core[patch]: fix beta, deprecated typing (#18877)

**Description:** 

While not technically incorrect, the TypeVar used for the `@beta`
decorator prevented pyright (and thus most vscode users) from correctly
seeing the types of functions/classes decorated with `@beta`.

This is in part due to a small bug in pyright
(https://github.com/microsoft/pyright/issues/7448 ) - however, the
`Type` bound in the typevar `C = TypeVar("C", Type, Callable)` is not
doing anything - classes are `Callables` by default, so by my
understanding binding to `Type` does not actually provide any more
safety - the modified annotation still works correctly for both
functions, properties, and classes.

---------

Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>
Co-authored-by: Bagatur <baskaryan@gmail.com>

libs/community/langchain_community/cache.py

@@ -403,7 +403,7 @@ class _RedisCacheBase(BaseCache, ABC):
         if results:
             for _, text in results.items():
                 try:
-                    generations.append(loads(text))
+                    generations.append(loads(cast(str, text)))
                 except Exception:
                     logger.warning(
                         "Retrieving a cache value that could not be deserialized "

libs/core/langchain_core/_api/beta_decorator.py

@@ -9,11 +9,12 @@ https://github.com/matplotlib/matplotlib/blob/main/lib/matplotlib/_api/deprecati
     This module is for internal use only.  Do not use it in your own code.
     We may change the API at any time with no warning.
 """
+
 import contextlib
 import functools
 import inspect
 import warnings
-from typing import Any, Callable, Generator, Type, TypeVar
+from typing import Any, Callable, Generator, Type, TypeVar, Union, cast
 
 from langchain_core._api.internal import is_caller_internal
 
@@ -25,7 +26,7 @@ class LangChainBetaWarning(DeprecationWarning):
 # PUBLIC API
 
 
-T = TypeVar("T", Type, Callable)
+T = TypeVar("T", bound=Union[Callable[..., Any], Type])
 
 
 def beta(
@@ -143,7 +144,7 @@ def beta(
                 obj.__init__ = functools.wraps(obj.__init__)(  # type: ignore[misc]
                     warn_if_direct_instance
                 )
-                return obj
+                return cast(T, obj)
 
         elif isinstance(obj, property):
             if not _obj_type:
@@ -202,7 +203,7 @@ def beta(
                 """
                 wrapper = functools.wraps(wrapped)(wrapper)
                 wrapper.__doc__ = new_doc
-                return wrapper
+                return cast(T, wrapper)
 
         old_doc = inspect.cleandoc(old_doc or "").strip("\n")
 
@@ -225,9 +226,10 @@ def beta(
         )
 
         if inspect.iscoroutinefunction(obj):
-            return finalize(awarning_emitting_wrapper, new_doc)
+            finalized = finalize(awarning_emitting_wrapper, new_doc)
         else:
-            return finalize(warning_emitting_wrapper, new_doc)
+            finalized = finalize(warning_emitting_wrapper, new_doc)
+        return cast(T, finalized)
 
     return beta
 

libs/core/langchain_core/_api/deprecation.py

@@ -14,7 +14,7 @@ import contextlib
 import functools
 import inspect
 import warnings
-from typing import Any, Callable, Generator, Type, TypeVar
+from typing import Any, Callable, Generator, Type, TypeVar, Union, cast
 
 from langchain_core._api.internal import is_caller_internal
 
@@ -30,7 +30,7 @@ class LangChainPendingDeprecationWarning(PendingDeprecationWarning):
 # PUBLIC API
 
 
-T = TypeVar("T", Type, Callable)
+T = TypeVar("T", bound=Union[Type, Callable[..., Any]])
 
 
 def deprecated(
@@ -182,7 +182,7 @@ def deprecated(
                 obj.__init__ = functools.wraps(obj.__init__)(  # type: ignore[misc]
                     warn_if_direct_instance
                 )
-                return obj
+                return cast(T, obj)
 
         elif isinstance(obj, property):
             if not _obj_type:
@@ -241,7 +241,7 @@ def deprecated(
                 """
                 wrapper = functools.wraps(wrapped)(wrapper)
                 wrapper.__doc__ = new_doc
-                return wrapper
+                return cast(T, wrapper)
 
         old_doc = inspect.cleandoc(old_doc or "").strip("\n")
 
@@ -267,9 +267,10 @@ def deprecated(
         )
 
         if inspect.iscoroutinefunction(obj):
-            return finalize(awarning_emitting_wrapper, new_doc)
+            finalized = finalize(awarning_emitting_wrapper, new_doc)
         else:
-            return finalize(warning_emitting_wrapper, new_doc)
+            finalized = finalize(warning_emitting_wrapper, new_doc)
+        return cast(T, finalized)
 
     return deprecate
 

libs/core/langchain_core/utils/function_calling.py

@@ -308,7 +308,7 @@ def convert_to_openai_function(
     elif isinstance(function, type) and issubclass(function, BaseModel):
         return cast(Dict, convert_pydantic_to_openai_function(function))
     elif isinstance(function, BaseTool):
-        return format_tool_to_openai_function(function)
+        return cast(Dict, format_tool_to_openai_function(function))
     elif callable(function):
         return convert_python_function_to_openai_function(function)
     else:

libs/core/tests/unit_tests/prompts/test_structured.py

@@ -23,7 +23,9 @@ def _fake_runnable(
 class FakeStructuredChatModel(FakeListChatModel):
     """Fake ChatModel for testing purposes."""
 
-    def with_structured_output(self, schema: Union[Dict, Type[BaseModel]]) -> Runnable:
+    def with_structured_output(
+        self, schema: Union[Dict, Type[BaseModel]], **kwargs: Any
+    ) -> Runnable:
         return RunnableLambda(partial(_fake_runnable, schema))
 
     @property

libs/experimental/langchain_experimental/graph_transformers/llm.py

@@ -1,5 +1,5 @@
 import asyncio
-from typing import Any, List, Optional, Sequence
+from typing import Any, List, Optional, Sequence, Type, cast
 
 from langchain_community.graphs.graph_document import GraphDocument, Node, Relationship
 from langchain_core.documents import Document
@@ -93,9 +93,14 @@ def optional_enum_field(
         return Field(..., description=description + additional_info, **field_kwargs)
 
 
+class _Graph(BaseModel):
+    nodes: Optional[List]
+    relationships: Optional[List]
+
+
 def create_simple_model(
     node_labels: Optional[List[str]] = None, rel_types: Optional[List[str]] = None
-) -> Any:
+) -> Type[_Graph]:
     """
     Simple model allows to limit node and/or relationship types.
     Doesn't have any node or relationship properties.
@@ -128,7 +133,7 @@ def create_simple_model(
             rel_types, description="The type of the relationship.", is_rel=True
         )
 
-    class DynamicGraph(BaseModel):
+    class DynamicGraph(_Graph):
         """Represents a graph document consisting of nodes and relationships."""
 
         nodes: Optional[List[SimpleNode]] = Field(description="List of nodes")
@@ -194,7 +199,7 @@ class LLMGraphTransformer:
         llm: BaseLanguageModel,
         allowed_nodes: List[str] = [],
         allowed_relationships: List[str] = [],
-        prompt: Optional[ChatPromptTemplate] = default_prompt,
+        prompt: ChatPromptTemplate = default_prompt,
         strict_mode: bool = True,
     ) -> None:
         if not hasattr(llm, "with_structured_output"):
@@ -217,7 +222,7 @@ class LLMGraphTransformer:
         an LLM based on the model's schema and constraints.
         """
         text = document.page_content
-        raw_schema = self.chain.invoke({"input": text})
+        raw_schema = cast(_Graph, self.chain.invoke({"input": text}))
         nodes = (
             [map_to_base_node(node) for node in raw_schema.nodes]
             if raw_schema.nodes
@@ -268,7 +273,7 @@ class LLMGraphTransformer:
         graph document.
         """
         text = document.page_content
-        raw_schema = await self.chain.ainvoke({"input": text})
+        raw_schema = cast(_Graph, await self.chain.ainvoke({"input": text}))
 
         nodes = (
             [map_to_base_node(node) for node in raw_schema.nodes]