feat(csr): add stripped dev output diagnostics

packages/csr/src/reactive-runtime.ts

@@ -191,6 +191,27 @@ export const REACTIVE_RUNTIME = String.raw`
     }
   }
 
+  /*__WRNEXUS_DEV_START__*/
+  var developmentWarnings = Object.create(null);
+  function warnOnce(code, message, element, detail) {
+    var key = code + "\\n" + message;
+    if (developmentWarnings[key]) return;
+    developmentWarnings[key] = true;
+    var payload = {
+      code: code,
+      message: message,
+      hydrationId: element && element.getAttribute ? element.getAttribute("data-wrn-hydration") : null,
+      detail: detail || null,
+    };
+    console.warn("[" + code + "] " + message, detail || "");
+    try {
+      window.dispatchEvent(new CustomEvent("wrnexus:diagnostic", { detail: payload }));
+    } catch (_) {
+      // CustomEvent can be unavailable in minimal DOM test environments.
+    }
+  }
+  /*__WRNEXUS_DEV_END__*/
+
   function scheduleUpdateHook(element, callback) {
     pendingUpdateHooks.set(element, callback);
     if (updateHooksScheduled) return;
@@ -3953,6 +3974,15 @@ export const REACTIVE_RUNTIME = String.raw`
         ? Promise.all(values)
         : values[values.length - 1];
     }
+    /*__WRNEXUS_DEV_START__*/
+    warnOnce(
+      "WRN-DEV-OUTPUT-UNHANDLED",
+      "Output '" + name + "' has no parent binding. Registered bindings: " +
+        (registry ? Object.keys(registry).join(", ") || "none" : "none") + ".",
+      root,
+      { output: name, registeredBindings: registry ? Object.keys(registry) : [] },
+    );
+    /*__WRNEXUS_DEV_END__*/
     return dispatchComponentEvent(root, name, payload);
   }