Fixed #28370 -- Deprecated the context arg of Field.from_db_value() and Expression.convert_value().

Unused since a0d166306fbdc41f49e6fadf4ec84b17eb147daa.

2 files changed, 32 insertions, 1 deletions

diff --git a/tests/from_db_value/models.py b/tests/from_db_value/models.py
index 2f2304ff0a..3968a193d6 100644
--- a/tests/from_db_value/models.py
+++ b/tests/from_db_value/models.py
@@ -17,7 +17,7 @@ class CashField(models.DecimalField):
         kwargs['decimal_places'] = 2
         super().__init__(**kwargs)
 
-    def from_db_value(self, value, expression, connection, context):
+    def from_db_value(self, value, expression, connection):
         cash = Cash(value)
         cash.vendor = connection.vendor
         return cash
@@ -28,3 +28,12 @@ class CashModel(models.Model):
 
     def __str__(self):
         return str(self.cash)
+
+
+class CashFieldDeprecated(CashField):
+    def from_db_value(self, value, expression, connection, context):
+        return super().from_db_value(value, expression, connection)
+
+
+class CashModelDeprecated(models.Model):
+    cash = CashFieldDeprecated()
diff --git a/tests/from_db_value/test_deprecated.py b/tests/from_db_value/test_deprecated.py
new file mode 100644
index 0000000000..f0e7ed92b7
--- /dev/null
+++ b/tests/from_db_value/test_deprecated.py
@@ -0,0 +1,22 @@
+import warnings
+
+from django.test import TestCase
+
+from .models import Cash, CashModelDeprecated
+
+
+class FromDBValueDeprecationTests(TestCase):
+
+    def test_deprecation(self):
+        CashModelDeprecated.objects.create(cash='12.50')
+        with warnings.catch_warnings(record=True) as warns:
+            warnings.simplefilter('always')
+            instance = CashModelDeprecated.objects.get()
+        self.assertIsInstance(instance.cash, Cash)
+        self.assertEqual(len(warns), 1)
+        msg = str(warns[0].message)
+        self.assertEqual(
+            msg,
+            'Remove the context parameter from CashFieldDeprecated.from_db_value(). '
+            'Support for it will be removed in Django 3.0.'
+        )