Fixed #26718 -- Added system check for existence of the fields specified by ForeignKey.to_field.

1 files changed, 50 insertions, 0 deletions

diff --git a/tests/invalid_models_tests/test_relative_fields.py b/tests/invalid_models_tests/test_relative_fields.py
index 8b95cf3e18..2534b345c2 100644
--- a/tests/invalid_models_tests/test_relative_fields.py
+++ b/tests/invalid_models_tests/test_relative_fields.py
@@ -763,6 +763,56 @@ class RelativeFieldTests(SimpleTestCase):
             errors = Child.check()
             self.assertFalse(errors)
 
+    def test_to_fields_exist(self):
+        class Parent(models.Model):
+            pass
+
+        class Child(models.Model):
+            a = models.PositiveIntegerField()
+            b = models.PositiveIntegerField()
+            parent = ForeignObject(
+                Parent,
+                on_delete=models.SET_NULL,
+                from_fields=('a', 'b'),
+                to_fields=('a', 'b'),
+            )
+
+        field = Child._meta.get_field('parent')
+        expected = [
+            Error(
+                "The to_field 'a' doesn't exist on the related model 'invalid_models_tests.Parent'.",
+                obj=field,
+                id='fields.E312',
+            ),
+            Error(
+                "The to_field 'b' doesn't exist on the related model 'invalid_models_tests.Parent'.",
+                obj=field,
+                id='fields.E312',
+            ),
+        ]
+        self.assertEqual(field.check(), expected)
+
+    def test_to_fields_not_checked_if_related_model_doesnt_exist(self):
+        class Child(models.Model):
+            a = models.PositiveIntegerField()
+            b = models.PositiveIntegerField()
+            parent = ForeignObject(
+                'invalid_models_tests.Parent',
+                on_delete=models.SET_NULL,
+                from_fields=('a', 'b'),
+                to_fields=('a', 'b'),
+            )
+
+        field = Child._meta.get_field('parent')
+        self.assertEqual(field.check(), [
+            Error(
+                "Field defines a relation with model 'invalid_models_tests.Parent', "
+                "which is either not installed, or is abstract.",
+                id='fields.E300',
+                obj=field,
+            ),
+        ])
+
 
 @isolate_apps('invalid_models_tests')
 class AccessorClashTests(SimpleTestCase):