rust_binary

Rust executable compiled with rustc.

Description

Compiles a Rust binary from a main crate. Direct Rust deps are passed through --extern; transitive rlibs are exposed as dependency search paths. The action key includes the resolved Rust compiler and linker identity.

Attributes

Attribute	Type	Required	Default	Description
crate_name	string	no	target name	Rust crate name passed to rustc; - and . are rewritten as _ when omitted
crate_root	string	no	src/main.rs	Package-relative binary root
edition	string	no	2021	Rust edition passed to rustc
features	list<string>	no	[]	Cargo feature names lowered to --cfg=feature=... flags
crate_features	list<string>	no	[]	Bazel-compatible alias for features
target	string	no	host target	Rust target triple passed to rustc --target
env	map<string, string>	no	{}	Environment variables for rustc, matching Buck2's env attribute
rustc_env	map<string, string>	no	{}	Bazel-compatible rustc environment variables
rustc_env_files	list<string>	no	[]	Files with NAME=value entries merged into the rustc environment before env and rustc_env
rustc_flags	list<string>	no	[]	Additional rustc flags appended after Once-managed flags
cap_lints	string	no	empty	Optional rustc lint cap passed as --cap-lints; generated Cargo dependencies use allow
linker	string	no	empty	Optional linker path passed as -C linker=...; defaults to cc for host Unix binary-like targets and to the Android NDK clang wrapper for Android targets when available
linker_flags	list<string>	no	[]	Additional linker flags lowered to -C link-arg=...
native_linkopts	list<string>	no	[]	Shared Rust compatibility attribute for native-producing Rust target kinds
exported_linker_flags	list<string>	no	[]	Buck-compatible alias for native linker flags propagated to downstream native consumers
exported_post_linker_flags	list<string>	no	[]	Buck-compatible propagated linker flags appended after normal exported linker flags
linker_script	string	no	empty	Package-relative linker script passed to the linker and included in the compile action inputs
android_abi	string	no	inferred	Android ABI directory for dynamic library outputs, such as arm64-v8a
android_api	int	no	23	Android API level used to select the NDK clang wrapper for Android targets
android_ndk	string	no	ANDROID_NDK_HOME	Android NDK root used to find clang wrapper linkers
data	list<string>	no	[]	Runtime data file globs available during once run and propagated from Rust dependencies
compile_data	list<string>	no	[]	Bazel-compatible compile-time data file globs included in the rustc action inputs
crate_aliases	map<string, string>	no	{}	Map dependency label, package name, or crate name to the local extern crate name
aliases	map<string, string>	no	{}	Bazel-compatible alias map from dependency label or crate name to local extern crate name
named_deps	map<string, string>	no	{}	Buck-compatible alias map from local extern crate name to dependency label or crate name
cargo_package	string	no	empty	Cargo package name used to select direct external deps from a cargo_dependencies dependency set. Defaults to CARGO_PKG_NAME when present
build_script	string	no	empty	Package-relative Cargo build script path run before rustc; common cargo:rustc-* stdout directives are consumed, dependency cargo:rustc-link-search outputs are replayed downstream, and direct dependency links metadata is consumed
args	list<string>	no	[]	Arguments passed to the executable during once run
run_env	map<string, string>	no	{}	Environment variables passed to the executable during once run
env_inherit	list<string>	no	[]	Host environment variable names inherited during once run before run_env overrides

Accepted but unsupported attributes: default_deps, doc_deps, doc_env, doc_link_style, doc_linker_flags, doc_named_deps, link_deps, link_style, mapped_srcs, proc_macro_deps, rpath, runtime_dependency_handling, and rustdoc_flags. Non-empty values fail validation.

Dependency Edges

Edge	Accepts	Description
deps	rust_crate, rust_proc_macro, rust_dependency_set	Rust crate dependencies consumed through --extern

Providers

The target emits rust_binary.

Capabilities

Capability	Output groups
build	binary
run	default

Outputs

Output	Location
Executable	.once/out/<target>/<crate_name> or .exe for Windows targets
Run result	.once/out/<target>/run/run.json
Run log	.once/out/<target>/run/stdout.log

Example

[[target]]
name = "hello"
kind = "rust_binary"
deps = ["cargo_dependencies"]
srcs = ["src/**/*.rs"]

[target.attrs]
crate_name = "hello"
edition = "2021"

[target.attrs.rustc_env]
CARGO_MANIFEST_DIR = "apps/hello"
CARGO_PKG_NAME = "hello"
CARGO_PKG_VERSION = "0.0.0"