core[patch]: retain string type coercion for various IDs (#26429)

- `BaseMedia.id`
- `BaseMessage.id`
- `ToolMessage.tool_call_id`

Note: with this change we are actually less restrictive on types for
initializing `id` than in pydantic V1-- e.g., pydantic V1 will error if
you pass a dict or tuple to `id`). Let me know if we should restrict
type coercion. For tool_call_id I just enumerated supported types.

libs/core/langchain_core/documents/base.py

@@ -6,7 +6,7 @@ from io import BufferedReader, BytesIO
 from pathlib import PurePath
 from typing import Any, Dict, Generator, List, Literal, Optional, Union, cast
 
-from pydantic import ConfigDict, Field, model_validator
+from pydantic import ConfigDict, Field, field_validator, model_validator
 
 from langchain_core.load.serializable import Serializable
 
@@ -40,6 +40,13 @@ class BaseMedia(Serializable):
     metadata: dict = Field(default_factory=dict)
     """Arbitrary metadata associated with the content."""
 
+    @field_validator("id", mode="before")
+    def cast_id_to_str(cls, id_value: Any) -> Optional[str]:
+        if id_value is not None:
+            return str(id_value)
+        else:
+            return id_value
+
 
 class Blob(BaseMedia):
     """Blob represents raw data by either reference or value.

libs/core/langchain_core/messages/base.py

@@ -2,7 +2,7 @@ from __future__ import annotations
 
 from typing import TYPE_CHECKING, Any, Dict, List, Optional, Sequence, Union, cast
 
-from pydantic import ConfigDict, Field
+from pydantic import ConfigDict, Field, field_validator
 
 from langchain_core.load.serializable import Serializable
 from langchain_core.utils import get_bolded_text
@@ -56,6 +56,13 @@ class BaseMessage(Serializable):
         extra="allow",
     )
 
+    @field_validator("id", mode="before")
+    def cast_id_to_str(cls, id_value: Any) -> Optional[str]:
+        if id_value is not None:
+            return str(id_value)
+        else:
+            return id_value
+
     def __init__(
         self, content: Union[str, List[Union[str, Dict]]], **kwargs: Any
     ) -> None:

libs/core/langchain_core/messages/tool.py

@@ -118,7 +118,7 @@ class ToolMessage(BaseMessage):
             pass
 
         tool_call_id = values["tool_call_id"]
-        if isinstance(tool_call_id, UUID):
+        if isinstance(tool_call_id, (UUID, int, float)):
             values["tool_call_id"] = str(tool_call_id)
         return values
 

libs/core/tests/unit_tests/documents/test_document.py

@@ -0,0 +1,12 @@
+from langchain_core.documents import Document
+
+
+def test_init() -> None:
+    for doc in [
+        Document(page_content="foo"),
+        Document(page_content="foo", metadata={"a": 1}),
+        Document(page_content="foo", id=None),
+        Document(page_content="foo", id="1"),
+        Document(page_content="foo", id=1),
+    ]:
+        assert isinstance(doc, Document)

libs/core/tests/unit_tests/test_messages.py

@@ -3,13 +3,13 @@ import uuid
 from typing import List, Type, Union
 
 import pytest
-from pydantic import ValidationError
 
 from langchain_core.documents import Document
 from langchain_core.load import dumpd, load
 from langchain_core.messages import (
     AIMessage,
     AIMessageChunk,
+    BaseMessage,
     ChatMessage,
     ChatMessageChunk,
     FunctionMessage,
@@ -33,6 +33,16 @@ from langchain_core.messages.tool import tool_call_chunk as create_tool_call_chu
 from langchain_core.utils._merge import merge_lists
 
 
+def test_message_init() -> None:
+    for doc in [
+        BaseMessage(type="foo", content="bar"),
+        BaseMessage(type="foo", content="bar", id=None),
+        BaseMessage(type="foo", content="bar", id="1"),
+        BaseMessage(type="foo", content="bar", id=1),
+    ]:
+        assert isinstance(doc, BaseMessage)
+
+
 def test_message_chunks() -> None:
     assert AIMessageChunk(content="I am", id="ai3") + AIMessageChunk(
         content=" indeed."
@@ -1001,9 +1011,6 @@ def test_tool_message_content() -> None:
 
 def test_tool_message_tool_call_id() -> None:
     ToolMessage("foo", tool_call_id="1")
-
-    # Currently we only handle UUID->str coercion manually.
     ToolMessage("foo", tool_call_id=uuid.uuid4())
-
-    with pytest.raises(ValidationError):
-        ToolMessage("foo", tool_call_id=1)
+    ToolMessage("foo", tool_call_id=1)
+    ToolMessage("foo", tool_call_id=1.0)