[5.0.x] Fixed #35359 -- Fixed migration operations ordering when adding fields referenced by GeneratedField.expression.

Thank you to Simon Charette for the review.

Backport of 9aeb38c296 from main.

django/db/migrations/autodetector.py

@@ -1035,6 +1035,8 @@ class MigrationAutodetector:
                     self.to_state,
                 )
             )
+        if field.generated:
+            dependencies.extend(self._get_dependencies_for_generated_field(field))
         # You can't just add NOT NULL fields with no default or fields
         # which don't allow empty strings as default.
         time_fields = (models.DateField, models.DateTimeField, models.TimeField)
@@ -1435,6 +1437,20 @@ class MigrationAutodetector:
             dependencies.append((through_app_label, through_object_name, None, True))
         return dependencies
 
+    def _get_dependencies_for_generated_field(self, field):
+        dependencies = []
+        referenced_base_fields = models.Q(field.expression).referenced_base_fields
+        newly_added_fields = sorted(self.new_field_keys - self.old_field_keys)
+        for app_label, model_name, added_field_name in newly_added_fields:
+            added_field = self.to_state.models[app_label, model_name].get_field(
+                added_field_name
+            )
+            if (
+                added_field.remote_field and added_field.remote_field.model
+            ) or added_field.name in referenced_base_fields:
+                dependencies.append((app_label, model_name, added_field.name, True))
+        return dependencies
+
     def _get_dependencies_for_model(self, app_label, model_name):
         """Return foreign key dependencies of the given model."""
         dependencies = []

docs/releases/5.0.5.txt

@@ -23,3 +23,7 @@ Bugfixes
 
 * Allowed importing ``aprefetch_related_objects`` from ``django.db.models``
   (:ticket:`35392`).
+
+* Fixed a bug in Django 5.0 that caused a migration crash when a
+  ``GeneratedField`` was added before any of the referenced fields from its
+  ``expression`` definition (:ticket:`35359`).

tests/migrations/test_autodetector.py

@@ -13,6 +13,7 @@ from django.db.migrations.graph import MigrationGraph
 from django.db.migrations.loader import MigrationLoader
 from django.db.migrations.questioner import MigrationQuestioner
 from django.db.migrations.state import ModelState, ProjectState
+from django.db.models.functions import Concat, Lower
 from django.test import SimpleTestCase, TestCase, ignore_warnings, override_settings
 from django.test.utils import isolate_lru_cache
 from django.utils.deprecation import RemovedInDjango51Warning
@@ -1370,6 +1371,82 @@ class AutodetectorTests(BaseAutodetectorTests):
         self.assertOperationFieldAttributes(changes, "testapp", 0, 2, auto_now_add=True)
         self.assertEqual(mocked_ask_method.call_count, 3)
 
+    def test_add_field_before_generated_field(self):
+        initial_state = ModelState(
+            "testapp",
+            "Author",
+            [
+                ("name", models.CharField(max_length=20)),
+            ],
+        )
+        updated_state = ModelState(
+            "testapp",
+            "Author",
+            [
+                ("name", models.CharField(max_length=20)),
+                ("surname", models.CharField(max_length=20)),
+                (
+                    "lower_full_name",
+                    models.GeneratedField(
+                        expression=Concat(Lower("name"), Lower("surname")),
+                        output_field=models.CharField(max_length=30),
+                        db_persist=True,
+                    ),
+                ),
+            ],
+        )
+        changes = self.get_changes([initial_state], [updated_state])
+        self.assertNumberMigrations(changes, "testapp", 1)
+        self.assertOperationTypes(changes, "testapp", 0, ["AddField", "AddField"])
+        self.assertOperationFieldAttributes(
+            changes, "testapp", 0, 1, expression=Concat(Lower("name"), Lower("surname"))
+        )
+
+    def test_add_fk_before_generated_field(self):
+        initial_state = ModelState(
+            "testapp",
+            "Author",
+            [
+                ("name", models.CharField(max_length=20)),
+            ],
+        )
+        updated_state = [
+            ModelState(
+                "testapp",
+                "Publisher",
+                [
+                    ("name", models.CharField(max_length=20)),
+                ],
+            ),
+            ModelState(
+                "testapp",
+                "Author",
+                [
+                    ("name", models.CharField(max_length=20)),
+                    (
+                        "publisher",
+                        models.ForeignKey("testapp.Publisher", models.CASCADE),
+                    ),
+                    (
+                        "lower_full_name",
+                        models.GeneratedField(
+                            expression=Concat("name", "publisher_id"),
+                            output_field=models.CharField(max_length=20),
+                            db_persist=True,
+                        ),
+                    ),
+                ],
+            ),
+        ]
+        changes = self.get_changes([initial_state], updated_state)
+        self.assertNumberMigrations(changes, "testapp", 1)
+        self.assertOperationTypes(
+            changes, "testapp", 0, ["CreateModel", "AddField", "AddField"]
+        )
+        self.assertOperationFieldAttributes(
+            changes, "testapp", 0, 2, expression=Concat("name", "publisher_id")
+        )
+
     def test_remove_field(self):
         """Tests autodetection of removed fields."""
         changes = self.get_changes([self.author_name], [self.author_empty])

tests/migrations/test_operations.py

@@ -8,7 +8,7 @@ from django.db.migrations.operations.fields import FieldOperation
 from django.db.migrations.state import ModelState, ProjectState
 from django.db.models import F
 from django.db.models.expressions import Value
-from django.db.models.functions import Abs, Pi
+from django.db.models.functions import Abs, Concat, Pi
 from django.db.transaction import atomic
 from django.test import (
     SimpleTestCase,
@@ -1372,6 +1372,54 @@ class OperationTests(OperationTestBase):
         self.assertEqual(definition[1], [])
         self.assertEqual(sorted(definition[2]), ["field", "model_name", "name"])
 
+    @skipUnlessDBFeature("supports_stored_generated_columns")
+    def test_add_generate_field(self):
+        app_label = "test_add_generate_field"
+        project_state = self.apply_operations(
+            app_label,
+            ProjectState(),
+            operations=[
+                migrations.CreateModel(
+                    "Rider",
+                    fields=[
+                        ("id", models.AutoField(primary_key=True)),
+                    ],
+                ),
+                migrations.CreateModel(
+                    "Pony",
+                    fields=[
+                        ("id", models.AutoField(primary_key=True)),
+                        ("name", models.CharField(max_length=20)),
+                        (
+                            "rider",
+                            models.ForeignKey(
+                                f"{app_label}.Rider", on_delete=models.CASCADE
+                            ),
+                        ),
+                        (
+                            "name_and_id",
+                            models.GeneratedField(
+                                expression=Concat(("name"), ("rider_id")),
+                                output_field=models.TextField(),
+                                db_persist=True,
+                            ),
+                        ),
+                    ],
+                ),
+            ],
+        )
+        Pony = project_state.apps.get_model(app_label, "Pony")
+        Rider = project_state.apps.get_model(app_label, "Rider")
+        rider = Rider.objects.create()
+        pony = Pony.objects.create(name="pony", rider=rider)
+        self.assertEqual(pony.name_and_id, str(pony.name) + str(rider.id))
+
+        new_rider = Rider.objects.create()
+        pony.rider = new_rider
+        pony.save()
+        pony.refresh_from_db()
+        self.assertEqual(pony.name_and_id, str(pony.name) + str(new_rider.id))
+
     def test_add_charfield(self):
         """
         Tests the AddField operation on TextField.