[1.11.x] Fixed #28188 -- Fixed crash when pickling model fields.

Regression in d2a26c1a90e837777dabdf3d67ceec4d2a70fb86.

Thanks Adam Alton for the report and test, and Adam Johnson for
suggesting the fix.

Backport of a9874d48b1b9d91988b9f299726ec4f559fb2f75 from master

1 files changed, 9 insertions, 0 deletions

diff --git a/tests/model_fields/tests.py b/tests/model_fields/tests.py
index a9c9794a3c..00f8338128 100644
--- a/tests/model_fields/tests.py
+++ b/tests/model_fields/tests.py
@@ -1,3 +1,5 @@
+import pickle
+
 from django import forms
 from django.db import models
 from django.test import SimpleTestCase, TestCase
@@ -76,6 +78,13 @@ class BasicFieldTests(TestCase):
         self.assertIsNotNone(f1)
         self.assertNotIn(f2, (None, 1, ''))
 
+    def test_field_instance_is_picklable(self):
+        """Field instances can be pickled."""
+        field = models.Field(max_length=100, default='a string')
+        # Must be picklable with this cached property populated (#28188).
+        field._get_default
+        pickle.dumps(field)
+
 
 class ChoicesTests(SimpleTestCase):