Fixed #33471 -- Made AlterField operation a noop when changing "choices".

This also allows customizing attributes of fields that don't affect
a column definition.

2 files changed, 24 insertions, 0 deletions

diff --git a/docs/howto/custom-model-fields.txt b/docs/howto/custom-model-fields.txt
index 2dedf05a11..c4621c8500 100644
--- a/docs/howto/custom-model-fields.txt
+++ b/docs/howto/custom-model-fields.txt
@@ -314,6 +314,26 @@ reconstructing the field::
     new_instance = MyField(*args, **kwargs)
     self.assertEqual(my_field_instance.some_attribute, new_instance.some_attribute)
 
+.. _custom-field-non_db_attrs:
+
+Field attributes not affecting database column definition
+---------------------------------------------------------
+
+.. versionadded:: 4.1
+
+You can override ``Field.non_db_attrs`` to customize attributes of a field that
+don't affect a column definition. It's used during model migrations to detect
+no-op ``AlterField`` operations.
+
+For example::
+
+    class CommaSepField(models.Field):
+
+        @property
+        def non_db_attrs(self):
+            return super().non_db_attrs + ("separator",)
+
+
 Changing a custom field's base class
 ------------------------------------
 
diff --git a/docs/releases/4.1.txt b/docs/releases/4.1.txt
index 4413fdfc9a..d83da638fc 100644
--- a/docs/releases/4.1.txt
+++ b/docs/releases/4.1.txt
@@ -288,6 +288,10 @@ Models
   on MariaDB and MySQL. For databases that do not support ``XOR``, the query
   will be converted to an equivalent using ``AND``, ``OR``, and ``NOT``.
 
+* The new :ref:`Field.non_db_attrs <custom-field-non_db_attrs>` attribute
+  allows customizing attributes of fields that don't affect a column
+  definition.
+
 Requests and Responses
 ~~~~~~~~~~~~~~~~~~~~~~