind_bazel", version = "1.0.0")

Licenses and acknowledgements

This library is heavily inspired by the pybind11-bazel project, which does the same thing for pybind11. As I have used some of the code from that repository, its license is included here, too.

In contrast to that project, though, nanobind does not support Python interpreter embedding, and endorses a few more size-related optimizations which I have included here.

Roadmap

• First successful test, e.g. on wjakob's nanobind example.
• A BCR release.
• A nanobind_shared_library target for a cc_shared_library using (lib)nanobind.
• Supporting custom nanobind build targets instead of the internal one.

Contributing

I welcome all contributions. If you encounter problems using these rules in your Bazel setup, please open an issue. If you'd like to help maintain the project, write me a message.