crates.io dependencies#

This directory is where third party crate dependencies are managed. There are two sets of crates: ./crates_no_std and ./crates_std. These are cargo based “null” Rust libraries that exist solely to express which crates to expose to Bazel via the a single unified hub. ./rust_crates is a Bazel repository that exposes these crates to Bazel.

Getting started#

Crates are split by whether they use std or no_std. By default, platforms are otherwise assumed to use std. Embedded platforms typically need to add @pigweed//pw_build/constraints/rust:no_std to their platform’s constraint_values:

platform(
    name = "mps2_an505",
    constraint_values = [
        "@pigweed//pw_build/constraints/arm:cortex-m33",
        "@pigweed//pw_build/constraints/rust:no_std",
        "@platforms//cpu:armv8-m",
        "@platforms//os:none",
    ],
)

Vendoring your own crates#

Pigweed’s pw_rust_crates_extension Bazel module extension allows the @rust_crates repo used by Pigweed to be overridden so alternative crate definitions may be used. This can be done by adding the following to your project’s MODULE.bazel:

local_repository(name = "rust_crates", path = "build/crates_io")

pw_rust_crates = use_extension(
    "@pigweed//pw_build:pw_rust_crates_extension.bzl",
    "pw_rust_crates_extension",
)
override_repo(pw_rust_crates, rust_crates = "rust_crates")

Adding a third party crate to Pigweed#

Add the crate to either or both of ./crates_no_std and ./crates_std by running the following command in the appropriate directory:
```
$ cargo add <crate_name> --features <additional_features>
```

Run cargo deny:

$ (cd crates_std; cargo deny check) && \
     (cd crates_no_std; cargo deny check)

Note

Install with cargo install --locked cargo-deny if not already installed.

Update ./rust_crates/alias_hub.BUILD by running the following command in the third_party/crates_io directory:
```
$ cargo run -- --config config.toml > rust_crates/alias_hub.BUILD
```