Rust Rules

This repo provides Rust build rules for the Please build system.

Basic usage

First add the plugin to your project. In plugins/BUILD:

plugin_repo(
    name = "rust",
    owner = "odonate",
    revision = "<Some git tag, commit, or other reference>",
)

Set up the Rust toolchain for your project in third_party/rust:

subinclude("///rust//build_defs:rust")

rust_toolchain(
    name = "toolchain",
    hashes = ["<hash>"],
    version = "X.XX.X",
    visibility = ["PUBLIC"],
)

Then add the plugin config to .plzconfig:

[Plugin "rust"]
Target = //plugins:rust

You can then compile and test Rust libraries like so:

subinclude("///rust//build_defs:rust")

rust_library(
    name = "lib",
    root = "src/lib.rs",
    modules = [
        "src/module_a.rs",
        "src/module_a/sub_module_a.rs",
        "src/module_b.rs",
        "src/module_b/sub_module_b.rs",
    ],
)

rust_test(
    name = "lib",
    root = "src/lib.rs",
    modules = [
        "src/module_a.rs",
        "src/module_a/sub_module_a.rs",
        "src/module_b.rs",
        "src/module_b/sub_module_b.rs",
    ],
)

You can define third-party crates using rust_crate:

subinclude("///rust//build_defs:rust")

rust_crate(
    name="libc",
    crate="libc",
    version="0.2.155",
    build_script="build.rs",
    edition="2015",
)

rust_crate(
    name="cfg_if",
    crate="cfg-if",
    version="1.0.0",
    edition="2018",
)

rust_crate(
    name="getrandom",
    crate="getrandom",
    version="0.2.15",
    edition="2018",
    features=["std"],
    deps=[":cfg_if", ":libc"],
)

rust_crate(
    name="rand_core",
    crate="rand_core",
    version="0.6.4",
    edition="2018",
    features=["alloc", "getrandom", "std"],
    deps = [":getrandom"],
)

To compile a binary, you can use rust_binary:

subinclude("///rust//build_defs:rust")

rust_binary(
    name = "bin",
    main = "src/main.rs",
    deps = [
        ":lib",
        "//third_party/rust:<rust_crate_name>",
    ],
)

Configuration

Plugins are configured through the Plugin section like so:

[Plugin "rust"]
SomeConfig = some-value

The available configuration options are:

Rustc

The path to the rustc compiler to use. Defaults to the toolchain's rustc.

[Plugin "rust"]
Rustc = //third_party/rust:toolchain_rustc

StdLib

The path to the stdlib to be linked by the compiler. Defaults to the toolchain's stdlib.

[Plugin "rust"]
StdLib = //third_party/rust:toolchain_stdlib

General notes

Rust Rules is based heavily on Cargo in its invocation of the rustc compiler. Care should be taken when defining third-party crates to ensure the correct depencies and their versions are supplied, required conditional compilation features are set, and correct Rust editions are used. This information can be found in the Cargo.toml file of the third-party crate. Unfortunately, at present, Rust Rules does not parse the Cargo.toml file to infer this information, so it must be supplied manually.

Contributing

Contributions are welcome! Please open or submit a pull request with your changes. Ensure that your code follows the existing style and includes tests where applicable.

Extra Features for Contribution

Here are some extra features that would be valuable additions to this project:

Additional Crate Types: The rust_crate rule currently only supports .rlib. Adding support for other crate types, particularly .bin, would be useful. Other types to support: staticlib, dylib, cdylib, proc-macro.
Improved Linking: Currently, there is a hacky method for getting the dependency directory for linking crates with the -L flag. A cleaner solution would enhance the build process.
Codegen Flags: Implementing support for the codegen -C metadata and -C extra-filename flags would better align with how Cargo fingerprints external crates and dependencies.
Build Script Outputs: Currently, only cargo:rustc-cfg: is supported in build scripts. Adding support for other outputs like cargo:rustc-rerun-if-xxx, cargo:rustc-link-xxx, and cargo:rustc-env would be beneficial. Additionally, parsing the Cargo.toml to check if any values should be overridden would provide more comprehensive functionality.
Target (OS and Architecture) Compatibility: This project has primarily been tested on unknown-linux-gnu x86_64 architecture. It would be nice to test and support other targets to ensure cross-platform compatibility.

odonate/rust-rules