Fixed #27369 -- Prevented widgets from being shared between form field instances.

django/forms/fields.py

@@ -94,6 +94,8 @@ class Field(object):
         widget = widget or self.widget
         if isinstance(widget, type):
             widget = widget()
+        else:
+            widget = copy.deepcopy(widget)
 
         # Trigger the localization machinery if needed.
         self.localize = localize

tests/forms_tests/field_tests/test_base.py

-from django.forms import Field
+from django.forms import ChoiceField, Field, Form, Select
 from django.test import SimpleTestCase
 
 
@@ -20,3 +20,17 @@ class BasicFieldsTests(SimpleTestCase):
 
         f = ComplexField()
         self.assertTrue(f.class_a_var)
+
+    def test_field_deepcopies_widget_instance(self):
+        class CustomChoiceField(ChoiceField):
+            widget = Select(attrs={'class': 'my-custom-class'})
+
+        class TestForm(Form):
+            field1 = CustomChoiceField(choices=[])
+            field2 = CustomChoiceField(choices=[])
+
+        f = TestForm()
+        f.fields['field1'].choices = [('1', '1')]
+        f.fields['field2'].choices = [('2', '2')]
+        self.assertEqual(f.fields['field1'].widget.choices, [('1', '1')])
+        self.assertEqual(f.fields['field2'].widget.choices, [('2', '2')])

tests/model_forms/tests.py

@@ -2867,7 +2867,7 @@ class FormFieldCallbackTests(SimpleTestCase):
                 fields = "__all__"
 
         Form = modelform_factory(Person, form=BaseForm)
-        self.assertIs(Form.base_fields['name'].widget, widget)
+        self.assertIsInstance(Form.base_fields['name'].widget, forms.Textarea)
 
     def test_factory_with_widget_argument(self):
         """ Regression for #15315: modelform_factory should accept widgets