rust_proc_macro

Rust procedural macro compiled with rustc.

Description

Compiles a Rust procedural macro for the execution host. Downstream Rust targets consume the output through --extern as a procedural-macro dependency instead of a normal target dependency.

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/lib.rs	Package-relative macro 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 propagated to downstream Rust binaries and tests
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
package_name	string	no	target name	Original Cargo package name when lowered from Cargo metadata
version	string	no	empty	Resolved Cargo package version when lowered from Cargo metadata
source	string	no	empty	Cargo source identifier
checksum	string	no	empty	Cargo.lock checksum for registry packages

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 by the procedural macro

Providers

The target emits rust_proc_macro.

Capabilities

Capability	Output groups
build	proc_macro

Outputs

Output	Location
Procedural macro library	.once/out/<target>/lib<crate_name>.dylib, .so, or .dll

Example

[[target]]
name = "identity"
kind = "rust_proc_macro"
srcs = ["src/**/*.rs"]

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