Fix mutable default arguments in OrderingFilter methods (#9742)

* Install and configure flake8-bugbear to spot mutable default arguments * Fix mutable default arguments in OrderingFilter methods - Fixed get_default_valid_fields() and get_valid_fields() methods in filters.py - Changed context={} default parameter to context=None to prevent mutable default anti-pattern - Added proper None checking with context = {} assignment inside methods Why this fix is important: - Mutable default arguments (context={}) create shared state across function calls - Same dict object gets reused, potentially causing unexpected side effects - This is a well-known Python anti-pattern that can lead to bugs What was changed: - Line 249: get_default_valid_fields(self, queryset, view, context=None) - Line 285: get_valid_fields(self, queryset, view, context=None) - Added 'if context is None: context = {}' in both methods Testing results: - All existing filter tests pass (pytest tests/test_filters.py) - Custom verification script confirms fix works correctly - Maintains backward compatibility - No breaking changes to API Addresses GitHub issue #9741 --------- Co-authored-by: Bruno Alla <alla.brunoo@gmail.com>

Author: killerdevildog

.pre-commit-config.yaml

@@ -18,6 +18,7 @@ repos:
  - id: flake8
  additional_dependencies:
  - flake8-tidy-imports
+ - flake8-bugbear
 - repo: https://github.com/adamchainz/blacken-docs
  rev: 1.20.0
  hooks:

rest_framework/filters.py

@@ -249,7 +249,9 @@ def get_default_ordering(self, view):
  return (ordering,)
  return ordering
 
- def get_default_valid_fields(self, queryset, view, context={}):
+ def get_default_valid_fields(self, queryset, view, context=None):
+ if context is None:
+ context = {}
  # If `ordering_fields` is not specified, then we determine a default
  # based on the serializer class, if one exists on the view.
  if hasattr(view, 'get_serializer_class'):
@@ -286,7 +288,9 @@ def get_default_valid_fields(self, queryset, view, context={}):
  )
  ]
 
- def get_valid_fields(self, queryset, view, context={}):
+ def get_valid_fields(self, queryset, view, context=None):
+ if context is None:
+ context = {}
  valid_fields = getattr(view, 'ordering_fields', self.ordering_fields)
 
  if valid_fields is None:

setup.cfg

@@ -1,3 +1,4 @@
 [flake8]
-ignore = E501,W503,W504
+extend-ignore = E501,W503,W504,B
+extend-select = B006
 banned-modules = json = use from rest_framework.utils import json!