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Refs #32508 -- Raised TypeError instead of using "assert" on unsupported operations for sliced querysets.

This commit is contained in:
Mariusz Felisiak 2021-03-10 09:16:28 +01:00 committed by GitHub
parent 6f5dbe9dbe
commit ba9a2b7544
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9 changed files with 60 additions and 30 deletions
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42
django/db/models/query.py
View File

@ -654,9 +654,6 @@ class QuerySet:
"earliest() and latest() require either fields as positional "
"arguments or 'get_latest_by' in the model's Meta."
)
assert not self.query.is_sliced, \
"Cannot change a query once a slice has been taken."
obj = self._chain()
obj.query.set_limits(high=1)
obj.query.clear_ordering(force_empty=True)
@ -664,9 +661,13 @@ class QuerySet:
return obj.get()
def earliest(self, *fields):
if self.query.is_sliced:
raise TypeError('Cannot change a query once a slice has been taken.')
return self._earliest(*fields)
def latest(self, *fields):
if self.query.is_sliced:
raise TypeError('Cannot change a query once a slice has been taken.')
return self.reverse()._earliest(*fields)
def first(self):
@ -684,8 +685,8 @@ class QuerySet:
Return a dictionary mapping each of the given IDs to the object with
that ID. If `id_list` isn't provided, evaluate the entire QuerySet.
"""
assert not self.query.is_sliced, \
"Cannot use 'limit' or 'offset' with in_bulk"
if self.query.is_sliced:
raise TypeError("Cannot use 'limit' or 'offset' with in_bulk().")
opts = self.model._meta
unique_fields = [
constraint.fields[0]
@ -721,9 +722,8 @@ class QuerySet:
def delete(self):
"""Delete the records in the current QuerySet."""
self._not_support_combined_queries('delete')
assert not self.query.is_sliced, \
"Cannot use 'limit' or 'offset' with delete."
if self.query.is_sliced:
raise TypeError("Cannot use 'limit' or 'offset' with delete().")
if self.query.distinct or self.query.distinct_fields:
raise TypeError('Cannot call delete() after .distinct().')
if self._fields is not None:
@ -772,8 +772,8 @@ class QuerySet:
fields to the appropriate values.
"""
self._not_support_combined_queries('update')
assert not self.query.is_sliced, \
"Cannot update a query once a slice has been taken."
if self.query.is_sliced:
raise TypeError('Cannot update a query once a slice has been taken.')
self._for_write = True
query = self.query.chain(sql.UpdateQuery)
query.add_update_values(kwargs)
@ -792,8 +792,8 @@ class QuerySet:
code (it requires too much poking around at model internals to be
useful at that level).
"""
assert not self.query.is_sliced, \
"Cannot update a query once a slice has been taken."
if self.query.is_sliced:
raise TypeError('Cannot update a query once a slice has been taken.')
query = self.query.chain(sql.UpdateQuery)
query.add_update_fields(values)
# Clear any annotations so that they won't be present in subqueries.
@ -970,10 +970,8 @@ class QuerySet:
return self._filter_or_exclude(True, args, kwargs)
def _filter_or_exclude(self, negate, args, kwargs):
if args or kwargs:
assert not self.query.is_sliced, \
"Cannot filter a query once a slice has been taken."
if (args or kwargs) and self.query.is_sliced:
raise TypeError('Cannot filter a query once a slice has been taken.')
clone = self._chain()
if self._defer_next_filter:
self._defer_next_filter = False
@ -1163,8 +1161,8 @@ class QuerySet:
def order_by(self, *field_names):
"""Return a new QuerySet instance with the ordering changed."""
assert not self.query.is_sliced, \
"Cannot reorder a query once a slice has been taken."
if self.query.is_sliced:
raise TypeError('Cannot reorder a query once a slice has been taken.')
obj = self._chain()
obj.query.clear_ordering(force_empty=False)
obj.query.add_ordering(*field_names)
@ -1175,8 +1173,8 @@ class QuerySet:
Return a new QuerySet instance that will select only distinct results.
"""
self._not_support_combined_queries('distinct')
assert not self.query.is_sliced, \
"Cannot create distinct fields once a slice has been taken."
if self.query.is_sliced:
raise TypeError('Cannot create distinct fields once a slice has been taken.')
obj = self._chain()
obj.query.add_distinct_fields(*field_names)
return obj
@ -1185,8 +1183,8 @@ class QuerySet:
order_by=None, select_params=None):
"""Add extra SQL fragments to the query."""
self._not_support_combined_queries('extra')
assert not self.query.is_sliced, \
"Cannot change a query once a slice has been taken"
if self.query.is_sliced:
raise TypeError('Cannot change a query once a slice has been taken.')
clone = self._chain()
clone.query.add_extra(select, select_params, where, params, tables, order_by)
return clone

4
django/db/models/sql/query.py
View File

@ -574,8 +574,8 @@ class Query(BaseExpression):
"""
assert self.model == rhs.model, \
"Cannot combine queries on two different base models."
assert not self.is_sliced, \
"Cannot combine queries once a slice has been taken."
if self.is_sliced:
raise TypeError('Cannot combine queries once a slice has been taken.')
assert self.distinct == rhs.distinct, \
"Cannot combine a unique query with a non-unique query."
assert self.distinct_fields == rhs.distinct_fields, \

3
docs/releases/4.0.txt
View File

@ -318,6 +318,9 @@ Miscellaneous
rather than via the recommended ``AdminSite.urls`` property, or
``AdminSite.get_urls()`` method.
* Unsupported operations on a sliced queryset now raise ``TypeError`` instead
of ``AssertionError``.
.. _deprecated-features-4.0:
Features deprecated in 4.0

4
tests/delete/tests.py
View File

@ -275,6 +275,10 @@ class OnDeleteTests(TestCase):
class DeletionTests(TestCase):
def test_sliced_queryset(self):
msg = "Cannot use 'limit' or 'offset' with delete()."
with self.assertRaisesMessage(TypeError, msg):
M.objects.all()[0:5].delete()
def test_m2m(self):
m = M.objects.create()

5
tests/distinct_on_fields/tests.py
View File

@ -98,6 +98,11 @@ class DistinctOnTests(TestCase):
c2 = c1.distinct('pk')
self.assertNotIn('OUTER JOIN', str(c2.query))
def test_sliced_queryset(self):
msg = 'Cannot create distinct fields once a slice has been taken.'
with self.assertRaisesMessage(TypeError, msg):
Staff.objects.all()[0:5].distinct('name')
def test_transform(self):
new_name = self.t1.name.upper()
self.assertNotEqual(self.t1.name, new_name)

10
tests/get_earliest_or_latest/tests.py
View File

@ -81,6 +81,11 @@ class EarliestOrLatestTests(TestCase):
Article.objects.model._meta.get_latest_by = ('pub_date', 'expire_date')
self.assertEqual(Article.objects.filter(pub_date=datetime(2005, 7, 28)).earliest(), a4)
def test_earliest_sliced_queryset(self):
msg = 'Cannot change a query once a slice has been taken.'
with self.assertRaisesMessage(TypeError, msg):
Article.objects.all()[0:5].earliest()
def test_latest(self):
# Because no Articles exist yet, latest() raises ArticleDoesNotExist.
with self.assertRaises(Article.DoesNotExist):
@ -143,6 +148,11 @@ class EarliestOrLatestTests(TestCase):
Article.objects.model._meta.get_latest_by = ('pub_date', 'expire_date')
self.assertEqual(Article.objects.filter(pub_date=datetime(2005, 7, 27)).latest(), a3)
def test_latest_sliced_queryset(self):
msg = 'Cannot change a query once a slice has been taken.'
with self.assertRaisesMessage(TypeError, msg):
Article.objects.all()[0:5].latest()
def test_latest_manual(self):
# You can still use latest() with a model that doesn't have
# "get_latest_by" set -- just pass in the field name manually.

5
tests/lookup/tests.py
View File

@ -244,6 +244,11 @@ class LookupTests(TestCase):
with self.assertRaisesMessage(ValueError, msg % field_name):
Model.objects.in_bulk(field_name=field_name)
def test_in_bulk_sliced_queryset(self):
msg = "Cannot use 'limit' or 'offset' with in_bulk()."
with self.assertRaisesMessage(TypeError, msg):
Article.objects.all()[0:5].in_bulk([self.a1.id, self.a2.id])
def test_values(self):
# values() returns a list of dictionaries instead of object instances --
# and you can specify which fields you want to retrieve.

15
tests/queries/tests.py
View File

@ -700,7 +700,8 @@ class Queries1Tests(TestCase):
)
self.assertQuerysetEqual(q.reverse(), [])
q.query.low_mark = 1
with self.assertRaisesMessage(AssertionError, 'Cannot change a query once a slice has been taken'):
msg = 'Cannot change a query once a slice has been taken.'
with self.assertRaisesMessage(TypeError, msg):
q.extra(select={'foo': "1"})
self.assertQuerysetEqual(q.defer('meal'), [])
self.assertQuerysetEqual(q.only('meal'), [])
@ -2359,15 +2360,18 @@ class QuerySetSupportsPythonIdioms(TestCase):
)
def test_slicing_cannot_filter_queryset_once_sliced(self):
with self.assertRaisesMessage(AssertionError, "Cannot filter a query once a slice has been taken."):
msg = 'Cannot filter a query once a slice has been taken.'
with self.assertRaisesMessage(TypeError, msg):
Article.objects.all()[0:5].filter(id=1)
def test_slicing_cannot_reorder_queryset_once_sliced(self):
with self.assertRaisesMessage(AssertionError, "Cannot reorder a query once a slice has been taken."):
msg = 'Cannot reorder a query once a slice has been taken.'
with self.assertRaisesMessage(TypeError, msg):
Article.objects.all()[0:5].order_by('id')
def test_slicing_cannot_combine_queries_once_sliced(self):
with self.assertRaisesMessage(AssertionError, "Cannot combine queries once a slice has been taken."):
msg = 'Cannot combine queries once a slice has been taken.'
with self.assertRaisesMessage(TypeError, msg):
Article.objects.all()[0:1] & Article.objects.all()[4:5]
def test_slicing_negative_indexing_not_supported_for_single_element(self):
@ -2417,7 +2421,8 @@ class WeirdQuerysetSlicingTests(TestCase):
self.assertQuerysetEqual(Article.objects.all()[0:0], [])
self.assertQuerysetEqual(Article.objects.all()[0:0][:10], [])
self.assertEqual(Article.objects.all()[:0].count(), 0)
with self.assertRaisesMessage(TypeError, 'Cannot reverse a query once a slice has been taken.'):
msg = 'Cannot change a query once a slice has been taken.'
with self.assertRaisesMessage(TypeError, msg):
Article.objects.all()[:0].latest('created')
def test_empty_resultset_sql(self):

2
tests/update/tests.py
View File

@ -130,7 +130,7 @@ class AdvancedTests(TestCase):
"""
method = DataPoint.objects.all()[:2].update
msg = 'Cannot update a query once a slice has been taken.'
with self.assertRaisesMessage(AssertionError, msg):
with self.assertRaisesMessage(TypeError, msg):
method(another_value='another thing')
def test_update_respects_to_field(self):