core,groq,openai,mistralai,robocorp,fireworks,anthropic[patch]: Update BaseModel subclass and instance checks to handle both v1 and proper namespaces (#24417)

After this PR chat models will correctly handle pydantic 2 with
bind_tools and with_structured_output.


```python
import pydantic
print(pydantic.__version__)
```
2.8.2

```python
from langchain_openai import ChatOpenAI
from pydantic import BaseModel, Field

class Add(BaseModel):
    x: int
    y: int

model = ChatOpenAI().bind_tools([Add])
print(model.invoke('2 + 5').tool_calls)

model = ChatOpenAI().with_structured_output(Add)
print(type(model.invoke('2 + 5')))
```

```
[{'name': 'Add', 'args': {'x': 2, 'y': 5}, 'id': 'call_PNUFa4pdfNOYXxIMHc6ps2Do', 'type': 'tool_call'}]
<class '__main__.Add'>
```


```python
from langchain_openai import ChatOpenAI
from pydantic.v1 import BaseModel, Field

class Add(BaseModel):
    x: int
    y: int

model = ChatOpenAI().bind_tools([Add])
print(model.invoke('2 + 5').tool_calls)

model = ChatOpenAI().with_structured_output(Add)
print(type(model.invoke('2 + 5')))
```

```python
[{'name': 'Add', 'args': {'x': 2, 'y': 5}, 'id': 'call_hhiHYP441cp14TtrHKx3Upg0', 'type': 'tool_call'}]
<class '__main__.Add'>
```

Addresses issues: https://github.com/langchain-ai/langchain/issues/22782

---------

Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

libs/standard-tests/langchain_standard_tests/unit_tests/chat_models.py

@@ -1,20 +1,58 @@
+"""Unit tests for chat models."""
 from abc import ABC, abstractmethod
 from typing import Any, List, Literal, Optional, Type
 
 import pytest
 from langchain_core.language_models import BaseChatModel
-from langchain_core.pydantic_v1 import BaseModel, Field, ValidationError
+from langchain_core.pydantic_v1 import BaseModel, Field
 from langchain_core.runnables import RunnableBinding
 from langchain_core.tools import tool
 
+from langchain_standard_tests.utils.pydantic import PYDANTIC_MAJOR_VERSION
 
-class Person(BaseModel):
+
+class Person(BaseModel):  # Used by some dependent tests. Should be deprecated.
     """Record attributes of a person."""
 
     name: str = Field(..., description="The name of the person.")
     age: int = Field(..., description="The age of the person.")
 
 
+def generate_schema_pydantic_v1_from_2() -> Any:
+    """Use to generate a schema from v1 namespace in pydantic 2."""
+    if PYDANTIC_MAJOR_VERSION != 2:
+        raise AssertionError("This function is only compatible with Pydantic v2.")
+    from pydantic.v1 import BaseModel, Field
+
+    class PersonB(BaseModel):
+        """Record attributes of a person."""
+
+        name: str = Field(..., description="The name of the person.")
+        age: int = Field(..., description="The age of the person.")
+
+    return PersonB
+
+
+def generate_schema_pydantic() -> Any:
+    """Works with either pydantic 1 or 2"""
+    from pydantic import BaseModel as BaseModelProper
+    from pydantic import Field as FieldProper
+
+    class PersonA(BaseModelProper):
+        """Record attributes of a person."""
+
+        name: str = FieldProper(..., description="The name of the person.")
+        age: int = FieldProper(..., description="The age of the person.")
+
+    return PersonA
+
+
+TEST_PYDANTIC_MODELS = [generate_schema_pydantic()]
+
+if PYDANTIC_MAJOR_VERSION == 2:
+    TEST_PYDANTIC_MODELS.append(generate_schema_pydantic_v1_from_2())
+
+
 @tool
 def my_adder_tool(a: int, b: int) -> int:
     """Takes two integers, a and b, and returns their sum."""
@@ -112,12 +150,18 @@ class ChatModelUnitTests(ChatModelTests):
         if not self.has_tool_calling:
             return
 
-        tool_model = model.bind_tools(
-            [Person, Person.schema(), my_adder_tool, my_adder], tool_choice="any"
-        )
+        tools = [my_adder_tool, my_adder]
+
+        for pydantic_model in TEST_PYDANTIC_MODELS:
+            tools.extend([pydantic_model, pydantic_model.schema()])
+
+        # Doing a mypy ignore here since some of the tools are from pydantic
+        # BaseModel 2 which isn't typed properly yet. This will need to be fixed
+        # so type checking does not become annoying to users.
+        tool_model = model.bind_tools(tools, tool_choice="any")  # type: ignore
         assert isinstance(tool_model, RunnableBinding)
 
-    @pytest.mark.parametrize("schema", [Person, Person.schema()])
+    @pytest.mark.parametrize("schema", TEST_PYDANTIC_MODELS)
     def test_with_structured_output(
         self,
         model: BaseChatModel,
@@ -129,6 +173,8 @@ class ChatModelUnitTests(ChatModelTests):
         assert model.with_structured_output(schema) is not None
 
     def test_standard_params(self, model: BaseChatModel) -> None:
+        from langchain_core.pydantic_v1 import BaseModel, ValidationError
+
         class ExpectedParams(BaseModel):
             ls_provider: str
             ls_model_name: str

libs/standard-tests/langchain_standard_tests/utils/pydantic.py

@@ -0,0 +1,14 @@
+"""Utilities for working with pydantic models."""
+
+
+def get_pydantic_major_version() -> int:
+    """Get the major version of Pydantic."""
+    try:
+        import pydantic
+
+        return int(pydantic.__version__.split(".")[0])
+    except ImportError:
+        return 0
+
+
+PYDANTIC_MAJOR_VERSION = get_pydantic_major_version()