Add derive-based protocol leaf declarations

examples/protocol_leaf_derive.rs

@@ -0,0 +1,46 @@
+use std::error::Error;
+
+use unshell::Leaf;
+use unshell::protocol::tree::{Endpoint, Ingress, LocalEvent, ProtocolEndpoint};
+
+#[derive(Leaf)]
+#[leaf(org = "org", product = "example", version = "v1", leaf_name = "echo")]
+#[leaf(procedures(call, stream))]
+struct EchoLeaf;
+
+fn path(parts: &[&str]) -> Vec<String> {
+    parts.iter().map(|part| (*part).to_owned()).collect()
+}
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let mut endpoint = ProtocolEndpoint::new(
+        path(&["agent"]),
+        Some(Vec::new()),
+        Vec::new(),
+        vec![EchoLeaf::protocol_leaf_spec()],
+    );
+
+    let hook_id = endpoint.allocate_hook_id();
+    let frame = endpoint.make_call(
+        path(&["agent"]),
+        Some(EchoLeaf::protocol_leaf_name()),
+        EchoLeaf::protocol_procedure_id("call").expect("known procedure suffix"),
+        Some(hook_id),
+        b"hello leaf".to_vec(),
+    )?;
+
+    let outcome = endpoint.receive(&Ingress::Parent, frame)?;
+    let Some(LocalEvent::Call { header, message }) = outcome.event else {
+        return Err("expected local leaf call".into());
+    };
+
+    assert_eq!(header.dst_leaf.as_deref(), Some("org.example.v1.echo"));
+    assert_eq!(message.procedure_id, "org.example.v1.echo.call");
+
+    println!(
+        "leaf={} procedure={}",
+        EchoLeaf::protocol_leaf_name(),
+        message.procedure_id
+    );
+    Ok(())
+}