From 64c23511162b8ae5d6e7b526d313ebe95510511e Mon Sep 17 00:00:00 2001
From: Olmo Maldonado <olmo.maldonado@gmail.com>
Date: Mon, 16 Dec 2024 11:26:36 -0800
Subject: [PATCH] fix(core): Make sure to return a callback manager if
 configure hooks (#7366)

Co-authored-by: jacoblee93 <jacoblee93@gmail.com>
---
 langchain-core/src/callbacks/manager.ts       | 33 +++++++++++--------
 .../src/callbacks/tests/manager.test.ts       | 18 ++++++++--
 2 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/langchain-core/src/callbacks/manager.ts b/langchain-core/src/callbacks/manager.ts
index dcabf602b838..55ad0484e480 100644
--- a/langchain-core/src/callbacks/manager.ts
+++ b/langchain-core/src/callbacks/manager.ts
@@ -1245,18 +1245,6 @@ export class CallbackManager
         }
       }
     }
-    if (inheritableTags || localTags) {
-      if (callbackManager) {
-        callbackManager.addTags(inheritableTags ?? []);
-        callbackManager.addTags(localTags ?? [], false);
-      }
-    }
-    if (inheritableMetadata || localMetadata) {
-      if (callbackManager) {
-        callbackManager.addMetadata(inheritableMetadata ?? {});
-        callbackManager.addMetadata(localMetadata ?? {}, false);
-      }
-    }
 
     for (const {
       contextVar,
@@ -1276,12 +1264,29 @@ export class CallbackManager
         handler = new (handlerClass as any)({});
       }
       if (handler !== undefined) {
-        if (!callbackManager?.handlers.some((h) => h.name === handler!.name)) {
-          callbackManager?.addHandler(handler, inheritable);
+        if (!callbackManager) {
+          callbackManager = new CallbackManager();
+        }
+
+        if (!callbackManager.handlers.some((h) => h.name === handler!.name)) {
+          callbackManager.addHandler(handler, inheritable);
         }
       }
     }
 
+    if (inheritableTags || localTags) {
+      if (callbackManager) {
+        callbackManager.addTags(inheritableTags ?? []);
+        callbackManager.addTags(localTags ?? [], false);
+      }
+    }
+    if (inheritableMetadata || localMetadata) {
+      if (callbackManager) {
+        callbackManager.addMetadata(inheritableMetadata ?? {});
+        callbackManager.addMetadata(localMetadata ?? {}, false);
+      }
+    }
+
     return callbackManager;
   }
 }
diff --git a/langchain-core/src/callbacks/tests/manager.test.ts b/langchain-core/src/callbacks/tests/manager.test.ts
index 7e947049006f..12f32890f2a7 100644
--- a/langchain-core/src/callbacks/tests/manager.test.ts
+++ b/langchain-core/src/callbacks/tests/manager.test.ts
@@ -1,7 +1,7 @@
 /* eslint-disable no-process-env */
-import { expect, test, beforeAll, afterEach } from "@jest/globals";
+import { afterEach, beforeAll, expect, test } from "@jest/globals";
 
-import { setContextVariable, registerConfigureHook } from "../../context.js";
+import { registerConfigureHook, setContextVariable } from "../../context.js";
 import { BaseCallbackHandler } from "../base.js";
 import { CallbackManager } from "../manager.js";
 
@@ -26,6 +26,20 @@ test("configure with empty array", async () => {
   expect(manager?.handlers.length).toBe(0);
 });
 
+test("configure with no arguments", async () => {
+  const manager = CallbackManager.configure();
+  expect(manager).toBe(undefined);
+});
+
+test("configure with no arguments but with handler", async () => {
+  setContextVariable("my_test_handler", handlerInstance);
+  registerConfigureHook({
+    contextVar: "my_test_handler",
+  });
+  const manager = CallbackManager.configure();
+  expect(manager?.handlers[0]).toBe(handlerInstance);
+});
+
 test("configure with one handler", async () => {
   const manager = CallbackManager.configure([handlerInstance]);
   expect(manager?.handlers[0]).toBe(handlerInstance);