chore(core): fix some ruff preview rules (#32785)

Co-authored-by: Mason Daugherty <mason@langchain.dev>

libs/core/langchain_core/_api/deprecation.py

@@ -361,7 +361,8 @@ def deprecated(
         # Modify the docstring to include a deprecation notice.
         if (
             _alternative
-            and _alternative.split(".")[-1].lower() == _alternative.split(".")[-1]
+            and _alternative.rsplit(".", maxsplit=1)[-1].lower()
+            == _alternative.rsplit(".", maxsplit=1)[-1]
         ):
             _alternative = f":meth:`~{_alternative}`"
         elif _alternative:
@@ -369,8 +370,8 @@ def deprecated(
 
         if (
             _alternative_import
-            and _alternative_import.split(".")[-1].lower()
-            == _alternative_import.split(".")[-1]
+            and _alternative_import.rsplit(".", maxsplit=1)[-1].lower()
+            == _alternative_import.rsplit(".", maxsplit=1)[-1]
         ):
             _alternative_import = f":meth:`~{_alternative_import}`"
         elif _alternative_import:
@@ -474,7 +475,7 @@ def warn_deprecated(
     if not message:
         message = ""
         package_ = (
-            package or name.split(".")[0].replace("_", "-")
+            package or name.split(".", maxsplit=1)[0].replace("_", "-")
             if "." in name
             else "LangChain"
         )
@@ -493,7 +494,7 @@ def warn_deprecated(
                 message += f" and will be removed {removal}"
 
         if alternative_import:
-            alt_package = alternative_import.split(".")[0].replace("_", "-")
+            alt_package = alternative_import.split(".", maxsplit=1)[0].replace("_", "-")
             if alt_package == package_:
                 message += f". Use {alternative_import} instead."
             else:

libs/core/langchain_core/embeddings/fake.py

@@ -119,7 +119,8 @@ class DeterministicFakeEmbedding(Embeddings, BaseModel):
         rng = np.random.default_rng(seed)
         return list(rng.normal(size=self.size))
 
-    def _get_seed(self, text: str) -> int:
+    @staticmethod
+    def _get_seed(text: str) -> int:
         """Get a seed for the random generator, using the hash of the text."""
         return int(hashlib.sha256(text.encode("utf-8")).hexdigest(), 16) % 10**8
 

libs/core/langchain_core/language_models/chat_models.py

@@ -148,8 +148,6 @@ def _format_for_tracing(messages: list[BaseMessage]) -> list[BaseMessage]:
                             "type": key,
                             key: block[key],
                         }
-                    else:
-                        pass
         messages_to_trace.append(message_to_trace)
 
     return messages_to_trace

libs/core/langchain_core/messages/ai.py

@@ -352,10 +352,7 @@ class AIMessageChunk(AIMessage, BaseMessageChunk):
 
         for chunk in self.tool_call_chunks:
             try:
-                if chunk["args"] is not None and chunk["args"] != "":
-                    args_ = parse_partial_json(chunk["args"])
-                else:
-                    args_ = {}
+                args_ = parse_partial_json(chunk["args"]) if chunk["args"] else {}
                 if isinstance(args_, dict):
                     tool_calls.append(
                         create_tool_call(

libs/core/langchain_core/messages/base.py

@@ -179,9 +179,7 @@ def merge_content(
         elif merged and isinstance(merged[-1], str):
             merged[-1] += content
         # If second content is an empty string, treat as a no-op
-        elif content == "":
-            pass
-        else:
+        elif content:
             # Otherwise, add the second content as a new element of the list
             merged.append(content)
     return merged

libs/core/langchain_core/output_parsers/json.py

@@ -46,11 +46,13 @@ class JsonOutputParser(BaseCumulativeTransformOutputParser[Any]):
     def _diff(self, prev: Optional[Any], next: Any) -> Any:
         return jsonpatch.make_patch(prev, next).patch
 
-    def _get_schema(self, pydantic_object: type[TBaseModel]) -> dict[str, Any]:
+    @staticmethod
+    def _get_schema(pydantic_object: type[TBaseModel]) -> dict[str, Any]:
         if issubclass(pydantic_object, pydantic.BaseModel):
             return pydantic_object.model_json_schema()
         return pydantic_object.schema()
 
+    @override
     def parse_result(self, result: list[Generation], *, partial: bool = False) -> Any:
         """Parse the result of an LLM call to a JSON object.
 

libs/core/langchain_core/output_parsers/list.py

@@ -155,6 +155,7 @@ class CommaSeparatedListOutputParser(ListOutputParser):
         """
         return ["langchain", "output_parsers", "list"]
 
+    @override
     def get_format_instructions(self) -> str:
         """Return the format instructions for the comma-separated list output."""
         return (
@@ -162,6 +163,7 @@ class CommaSeparatedListOutputParser(ListOutputParser):
             "eg: `foo, bar, baz` or `foo,bar,baz`"
         )
 
+    @override
     def parse(self, text: str) -> list[str]:
         """Parse the output of an LLM call.
 
@@ -224,6 +226,7 @@ class MarkdownListOutputParser(ListOutputParser):
     pattern: str = r"^\s*[-*]\s([^\n]+)$"
     """The pattern to match a Markdown list item."""
 
+    @override
     def get_format_instructions(self) -> str:
         """Return the format instructions for the Markdown list output."""
         return "Your response should be a markdown list, eg: `- foo\n- bar\n- baz`"

libs/core/langchain_core/output_parsers/string.py

@@ -1,5 +1,7 @@
 """String output parser."""
 
+from typing_extensions import override
+
 from langchain_core.output_parsers.transform import BaseTransformOutputParser
 
 
@@ -29,6 +31,7 @@ class StrOutputParser(BaseTransformOutputParser[str]):
         """Return the output parser type for serialization."""
         return "default"
 
+    @override
     def parse(self, text: str) -> str:
         """Returns the input text with no changes."""
         return text

libs/core/langchain_core/prompts/base.py

@@ -210,7 +210,7 @@ class BasePromptTemplate(
         if self.metadata:
             config["metadata"] = {**config["metadata"], **self.metadata}
         if self.tags:
-            config["tags"] = config["tags"] + self.tags
+            config["tags"] += self.tags
         return self._call_with_config(
             self._format_prompt_with_error_handling,
             input,

libs/core/langchain_core/prompts/string.py

@@ -166,7 +166,7 @@ def mustache_schema(
                 prefix = section_stack.pop()
         elif type_ in {"section", "inverted section"}:
             section_stack.append(prefix)
-            prefix = prefix + tuple(key.split("."))
+            prefix += tuple(key.split("."))
             fields[prefix] = False
         elif type_ in {"variable", "no escape"}:
             fields[prefix + tuple(key.split("."))] = True

libs/core/langchain_core/runnables/graph_mermaid.py

@@ -155,7 +155,7 @@ def draw_mermaid(
         nonlocal mermaid_graph
         self_loop = len(edges) == 1 and edges[0].source == edges[0].target
         if prefix and not self_loop:
-            subgraph = prefix.split(":")[-1]
+            subgraph = prefix.rsplit(":", maxsplit=1)[-1]
             if subgraph in seen_subgraphs:
                 msg = (
                     f"Found duplicate subgraph '{subgraph}' -- this likely means that "
@@ -214,7 +214,7 @@ def draw_mermaid(
 
     # Add remaining subgraphs with edges
     for prefix, edges_ in edge_groups.items():
-        if ":" in prefix or prefix == "":
+        if not prefix or ":" in prefix:
             continue
         add_subgraph(edges_, prefix)
         seen_subgraphs.add(prefix)

libs/core/langchain_core/tracers/core.py

@@ -82,7 +82,7 @@ class _TracerCore(ABC):
         """Map of run ID to (trace_id, dotted_order). Cleared when tracer GCed."""
 
     @abstractmethod
-    def _persist_run(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:
+    def _persist_run(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:
         """Persist a run."""
 
     @staticmethod
@@ -108,7 +108,7 @@ class _TracerCore(ABC):
         except:  # noqa: E722
             return msg
 
-    def _start_trace(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # type: ignore[return]
+    def _start_trace(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # type: ignore[return]
         current_dotted_order = run.start_time.strftime("%Y%m%dT%H%M%S%fZ") + str(run.id)
         if run.parent_run_id:
             if parent := self.order_map.get(run.parent_run_id):
@@ -538,7 +538,7 @@ class _TracerCore(ABC):
         """Return self copied."""
         return self
 
-    def _end_trace(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _end_trace(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """End a trace for a run.
 
         Args:
@@ -546,7 +546,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_run_create(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_run_create(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process a run upon creation.
 
         Args:
@@ -554,7 +554,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_run_update(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_run_update(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process a run upon update.
 
         Args:
@@ -562,7 +562,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_llm_start(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_llm_start(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the LLM Run upon start.
 
         Args:
@@ -575,7 +575,7 @@ class _TracerCore(ABC):
         run: Run,  # noqa: ARG002
         token: str,  # noqa: ARG002
         chunk: Optional[Union[GenerationChunk, ChatGenerationChunk]],  # noqa: ARG002
-    ) -> Union[None, Coroutine[Any, Any, None]]:
+    ) -> Union[Coroutine[Any, Any, None], None]:
         """Process new LLM token.
 
         Args:
@@ -585,7 +585,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_llm_end(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_llm_end(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the LLM Run.
 
         Args:
@@ -593,7 +593,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_llm_error(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_llm_error(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the LLM Run upon error.
 
         Args:
@@ -601,7 +601,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_chain_start(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_chain_start(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the Chain Run upon start.
 
         Args:
@@ -609,7 +609,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_chain_end(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_chain_end(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the Chain Run.
 
         Args:
@@ -617,7 +617,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_chain_error(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_chain_error(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the Chain Run upon error.
 
         Args:
@@ -625,7 +625,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_tool_start(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_tool_start(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the Tool Run upon start.
 
         Args:
@@ -633,7 +633,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_tool_end(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_tool_end(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the Tool Run.
 
         Args:
@@ -641,7 +641,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_tool_error(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_tool_error(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the Tool Run upon error.
 
         Args:
@@ -649,7 +649,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_chat_model_start(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_chat_model_start(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the Chat Model Run upon start.
 
         Args:
@@ -657,7 +657,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_retriever_start(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_retriever_start(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the Retriever Run upon start.
 
         Args:
@@ -665,7 +665,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_retriever_end(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_retriever_end(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the Retriever Run.
 
         Args:
@@ -673,7 +673,7 @@ class _TracerCore(ABC):
         """
         return None
 
-    def _on_retriever_error(self, run: Run) -> Union[None, Coroutine[Any, Any, None]]:  # noqa: ARG002
+    def _on_retriever_error(self, run: Run) -> Union[Coroutine[Any, Any, None], None]:  # noqa: ARG002
         """Process the Retriever Run upon error.
 
         Args:

libs/core/langchain_core/utils/aiter.py

@@ -37,7 +37,7 @@ _no_default = object()
 # before 3.10, the builtin anext() was not available
 def py_anext(
     iterator: AsyncIterator[T], default: Union[T, Any] = _no_default
-) -> Awaitable[Union[T, None, Any]]:
+) -> Awaitable[Union[T, Any, None]]:
     """Pure-Python implementation of anext() for testing purposes.
 
     Closely matches the builtin anext() C implementation.

libs/core/langchain_core/utils/mustache.py

@@ -82,7 +82,7 @@ def l_sa_check(
     """
     # If there is a newline, or the previous tag was a standalone
     if literal.find("\n") != -1 or is_standalone:
-        padding = literal.split("\n")[-1]
+        padding = literal.rsplit("\n", maxsplit=1)[-1]
 
         # If all the characters since the last newline are spaces
         # Then the next tag could be a standalone

libs/core/langchain_core/utils/utils.py

@@ -134,7 +134,7 @@ def guard_import(
     try:
         module = importlib.import_module(module_name, package)
     except (ImportError, ModuleNotFoundError) as e:
-        pip_name = pip_name or module_name.split(".")[0].replace("_", "-")
+        pip_name = pip_name or module_name.split(".", maxsplit=1)[0].replace("_", "-")
         msg = (
             f"Could not import {module_name} python package. "
             f"Please install it with `pip install {pip_name}`."