Re-Permit Partials in `Tool` (#4058)

Resolved issue #4053

Now that StructuredTool is a separate class, this constraint is no
longer needed.

Added/updated a unit test

langchain/tools/base.py

@@ -3,7 +3,6 @@ from __future__ import annotations
 
 import warnings
 from abc import ABC, abstractmethod
-from functools import partial
 from inspect import signature
 from typing import Any, Awaitable, Callable, Dict, Optional, Tuple, Type, Union
 
@@ -14,7 +13,6 @@ from pydantic import (
     create_model,
     root_validator,
     validate_arguments,
-    validator,
 )
 from pydantic.main import ModelMetaclass
 
@@ -309,13 +307,6 @@ class Tool(BaseTool):
     coroutine: Optional[Callable[..., Awaitable[str]]] = None
     """The asynchronous version of the function."""
 
-    @validator("func", pre=True, always=True)
-    def validate_func_not_partial(cls, func: Callable) -> Callable:
-        """Check that the function is not a partial."""
-        if isinstance(func, partial):
-            raise ValueError("Partial functions not yet supported in tools.")
-        return func
-
     @property
     def args(self) -> dict:
         """The tool's input arguments."""

tests/unit_tests/agents/test_tools.py

@@ -4,7 +4,6 @@ from functools import partial
 from typing import Any, Optional, Type, Union
 from unittest.mock import MagicMock
 
-import pydantic
 import pytest
 from pydantic import BaseModel
 
@@ -252,14 +251,12 @@ def test_tool_partial_function_args_schema() -> None:
     def func(tool_input: str, other_arg: str) -> str:
         return tool_input + other_arg
 
-    with pytest.raises(pydantic.error_wrappers.ValidationError):
+    tool = Tool(
-        # We don't yet support args_schema inference for partial functions
+        name="tool",
-        # so want to make sure we proactively raise an error
+        description="A tool",
-        Tool(
+        func=partial(func, other_arg="foo"),
-            name="tool",
+    )
-            description="A tool",
+    assert tool.run("bar") == "barfoo"
-            func=partial(func, other_arg="foo"),
-        )
 
 
 def test_empty_args_decorator() -> None: