core[patch]: Add ruff rules for PLW (Pylint Warnings) (#29288)

See https://docs.astral.sh/ruff/rules/#warning-w_1

---------

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

libs/core/langchain_core/messages/utils.py

@@ -504,7 +504,7 @@ def filter_messages(
                         )
                     ]
 
-                msg = msg.model_copy(
+                msg = msg.model_copy(  # noqa: PLW2901
                     update={"tool_calls": tool_calls, "content": content}
                 )
             elif (

libs/core/langchain_core/output_parsers/json.py

@@ -125,5 +125,11 @@ class JsonOutputParser(BaseCumulativeTransformOutputParser[Any]):
 
 # For backwards compatibility
 SimpleJsonOutputParser = JsonOutputParser
-parse_partial_json = parse_partial_json
-parse_and_check_json_markdown = parse_and_check_json_markdown
+
+
+__all__ = [
+    "JsonOutputParser",
+    "SimpleJsonOutputParser",  # For backwards compatibility
+    "parse_partial_json",  # For backwards compatibility
+    "parse_and_check_json_markdown",  # For backwards compatibility
+]

libs/core/langchain_core/output_parsers/list.py

@@ -73,9 +73,10 @@ class ListOutputParser(BaseTransformOutputParser[list[str]]):
                 chunk_content = chunk.content
                 if not isinstance(chunk_content, str):
                     continue
-                chunk = chunk_content
-            # add current chunk to buffer
-            buffer += chunk
+                buffer += chunk_content
+            else:
+                # add current chunk to buffer
+                buffer += chunk
             # parse buffer into a list of parts
             try:
                 done_idx = 0
@@ -105,9 +106,10 @@ class ListOutputParser(BaseTransformOutputParser[list[str]]):
                 chunk_content = chunk.content
                 if not isinstance(chunk_content, str):
                     continue
-                chunk = chunk_content
-            # add current chunk to buffer
-            buffer += chunk
+                buffer += chunk_content
+            else:
+                # add current chunk to buffer
+                buffer += chunk
             # parse buffer into a list of parts
             try:
                 done_idx = 0

libs/core/langchain_core/tracers/evaluation.py

@@ -29,7 +29,6 @@ _TRACERS: weakref.WeakSet[EvaluatorCallbackHandler] = weakref.WeakSet()
 
 def wait_for_all_evaluators() -> None:
     """Wait for all tracers to finish."""
-    global _TRACERS
     for tracer in list(_TRACERS):
         if tracer is not None:
             tracer.wait_for_futures()
@@ -100,7 +99,6 @@ class EvaluatorCallbackHandler(BaseTracer):
         self.project_name = project_name
         self.logged_eval_results: dict[tuple[str, str], list[EvaluationResult]] = {}
         self.lock = threading.Lock()
-        global _TRACERS
         _TRACERS.add(self)
 
     def _evaluate_in_project(self, run: Run, evaluator: langsmith.RunEvaluator) -> None:

libs/core/langchain_core/tracers/langchain.py

@@ -41,7 +41,6 @@ def log_error_once(method: str, exception: Exception) -> None:
         method: The method that raised the exception.
         exception: The exception that was raised.
     """
-    global _LOGGED
     if (method, type(exception)) in _LOGGED:
         return
     _LOGGED.add((method, type(exception)))
@@ -61,7 +60,7 @@ def get_client() -> Client:
 
 def _get_executor() -> ThreadPoolExecutor:
     """Get the executor."""
-    global _EXECUTOR
+    global _EXECUTOR  # noqa: PLW0603
     if _EXECUTOR is None:
         _EXECUTOR = ThreadPoolExecutor()
     return _EXECUTOR

libs/core/langchain_core/utils/_merge.py

@@ -96,9 +96,12 @@ def merge_lists(left: Optional[list], *others: Optional[list]) -> Optional[list]
                     if to_merge:
                         # TODO: Remove this once merge_dict is updated with special
                         # handling for 'type'.
-                        if "type" in e:
-                            e = {k: v for k, v in e.items() if k != "type"}
-                        merged[to_merge[0]] = merge_dicts(merged[to_merge[0]], e)
+                        new_e = (
+                            {k: v for k, v in e.items() if k != "type"}
+                            if "type" in e
+                            else e
+                        )
+                        merged[to_merge[0]] = merge_dicts(merged[to_merge[0]], new_e)
                     else:
                         merged.append(e)
                 else:

libs/core/langchain_core/utils/json.py

@@ -64,11 +64,14 @@ def parse_partial_json(s: str, *, strict: bool = False) -> Any:
 
     # Process each character in the string one at a time.
     for char in s:
+        new_char = char
         if is_inside_string:
             if char == '"' and not escaped:
                 is_inside_string = False
             elif char == "\n" and not escaped:
-                char = "\\n"  # Replace the newline character with the escape sequence.
+                new_char = (
+                    "\\n"  # Replace the newline character with the escape sequence.
+                )
             elif char == "\\":
                 escaped = not escaped
             else:
@@ -89,7 +92,7 @@ def parse_partial_json(s: str, *, strict: bool = False) -> Any:
                     return None
 
         # Append the processed character to the new string.
-        new_chars.append(char)
+        new_chars.append(new_char)
 
     # If we're still inside a string at the end of processing,
     # we need to close the string.

libs/core/langchain_core/utils/mustache.py

@@ -125,8 +125,6 @@ def parse_tag(template: str, l_del: str, r_del: str) -> tuple[tuple[str, str], s
         ChevronError: If the tag is unclosed.
         ChevronError: If the set delimiter tag is unclosed.
     """
-    global _CURRENT_LINE, _LAST_TAG_LINE
-
     tag_types = {
         "!": "comment",
         "#": "section",
@@ -352,32 +350,33 @@ def _get_key(
             if scope in (0, False):
                 return scope
 
+            resolved_scope = scope
             # For every dot separated key
             for child in key.split("."):
                 # Return an empty string if falsy, with two exceptions
                 # 0 should return 0, and False should return False
-                if scope in (0, False):
-                    return scope
+                if resolved_scope in (0, False):
+                    return resolved_scope
                 # Move into the scope
                 try:
                     # Try subscripting (Normal dictionaries)
-                    scope = cast(dict[str, Any], scope)[child]
+                    resolved_scope = cast(dict[str, Any], resolved_scope)[child]
                 except (TypeError, AttributeError):
                     try:
-                        scope = getattr(scope, child)
+                        resolved_scope = getattr(resolved_scope, child)
                     except (TypeError, AttributeError):
                         # Try as a list
-                        scope = scope[int(child)]  # type: ignore
+                        resolved_scope = resolved_scope[int(child)]  # type: ignore
 
             try:
                 # This allows for custom falsy data types
                 # https://github.com/noahmorrison/chevron/issues/35
-                if scope._CHEVRON_return_scope_when_falsy:  # type: ignore
-                    return scope
+                if resolved_scope._CHEVRON_return_scope_when_falsy:  # type: ignore
+                    return resolved_scope
             except AttributeError:
-                if scope in (0, False):
-                    return scope
-                return scope or ""
+                if resolved_scope in (0, False):
+                    return resolved_scope
+                return resolved_scope or ""
         except (AttributeError, KeyError, IndexError, ValueError):
             # We couldn't find the key in the current scope
             # We'll try again on the next pass

libs/core/pyproject.toml

@@ -77,7 +77,7 @@ target-version = "py39"
 
 
 [tool.ruff.lint]
-select = [ "ANN", "ASYNC", "B", "C4", "COM", "DJ", "E", "EM", "EXE", "F", "FLY", "FURB", "I", "ICN", "INT", "LOG", "N", "NPY", "PD", "PIE", "PTH", "Q", "RSE", "S", "SIM", "SLOT", "T10", "T201", "TC", "TID", "TRY", "UP", "W", "YTT",]
+select = [ "ANN", "ASYNC", "B", "C4", "COM", "DJ", "E", "EM", "EXE", "F", "FLY", "FURB", "I", "ICN", "INT", "LOG", "N", "NPY", "PD", "PIE", "PLW", "PTH", "Q", "RSE", "S", "SIM", "SLOT", "T10", "T201", "TC", "TID", "TRY", "UP", "W", "YTT",]
 ignore = [ "ANN401", "COM812", "UP007", "S110", "S112", "TC001", "TC002", "TC003"]
 flake8-type-checking.runtime-evaluated-base-classes = ["pydantic.BaseModel","langchain_core.load.serializable.Serializable","langchain_core.runnables.base.RunnableSerializable"]
 flake8-annotations.allow-star-arg-any = true
@@ -96,6 +96,7 @@ filterwarnings = [ "ignore::langchain_core._api.beta_decorator.LangChainBetaWarn
 classmethod-decorators = [ "classmethod", "langchain_core.utils.pydantic.pre_init", "pydantic.field_validator", "pydantic.v1.root_validator",]
 
 [tool.ruff.lint.per-file-ignores]
+"langchain_core/utils/mustache.py" = [ "PLW0603",]
 "tests/unit_tests/prompts/test_chat.py" = [ "E501",]
 "tests/unit_tests/runnables/test_runnable.py" = [ "E501",]
 "tests/unit_tests/runnables/test_graph.py" = [ "E501",]

libs/core/tests/unit_tests/test_imports.py

@@ -22,7 +22,7 @@ def try_to_import(module_name: str) -> tuple[int, str]:
         getattr(module, cls_)
 
     result = subprocess.run(
-        ["python", "-c", f"import langchain_core.{module_name}"],
+        ["python", "-c", f"import langchain_core.{module_name}"], check=True
     )
     return result.returncode, module_name