Refs #32508 -- Raised Type/ValueError instead of using "assert" in django.db.models.

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>

django/db/models/base.py

@@ -947,12 +947,12 @@ class Model(metaclass=ModelBase):
                     field.delete_cached_value(self)
 
     def delete(self, using=None, keep_parents=False):
+        if self.pk is None:
+            raise ValueError(
+                "%s object can't be deleted because its %s attribute is set "
+                "to None." % (self._meta.object_name, self._meta.pk.attname)
+            )
         using = using or router.db_for_write(self.__class__, instance=self)
-        assert self.pk is not None, (
-            "%s object can't be deleted because its %s attribute is set to None." %
-            (self._meta.object_name, self._meta.pk.attname)
-        )
-
         collector = Collector(using=using)
         collector.collect([self], keep_parents=keep_parents)
         return collector.delete()

django/db/models/fields/__init__.py

@@ -2484,10 +2484,11 @@ class AutoFieldMixin:
         return value
 
     def contribute_to_class(self, cls, name, **kwargs):
-        assert not cls._meta.auto_field, (
+        if cls._meta.auto_field:
-            "Model %s can't have more than one auto-generated field."
+            raise ValueError(
-            % cls._meta.label
+                "Model %s can't have more than one auto-generated field."
-        )
+                % cls._meta.label
+            )
         super().contribute_to_class(cls, name, **kwargs)
         cls._meta.auto_field = self
 

django/db/models/fields/related.py

@@ -815,13 +815,13 @@ class ForeignKey(ForeignObject):
         try:
             to._meta.model_name
         except AttributeError:
-            assert isinstance(to, str), (
+            if not isinstance(to, str):
-                "%s(%r) is invalid. First parameter to ForeignKey must be "
+                raise TypeError(
-                "either a model, a model name, or the string %r" % (
+                    '%s(%r) is invalid. First parameter to ForeignKey must be '
-                    self.__class__.__name__, to,
+                    'either a model, a model name, or the string %r' % (
-                    RECURSIVE_RELATIONSHIP_CONSTANT,
+                        self.__class__.__name__, to, RECURSIVE_RELATIONSHIP_CONSTANT,
+                    )
                 )
-            )
         else:
             # For backwards compatibility purposes, we need to *try* and set
             # the to_field during FK construction. It won't be guaranteed to
@@ -1169,18 +1169,20 @@ class ManyToManyField(RelatedField):
         try:
             to._meta
         except AttributeError:
-            assert isinstance(to, str), (
+            if not isinstance(to, str):
-                "%s(%r) is invalid. First parameter to ManyToManyField must be "
+                raise TypeError(
-                "either a model, a model name, or the string %r" %
+                    '%s(%r) is invalid. First parameter to ManyToManyField '
-                (self.__class__.__name__, to, RECURSIVE_RELATIONSHIP_CONSTANT)
+                    'must be either a model, a model name, or the string %r' % (
-            )
+                        self.__class__.__name__, to, RECURSIVE_RELATIONSHIP_CONSTANT,
+                    )
+                )
 
         if symmetrical is None:
             symmetrical = (to == RECURSIVE_RELATIONSHIP_CONSTANT)
 
-        if through is not None:
+        if through is not None and db_table is not None:
-            assert db_table is None, (
+            raise ValueError(
-                "Cannot specify a db_table if an intermediary model is used."
+                'Cannot specify a db_table if an intermediary model is used.'
             )
 
         kwargs['rel'] = self.rel_class(

django/db/models/functions/datetime.py

@@ -214,9 +214,10 @@ class TruncBase(TimezoneMixin, Transform):
         copy = super().resolve_expression(query, allow_joins, reuse, summarize, for_save)
         field = copy.lhs.output_field
         # DateTimeField is a subclass of DateField so this works for both.
-        assert isinstance(field, (DateField, TimeField)), (
+        if not isinstance(field, (DateField, TimeField)):
-            "%r isn't a DateField, TimeField, or DateTimeField." % field.name
+            raise TypeError(
-        )
+                "%r isn't a DateField, TimeField, or DateTimeField." % field.name
+            )
         # If self.output_field was None, then accessing the field will trigger
         # the resolver to assign it to self.lhs.output_field.
         if not isinstance(copy.output_field, (DateField, DateTimeField, TimeField)):

django/db/models/indexes.py

@@ -161,10 +161,11 @@ class Index:
             column_names[0][:7],
             '%s_%s' % (names_digest(*hash_data, length=6), self.suffix),
         )
-        assert len(self.name) <= self.max_name_length, (
+        if len(self.name) > self.max_name_length:
-            'Index too long for multiple database support. Is self.suffix '
+            raise ValueError(
-            'longer than 3 characters?'
+                'Index too long for multiple database support. Is self.suffix '
-        )
+                'longer than 3 characters?'
+            )
         if self.name[0] == '_' or self.name[0].isdigit():
             self.name = 'D%s' % self.name[1:]
 

django/db/models/query.py

@@ -291,10 +291,14 @@ class QuerySet:
                 'QuerySet indices must be integers or slices, not %s.'
                 % type(k).__name__
             )
-        assert ((not isinstance(k, slice) and (k >= 0)) or
+        if (
-                (isinstance(k, slice) and (k.start is None or k.start >= 0) and
+            (isinstance(k, int) and k < 0) or
-                 (k.stop is None or k.stop >= 0))), \
+            (isinstance(k, slice) and (
-            "Negative indexing is not supported."
+                (k.start is not None and k.start < 0) or
+                (k.stop is not None and k.stop < 0)
+            ))
+        ):
+            raise ValueError('Negative indexing is not supported.')
 
         if self._result_cache is not None:
             return self._result_cache[k]
@@ -480,7 +484,8 @@ class QuerySet:
         # PostgreSQL via the RETURNING ID clause. It should be possible for
         # Oracle as well, but the semantics for extracting the primary keys is
         # trickier so it's not done yet.
-        assert batch_size is None or batch_size > 0
+        if batch_size is not None and batch_size <= 0:
+            raise ValueError('Batch size must be a positive integer.')
         # Check that the parents share the same concrete model with the our
         # model to detect the inheritance pattern ConcreteGrandParent ->
         # MultiTableParent -> ProxyChild. Simply checking self.model._meta.proxy
@@ -900,10 +905,10 @@ class QuerySet:
         Return a list of date objects representing all available dates for
         the given field_name, scoped to 'kind'.
         """
-        assert kind in ('year', 'month', 'week', 'day'), \
+        if kind not in ('year', 'month', 'week', 'day'):
-            "'kind' must be one of 'year', 'month', 'week', or 'day'."
+            raise ValueError("'kind' must be one of 'year', 'month', 'week', or 'day'.")
-        assert order in ('ASC', 'DESC'), \
+        if order not in ('ASC', 'DESC'):
-            "'order' must be either 'ASC' or 'DESC'."
+            raise ValueError("'order' must be either 'ASC' or 'DESC'.")
         return self.annotate(
             datefield=Trunc(field_name, kind, output_field=DateField()),
             plain_field=F(field_name)
@@ -916,10 +921,13 @@ class QuerySet:
         Return a list of datetime objects representing all available
         datetimes for the given field_name, scoped to 'kind'.
         """
-        assert kind in ('year', 'month', 'week', 'day', 'hour', 'minute', 'second'), \
+        if kind not in ('year', 'month', 'week', 'day', 'hour', 'minute', 'second'):
-            "'kind' must be one of 'year', 'month', 'week', 'day', 'hour', 'minute', or 'second'."
+            raise ValueError(
-        assert order in ('ASC', 'DESC'), \
+                "'kind' must be one of 'year', 'month', 'week', 'day', "
-            "'order' must be either 'ASC' or 'DESC'."
+                "'hour', 'minute', or 'second'."
+            )
+        if order not in ('ASC', 'DESC'):
+            raise ValueError("'order' must be either 'ASC' or 'DESC'.")
         if settings.USE_TZ:
             if tzinfo is None:
                 tzinfo = timezone.get_current_timezone()

django/db/models/sql/query.py

@@ -567,14 +567,14 @@ class Query(BaseExpression):
         The 'connector' parameter describes how to connect filters from the
         'rhs' query.
         """
-        assert self.model == rhs.model, \
+        if self.model != rhs.model:
-            "Cannot combine queries on two different base models."
+            raise TypeError('Cannot combine queries on two different base models.')
         if self.is_sliced:
             raise TypeError('Cannot combine queries once a slice has been taken.')
-        assert self.distinct == rhs.distinct, \
+        if self.distinct != rhs.distinct:
-            "Cannot combine a unique query with a non-unique query."
+            raise TypeError('Cannot combine a unique query with a non-unique query.')
-        assert self.distinct_fields == rhs.distinct_fields, \
+        if self.distinct_fields != rhs.distinct_fields:
-            "Cannot combine queries with different distinct fields."
+            raise TypeError('Cannot combine queries with different distinct fields.')
 
         # Work out how to relabel the rhs aliases, if necessary.
         change_map = {}

tests/bulk_create/tests.py

@@ -347,3 +347,8 @@ class BulkCreateTests(TestCase):
         )
         with self.assertRaisesMessage(ValueError, msg):
             NullableFields.objects.bulk_create([NullableFields(auto_field=parent)])
+
+    def test_invalid_batch_size_exception(self):
+        msg = 'Batch size must be a positive integer.'
+        with self.assertRaisesMessage(ValueError, msg):
+            Country.objects.bulk_create([], batch_size=-1)

tests/dates/tests.py

@@ -98,11 +98,12 @@ class DatesTests(TestCase):
 
     def test_dates_fails_when_given_invalid_kind_argument(self):
         msg = "'kind' must be one of 'year', 'month', 'week', or 'day'."
-        with self.assertRaisesMessage(AssertionError, msg):
+        with self.assertRaisesMessage(ValueError, msg):
             Article.objects.dates("pub_date", "bad_kind")
 
     def test_dates_fails_when_given_invalid_order_argument(self):
-        with self.assertRaisesMessage(AssertionError, "'order' must be either 'ASC' or 'DESC'."):
+        msg = "'order' must be either 'ASC' or 'DESC'."
+        with self.assertRaisesMessage(ValueError, msg):
             Article.objects.dates("pub_date", "year", order="bad order")
 
     @override_settings(USE_TZ=False)

tests/datetimes/tests.py

@@ -199,3 +199,16 @@ class DateTimesTests(TestCase):
         Article.objects.create(pub_date=dt, published_on=dt.date(), title="Don't put dates into datetime functions!")
         with self.assertRaisesMessage(ValueError, "Cannot truncate DateField 'published_on' to DateTimeField"):
             list(Article.objects.datetimes('published_on', 'second'))
+
+    def test_datetimes_fails_when_given_invalid_kind_argument(self):
+        msg = (
+            "'kind' must be one of 'year', 'month', 'week', 'day', 'hour', "
+            "'minute', or 'second'."
+        )
+        with self.assertRaisesMessage(ValueError, msg):
+            Article.objects.datetimes('pub_date', 'bad_kind')
+
+    def test_datetimes_fails_when_given_invalid_order_argument(self):
+        msg = "'order' must be either 'ASC' or 'DESC'."
+        with self.assertRaisesMessage(ValueError, msg):
+            Article.objects.datetimes('pub_date', 'year', order='bad order')

tests/db_functions/datetime/test_extract_trunc.py

@@ -655,7 +655,8 @@ class DateFunctionTests(TestCase):
         with self.assertRaisesMessage(ValueError, msg):
             list(DTModel.objects.annotate(truncated=Trunc('start_datetime', 'year', output_field=IntegerField())))
 
-        with self.assertRaisesMessage(AssertionError, "'name' isn't a DateField, TimeField, or DateTimeField."):
+        msg = "'name' isn't a DateField, TimeField, or DateTimeField."
+        with self.assertRaisesMessage(TypeError, msg):
             list(DTModel.objects.annotate(truncated=Trunc('name', 'year', output_field=DateTimeField())))
 
         with self.assertRaisesMessage(ValueError, "Cannot truncate DateField 'start_date' to DateTimeField"):

tests/delete/tests.py

@@ -280,6 +280,12 @@ class DeletionTests(TestCase):
         with self.assertRaisesMessage(TypeError, msg):
             M.objects.all()[0:5].delete()
 
+    def test_pk_none(self):
+        m = M()
+        msg = "M object can't be deleted because its id attribute is set to None."
+        with self.assertRaisesMessage(ValueError, msg):
+            m.delete()
+
     def test_m2m(self):
         m = M.objects.create()
         r = R.objects.create()

tests/distinct_on_fields/tests.py

@@ -87,9 +87,14 @@ class DistinctOnTests(TestCase):
             self.assertSequenceEqual(qset, expected)
             self.assertEqual(qset.count(), len(expected))
 
-        # Combining queries with different distinct_fields is not allowed.
+        # Combining queries with non-unique query is not allowed.
         base_qs = Celebrity.objects.all()
-        with self.assertRaisesMessage(AssertionError, "Cannot combine queries with different distinct fields."):
+        msg = 'Cannot combine a unique query with a non-unique query.'
+        with self.assertRaisesMessage(TypeError, msg):
+            base_qs.distinct('id') & base_qs
+        # Combining queries with different distinct_fields is not allowed.
+        msg = 'Cannot combine queries with different distinct fields.'
+        with self.assertRaisesMessage(TypeError, msg):
             base_qs.distinct('id') & base_qs.distinct('name')
 
         # Test join unreffing

tests/invalid_models_tests/test_models.py

@@ -1591,6 +1591,18 @@ class OtherModelTests(SimpleTestCase):
         ])
 
 
+class MultipleAutoFieldsTests(TestCase):
+    def test_multiple_autofields(self):
+        msg = (
+            "Model invalid_models_tests.MultipleAutoFields can't have more "
+            "than one auto-generated field."
+        )
+        with self.assertRaisesMessage(ValueError, msg):
+            class MultipleAutoFields(models.Model):
+                auto1 = models.AutoField(primary_key=True)
+                auto2 = models.AutoField(primary_key=True)
+
+
 @isolate_apps('invalid_models_tests')
 class JSONFieldTests(TestCase):
     @skipUnlessDBFeature('supports_json_field')

tests/model_fields/test_foreignkey.py

@@ -147,3 +147,12 @@ class ForeignKeyTests(TestCase):
         )
         with self.assertRaisesMessage(FieldError, msg):
             Related._meta.get_field('child').related_fields
+
+    def test_invalid_to_parameter(self):
+        msg = (
+            "ForeignKey(1) is invalid. First parameter to ForeignKey must be "
+            "either a model, a model name, or the string 'self'"
+        )
+        with self.assertRaisesMessage(TypeError, msg):
+            class MyModel(models.Model):
+                child = models.ForeignKey(1, models.CASCADE)

tests/model_fields/test_manytomanyfield.py

@@ -59,6 +59,34 @@ class ManyToManyFieldTests(SimpleTestCase):
         assert_app_model_resolved('model_fields')
         assert_app_model_resolved('tests')
 
+    def test_invalid_to_parameter(self):
+        msg = (
+            "ManyToManyField(1) is invalid. First parameter to "
+            "ManyToManyField must be either a model, a model name, or the "
+            "string 'self'"
+        )
+        with self.assertRaisesMessage(TypeError, msg):
+            class MyModel(models.Model):
+                m2m = models.ManyToManyField(1)
+
+    @isolate_apps('model_fields')
+    def test_through_db_table_mutually_exclusive(self):
+        class Child(models.Model):
+            pass
+
+        class Through(models.Model):
+            referred = models.ForeignKey(Child, on_delete=models.CASCADE)
+            referent = models.ForeignKey(Child, on_delete=models.CASCADE)
+
+        msg = 'Cannot specify a db_table if an intermediary model is used.'
+        with self.assertRaisesMessage(ValueError, msg):
+            class MyModel(models.Model):
+                m2m = models.ManyToManyField(
+                    Child,
+                    through='Through',
+                    db_table='custom_name',
+                )
+
 
 class ManyToManyFieldDBTests(TestCase):
 

tests/model_indexes/tests.py

@@ -173,8 +173,11 @@ class SimpleIndexesTests(SimpleTestCase):
 
         # suffix can't be longer than 3 characters.
         long_field_index.suffix = 'suff'
-        msg = 'Index too long for multiple database support. Is self.suffix longer than 3 characters?'
+        msg = (
-        with self.assertRaisesMessage(AssertionError, msg):
+            'Index too long for multiple database support. Is self.suffix '
+            'longer than 3 characters?'
+        )
+        with self.assertRaisesMessage(ValueError, msg):
             long_field_index.set_name_with_model(Book)
 
     @isolate_apps('model_indexes')

tests/queries/tests.py

@@ -417,9 +417,10 @@ class Queries1Tests(TestCase):
     def test_heterogeneous_qs_combination(self):
         # Combining querysets built on different models should behave in a well-defined
         # fashion. We raise an error.
-        with self.assertRaisesMessage(AssertionError, 'Cannot combine queries on two different base models.'):
+        msg = 'Cannot combine queries on two different base models.'
+        with self.assertRaisesMessage(TypeError, msg):
             Author.objects.all() & Tag.objects.all()
-        with self.assertRaisesMessage(AssertionError, 'Cannot combine queries on two different base models.'):
+        with self.assertRaisesMessage(TypeError, msg):
             Author.objects.all() | Tag.objects.all()
 
     def test_ticket3141(self):
@@ -1226,10 +1227,11 @@ class Queries3Tests(TestCase):
         # This shouldn't create an infinite loop.
         self.assertQuerysetEqual(Valid.objects.all(), [])
 
-    def test_ticket8683(self):
+    def test_datetimes_invalid_field(self):
         # An error should be raised when QuerySet.datetimes() is passed the
         # wrong type of field.
-        with self.assertRaisesMessage(AssertionError, "'name' isn't a DateField, TimeField, or DateTimeField."):
+        msg = "'name' isn't a DateField, TimeField, or DateTimeField."
+        with self.assertRaisesMessage(TypeError, msg):
             Item.objects.datetimes('name', 'month')
 
     def test_ticket22023(self):
@@ -2405,13 +2407,17 @@ class QuerySetSupportsPythonIdioms(TestCase):
 
     def test_slicing_negative_indexing_not_supported_for_single_element(self):
         """hint: inverting your ordering might do what you need"""
-        with self.assertRaisesMessage(AssertionError, "Negative indexing is not supported."):
+        msg = 'Negative indexing is not supported.'
+        with self.assertRaisesMessage(ValueError, msg):
             Article.objects.all()[-1]
 
     def test_slicing_negative_indexing_not_supported_for_range(self):
         """hint: inverting your ordering might do what you need"""
-        with self.assertRaisesMessage(AssertionError, "Negative indexing is not supported."):
+        msg = 'Negative indexing is not supported.'
+        with self.assertRaisesMessage(ValueError, msg):
             Article.objects.all()[0:-5]
+        with self.assertRaisesMessage(ValueError, msg):
+            Article.objects.all()[-1:]
 
     def test_invalid_index(self):
         msg = 'QuerySet indices must be integers or slices, not str.'

tests/schema/fields.py

@@ -32,8 +32,10 @@ class CustomManyToManyField(RelatedField):
         )
         self.swappable = swappable
         self.db_table = db_table
-        if kwargs['rel'].through is not None:
+        if kwargs['rel'].through is not None and self.db_table is not None:
-            assert self.db_table is None, "Cannot specify a db_table if an intermediary model is used."
+            raise ValueError(
+                'Cannot specify a db_table if an intermediary model is used.'
+            )
         super().__init__(
             related_name=related_name,
             related_query_name=related_query_name,

tests/validation/models.py

@@ -125,18 +125,3 @@ class GenericIPAddressTestModel(models.Model):
 
 class GenericIPAddrUnpackUniqueTest(models.Model):
     generic_v4unpack_ip = models.GenericIPAddressField(null=True, blank=True, unique=True, unpack_ipv4=True)
-
-
-# A model can't have multiple AutoFields
-# Refs #12467.
-assertion_error = None
-try:
-    class MultipleAutoFields(models.Model):
-        auto1 = models.AutoField(primary_key=True)
-        auto2 = models.AutoField(primary_key=True)
-except AssertionError as exc:
-    assertion_error = exc
-assert str(assertion_error) == (
-    "Model validation.MultipleAutoFields can't have more than one "
-    "auto-generated field."
-)