Refs #10929 -- Stopped forcing empty result value by PostgreSQL aggregates.

Per deprecation timeline.

django/contrib/postgres/aggregates/general.py

@@ -3,7 +3,7 @@ import warnings
 
 from django.contrib.postgres.fields import ArrayField
 from django.db.models import Aggregate, BooleanField, JSONField, TextField, Value
-from django.utils.deprecation import RemovedInDjango50Warning, RemovedInDjango51Warning
+from django.utils.deprecation import RemovedInDjango51Warning
 
 from .mixins import OrderableAggMixin
 
@@ -19,47 +19,11 @@ __all__ = [
 ]
 
 
-# RemovedInDjango50Warning
-NOT_PROVIDED = object()
-
-
-class DeprecatedConvertValueMixin:
-    def __init__(self, *expressions, default=NOT_PROVIDED, **extra):
-        if default is NOT_PROVIDED:
-            default = None
-            self._default_provided = False
-        else:
-            self._default_provided = True
-        super().__init__(*expressions, default=default, **extra)
-
-    def resolve_expression(self, *args, **kwargs):
-        resolved = super().resolve_expression(*args, **kwargs)
-        if not self._default_provided:
-            resolved.empty_result_set_value = getattr(
-                self, "deprecation_empty_result_set_value", self.deprecation_value
-            )
-        return resolved
-
-    def convert_value(self, value, expression, connection):
-        if value is None and not self._default_provided:
-            warnings.warn(self.deprecation_msg, category=RemovedInDjango50Warning)
-            return self.deprecation_value
-        return value
-
-
-class ArrayAgg(DeprecatedConvertValueMixin, OrderableAggMixin, Aggregate):
+class ArrayAgg(OrderableAggMixin, Aggregate):
     function = "ARRAY_AGG"
     template = "%(function)s(%(distinct)s%(expressions)s %(ordering)s)"
     allow_distinct = True
 
-    # RemovedInDjango50Warning
-    deprecation_value = property(lambda self: [])
-    deprecation_msg = (
-        "In Django 5.0, ArrayAgg() will return None instead of an empty list "
-        "if there are no rows. Pass default=None to opt into the new behavior "
-        "and silence this warning or default=[] to keep the previous behavior."
-    )
-
     @property
     def output_field(self):
         return ArrayField(self.source_expressions[0].output_field)
@@ -87,27 +51,14 @@ class BoolOr(Aggregate):
     output_field = BooleanField()
 
 
-class JSONBAgg(DeprecatedConvertValueMixin, OrderableAggMixin, Aggregate):
+class JSONBAgg(OrderableAggMixin, Aggregate):
     function = "JSONB_AGG"
     template = "%(function)s(%(distinct)s%(expressions)s %(ordering)s)"
     allow_distinct = True
     output_field = JSONField()
 
-    # RemovedInDjango50Warning
-    deprecation_value = "[]"
-    deprecation_empty_result_set_value = property(lambda self: [])
-    deprecation_msg = (
-        "In Django 5.0, JSONBAgg() will return None instead of an empty list "
-        "if there are no rows. Pass default=None to opt into the new behavior "
-        "and silence this warning or default=[] to keep the previous "
-        "behavior."
-    )
-
     # RemovedInDjango51Warning: When the deprecation ends, remove __init__().
-    #
-    # RemovedInDjango50Warning: When the deprecation ends, replace with:
-    # def __init__(self, *expressions, default=None, **extra):
-    def __init__(self, *expressions, default=NOT_PROVIDED, **extra):
+    def __init__(self, *expressions, default=None, **extra):
         super().__init__(*expressions, default=default, **extra)
         if (
             isinstance(default, Value)
@@ -136,20 +87,12 @@ class JSONBAgg(DeprecatedConvertValueMixin, OrderableAggMixin, Aggregate):
                 )
 
 
-class StringAgg(DeprecatedConvertValueMixin, OrderableAggMixin, Aggregate):
+class StringAgg(OrderableAggMixin, Aggregate):
     function = "STRING_AGG"
     template = "%(function)s(%(distinct)s%(expressions)s %(ordering)s)"
     allow_distinct = True
     output_field = TextField()
 
-    # RemovedInDjango50Warning
-    deprecation_value = ""
-    deprecation_msg = (
-        "In Django 5.0, StringAgg() will return None instead of an empty "
-        "string if there are no rows. Pass default=None to opt into the new "
-        'behavior and silence this warning or default="" to keep the previous behavior.'
-    )
-
     def __init__(self, expression, delimiter, **extra):
         delimiter_expr = Value(str(delimiter))
         super().__init__(expression, delimiter_expr, **extra)

docs/ref/contrib/postgres/aggregates.txt

@@ -52,12 +52,11 @@ General-purpose aggregation functions
             from django.db.models import F
             F('some_field').desc()
 
-    .. deprecated:: 4.0
+    .. versionchanged:: 5.0
 
-        If there are no rows and ``default`` is not provided, ``ArrayAgg``
-        returns an empty list instead of ``None``. This behavior is deprecated
-        and will be removed in Django 5.0. If you need it, explicitly set
-        ``default`` to ``Value([])``.
+        In older versions, if there are no rows and ``default`` is not
+        provided, ``ArrayAgg`` returned an empty list instead of ``None``. If
+        you need it, explicitly set ``default`` to ``Value([])``.
 
 ``BitAnd``
 ----------
@@ -173,12 +172,11 @@ General-purpose aggregation functions
             {'parking': True, 'double_bed': True}
         ]}]>
 
-    .. deprecated:: 4.0
+    .. versionchanged:: 5.0
 
-        If there are no rows and ``default`` is not provided, ``JSONBAgg``
-        returns an empty list instead of ``None``. This behavior is deprecated
-        and will be removed in Django 5.0. If you need it, explicitly set
-        ``default`` to ``Value('[]')``.
+        In older versions, if there are no rows and ``default`` is not
+        provided, ``JSONBAgg`` returned an empty list instead of ``None``. If
+        you need it, explicitly set ``default`` to ``Value([])``.
 
 ``StringAgg``
 -------------
@@ -232,12 +230,11 @@ General-purpose aggregation functions
             'headline': 'NASA uses Python', 'publication_names': 'Science News, The Python Journal'
         }]>
 
-    .. deprecated:: 4.0
+    .. versionchanged:: 5.0
 
-        If there are no rows and ``default`` is not provided, ``StringAgg``
-        returns an empty string instead of ``None``. This behavior is
-        deprecated and will be removed in Django 5.0. If you need it,
-        explicitly set ``default`` to ``Value('')``.
+        In older versions, if there are no rows and ``default`` is not
+        provided, ``StringAgg`` returned an empty string instead of ``None``.
+        If you need it, explicitly set ``default`` to ``Value("")``.
 
 Aggregate functions for statistics
 ==================================

docs/releases/5.0.txt

@@ -270,6 +270,10 @@ to remove usage of these features.
 * The ``extra_tests`` argument for ``DiscoverRunner.build_suite()`` and
   ``DiscoverRunner.run_tests()`` is removed.
 
+* The ``django.contrib.postgres.aggregates.ArrayAgg``, ``JSONBAgg``, and
+  ``StringAgg`` aggregates no longer return ``[]``, ``[]``, and ``''``,
+  respectively, when there are no rows.
+
 See :ref:`deprecated-features-4.1` for details on these changes, including how
 to remove usage of these features.
 

tests/postgres_tests/test_aggregates.py

@@ -16,7 +16,7 @@ from django.db.models.functions import Cast, Concat, Substr
 from django.test import skipUnlessDBFeature
 from django.test.utils import Approximate, ignore_warnings
 from django.utils import timezone
-from django.utils.deprecation import RemovedInDjango50Warning, RemovedInDjango51Warning
+from django.utils.deprecation import RemovedInDjango51Warning
 
 from . import PostgreSQLTestCase
 from .models import AggregateTestModel, HotelReservation, Room, StatTestModel
@@ -84,36 +84,35 @@ class TestGeneralAggregate(PostgreSQLTestCase):
             ]
         )
 
-    @ignore_warnings(category=RemovedInDjango50Warning)
     def test_empty_result_set(self):
         AggregateTestModel.objects.all().delete()
         tests = [
-            (ArrayAgg("char_field"), []),
-            (ArrayAgg("integer_field"), []),
-            (ArrayAgg("boolean_field"), []),
-            (BitAnd("integer_field"), None),
-            (BitOr("integer_field"), None),
-            (BoolAnd("boolean_field"), None),
-            (BoolOr("boolean_field"), None),
-            (JSONBAgg("integer_field"), []),
-            (StringAgg("char_field", delimiter=";"), ""),
+            ArrayAgg("char_field"),
+            ArrayAgg("integer_field"),
+            ArrayAgg("boolean_field"),
+            BitAnd("integer_field"),
+            BitOr("integer_field"),
+            BoolAnd("boolean_field"),
+            BoolOr("boolean_field"),
+            JSONBAgg("integer_field"),
+            StringAgg("char_field", delimiter=";"),
         ]
         if connection.features.has_bit_xor:
             tests.append((BitXor("integer_field"), None))
-        for aggregation, expected_result in tests:
+        for aggregation in tests:
             with self.subTest(aggregation=aggregation):
                 # Empty result with non-execution optimization.
                 with self.assertNumQueries(0):
                     values = AggregateTestModel.objects.none().aggregate(
                         aggregation=aggregation,
                     )
-                    self.assertEqual(values, {"aggregation": expected_result})
+                    self.assertEqual(values, {"aggregation": None})
                 # Empty result when query must be executed.
                 with self.assertNumQueries(1):
                     values = AggregateTestModel.objects.aggregate(
                         aggregation=aggregation,
                     )
-                    self.assertEqual(values, {"aggregation": expected_result})
+                    self.assertEqual(values, {"aggregation": None})
 
     def test_default_argument(self):
         AggregateTestModel.objects.all().delete()
@@ -153,57 +152,6 @@ class TestGeneralAggregate(PostgreSQLTestCase):
                     )
                     self.assertEqual(values, {"aggregation": expected_result})
 
-    def test_convert_value_deprecation(self):
-        AggregateTestModel.objects.all().delete()
-        queryset = AggregateTestModel.objects.all()
-
-        with self.assertWarnsMessage(
-            RemovedInDjango50Warning, ArrayAgg.deprecation_msg
-        ):
-            queryset.aggregate(aggregation=ArrayAgg("boolean_field"))
-
-        with self.assertWarnsMessage(
-            RemovedInDjango50Warning, JSONBAgg.deprecation_msg
-        ):
-            queryset.aggregate(aggregation=JSONBAgg("integer_field"))
-
-        with self.assertWarnsMessage(
-            RemovedInDjango50Warning, StringAgg.deprecation_msg
-        ):
-            queryset.aggregate(aggregation=StringAgg("char_field", delimiter=";"))
-
-        # No warnings raised if default argument provided.
-        self.assertEqual(
-            queryset.aggregate(aggregation=ArrayAgg("boolean_field", default=None)),
-            {"aggregation": None},
-        )
-        self.assertEqual(
-            queryset.aggregate(aggregation=JSONBAgg("integer_field", default=None)),
-            {"aggregation": None},
-        )
-        self.assertEqual(
-            queryset.aggregate(
-                aggregation=StringAgg("char_field", delimiter=";", default=None),
-            ),
-            {"aggregation": None},
-        )
-        self.assertEqual(
-            queryset.aggregate(
-                aggregation=ArrayAgg("boolean_field", default=Value([]))
-            ),
-            {"aggregation": []},
-        )
-        self.assertEqual(
-            queryset.aggregate(aggregation=JSONBAgg("integer_field", default=[])),
-            {"aggregation": []},
-        )
-        self.assertEqual(
-            queryset.aggregate(
-                aggregation=StringAgg("char_field", delimiter=";", default=Value("")),
-            ),
-            {"aggregation": ""},
-        )
-
     @ignore_warnings(category=RemovedInDjango51Warning)
     def test_jsonb_agg_default_str_value(self):
         AggregateTestModel.objects.all().delete()