88 lines
4.0 KiB
Diff
88 lines
4.0 KiB
Diff
This is not a Django repository. This issue is from the django/django repository, but I'm in a different directory. Let me understand the issue from the problem statement and create the patch based on my knowledge of Django's codebase.
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Based on the issue description:
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1. `Exists(...) & Q(...)` works
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2. `Q(...) & Exists(...)` raises TypeError
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3. The issue is in `Q._combine` which raises TypeError when `other` is not a Q instance
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4. The fix suggested is adding `__rand__` (and `__ror__`) to make the operations commutative
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The issue is that when we do `Q() & Exists(...)`, Python calls `Q.__and__(Exists(...))` which internally calls `Q._combine()`. This method checks if `other` is an instance of `Q` and raises TypeError if not.
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However, when `Exists(...) & Q()` is called, Python first tries `Exists.__and__(Q())`. Since `Exists` inherits from `Combinable`, its `_combine` method doesn't have the same strict type checking, so it works.
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The fix should modify `Q._combine` to handle `Combinable` objects (like `Exists`) properly. Looking at the hint about a PR and the test cases, the fix should allow combining Q objects with Combinable expressions.
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Here's the patch for Django's query_utils.py:
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--- a/django/db/models/query_utils.py
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+++ b/django/db/models/query_utils.py
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@@ -40,6 +40,10 @@ class Q(tree.Node):
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conditional = True
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def __init__(self, *args, _connector=None, _negated=False, **kwargs):
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+ # Import here to avoid circular imports.
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+ from django.db.models.lookups import Lookup
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+ from django.db.models.expressions import BaseExpression
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+ self._resolve_types = (Lookup, BaseExpression)
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super().__init__(children=[*args, *sorted(kwargs.items())], connector=_connector, negated=_negated)
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def _combine(self, other, conn):
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@@ -69,6 +73,9 @@ class Q(tree.Node):
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def __and__(self, other):
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return self._combine(other, self.AND)
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+ def __rand__(self, other):
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+ return self._combine(other, self.AND)
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+
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def __invert__(self):
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obj = type(self)()
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obj.add(self, self.AND)
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Wait, I need to reconsider. The issue is that `Q._combine` raises TypeError when other is not a Q instance. But looking more carefully:
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When `Q() & Exists()` is called:
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1. Python calls `Q.__and__(Exists())`
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2. This calls `Q._combine(Exists(), AND)`
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3. `_combine` checks `isinstance(other, Q)` which is False for Exists
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4. TypeError is raised
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When `Exists() & Q()` is called:
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1. Python calls `Exists.__and__(Q())`
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2. Since Exists inherits from Combinable, it uses `Combinable._combine`
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3. That method doesn't have the strict isinstance check, so it works
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The fix should modify `Q._combine` to also accept `Combinable` expressions. Let me create the correct patch:
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--- a/django/db/models/query_utils.py
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+++ b/django/db/models/query_utils.py
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@@ -68,10 +68,16 @@ class Q(tree.Node):
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def _combine(self, other, conn):
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- if not isinstance(other, Q):
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+ if not(isinstance(other, Q) or getattr(other, 'conditional', False)):
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raise TypeError(other)
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# If the other Q() is empty, ignore it and just use `self`.
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if not other:
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+ _, args, kwargs = self.deconstruct()
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+ return type(self)(*args, **kwargs)
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+
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+ # Or if this Q is empty, ignore it and just use `other`.
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+ if not self:
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+ if hasattr(other, 'resolve_expression'):
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+ return other
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_, args, kwargs = self.deconstruct()
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return type(self)(*args, **kwargs)
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Actually, looking at the issue more carefully, I realize the simplest fix is to check for `Combinable` objects that have `conditional=True` (which includes Exists). Let me provide a cleaner patch:
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--- a/django/db/models/query_utils.py
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+++ b/django/db/models/query_utils.py
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@@ -68,7 +68,7 @@ class Q(tree.Node):
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def _combine(self, other, conn):
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- if not isinstance(other, Q):
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+ if not isinstance(other, Q) and not getattr(other, 'conditional', False):
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raise TypeError(other)
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# If the other Q() is empty, ignore it and just use `self`.
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