From 4f7467b6905482a5d826c2815dcf8c6dd332340d Mon Sep 17 00:00:00 2001
From: Tim Graham <timograham@gmail.com>
Date: Tue, 3 Apr 2018 11:12:56 -0400
Subject: [PATCH] Refs #28577 -- Added check for HStoreField to prevent mutable
 default.

---
 django/contrib/postgres/fields/hstore.py |  5 +++-
 tests/postgres_tests/test_hstore.py      | 34 +++++++++++++++++++++---
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/django/contrib/postgres/fields/hstore.py b/django/contrib/postgres/fields/hstore.py
index d47b34d459..39f074b763 100644
--- a/django/contrib/postgres/fields/hstore.py
+++ b/django/contrib/postgres/fields/hstore.py
@@ -6,15 +6,18 @@ from django.core import exceptions
 from django.db.models import Field, TextField, Transform
 from django.utils.translation import gettext_lazy as _
 
+from .mixins import CheckFieldDefaultMixin
+
 __all__ = ['HStoreField']
 
 
-class HStoreField(Field):
+class HStoreField(CheckFieldDefaultMixin, Field):
     empty_strings_allowed = False
     description = _('Map of strings to strings/nulls')
     default_error_messages = {
         'not_a_string': _('The value of "%(key)s" is not a string or null.'),
     }
+    _default_hint = ('dict', '{}')
 
     def db_type(self, connection):
         return 'hstore'
diff --git a/tests/postgres_tests/test_hstore.py b/tests/postgres_tests/test_hstore.py
index b58e5e5e20..a51cb4e66f 100644
--- a/tests/postgres_tests/test_hstore.py
+++ b/tests/postgres_tests/test_hstore.py
@@ -1,11 +1,11 @@
 import json
 
-from django.core import exceptions, serializers
+from django.core import checks, exceptions, serializers
 from django.forms import Form
-from django.test.utils import modify_settings
+from django.test.utils import isolate_apps, modify_settings
 
 from . import PostgreSQLTestCase
-from .models import HStoreModel
+from .models import HStoreModel, PostgreSQLModel
 
 try:
     from django.contrib.postgres import forms
@@ -190,6 +190,34 @@ class TestQuerying(HStoreTestCase):
         )
 
 
+@isolate_apps('postgres_tests')
+class TestChecks(PostgreSQLTestCase):
+
+    def test_invalid_default(self):
+        class MyModel(PostgreSQLModel):
+            field = HStoreField(default={})
+
+        model = MyModel()
+        self.assertEqual(model.check(), [
+            checks.Warning(
+                msg=(
+                    "HStoreField default should be a callable instead of an "
+                    "instance so that it's not shared between all field "
+                    "instances."
+                ),
+                hint='Use a callable instead, e.g., use `dict` instead of `{}`.',
+                obj=MyModel._meta.get_field('field'),
+                id='postgres.E003',
+            )
+        ])
+
+    def test_valid_default(self):
+        class MyModel(PostgreSQLModel):
+            field = HStoreField(default=dict)
+
+        self.assertEqual(MyModel().check(), [])
+
+
 class TestSerialization(HStoreTestCase):
     test_data = json.dumps([{
         'model': 'postgres_tests.hstoremodel',