homecore-plugins

WASM integration plugin runtime for HOMECORE with native Rust runtime (P1) and Wasmtime JIT sandbox support (P2).

P1 scaffold: manifest parsing, plugin traits, and in-memory native Rust plugin registry. Wasmtime sandbox (P2) and hot-reload (P3) are deferred.

What this crate does

homecore-plugins provides a trait-based plugin system that can host both native Rust plugins (in-process) and WASM plugins (Wasmtime sandbox, P2). It defines:

• PluginManifest — JSON schema for plugin metadata (superset of Home Assistant's manifest.json), validated at load time
• HomeCorePlugin trait — async lifecycle hooks (setup, teardown, state changed handlers)
• PluginRuntime trait — abstraction over execution environments (native vs WASM)
• InProcessRuntime — built-in runtime for first-party Rust plugins (P1)
• PluginRegistry — manages loading, unloading, and querying plugins
• Host ABI (stubs) — C-compatible function signatures for WASM ↔ homecore calls (wiring in P2)

The system is designed to be feature-gated: compile with --features wasmtime to unlock JIT sandbox support for untrusted third-party plugins.

Features

• Native Rust plugins — first-party integrations compiled into the binary, zero sandbox overhead (P1)
• WASM plugin framework — trait-based abstraction ready for Wasmtime JIT (P2) or wasm3 interpreter (P3)
• PluginManifest validation — required fields enforced at load time; superset of HA manifest fields
• Async plugin lifecycle — setup() and teardown() for resource management
• State change subscriptions — plugins can subscribe to entity state changes with handler callbac
• Config entry lifecycle — plugin receives config when registered; P3 adds hot-reload
• Feature-gated runtimes — Wasmtime (30 MB, P2) and wasm3 (50 kB, P3) are optional dependencies
• Manifest inheritance from Home Assistant — codeowners, requirements, documentation, issue_tracker, IoT classification

Capabilities

Comparison to Home Assistant

Performance

• Native plugin overhead — same as regular Rust function calls; no sandbox cost
• WASM plugin sandbox — Wasmtime JIT ~5 ms per call (after warmup); memory overhead ~10 MB per instance
• Manifest parsing — < 1 ms (serde_json)
• Registry operations — O(1) plugin lookup (DashMap); O(n) for list()
• No per-crate benchmarks yet — a follow-up issue tracks baseline measurements

Usage

Native plugin (P1):

use homecore_plugins::{HomeCorePlugin, PluginManifest, InProcessRuntime};
use async_trait::async_trait;

struct MyPlugin;

#[async_trait]
impl HomeCorePlugin for MyPlugin {
    async fn setup(&mut self) -> Result<(), homecore_plugins::PluginError> {
        println!("Plugin setup");
        Ok(())
    }

    async fn teardown(&mut self) -> Result<(), homecore_plugins::PluginError> {
        println!("Plugin teardown");
        Ok(())
    }

    async fn on_state_changed(&mut self, _event: &homecore_plugins::StateChangedEventJson) -> Result<(), homecore_plugins::PluginError> {
        Ok(())
    }
}

#[tokio::main]
async fn main() {
    let manifest = PluginManifest {
        domain: "my_plugin".to_string(),
        name: "My Plugin".to_string(),
        ..Default::default()
    };

    let mut runtime = InProcessRuntime::new();
    let plugin_id = runtime.load(manifest.clone(), MyPlugin).await.expect("load plugin");
    println!("Loaded plugin: {:?}", plugin_id);
    runtime.unload(&plugin_id).await.ok();
}

WASM plugin (P2 example):

# Build a WASM plugin (requires --features wasmtime)
cargo build -p homecore-plugin-example --target wasm32-unknown-unknown --release

# The WasmtimeRuntime will be available at P2:
# let mut runtime = WasmtimeRuntime::new();
# let plugin_id = runtime.load(wasm_bytes, manifest).await?;

Relation to other HOMECORE crates

homecore-plugins (plugin registry + runtime abstraction)
├─ homecore (state machine; plugins receive state changes)
├─ homecore-plugin-example (reference WASM plugin)
├─ homecore-server (loads plugins at startup)
└─ homecore-automation (can invoke handlers via service calls)

Security Notes

P1 (this release): No sandbox. Native Rust plugins have full process access.

P2 (planned): Wasmtime JIT sandbox is opt-in via --features wasmtime. WASM plugins run in isolated memory with explicit host ABI calls to access homecore state. The host ABI is frozen before P2 begins (ADR-128 §8 risk mitigation).

P4+: Ed25519 signature verification and permission enforcement for third-party Cog registry distribution.

References

• ADR-128: HOMECORE Integration Plugin System
• homecore-plugin-example: reference WASM plugin
• Host ABI spec
• README — wifi-densepose