`rust_mobile_library`

Rust library materialized by Apple and Android native consumers.

Description#

Describes one first-party Rust library target that Apple and Android consumers can materialize for their platform. Apple consumers declare a staticlib compile, and Android consumers declare a cdylib compile. Each consumer only declares the variant it needs, so Android-only builds do not require the Apple Rust target and Apple-only builds do not require the Android linker.

The target emits native provider fields for Apple and Android app targets. It also emits rust_mobile_crate, which lets another rust_mobile_library consume it. Dependencies are materialized recursively for the platform that requested the native output, so one mobile crate graph can serve both platforms without compiling the unused variant. It does not emit rust_crate, because there is no single rlib output for downstream host Rust compilation.

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 library 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`
`apple_target`	string	yes		Rust target triple for the Apple static library compile
`android_target`	string	yes		Rust target triple for the Android shared library compile
`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_flags`	list<string>	no	`[]`	Additional linker flags lowered to `-C link-arg=...`
`native_linkopts`	list<string>	no	`[]`	Linker flags propagated to Apple app or framework targets
`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 each platform linker and included in compile action inputs
`android_abi`	string	no	inferred	Android Application Binary Interface directory for the Android shared library output, such as `arm64-v8a`
`android_api`	int	no	`23`	Android platform level used to select the Android Native Development Kit clang wrapper
`android_ndk`	string	no	`ANDROID_NDK_HOME`	Android Native Development Kit root used to find clang wrapper linkers
`data`	list<string>	no	`[]`	Runtime data file globs propagated through each materialized platform provider
`compile_data`	list<string>	no	`[]`	Bazel-compatible compile-time data file globs included in each platform rustc action input set
`build_script`	string	no	empty	Package-relative Cargo build script path run before each platform compile

Dependency Edges#

Edge	Accepts	Description
`deps`	`rust_mobile_crate`	Rust mobile crate dependencies compiled recursively for the same Apple or Android target as the consumer

Providers#

The target emits rust_mobile_crate, native_linkable, apple_linkable, and android_native_library.

Provider Record#

Field	Type	Meaning
`label_id`	string	Original target label id
`mobile_deps`	list<record>	Deferred Rust mobile dependency providers materialized for the requesting platform
`transitive_sources`	list<string>	Rust sources from this target and its mobile crate dependencies
`transitive_data`	list<string>	Runtime data propagated from this target and its mobile crate dependencies

Apple consumers materialize archive, staticlib, transitive_archives, and transitive_linkopts while collecting their link inputs. Android consumers materialize android_abi, dylib, android_native_libraries, and transitive_android_native_libraries while collecting native libraries.

Capabilities#

Capability	Output groups
`build`	none

Outputs#

Output	Location
Apple static library	`.once/out/<consumer>/rust-mobile/<target>/apple/lib<crate_name>.a` or `.lib`
Android shared library	`.once/out/<consumer>/rust-mobile/<target>/android/lib<crate_name>.so`

Example#

toml

[[target]]
name = "SharedRust"
kind = "rust_mobile_library"
deps = ["./SharedCore"]
srcs = ["shared/src/**/*.rs"]

[target.attrs]
crate_name = "shared"
crate_root = "shared/src/lib.rs"
edition = "2021"
apple_target = "aarch64-apple-ios-sim"
android_target = "aarch64-linux-android"
android_abi = "arm64-v8a"
android_api = 24

[[target]]
name = "SharedCore"
kind = "rust_mobile_library"
srcs = ["core/src/**/*.rs"]

[target.attrs]
crate_name = "shared_core"
crate_root = "core/src/lib.rs"
apple_target = "aarch64-apple-ios-sim"
android_target = "aarch64-linux-android"
android_abi = "arm64-v8a"