Enable RUF017

.ruff.toml

@@ -243,7 +243,7 @@ select = [
     "RUF013",  # PEP 484 prohibits implicit `Optional`
 #    "RUF015",  # Prefer `next({iterable})` over single element slice
     "RUF016",  # Slice in indexed access to type `{value_type}` uses type `{index_type}` instead of an integer
-#    "RUF017",  # Avoid quadratic list summation
+    "RUF017",  # Avoid quadratic list summation
     "RUF018",  # Avoid assignment expressions in `assert` statements
     "RUF019",  # Unnecessary key check before dictionary access
     "RUF020",  # `{never_like} | T` is equivalent to `T`

sphinx/domains/python.py

@@ -5,7 +5,9 @@ from __future__ import annotations
 import ast
 import builtins
 import contextlib
+import functools
 import inspect
+import operator
 import re
 import token
 import typing
@@ -185,7 +187,7 @@ def _parse_annotation(annotation: str, env: BuildEnvironment) -> list[Node]:
             result.append(addnodes.desc_sig_punctuation('', ']'))
             return result
         if isinstance(node, ast.Module):
-            return sum((unparse(e) for e in node.body), [])
+            return functools.reduce(operator.iadd, (unparse(e) for e in node.body), [])
         if isinstance(node, ast.Name):
             return [nodes.Text(node.id)]
         if isinstance(node, ast.Subscript):

sphinx/ext/autodoc/__init__.py

@@ -7,6 +7,8 @@ for those who like elaborate docstrings.
 
 from __future__ import annotations
 
+import functools
+import operator
 import re
 import sys
 import warnings
@@ -923,7 +925,7 @@ class Documenter:
             except PycodeError:
                 pass
 
-        docstrings: list[str] = sum(self.get_doc() or [], [])
+        docstrings: list[str] = functools.reduce(operator.iadd, self.get_doc() or [], [])
         if ismock(self.object) and not docstrings:
             logger.warning(__('A mocked object is detected: %r'),
                            self.name, type='autodoc')
@@ -2054,7 +2056,8 @@ class DataDocumenter(GenericAliasMixin,
             return True
         else:
             doc = self.get_doc() or []
-            docstring, metadata = separate_metadata('\n'.join(sum(doc, [])))
+            docstring, metadata = separate_metadata(
+                '\n'.join(functools.reduce(operator.iadd, doc, [])))
             if 'hide-value' in metadata:
                 return True
 
@@ -2625,7 +2628,8 @@ class AttributeDocumenter(GenericAliasMixin, SlotsMixin,  # type: ignore[misc]
         else:
             doc = self.get_doc()
             if doc:
-                docstring, metadata = separate_metadata('\n'.join(sum(doc, [])))
+                docstring, metadata = separate_metadata(
+                    '\n'.join(functools.reduce(operator.iadd, doc, [])))
                 if 'hide-value' in metadata:
                     return True
 

sphinx/ext/autosummary/__init__.py

@@ -48,7 +48,9 @@ This can be used as the default role to make links 'smart'.
 
 from __future__ import annotations
 
+import functools
 import inspect
+import operator
 import os
 import posixpath
 import re
@@ -651,7 +653,8 @@ def import_by_name(
             tried.append(prefixed_name)
             errors.append(exc)
 
-    exceptions: list[BaseException] = sum((e.exceptions for e in errors), [])
+    exceptions: list[BaseException] = functools.reduce(
+        operator.iadd, (e.exceptions for e in errors), [])
     raise ImportExceptionGroup('no module named %s' % ' or '.join(tried), exceptions)
 
 

sphinx/ext/todo.py

@@ -7,6 +7,8 @@ with a backlink to the original location.
 
 from __future__ import annotations
 
+import functools
+import operator
 from typing import TYPE_CHECKING, Any, cast
 
 from docutils import nodes
@@ -129,7 +131,8 @@ class TodoListProcessor:
         self.process(doctree, docname)
 
     def process(self, doctree: nodes.document, docname: str) -> None:
-        todos: list[todo_node] = sum(self.domain.todos.values(), [])
+        todos: list[todo_node] = functools.reduce(
+            operator.iadd, self.domain.todos.values(), [])
         for node in list(doctree.findall(todolist)):
             if not self.config.todo_include_todos:
                 node.parent.remove(node)

sphinx/pycode/parser.py

@@ -4,8 +4,10 @@ from __future__ import annotations
 
 import ast
 import contextlib
+import functools
 import inspect
 import itertools
+import operator
 import re
 import tokenize
 from inspect import Signature
@@ -350,9 +352,8 @@ class VariableCommentPicker(ast.NodeVisitor):
         """Handles Assign node and pick up a variable comment."""
         try:
             targets = get_assign_targets(node)
-            varnames: list[str] = sum(
+            varnames: list[str] = functools.reduce(
-                [get_lvar_names(t, self=self.get_self()) for t in targets], [],
+                operator.iadd, [get_lvar_names(t, self=self.get_self()) for t in targets], [])
-            )
             current_line = self.get_line(node.lineno)
         except TypeError:
             return  # this assignment is not new definition!

tests/test_ext_autodoc.py

@@ -4,6 +4,8 @@ This tests mainly the Documenters; the auto directives are tested in a test
 source file translated by test_build.
 """
 
+import functools
+import operator
 import sys
 from types import SimpleNamespace
 from unittest.mock import Mock
@@ -330,7 +332,7 @@ def test_get_doc(app):
         inst.format_signature()  # handle docstring signatures!
         ds = inst.get_doc()
         # for testing purposes, concat them and strip the empty line at the end
-        res = sum(ds, [])[:-1]
+        res = functools.reduce(operator.iadd, ds, [])[:-1]
         print(res)
         return res