Refs #11964, #26167 -- Made Expressions deconstructible.

django/db/models/expressions.py

@@ -5,6 +5,7 @@ from django.core.exceptions import EmptyResultSet, FieldError
 from django.db.backends import utils as backend_utils
 from django.db.models import fields
 from django.db.models.query_utils import Q
+from django.utils.deconstruct import deconstructible
 from django.utils.functional import cached_property
 
 
@@ -117,6 +118,7 @@ class Combinable:
         )
 
 
+@deconstructible
 class BaseExpression:
     """
     Base class for all query expressions.
@@ -339,6 +341,27 @@ class BaseExpression:
             if expr:
                 yield from expr.flatten()
 
+    def __eq__(self, other):
+        if self.__class__ != other.__class__:
+            return False
+        path, args, kwargs = self.deconstruct()
+        other_path, other_args, other_kwargs = other.deconstruct()
+        if (path, args) == (other_path, other_args):
+            kwargs = kwargs.copy()
+            other_kwargs = other_kwargs.copy()
+            output_field = type(kwargs.pop('output_field', None))
+            other_output_field = type(other_kwargs.pop('output_field', None))
+            if output_field == other_output_field:
+                return kwargs == other_kwargs
+        return False
+
+    def __hash__(self):
+        path, args, kwargs = self.deconstruct()
+        h = hash(path) ^ hash(args)
+        for kwarg in kwargs.items():
+            h ^= hash(kwarg)
+        return h
+
 
 class Expression(BaseExpression, Combinable):
     """
@@ -445,6 +468,7 @@ class TemporalSubtraction(CombinedExpression):
         return connection.ops.subtract_temporals(self.lhs.output_field.get_internal_type(), lhs, rhs)
 
 
+@deconstructible
 class F(Combinable):
     """
     An object capable of resolving references to existing query objects.
@@ -468,6 +492,12 @@ class F(Combinable):
     def desc(self, **kwargs):
         return OrderBy(self, descending=True, **kwargs)
 
+    def __eq__(self, other):
+        return self.__class__ == other.__class__ and self.name == other.name
+
+    def __hash__(self):
+        return hash(self.name)
+
 
 class ResolvedOuterRef(F):
     """
@@ -647,6 +677,12 @@ class RawSQL(Expression):
     def get_group_by_cols(self):
         return [self]
 
+    def __hash__(self):
+        h = hash(self.sql) ^ hash(self._output_field)
+        for param in self.params:
+            h ^= hash(param)
+        return h
+
 
 class Star(Expression):
     def __repr__(self):

tests/expressions/tests.py

@@ -5,7 +5,7 @@ from copy import deepcopy
 
 from django.core.exceptions import FieldError
 from django.db import DatabaseError, connection, models, transaction
-from django.db.models import TimeField, UUIDField
+from django.db.models import CharField, TimeField, UUIDField
 from django.db.models.aggregates import (
     Avg, Count, Max, Min, StdDev, Sum, Variance,
 )
@@ -18,7 +18,9 @@ from django.db.models.functions import (
 )
 from django.db.models.sql import constants
 from django.db.models.sql.datastructures import Join
-from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature
+from django.test import (
+    SimpleTestCase, TestCase, skipIfDBFeature, skipUnlessDBFeature,
+)
 from django.test.utils import Approximate
 
 from .models import (
@@ -653,17 +655,42 @@ class IterableLookupInnerExpressionsTests(TestCase):
         self.assertQuerysetEqual(queryset, ["<Result: Result at 2016-02-04 15:00:00>"])
 
 
-class ExpressionsTests(TestCase):
+class FTests(SimpleTestCase):
 
-    def test_F_object_deepcopy(self):
+    def test_deepcopy(self):
-        """
-        Make sure F objects can be deepcopied (#23492)
-        """
         f = F("foo")
         g = deepcopy(f)
         self.assertEqual(f.name, g.name)
 
-    def test_f_reuse(self):
+    def test_deconstruct(self):
+        f = F('name')
+        path, args, kwargs = f.deconstruct()
+        self.assertEqual(path, 'django.db.models.expressions.F')
+        self.assertEqual(args, (f.name,))
+        self.assertEqual(kwargs, {})
+
+    def test_equal(self):
+        f = F('name')
+        same_f = F('name')
+        other_f = F('username')
+        self.assertEqual(f, same_f)
+        self.assertNotEqual(f, other_f)
+
+    def test_hash(self):
+        d = {F('name'): 'Bob'}
+        self.assertIn(F('name'), d)
+        self.assertEqual(d[F('name')], 'Bob')
+
+    def test_not_equal_Value(self):
+        f = F('name')
+        value = Value('name')
+        self.assertNotEqual(f, value)
+        self.assertNotEqual(value, f)
+
+
+class ExpressionsTests(TestCase):
+
+    def test_F_reuse(self):
         f = F('id')
         n = Number.objects.create(integer=-1)
         c = Company.objects.create(
@@ -1238,6 +1265,42 @@ class ValueTests(TestCase):
         UUID.objects.update(uuid=Value(uuid.UUID('12345678901234567890123456789012'), output_field=UUIDField()))
         self.assertEqual(UUID.objects.get().uuid, uuid.UUID('12345678901234567890123456789012'))
 
+    def test_deconstruct(self):
+        value = Value('name')
+        path, args, kwargs = value.deconstruct()
+        self.assertEqual(path, 'django.db.models.expressions.Value')
+        self.assertEqual(args, (value.value,))
+        self.assertEqual(kwargs, {})
+
+    def test_deconstruct_output_field(self):
+        value = Value('name', output_field=CharField())
+        path, args, kwargs = value.deconstruct()
+        self.assertEqual(path, 'django.db.models.expressions.Value')
+        self.assertEqual(args, (value.value,))
+        self.assertEqual(len(kwargs), 1)
+        self.assertEqual(kwargs['output_field'].deconstruct(), CharField().deconstruct())
+
+    def test_equal(self):
+        value = Value('name')
+        same_value = Value('name')
+        other_value = Value('username')
+        self.assertEqual(value, same_value)
+        self.assertNotEqual(value, other_value)
+
+    def test_hash(self):
+        d = {Value('name'): 'Bob'}
+        self.assertIn(Value('name'), d)
+        self.assertEqual(d[Value('name')], 'Bob')
+
+    def test_equal_output_field(self):
+        value = Value('name', output_field=CharField())
+        same_value = Value('name', output_field=CharField())
+        other_value = Value('name', output_field=TimeField())
+        no_output_field = Value('name')
+        self.assertEqual(value, same_value)
+        self.assertNotEqual(value, other_value)
+        self.assertNotEqual(value, no_output_field)
+
 
 class ReprTests(TestCase):