Fixed #28542 -- Fixed deletion of primary key constraint if the new field is unique.

1 files changed, 30 insertions, 14 deletions

diff --git a/tests/schema/tests.py b/tests/schema/tests.py
index cc2d5384f8..3a66c2ae7a 100644
--- a/tests/schema/tests.py
+++ b/tests/schema/tests.py
@@ -1098,34 +1098,50 @@ class SchemaTests(TransactionTestCase):
         Should be able to rename an IntegerField(primary_key=True) to
         IntegerField(unique=True).
         """
-        class IntegerUnique(Model):
+        with connection.schema_editor() as editor:
+            editor.create_model(IntegerPK)
+        # Delete the old PK
+        old_field = IntegerPK._meta.get_field('i')
+        new_field = IntegerField(unique=True)
+        new_field.model = IntegerPK
+        new_field.set_attributes_from_name('i')
+        with connection.schema_editor() as editor:
+            editor.alter_field(IntegerPK, old_field, new_field, strict=True)
+        # The primary key constraint is gone. Result depends on database:
+        # 'id' for SQLite, None for others (must not be 'i').
+        self.assertIn(self.get_primary_key(IntegerPK._meta.db_table), ('id', None))
+
+        # Set up a model class as it currently stands. The original IntegerPK
+        # class is now out of date and some backends make use of the whole
+        # model class when modifying a field (such as sqlite3 when remaking a
+        # table) so an outdated model class leads to incorrect results.
+        class Transitional(Model):
             i = IntegerField(unique=True)
-            j = IntegerField(primary_key=True)
+            j = IntegerField(unique=True)
 
             class Meta:
                 app_label = 'schema'
                 apps = new_apps
                 db_table = 'INTEGERPK'
 
-        with connection.schema_editor() as editor:
-            editor.create_model(IntegerPK)
-
         # model requires a new PK
-        old_field = IntegerPK._meta.get_field('j')
+        old_field = Transitional._meta.get_field('j')
         new_field = IntegerField(primary_key=True)
-        new_field.model = IntegerPK
+        new_field.model = Transitional
         new_field.set_attributes_from_name('j')
 
         with connection.schema_editor() as editor:
-            editor.alter_field(IntegerPK, old_field, new_field, strict=True)
+            editor.alter_field(Transitional, old_field, new_field, strict=True)
 
-        old_field = IntegerPK._meta.get_field('i')
-        new_field = IntegerField(unique=True)
-        new_field.model = IntegerPK
-        new_field.set_attributes_from_name('i')
+        # Create a model class representing the updated model.
+        class IntegerUnique(Model):
+            i = IntegerField(unique=True)
+            j = IntegerField(primary_key=True)
 
-        with connection.schema_editor() as editor:
-            editor.alter_field(IntegerPK, old_field, new_field, strict=True)
+            class Meta:
+                app_label = 'schema'
+                apps = new_apps
+                db_table = 'INTEGERPK'
 
         # Ensure unique constraint works.
         IntegerUnique.objects.create(i=1, j=1)