core[minor],langchain[patch],community[patch]: Move InMemory and File implementations of Chat History to core (#20752)

This PR moves the implementations for chat history to core. So it's
easier to determine which dependencies need to be broken / add
deprecation warnings

libs/community/langchain_community/chat_message_histories/file.py

@@ -1,45 +1,5 @@
-import json
-import logging
-from pathlib import Path
-from typing import List
+from langchain_core.chat_history import FileChatMessageHistory
 
-from langchain_core.chat_history import BaseChatMessageHistory
-from langchain_core.messages import (
-    BaseMessage,
-    messages_from_dict,
-    messages_to_dict,
-)
-
-logger = logging.getLogger(__name__)
-
-
-class FileChatMessageHistory(BaseChatMessageHistory):
-    """
-    Chat message history that stores history in a local file.
-
-    Args:
-        file_path: path of the local file to store the messages.
-    """
-
-    def __init__(self, file_path: str):
-        self.file_path = Path(file_path)
-        if not self.file_path.exists():
-            self.file_path.touch()
-            self.file_path.write_text(json.dumps([]))
-
-    @property
-    def messages(self) -> List[BaseMessage]:  # type: ignore
-        """Retrieve the messages from the local file"""
-        items = json.loads(self.file_path.read_text())
-        messages = messages_from_dict(items)
-        return messages
-
-    def add_message(self, message: BaseMessage) -> None:
-        """Append the message to the record in the local file"""
-        messages = messages_to_dict(self.messages)
-        messages.append(messages_to_dict([message])[0])
-        self.file_path.write_text(json.dumps(messages))
-
-    def clear(self) -> None:
-        """Clear session memory from the local file"""
-        self.file_path.write_text(json.dumps([]))
+__all__ = [
+    "FileChatMessageHistory",
+]

libs/community/langchain_community/chat_message_histories/in_memory.py

@@ -1,31 +1,5 @@
-from typing import List, Sequence
+from langchain_core.chat_history import InMemoryChatMessageHistory as ChatMessageHistory
 
-from langchain_core.chat_history import BaseChatMessageHistory
-from langchain_core.messages import BaseMessage
-from langchain_core.pydantic_v1 import BaseModel, Field
-
-
-class ChatMessageHistory(BaseChatMessageHistory, BaseModel):
-    """In memory implementation of chat message history.
-
-    Stores messages in an in memory list.
-    """
-
-    messages: List[BaseMessage] = Field(default_factory=list)
-
-    async def aget_messages(self) -> List[BaseMessage]:
-        return self.messages
-
-    def add_message(self, message: BaseMessage) -> None:
-        """Add a self-created message to the store"""
-        self.messages.append(message)
-
-    async def aadd_messages(self, messages: Sequence[BaseMessage]) -> None:
-        """Add messages to the store"""
-        self.add_messages(messages)
-
-    def clear(self) -> None:
-        self.messages = []
-
-    async def aclear(self) -> None:
-        self.clear()
+__all__ = [
+    "ChatMessageHistory",
+]

libs/core/langchain_core/chat_history.py

@@ -16,7 +16,9 @@
 """  # noqa: E501
 from __future__ import annotations
 
+import json
 from abc import ABC, abstractmethod
+from pathlib import Path
 from typing import List, Sequence, Union
 
 from langchain_core.messages import (
@@ -24,7 +26,10 @@ from langchain_core.messages import (
     BaseMessage,
     HumanMessage,
     get_buffer_string,
+    messages_from_dict,
+    messages_to_dict,
 )
+from langchain_core.pydantic_v1 import BaseModel, Field
 from langchain_core.runnables import run_in_executor
 
 
@@ -184,3 +189,61 @@ class BaseChatMessageHistory(ABC):
     def __str__(self) -> str:
         """Return a string representation of the chat history."""
         return get_buffer_string(self.messages)
+
+
+class InMemoryChatMessageHistory(BaseChatMessageHistory, BaseModel):
+    """In memory implementation of chat message history.
+
+    Stores messages in an in memory list.
+    """
+
+    messages: List[BaseMessage] = Field(default_factory=list)
+
+    async def aget_messages(self) -> List[BaseMessage]:
+        return self.messages
+
+    def add_message(self, message: BaseMessage) -> None:
+        """Add a self-created message to the store"""
+        self.messages.append(message)
+
+    async def aadd_messages(self, messages: Sequence[BaseMessage]) -> None:
+        """Add messages to the store"""
+        self.add_messages(messages)
+
+    def clear(self) -> None:
+        self.messages = []
+
+    async def aclear(self) -> None:
+        self.clear()
+
+
+class FileChatMessageHistory(BaseChatMessageHistory):
+    """Chat message history that stores history in a local file."""
+
+    def __init__(self, file_path: str) -> None:
+        """Initialize the file path for the chat history.
+
+        Args:
+            file_path: The path to the local file to store the chat history.
+        """
+        self.file_path = Path(file_path)
+        if not self.file_path.exists():
+            self.file_path.touch()
+            self.file_path.write_text(json.dumps([]))
+
+    @property
+    def messages(self) -> List[BaseMessage]:  # type: ignore
+        """Retrieve the messages from the local file"""
+        items = json.loads(self.file_path.read_text())
+        messages = messages_from_dict(items)
+        return messages
+
+    def add_message(self, message: BaseMessage) -> None:
+        """Append the message to the record in the local file"""
+        messages = messages_to_dict(self.messages)
+        messages.append(messages_to_dict([message])[0])
+        self.file_path.write_text(json.dumps(messages))
+
+    def clear(self) -> None:
+        """Clear session memory from the local file"""
+        self.file_path.write_text(json.dumps([]))

libs/core/tests/unit_tests/chat_history/test_file_chat_message_history.py

@@ -3,9 +3,9 @@ from pathlib import Path
 from typing import Generator
 
 import pytest
-from langchain_core.messages import AIMessage, HumanMessage
 
-from langchain_community.chat_message_histories import FileChatMessageHistory
+from langchain_core.chat_history import FileChatMessageHistory
+from langchain_core.messages import AIMessage, HumanMessage
 
 
 @pytest.fixture

libs/langchain/langchain/memory/chat_memory.py

@@ -2,8 +2,10 @@ import warnings
 from abc import ABC
 from typing import Any, Dict, Optional, Tuple
 
-from langchain_community.chat_message_histories.in_memory import ChatMessageHistory
-from langchain_core.chat_history import BaseChatMessageHistory
+from langchain_core.chat_history import (
+    BaseChatMessageHistory,
+    InMemoryChatMessageHistory,
+)
 from langchain_core.memory import BaseMemory
 from langchain_core.messages import AIMessage, HumanMessage
 from langchain_core.pydantic_v1 import Field
@@ -14,7 +16,9 @@ from langchain.memory.utils import get_prompt_input_key
 class BaseChatMemory(BaseMemory, ABC):
     """Abstract base class for chat memory."""
 
-    chat_memory: BaseChatMessageHistory = Field(default_factory=ChatMessageHistory)
+    chat_memory: BaseChatMessageHistory = Field(
+        default_factory=InMemoryChatMessageHistory
+    )
     output_key: Optional[str] = None
     input_key: Optional[str] = None
     return_messages: bool = False