From 7c18b22e2fa70aa8dcfadb33beb17933abdf7ee4 Mon Sep 17 00:00:00 2001
From: Hasan Ramezani <hasan.r67@gmail.com>
Date: Sun, 13 Dec 2020 22:41:20 +0100
Subject: [PATCH] Fixed #32256 -- Fixed migration optimization crash when
 swapping field names.

This disables optimization of RenameField operation when an old field
name is referenced in subsequent operations.

Co-authored-by: InvalidInterrupt <InvalidInterrupt@users.noreply.github.com>
---
 django/db/migrations/operations/fields.py |  7 +++++--
 tests/migrations/test_optimizer.py        | 17 +++++++++++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/django/db/migrations/operations/fields.py b/django/db/migrations/operations/fields.py
index 8e494fd595..728105ea05 100644
--- a/django/db/migrations/operations/fields.py
+++ b/django/db/migrations/operations/fields.py
@@ -392,8 +392,11 @@ class RenameField(FieldOperation):
                 ),
             ]
         # Skip `FieldOperation.reduce` as we want to run `references_field`
-        # against self.new_name.
+        # against self.old_name and self.new_name.
         return (
             super(FieldOperation, self).reduce(operation, app_label) or
-            not operation.references_field(self.model_name, self.new_name, app_label)
+            not (
+                operation.references_field(self.model_name, self.old_name, app_label) or
+                operation.references_field(self.model_name, self.new_name, app_label)
+            )
         )
diff --git a/tests/migrations/test_optimizer.py b/tests/migrations/test_optimizer.py
index 9bb1aafebd..0caaf66f9e 100644
--- a/tests/migrations/test_optimizer.py
+++ b/tests/migrations/test_optimizer.py
@@ -572,6 +572,23 @@ class OptimizerTests(SimpleTestCase):
             ],
         )
 
+    def test_swapping_fields_names(self):
+        self.assertDoesNotOptimize(
+            [
+                migrations.CreateModel(
+                    'MyModel',
+                    [
+                        ('field_a', models.IntegerField()),
+                        ('field_b', models.IntegerField()),
+                    ],
+                ),
+                migrations.RunPython(migrations.RunPython.noop),
+                migrations.RenameField('MyModel', 'field_a', 'field_c'),
+                migrations.RenameField('MyModel', 'field_b', 'field_a'),
+                migrations.RenameField('MyModel', 'field_c', 'field_b'),
+            ],
+        )
+
     def test_create_model_remove_field(self):
         """
         RemoveField should optimize into CreateModel.