Refs #21127 -- Required on_delete for ForeignKey/OneToOneField.

Per deprecation timeline.

django/db/models/fields/related.py

@@ -20,7 +20,6 @@ from django.utils.encoding import force_text
 from django.utils.functional import cached_property, curry
 from django.utils.lru_cache import lru_cache
 from django.utils.translation import ugettext_lazy as _
-from django.utils.version import get_docs_version
 
 from . import Field
 from .related_descriptors import (
@@ -789,7 +788,7 @@ class ForeignKey(ForeignObject):
     }
     description = _("Foreign Key (type determined by related field)")
 
-    def __init__(self, to, on_delete=None, related_name=None, related_query_name=None,
+    def __init__(self, to, on_delete, related_name=None, related_query_name=None,
                  limit_choices_to=None, parent_link=False, to_field=None,
                  db_constraint=True, **kwargs):
         try:
@@ -808,29 +807,6 @@ class ForeignKey(ForeignObject):
             # be correct until contribute_to_class is called. Refs #12190.
             to_field = to_field or (to._meta.pk and to._meta.pk.name)
 
-        if on_delete is None:
-            warnings.warn(
-                "on_delete will be a required arg for %s in Django 2.0. Set "
-                "it to models.CASCADE on models and in existing migrations "
-                "if you want to maintain the current default behavior. "
-                "See https://docs.djangoproject.com/en/%s/ref/models/fields/"
-                "#django.db.models.ForeignKey.on_delete" % (
-                    self.__class__.__name__,
-                    get_docs_version(),
-                ),
-                RemovedInDjango20Warning, 2)
-            on_delete = CASCADE
-
-        elif not callable(on_delete):
-            warnings.warn(
-                "The signature for {0} will change in Django 2.0. "
-                "Pass to_field='{1}' as a kwarg instead of as an arg.".format(
-                    self.__class__.__name__,
-                    on_delete,
-                ),
-                RemovedInDjango20Warning, 2)
-            on_delete, to_field = to_field, on_delete
-
         kwargs['rel'] = self.rel_class(
             self, to, to_field,
             related_name=related_name,
@@ -1028,33 +1004,8 @@ class OneToOneField(ForeignKey):
 
     description = _("One-to-one relationship")
 
-    def __init__(self, to, on_delete=None, to_field=None, **kwargs):
+    def __init__(self, to, on_delete, to_field=None, **kwargs):
         kwargs['unique'] = True
-
-        if on_delete is None:
-            warnings.warn(
-                "on_delete will be a required arg for %s in Django 2.0. Set "
-                "it to models.CASCADE on models and in existing migrations "
-                "if you want to maintain the current default behavior. "
-                "See https://docs.djangoproject.com/en/%s/ref/models/fields/"
-                "#django.db.models.ForeignKey.on_delete" % (
-                    self.__class__.__name__,
-                    get_docs_version(),
-                ),
-                RemovedInDjango20Warning, 2)
-            on_delete = CASCADE
-
-        elif not callable(on_delete):
-            warnings.warn(
-                "The signature for {0} will change in Django 2.0. "
-                "Pass to_field='{1}' as a kwarg instead of as an arg.".format(
-                    self.__class__.__name__,
-                    on_delete,
-                ),
-                RemovedInDjango20Warning, 2)
-            to_field = on_delete
-            on_delete = CASCADE  # Avoid warning in superclass
-
         super(OneToOneField, self).__init__(to, on_delete, to_field=to_field, **kwargs)
 
     def deconstruct(self):

docs/ref/models/fields.txt

@@ -1277,11 +1277,6 @@ relation works.
             null=True,
         )
 
-    .. deprecated:: 1.9
-
-        :attr:`~ForeignKey.on_delete` will become a required argument in Django
-        2.0. In older versions it defaults to ``CASCADE``.
-
 The possible values for :attr:`~ForeignKey.on_delete` are found in
 :mod:`django.db.models`:
 

docs/releases/2.0.txt

@@ -249,3 +249,6 @@ these features.
   relative ones when the path is identical is also removed.
 
 * ``Field.rel`` and ``Field.remote_field.to`` are removed.
+
+* The ``on_delete`` argument for ``ForeignKey`` and ``OneToOneField`` are now
+  required.

tests/invalid_models_tests/test_relative_fields.py

@@ -1,17 +1,12 @@
 # -*- encoding: utf-8 -*-
 from __future__ import unicode_literals
 
-import warnings
-
 from django.core.checks import Error, Warning as DjangoWarning
 from django.db import models
 from django.db.models.fields.related import ForeignObject
-from django.test import ignore_warnings
 from django.test.testcases import SimpleTestCase, skipIfDBFeature
 from django.test.utils import isolate_apps, override_settings
 from django.utils import six
-from django.utils.deprecation import RemovedInDjango20Warning
-from django.utils.version import get_docs_version
 
 
 @isolate_apps('invalid_models_tests')
@@ -29,88 +24,6 @@ class RelativeFieldTests(SimpleTestCase):
         errors = field.check()
         self.assertEqual(errors, [])
 
-    @ignore_warnings(category=RemovedInDjango20Warning)
-    def test_valid_foreign_key_without_on_delete(self):
-        class Target(models.Model):
-            model = models.IntegerField()
-
-        class Model(models.Model):
-            field = models.ForeignKey(Target, related_name='+')
-
-    def test_foreign_key_without_on_delete_warning(self):
-        with warnings.catch_warnings(record=True) as warns:
-            warnings.simplefilter('always')  # prevent warnings from appearing as errors
-
-            class Target(models.Model):
-                model = models.IntegerField()
-
-            class Model(models.Model):
-                field = models.ForeignKey(Target, related_name='+')
-
-            self.assertEqual(len(warns), 1)
-            self.assertEqual(
-                str(warns[0].message),
-                'on_delete will be a required arg for ForeignKey in Django '
-                '2.0. Set it to models.CASCADE on models and in existing '
-                'migrations if you want to maintain the current default '
-                'behavior. See https://docs.djangoproject.com/en/%s/ref/models/fields/'
-                '#django.db.models.ForeignKey.on_delete' % get_docs_version(),
-            )
-
-    def test_foreign_key_to_field_as_arg(self):
-        with warnings.catch_warnings(record=True) as warns:
-            warnings.simplefilter('always')  # prevent warnings from appearing as errors
-
-            class Target(models.Model):
-                model = models.IntegerField()
-
-            class Model(models.Model):
-                field = models.ForeignKey(Target, 'id')
-
-            self.assertEqual(len(warns), 1)
-            self.assertEqual(
-                str(warns[0].message),
-                "The signature for ForeignKey will change in Django 2.0. "
-                "Pass to_field='id' as a kwarg instead of as an arg."
-            )
-
-    def test_one_to_one_field_without_on_delete_warning(self):
-        with warnings.catch_warnings(record=True) as warns:
-            warnings.simplefilter('always')  # prevent warnings from appearing as errors
-
-            class Target(models.Model):
-                model = models.IntegerField()
-
-            class Model(models.Model):
-                field = models.OneToOneField(Target, related_name='+')
-
-            self.assertEqual(len(warns), 1)
-            self.assertEqual(
-                str(warns[0].message),
-                'on_delete will be a required arg for OneToOneField in Django '
-                '2.0. Set it to models.CASCADE on models and in existing '
-                'migrations if you want to maintain the current default '
-                'behavior. See https://docs.djangoproject.com/en/%s/ref/models/fields/'
-                '#django.db.models.ForeignKey.on_delete' % get_docs_version(),
-            )
-
-    def test_one_to_one_field_to_field_as_arg(self):
-        with warnings.catch_warnings(record=True) as warns:
-            warnings.simplefilter('always')  # prevent warnings from appearing as errors
-
-            class Target(models.Model):
-                model = models.IntegerField()
-
-            class Model(models.Model):
-                field = models.OneToOneField(Target, 'id')
-
-            self.assertEqual(len(warns), 1)
-            self.assertEqual(
-                str(warns[0].message),
-                "The signature for OneToOneField will change in Django 2.0. "
-                "Pass to_field='id' as a kwarg instead of as an arg."
-            )
-
     def test_foreign_key_to_missing_model(self):
         # Model names are resolved when a model is being created, so we cannot
         # test relative fields in isolation and we need to attach them to a