core[patch]: Fix runnable with message history (#14629)

Fix bug shown in #14458. Namely, that saving inputs to history fails
when the input to base runnable is a list of messages

libs/core/langchain_core/runnables/history.py

@@ -1,13 +1,17 @@
 from __future__ import annotations
 
 import asyncio
+import inspect
 from typing import (
     TYPE_CHECKING,
     Any,
+    Callable,
+    Dict,
     List,
     Optional,
     Sequence,
     Type,
+    Union,
 )
 
 from langchain_core.chat_history import BaseChatMessageHistory
@@ -25,8 +29,6 @@ if TYPE_CHECKING:
     from langchain_core.runnables.config import RunnableConfig
     from langchain_core.tracers.schemas import Run
 
-import inspect
-from typing import Callable, Dict, Union
 
 MessagesOrDictWithMessages = Union[Sequence["BaseMessage"], Dict[str, Any]]
 GetSessionHistoryCallable = Callable[..., BaseChatMessageHistory]
@@ -35,13 +37,9 @@ GetSessionHistoryCallable = Callable[..., BaseChatMessageHistory]
 class RunnableWithMessageHistory(RunnableBindingBase):
     """A runnable that manages chat message history for another runnable.
 
-    Base runnable must have inputs and outputs that can be converted to a list of
-        BaseMessages.
+    Base runnable must have inputs and outputs that can be converted to a list of BaseMessages.
 
-    RunnableWithMessageHistory must always be called with a config that contains
-        session_id, e.g.:
-
-        ``{"configurable": {"session_id": "<SESSION_ID>"}}`
+    RunnableWithMessageHistory must always be called with a config that contains session_id, e.g. ``{"configurable": {"session_id": "<SESSION_ID>"}}`.
 
     Example (dict input):
         .. code-block:: python
@@ -82,9 +80,7 @@ class RunnableWithMessageHistory(RunnableBindingBase):
             # -> "The inverse of cosine is called arccosine ..."
 
 
-    Here's an example that uses an in memory chat history, and a factory that
-    takes in two keys (user_id and conversation id) to create a chat history instance.
-
+    Example (get_session_history takes two keys, user_id and conversation id):
         .. code-block:: python
 
             store = {}
@@ -164,46 +160,43 @@ class RunnableWithMessageHistory(RunnableBindingBase):
         """Initialize RunnableWithMessageHistory.
 
         Args:
-            runnable: The base Runnable to be wrapped.
-
-                Must take as input one of:
-                - A sequence of BaseMessages
-                - A dict with one key for all messages
-                - A dict with one key for the current input string/message(s) and
+            runnable: The base Runnable to be wrapped. Must take as input one of:
+                1. A sequence of BaseMessages
+                2. A dict with one key for all messages
+                3. A dict with one key for the current input string/message(s) and
                     a separate key for historical messages. If the input key points
                     to a string, it will be treated as a HumanMessage in history.
 
                 Must return as output one of:
-                - A string which can be treated as an AIMessage
-                - A BaseMessage or sequence of BaseMessages
-                - A dict with a key for a BaseMessage or sequence of BaseMessages
+                1. A string which can be treated as an AIMessage
+                2. A BaseMessage or sequence of BaseMessages
+                3. A dict with a key for a BaseMessage or sequence of BaseMessages
 
             get_session_history: Function that returns a new BaseChatMessageHistory.
                 This function should either take a single positional argument
                 `session_id` of type string and return a corresponding
                 chat message history instance.
+                .. code-block:: python
 
-                ```python
                     def get_session_history(
                         session_id: str,
                         *,
                         user_id: Optional[str]=None
                     ) -> BaseChatMessageHistory:
                       ...
-                ```
 
                 Or it should take keyword arguments that match the keys of
                 `session_history_config_specs` and return a corresponding
                 chat message history instance.
 
-                ```python
+                .. code-block:: python
+
                     def get_session_history(
                         *,
                         user_id: str,
                         thread_id: str,
                     ) -> BaseChatMessageHistory:
                         ...
-                ```
 
             input_messages_key: Must be specified if the base runnable accepts a dict
                 as input.
@@ -350,6 +343,12 @@ class RunnableWithMessageHistory(RunnableBindingBase):
         input_val = inputs[self.input_messages_key or "input"]
         input_messages = self._get_input_messages(input_val)
 
+        # If historic messages were prepended to the input messages, remove them to
+        # avoid adding duplicate messages to history.
+        if not self.history_messages_key:
+            historic_messages = config["configurable"]["message_history"].messages
+            input_messages = input_messages[len(historic_messages) :]
+
         # Get the output messages
         output_val = load(run.outputs)
         output_messages = self._get_output_messages(output_val)

libs/core/tests/unit_tests/runnables/test_history.py

@@ -1,4 +1,4 @@
-from typing import Any, Callable, Dict, List, Sequence, Union
+from typing import Any, Callable, Dict, List, Optional, Sequence, Union
 
 from langchain_core.messages import AIMessage, BaseMessage, HumanMessage, SystemMessage
 from langchain_core.pydantic_v1 import BaseModel
@@ -18,8 +18,10 @@ def test_interfaces() -> None:
     assert str(history) == "System: system\nHuman: human 1\nAI: ai\nHuman: human 2"
 
 
-def _get_get_session_history() -> Callable[..., ChatMessageHistory]:
-    chat_history_store = {}
+def _get_get_session_history(
+    *, store: Optional[Dict[str, Any]] = None
+) -> Callable[..., ChatMessageHistory]:
+    chat_history_store = store if store is not None else {}
 
     def get_session_history(session_id: str, **kwargs: Any) -> ChatMessageHistory:
         if session_id not in chat_history_store:
@@ -34,13 +36,24 @@ def test_input_messages() -> None:
         lambda messages: "you said: "
         + "\n".join(str(m.content) for m in messages if isinstance(m, HumanMessage))
     )
-    get_session_history = _get_get_session_history()
+    store: Dict = {}
+    get_session_history = _get_get_session_history(store=store)
     with_history = RunnableWithMessageHistory(runnable, get_session_history)
     config: RunnableConfig = {"configurable": {"session_id": "1"}}
     output = with_history.invoke([HumanMessage(content="hello")], config)
     assert output == "you said: hello"
     output = with_history.invoke([HumanMessage(content="good bye")], config)
     assert output == "you said: hello\ngood bye"
+    assert store == {
+        "1": ChatMessageHistory(
+            messages=[
+                HumanMessage(content="hello"),
+                AIMessage(content="you said: hello"),
+                HumanMessage(content="good bye"),
+                AIMessage(content="you said: hello\ngood bye"),
+            ]
+        )
+    }
 
 
 def test_input_dict() -> None: