`cargo_workspace`

Native Cargo project seed.

Description#

cargo_workspace runs cargo metadata --locked --offline and emits ordinary first-party and external Rust targets. First-party packages become rust_library, rust_binary, rust_test, or rust_proc_macro targets. Locked external packages use the same fine-grained lowering as cargo_dependencies.

Cargo remains authoritative for workspace membership, targets, features, renamed dependencies, build scripts, versions, and checksums. By default, Once snapshots locked external package trees from Cargo's local cache into each target's output. The repository stays unchanged. A pre-existing vendored source directory can be selected explicitly. Targets whose required-features are not selected are omitted, matching Cargo's target selection. Generated test targets include development dependencies. Cargo target names are normalized to valid Rust crate identifiers while binary names retain their manifest spelling. Multi-output libraries emit one target per declared Rust library crate type. Cargo's workspace member list determines which packages are first-party, so local path dependencies outside that list remain ordinary dependency targets.

Attributes#

Attribute	Type	Required	Default	Description
`manifest`	string	no	`Cargo.toml`	Package-relative Cargo manifest
`lockfile`	string	no	`Cargo.lock`	Package-relative authoritative lockfile
`resolver_inputs`	list<string>	no	`srcs`	Text inputs available while deriving the graph
`metadata_file`	string	no		Optional checked Cargo metadata snapshot
`host_metadata_file`	string	no		Optional host metadata snapshot for cross-compilation
`vendor_dir`	string	no	Once-managed	Optional package-relative pre-vendored external sources
`features`	list<string>	no	`[]`	Selected Cargo features
`all_features`	bool	no	`false`	Select every Cargo feature
`no_default_features`	bool	no	`false`	Disable default Cargo features
`target`	string	no	host	Destination Rust target triple
`dep_rustc_flags`	list<string>	no	`[]`	Additional flags for external packages

Providers#

The target emits cargo_workspace.

Capabilities#

Capability	Output groups
`build`	none

Direct Use#

On a fresh clone, populate Cargo's local source cache from the lockfile:

bash

cargo fetch --locked

Once never performs that network operation while loading or building the graph.

Discover and preview the native project:

bash

once query native-projects
once query native-project cargo

Initialize the seed:

bash

once edit init-native-project cargo

The imported target is equivalent to:

toml

[[target]]
name = "cargo"
kind = "cargo_workspace"
srcs = ["Cargo.toml"]

[target.attrs]
resolver_inputs = ["Cargo.toml", "Cargo.lock", "**/Cargo.toml", ".cargo/config", ".cargo/config.toml"]

Keep this seed as the only Once target while Cargo metadata describes the complete build. Add explicit targets beside it for exceptional cross-language or packaging boundaries. Use a project Starlark module only when those exceptions share reusable behavior that the built-in target kinds cannot express.

Sources#

Cargo metadata defines the native project graph.
The Cargo lockfile defines resolved versions and checksums.