move best-effort v1 conversion

libs/core/langchain_core/language_models/chat_models.py

@@ -58,9 +58,7 @@ from langchain_core.messages import (
     is_data_content_block,
     message_chunk_to_message,
 )
-from langchain_core.messages import content_blocks as types
 from langchain_core.messages.ai import _LC_ID_PREFIX
-from langchain_core.messages.v1 import AIMessage as AIMessageV1
 from langchain_core.outputs import (
     ChatGeneration,
     ChatGenerationChunk,
@@ -222,23 +220,6 @@ def _format_ls_structured_output(ls_structured_output_format: Optional[dict]) ->
     return ls_structured_output_format_dict
 
 
-def _convert_to_v1(message: AIMessage) -> AIMessageV1:
-    """Best-effort conversion of a V0 AIMessage to V1."""
-    if isinstance(message.content, str):
-        content: list[types.ContentBlock] = []
-        if message.content:
-            content = [{"type": "text", "text": message.content}]
-
-    for tool_call in message.tool_calls:
-        content.append(tool_call)
-
-    return AIMessageV1(
-        content=content,
-        usage_metadata=message.usage_metadata,
-        response_metadata=message.response_metadata,
-    )
-
-
 class BaseChatModel(BaseLanguageModel[BaseMessage], ABC):
     """Base class for chat models.
 

libs/core/langchain_core/prompt_values.py

@@ -8,9 +8,9 @@ from __future__ import annotations
 
 from abc import ABC, abstractmethod
 from collections.abc import Sequence
-from typing import Literal, cast
+from typing import Literal, Union, cast
 
-from typing_extensions import TypedDict
+from typing_extensions import TypedDict, overload
 
 from langchain_core.load.serializable import Serializable
 from langchain_core.messages import (
@@ -19,6 +19,52 @@ from langchain_core.messages import (
     HumanMessage,
     get_buffer_string,
 )
+from langchain_core.messages import content_blocks as types
+from langchain_core.messages import AIMessage, HumanMessage, SystemMessage, ToolMessage
+from langchain_core.messages.v1 import AIMessage as AIMessageV1
+from langchain_core.messages.v1 import HumanMessage as HumanMessageV1
+from langchain_core.messages.v1 import MessageV1
+from langchain_core.messages.v1 import SystemMessage as SystemMessageV1
+from langchain_core.messages.v1 import ToolMessage as ToolMessageV1
+
+
+def _convert_to_v1(message: BaseMessage) -> MessageV1:
+    """Best-effort conversion of a V0 AIMessage to V1."""
+    if isinstance(message.content, str):
+        content: list[types.ContentBlock] = []
+        if message.content:
+            content = [{"type": "text", "text": message.content}]
+    else:
+        content = []
+        for block in message.content:
+            if isinstance(block, str):
+                content.append({"type": "text", "text": block})
+            elif isinstance(block, dict):
+                content.append(block)
+            else:
+                pass
+
+    if isinstance(message, HumanMessage):
+        return HumanMessageV1(content=content)
+    if isinstance(message, AIMessage):
+        for tool_call in message.tool_calls:
+            content.append(tool_call)
+        return AIMessageV1(
+            content=content,
+            usage_metadata=message.usage_metadata,
+            response_metadata=message.response_metadata,
+            tool_calls=message.tool_calls,
+        )
+    if isinstance(message, SystemMessage):
+        return SystemMessageV1(content=content)
+    if isinstance(message, ToolMessage):
+        return ToolMessageV1(
+            tool_call_id=message.tool_call_id,
+            content=content,
+            artifact=message.artifact,
+        )
+    error_message = f"Unsupported message type: {type(message)}"
+    raise TypeError(error_message)
 
 
 class PromptValue(Serializable, ABC):
@@ -75,6 +121,26 @@ class StringPromptValue(PromptValue):
         """Return prompt as messages."""
         return [HumanMessage(content=self.text)]
 
+    @overload
+    def to_messages(
+        self, output_version: Literal["v0"] = "v0"
+    ) -> list[BaseMessage]: ...
+
+    @overload
+    def to_messages(self, output_version: Literal["v1"]) -> list[MessageV1]: ...
+
+    def to_messages(
+        self, output_version: Literal["v0", "v1"] = "v0"
+    ) -> Union[list[BaseMessage], list[MessageV1]]:
+        """Return prompt as a list of messages.
+
+        Args:
+            output_version: The output version, either "v0" (default) or "v1".
+        """
+        if output_version == "v1":
+            return [HumanMessageV1(content=self.text)]
+        return [HumanMessage(content=self.text)]
+
 
 class ChatPromptValue(PromptValue):
     """Chat prompt value.
@@ -89,8 +155,24 @@ class ChatPromptValue(PromptValue):
         """Return prompt as string."""
         return get_buffer_string(self.messages)
 
-    def to_messages(self) -> list[BaseMessage]:
+    @overload
-        """Return prompt as a list of messages."""
+    def to_messages(
+        self, output_version: Literal["v0"] = "v0"
+    ) -> list[BaseMessage]: ...
+
+    @overload
+    def to_messages(self, output_version: Literal["v1"]) -> list[MessageV1]: ...
+
+    def to_messages(
+        self, output_version: Literal["v0", "v1"] = "v0"
+    ) -> Union[list[BaseMessage], list[MessageV1]]:
+        """Return prompt as a list of messages.
+
+        Args:
+            output_version: The output version, either "v0" (default) or "v1".
+        """
+        if output_version == "v1":
+            return [_convert_to_v1(m) for m in self.messages]
         return list(self.messages)
 
     @classmethod