feat(langchain): Support BaseCallbackManager

While implementing #4479, I noticed that our Langchain integration lacks support for the `local_callbacks` having type `BaseCallbackManager`, which according to the type hint is possible.

This change adds support for this case.

Author: szokeasaurusrex

sentry_sdk/integrations/langchain.py

@@ -22,6 +22,7 @@
     from langchain_core.callbacks import (
         manager,
         BaseCallbackHandler,
+        BaseCallbackManager,
         Callbacks,
     )
     from langchain_core.agents import AgentAction, AgentFinish
@@ -436,11 +437,42 @@ def new_configure(
                 **kwargs,
             )
 
-        callbacks_list = local_callbacks or []
+        # Lambda for lazy initialization of the SentryLangchainCallback
+        sentry_handler_factory = lambda: SentryLangchainCallback(
+            integration.max_spans,
+            integration.include_prompts,
+            integration.tiktoken_encoding_name,
+        )
+
+        local_callbacks = local_callbacks or []
+
+        # Handle each possible type of local_callbacks. For each type, we
+        # extract the list of callbacks to check for SentryLangchainCallback,
+        # and define a function that would add the SentryLangchainCallback
+        # to the existing callbacks list.
+        if isinstance(local_callbacks, BaseCallbackManager):
+            callbacks_list = local_callbacks.handlers
+
+            # For BaseCallbackManager, we want to copy the manager and add the
+            # SentryLangchainCallback to the copy.
+            def local_callbacks_with_sentry():
+                new_manager = local_callbacks.copy()
+                new_manager.handlers = [*new_manager.handlers, sentry_handler_factory()]
+                return new_manager
+
+        elif isinstance(local_callbacks, BaseCallbackHandler):
+            callbacks_list = [local_callbacks]
 
-        if isinstance(callbacks_list, BaseCallbackHandler):
-            callbacks_list = [callbacks_list]
-        elif not isinstance(callbacks_list, list):
+            def local_callbacks_with_sentry():
+                return [local_callbacks, sentry_handler_factory()]
+
+        elif isinstance(local_callbacks, list):
+            callbacks_list = local_callbacks
+
+            def local_callbacks_with_sentry():
+                return [*local_callbacks, sentry_handler_factory()]
+
+        else:
             logger.debug("Unknown callback type: %s", callbacks_list)
             # Just proceed with original function call
             return f(
@@ -452,20 +484,12 @@ def new_configure(
             )
 
         if not any(isinstance(cb, SentryLangchainCallback) for cb in callbacks_list):
-            # Avoid mutating the existing callbacks list
-            callbacks_list = [
-                *callbacks_list,
-                SentryLangchainCallback(
-                    integration.max_spans,
-                    integration.include_prompts,
-                    integration.tiktoken_encoding_name,
-                ),
-            ]
+            local_callbacks = local_callbacks_with_sentry()
 
         return f(
             callback_manager_cls,
             inheritable_callbacks,
-            callbacks_list,
+            local_callbacks,
             *args,
             **kwargs,
         )

tests/integrations/langchain/test_langchain.py

@@ -1,4 +1,5 @@
 from typing import List, Optional, Any, Iterator
+from unittest import mock
 from unittest.mock import Mock
 
 import pytest
@@ -12,12 +13,15 @@
     # Langchain < 0.2
     from langchain_community.chat_models import ChatOpenAI
 
-from langchain_core.callbacks import CallbackManagerForLLMRun
+from langchain_core.callbacks import BaseCallbackManager, CallbackManagerForLLMRun
 from langchain_core.messages import BaseMessage, AIMessageChunk
 from langchain_core.outputs import ChatGenerationChunk
 
 from sentry_sdk import start_transaction
-from sentry_sdk.integrations.langchain import LangchainIntegration
+from sentry_sdk.integrations.langchain import (
+    LangchainIntegration,
+    SentryLangchainCallback,
+)
 from langchain.agents import tool, AgentExecutor, create_openai_tools_agent
 from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
 
@@ -342,3 +346,131 @@ def test_span_origin(sentry_init, capture_events):
     assert event["contexts"]["trace"]["origin"] == "manual"
     for span in event["spans"]:
         assert span["origin"] == "auto.ai.langchain"
+
+
+def test_langchain_callback_manager(sentry_init):
+    sentry_init(
+        integrations=[LangchainIntegration()],
+        traces_sample_rate=1.0,
+    )
+    local_manager = BaseCallbackManager(handlers=[])
+
+    with mock.patch("sentry_sdk.integrations.langchain.manager") as mock_manager_module:
+        mock_configure = mock_manager_module._configure
+
+        # Explicitly re-run setup_once, so that mock_manager_module._configure gets patched
+        LangchainIntegration.setup_once()
+
+        callback_manager_cls = Mock()
+
+        mock_manager_module._configure(
+            callback_manager_cls, local_callbacks=local_manager
+        )
+
+        assert mock_configure.call_count == 1
+
+        call_args = mock_configure.call_args
+        assert call_args.args[0] is callback_manager_cls
+
+        passed_manager = call_args.args[2]
+        assert passed_manager is not local_manager
+        assert local_manager.handlers == []
+
+        [handler] = passed_manager.handlers
+        assert isinstance(handler, SentryLangchainCallback)
+
+
+def test_langchain_callback_manager_with_sentry_callback(sentry_init):
+    sentry_init(
+        integrations=[LangchainIntegration()],
+        traces_sample_rate=1.0,
+    )
+    sentry_callback = SentryLangchainCallback(0, False)
+    local_manager = BaseCallbackManager(handlers=[sentry_callback])
+
+    with mock.patch("sentry_sdk.integrations.langchain.manager") as mock_manager_module:
+        mock_configure = mock_manager_module._configure
+
+        # Explicitly re-run setup_once, so that mock_manager_module._configure gets patched
+        LangchainIntegration.setup_once()
+
+        callback_manager_cls = Mock()
+
+        mock_manager_module._configure(
+            callback_manager_cls, local_callbacks=local_manager
+        )
+
+        assert mock_configure.call_count == 1
+
+        call_args = mock_configure.call_args
+        assert call_args.args[0] is callback_manager_cls
+
+        passed_manager = call_args.args[2]
+        assert passed_manager is local_manager
+
+        [handler] = passed_manager.handlers
+        assert handler is sentry_callback
+
+
+def test_langchain_callback_list(sentry_init):
+    sentry_init(
+        integrations=[LangchainIntegration()],
+        traces_sample_rate=1.0,
+    )
+    local_callbacks = []
+
+    with mock.patch("sentry_sdk.integrations.langchain.manager") as mock_manager_module:
+        mock_configure = mock_manager_module._configure
+
+        # Explicitly re-run setup_once, so that mock_manager_module._configure gets patched
+        LangchainIntegration.setup_once()
+
+        callback_manager_cls = Mock()
+
+        mock_manager_module._configure(
+            callback_manager_cls, local_callbacks=local_callbacks
+        )
+
+        assert mock_configure.call_count == 1
+
+        call_args = mock_configure.call_args
+        assert call_args.args[0] is callback_manager_cls
+
+        passed_callbacks = call_args.args[2]
+        assert passed_callbacks is not local_callbacks
+        assert local_callbacks == []
+
+        [handler] = passed_callbacks
+        assert isinstance(handler, SentryLangchainCallback)
+
+
+def test_langchain_callback_list_existing_callback(sentry_init):
+    sentry_init(
+        integrations=[LangchainIntegration()],
+        traces_sample_rate=1.0,
+    )
+    sentry_callback = SentryLangchainCallback(0, False)
+    local_callbacks = [sentry_callback]
+
+    with mock.patch("sentry_sdk.integrations.langchain.manager") as mock_manager_module:
+        mock_configure = mock_manager_module._configure
+
+        # Explicitly re-run setup_once, so that mock_manager_module._configure gets patched
+        LangchainIntegration.setup_once()
+
+        callback_manager_cls = Mock()
+
+        mock_manager_module._configure(
+            callback_manager_cls, local_callbacks=local_callbacks
+        )
+
+        assert mock_configure.call_count == 1
+
+        call_args = mock_configure.call_args
+        assert call_args.args[0] is callback_manager_cls
+
+        passed_callbacks = call_args.args[2]
+        assert passed_callbacks is local_callbacks
+
+        [handler] = passed_callbacks
+        assert handler is sentry_callback