Cargo Feature Flags

HORUS uses Cargo feature flags to keep the default binary small while allowing opt-in to heavier capabilities. This page lists every feature flag across the workspace.

`horus` (Main Crate)

The crate you add to Cargo.toml. Re-exports horus_core and horus_library.

[dependencies]
horus = "0.1"

Feature	Default	What It Enables
`macros`	Yes	Procedural macros: `message!`, `service!`, `action!`, `node!`, `hlog!`
`telemetry`	Yes	Live monitoring export (HTTP, UDP, file)
`blackbox`	Yes	Post-mortem flight recorder via `.blackbox(size_mb)`
`mdns`	No	Zero-config peer discovery via mDNS/DNS-SD

Disabling defaults

To build a minimal binary without macros, telemetry, or blackbox:

[dependencies]
horus = { version = "0.1", default-features = false }

To selectively re-enable:

[dependencies]
horus = { version = "0.1", default-features = false, features = ["macros"] }

Enabling mDNS discovery

[dependencies]
horus = { version = "0.1", features = ["mdns"] }

This pulls in the mdns-sd crate and enables automatic peer discovery on the local network.

`horus_library` (Message & Transform Library)

These flags control optional blocking/async APIs in the transform frame system.

Feature	Default	What It Enables
`wait`	No	Blocking `wait_for_transform()` using condvar — zero overhead when disabled
`async-wait`	No	Async `wait_for_transform_async()` using `tokio::sync::Notify` — pulls in `tokio`

Usage

[dependencies]
horus_library = { version = "0.1", features = ["wait"] }

// Only available with "wait" feature
let tf = tf_tree.wait_for_transform("lidar", "world", Duration::from_secs(1))?;

[dependencies]
horus_library = { version = "0.1", features = ["async-wait"] }

// Only available with "async-wait" feature
let tf = tf_tree.wait_for_transform_async("lidar", "world", Duration::from_secs(1)).await?;

`horus_core` (Runtime)

These mirror the horus crate flags and are typically set transitively.

Feature	Default	What It Enables
`macros`	Yes	Includes `horus_macros` proc-macro crate
`telemetry`	Yes	Telemetry export subsystem
`blackbox`	Yes	Flight recorder subsystem
`mdns`	No	mDNS service discovery (`mdns-sd` v0.11)
`test-utils`	No	Test utilities like `MockTopic` for downstream crate testing

Using test-utils

Enable test-utils in dev-dependencies for testing:

[dev-dependencies]
horus_core = { version = "0.1", features = ["test-utils"] }

`horus_py` (Python Bindings)

Feature	Default	What It Enables
`extension-module`	Yes	Required for building the `.so` Python extension

Important: Disable when running Rust unit tests (test binary cannot link against libpython):

cargo test -p horus_py --no-default-features

`horus_manager` (CLI)

Feature	Default	What It Enables
`mdns`	No	mDNS discovery for `horus` CLI commands
`schema`	No	JSON Schema generation for manifest types (`schemars`)

Summary Table

Crate	Feature	Default	Dependency
`horus`	`macros`	Yes	`horus_macros`
`horus`	`telemetry`	Yes	— (marker)
`horus`	`blackbox`	Yes	— (marker)
`horus`	`mdns`	No	`mdns-sd`
`horus_library`	`wait`	No	— (condvar)
`horus_library`	`async-wait`	No	`tokio`
`horus_core`	`test-utils`	No	— (marker)
`horus_py`	`extension-module`	Yes	`pyo3`
`horus_manager`	`schema`	No	`schemars`

Cargo Feature Flags

horus (Main Crate)

Disabling defaults

Enabling mDNS discovery

horus_library (Message & Transform Library)

Usage

horus_core (Runtime)