Fixed #25172 -- Fixed check framework to work with multiple databases.

django/db/models/fields/__init__.py

@@ -19,7 +19,7 @@
 # django.core.exceptions. It is retained here for backwards compatibility
 # purposes.
 from django.core.exceptions import FieldDoesNotExist  # NOQA
-from django.db import connection
+from django.db import connection, connections, router
 from django.db.models.lookups import (
     Lookup, RegisterLookupMixin, Transform, default_lookups,
 )
@@ -315,7 +315,11 @@ def _check_null_allowed_for_primary_keys(self):
             return []
 
     def _check_backend_specific_checks(self, **kwargs):
-        return connection.validation.check_field(self, **kwargs)
+        app_label = self.model._meta.app_label
+        for db in connections:
+            if router.allow_migrate(db, app_label, model=self.model):
+                return connections[db].validation.check_field(self, **kwargs)
+        return []
 
     def _check_deprecation_details(self):
         if self.system_check_removed_details is not None:

tests/check_framework/test_multi_db.py

@@ -0,0 +1,43 @@
+from django.db import connections, models
+from django.test import TestCase, mock
+from django.test.utils import override_settings
+
+from .tests import IsolateModelsMixin
+
+
+class TestRouter(object):
+    """
+    Routes to the 'other' database if the model name starts with 'Other'.
+    """
+    def allow_migrate(self, db, app_label, model=None, **hints):
+        return db == ('other' if model._meta.verbose_name.startswith('other') else 'default')
+
+
+@override_settings(DATABASE_ROUTERS=[TestRouter()])
+class TestMultiDBChecks(IsolateModelsMixin, TestCase):
+    multi_db = True
+
+    def _patch_check_field_on(self, db):
+        return mock.patch.object(connections[db].validation, 'check_field')
+
+    def test_checks_called_on_the_default_database(self):
+        class Model(models.Model):
+            field = models.CharField(max_length=100)
+
+        model = Model()
+        with self._patch_check_field_on('default') as mock_check_field_default:
+            with self._patch_check_field_on('other') as mock_check_field_other:
+                model.check()
+                self.assertTrue(mock_check_field_default.called)
+                self.assertFalse(mock_check_field_other.called)
+
+    def test_checks_called_on_the_other_database(self):
+        class OtherModel(models.Model):
+            field = models.CharField(max_length=100)
+
+        model = OtherModel()
+        with self._patch_check_field_on('other') as mock_check_field_other:
+            with self._patch_check_field_on('default') as mock_check_field_default:
+                model.check()
+                self.assertTrue(mock_check_field_other.called)
+                self.assertFalse(mock_check_field_default.called)

tests/invalid_models_tests/test_backend_specific.py

@@ -1,37 +1,31 @@
 # -*- encoding: utf-8 -*-
 from __future__ import unicode_literals
 
-from types import MethodType
-
 from django.core.checks import Error
-from django.db import connection, models
+from django.db import connections, models
+from django.test import mock
 
 from .base import IsolatedModelsTestCase
 
 
+def dummy_allow_migrate(db, app_label, **hints):
+    # Prevent checks from being run on the 'other' database, which doesn't have
+    # its check_field() method mocked in the test.
+    return db == 'default'
+
+
 class BackendSpecificChecksTests(IsolatedModelsTestCase):
 
+    @mock.patch('django.db.models.fields.router.allow_migrate', new=dummy_allow_migrate)
     def test_check_field(self):
         """ Test if backend specific checks are performed. """
-
         error = Error('an error', hint=None)
 
-        def mock(self, field, **kwargs):
-            return [error]
-
         class Model(models.Model):
             field = models.IntegerField()
 
         field = Model._meta.get_field('field')
-
-        # Mock connection.validation.check_field method.
-        v = connection.validation
-        old_check_field = v.check_field
-        v.check_field = MethodType(mock, v)
-        try:
+        with mock.patch.object(connections['default'].validation, 'check_field', return_value=[error]):
             errors = field.check()
-        finally:
-            # Unmock connection.validation.check_field method.
-            v.check_field = old_check_field
 
         self.assertEqual(errors, [error])

tests/postgres_tests/test_array.py

@@ -14,6 +14,7 @@
 from .models import (
     ArrayFieldSubclass, CharArrayModel, DateTimeArrayModel, IntegerArrayModel,
     NestedIntegerArrayModel, NullableIntegerArrayModel, OtherTypesArrayModel,
+    PostgreSQLModel,
 )
 
 try:
@@ -246,16 +247,20 @@ def test_usage_in_subquery(self):
 class TestChecks(PostgreSQLTestCase):
 
     def test_field_checks(self):
-        field = ArrayField(models.CharField())
-        field.set_attributes_from_name('field')
-        errors = field.check()
+        class MyModel(PostgreSQLModel):
+            field = ArrayField(models.CharField())
+
+        model = MyModel()
+        errors = model.check()
         self.assertEqual(len(errors), 1)
         self.assertEqual(errors[0].id, 'postgres.E001')
 
     def test_invalid_base_fields(self):
-        field = ArrayField(models.ManyToManyField('postgres_tests.IntegerArrayModel'))
-        field.set_attributes_from_name('field')
-        errors = field.check()
+        class MyModel(PostgreSQLModel):
+            field = ArrayField(models.ManyToManyField('postgres_tests.IntegerArrayModel'))
+
+        model = MyModel()
+        errors = model.check()
         self.assertEqual(len(errors), 1)
         self.assertEqual(errors[0].id, 'postgres.E002')