From cc6bcc6ff5cab320c5e5ae2760549a6c732067d8 Mon Sep 17 00:00:00 2001
From: shanghui <shangdahao@gmail.com>
Date: Fri, 29 Dec 2017 09:22:20 +0800
Subject: [PATCH] Fixed #28867 -- Added system check for a model property that
 clashes with a related field accessor.

---
 django/db/models/base.py                  | 27 ++++++++++++++++++++---
 docs/ref/checks.txt                       |  2 ++
 tests/invalid_models_tests/test_models.py | 16 ++++++++++++++
 3 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/django/db/models/base.py b/django/db/models/base.py
index 19648fbed9..972da7bb06 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -1191,9 +1191,10 @@ class Model(metaclass=ModelBase):
                 *cls._check_long_column_names(),
             ]
             clash_errors = (
-                cls._check_id_field() +
-                cls._check_field_name_clashes() +
-                cls._check_model_name_db_lookup_clashes()
+                *cls._check_id_field(),
+                *cls._check_field_name_clashes(),
+                *cls._check_model_name_db_lookup_clashes(),
+                *cls._check_property_name_related_field_accessor_clashes(),
             )
             errors.extend(clash_errors)
             # If there are field name clashes, hide consequent column name
@@ -1421,6 +1422,26 @@ class Model(metaclass=ModelBase):
             )
         return errors
 
+    @classmethod
+    def _check_property_name_related_field_accessor_clashes(cls):
+        errors = []
+        property_names = cls._meta._property_names
+        related_field_accessors = (
+            f.get_attname() for f in cls._meta._get_fields(reverse=False)
+            if f.is_relation and f.related_model is not None
+        )
+        for accessor in related_field_accessors:
+            if accessor in property_names:
+                errors.append(
+                    checks.Error(
+                        "The property '%s' clashes with a related field "
+                        "accessor." % accessor,
+                        obj=cls,
+                        id='models.E025',
+                    )
+                )
+        return errors
+
     @classmethod
     def _check_index_together(cls):
         """Check the value of "index_together" option."""
diff --git a/docs/ref/checks.txt b/docs/ref/checks.txt
index db86c49ee0..6310500d0c 100644
--- a/docs/ref/checks.txt
+++ b/docs/ref/checks.txt
@@ -292,6 +292,8 @@ Models
   underscore as it collides with the query lookup syntax.
 * **models.E024**: The model name ``<model>`` cannot contain double underscores
   as it collides with the query lookup syntax.
+* **models.E025**: The property ``<property name>`` clashes with a related
+  field accessor.
 
 Security
 --------
diff --git a/tests/invalid_models_tests/test_models.py b/tests/invalid_models_tests/test_models.py
index 85d7bca366..b271ddf55c 100644
--- a/tests/invalid_models_tests/test_models.py
+++ b/tests/invalid_models_tests/test_models.py
@@ -706,6 +706,22 @@ class OtherModelTests(SimpleTestCase):
             )
         ])
 
+    def test_property_and_related_field_accessor_clash(self):
+        class Model(models.Model):
+            fk = models.ForeignKey('self', models.CASCADE)
+
+            @property
+            def fk_id(self):
+                pass
+
+        self.assertEqual(Model.check(), [
+            Error(
+                "The property 'fk_id' clashes with a related field accessor.",
+                obj=Model,
+                id='models.E025',
+            )
+        ])
+
     @override_settings(TEST_SWAPPED_MODEL_BAD_VALUE='not-a-model')
     def test_swappable_missing_app_name(self):
         class Model(models.Model):