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Fix mutable default arguments in OrderingFilter methods

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- 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
This commit is contained in:
Quaylyn Rimer 2025-07-17 18:41:59 -06:00
parent 2ae8c117da
commit 0b5cbea68e
1 changed files with 6 additions and 2 deletions
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8
rest_framework/filters.py
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@ -249,7 +249,9 @@ class OrderingFilter(BaseFilterBackend):
return (ordering,) return (ordering,)
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 # If `ordering_fields` is not specified, then we determine a default
# based on the serializer class, if one exists on the view. # based on the serializer class, if one exists on the view.
if hasattr(view, 'get_serializer_class'): if hasattr(view, 'get_serializer_class'):
@ -286,7 +288,9 @@ class OrderingFilter(BaseFilterBackend):
) )
] ]
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) valid_fields = getattr(view, 'ordering_fields', self.ordering_fields)
if valid_fields is None: if valid_fields is None: