sdk: readable clients (no Empty wrapper, no unused error module), documented examples with tests

sdk/tests/plugins/consumer/src/main.rs

@@ -11,6 +11,23 @@ impl Consumer {
             .on_notify(|name, _| eprintln!("typed progress: {name}"))
             .await? as i32)
     }
+    /// Connect to a world endpoint from the real core.
+    async fn world_endpoint(&self) -> Result<u64> {
+        let control = probe::control::connect("/state/control").await?;
+        let received = std::rc::Rc::new(std::cell::Cell::new(false));
+        let progress = received.clone();
+        let result = control
+            .stats()
+            .on_notify(move |name, value| {
+                progress.set(name == "endpoint-progress" && value["value"] == 7);
+            })
+            .await?;
+        assert!(
+            received.get(),
+            "the endpoint must deliver progress before its result"
+        );
+        Ok(result)
+    }
     /// Connect to the provider's endpoint and receive its notification.
     async fn endpoint(&self) -> Result<u64> {
         let control = probe::control::connect("/endpoint").await?;