There are two GN target templates which should be used for Rust projects:
rustc_library defines a library which can be used by other targets.rustc_binary defines an executable.The garnet/examples/rust directory has some examples of Rust packages that use these targets, as do the Rust FIDL examples.
If you want to test out Fuchsia with your own custom-built versions of rustc or cargo, you can set the rustc_prefix argument to fx set, like this:
fx set core.x64 --release --args "rustc_prefix=\"/path/to/bin/dir\""
Fuchsia Rust targets are not built with Cargo during a normal build, and as such, do not require Cargo.toml files. However, having a Cargo.toml file for your target is useful for integration with IDEs such as Intellij and VSCode, and for using the fargo tool to build and test targets without going through a full GN build and run cycle each time.
A Cargo.toml file can be automatically generated for rustc_library and rustc_binary targets based on their .gn file definitions by running:
fx gen-cargo path/from/fuchsia/root/to/target:label
Or, if you're already in a directory with a single Rust target, fx gen-cargo alone should work too.
You must build the target via a regular Fuchsia build before running this command.
You can generate and browse HTML documentation for your target and its dependencies by running:
fx rustdoc path/from/fuchsia/root/to/target:label --open
You can run unit tests on connected devices using fx, with the fx run-test {package name} command, assuming your package in BUILD.gn has with_unit_tests = true.
fx run-test, you can't override package_name="..." in your package or test_package declaration. This issue is tracked by BLD-338.We don't currently have a style guide for Rust, but you should run fx rustfmt or fx format-code before submitting. We mostly use the rustfmt defaults, but have a couple custom settings.
If you're new to Rust, and would like someone to review your changes to validate that your usage of Rust is idiomatic, contact one of the following (or add them as a reviewer to your change.)
(To volunteer for this, please add yourself to the list above and upload the change with one of the above as the reviewer).
Public discussion happens on the rust@fuchsia.com mailing list. For Googler-only channels, see go/fuchsia-rust-googlers.