Refs #27236 -- Reverted "Refs #27236 -- Added generic mechanism to handle the deprecation of migration operations."

This reverts commit 41019e48bbf082c985e6ba3bad34d118b903bff1.

12 files changed, 24 insertions, 230 deletions

diff --git a/django/core/checks/__init__.py b/django/core/checks/__init__.py
index deea0d471a..998ab9dee2 100644
--- a/django/core/checks/__init__.py
+++ b/django/core/checks/__init__.py
@@ -19,7 +19,6 @@ import django.core.checks.caches  # NOQA isort:skip
 import django.core.checks.compatibility.django_4_0  # NOQA isort:skip
 import django.core.checks.database  # NOQA isort:skip
 import django.core.checks.files  # NOQA isort:skip
-import django.core.checks.migrations  # NOQA isort:skip
 import django.core.checks.model_checks  # NOQA isort:skip
 import django.core.checks.security.base  # NOQA isort:skip
 import django.core.checks.security.csrf  # NOQA isort:skip
diff --git a/django/core/checks/migrations.py b/django/core/checks/migrations.py
deleted file mode 100644
index 92649a59a9..0000000000
--- a/django/core/checks/migrations.py
+++ /dev/null
@@ -1,12 +0,0 @@
-from django.core.checks import Tags, register
-
-
-@register(Tags.migrations)
-def check_migration_operations(**kwargs):
-    from django.db.migrations.loader import MigrationLoader
-
-    errors = []
-    loader = MigrationLoader(None, ignore_no_migrations=True)
-    for migration in loader.disk_migrations.values():
-        errors.extend(migration.check())
-    return errors
diff --git a/django/core/checks/registry.py b/django/core/checks/registry.py
index 328209130a..f4bdea8691 100644
--- a/django/core/checks/registry.py
+++ b/django/core/checks/registry.py
@@ -15,7 +15,6 @@ class Tags:
     compatibility = "compatibility"
     database = "database"
     files = "files"
-    migrations = "migrations"
     models = "models"
     security = "security"
     signals = "signals"
diff --git a/django/db/migrations/migration.py b/django/db/migrations/migration.py
index 7cc3e22361..ea9d02a94a 100644
--- a/django/db/migrations/migration.py
+++ b/django/db/migrations/migration.py
@@ -219,12 +219,6 @@ class Migration:
             name = new_name
         return name
 
-    def check(self):
-        errors = []
-        for operation in self.operations:
-            errors.extend(operation.check_deprecation_details())
-        return errors
-
 
 class SwappableTuple(tuple):
     """
diff --git a/django/db/migrations/operations/base.py b/django/db/migrations/operations/base.py
index 40128174c7..7d4dff2597 100644
--- a/django/db/migrations/operations/base.py
+++ b/django/db/migrations/operations/base.py
@@ -1,8 +1,7 @@
 from django.db import router
-from django.utils.deprecation import DeprecationForHistoricalMigrationMixin
 
 
-class Operation(DeprecationForHistoricalMigrationMixin):
+class Operation:
     """
     Base class for migration operations.
 
@@ -34,8 +33,6 @@ class Operation(DeprecationForHistoricalMigrationMixin):
 
     serialization_expand_args = []
 
-    check_type = "migrations"
-
     def __new__(cls, *args, **kwargs):
         # We capture the arguments to make returning them trivial
         self = object.__new__(cls)
diff --git a/docs/ref/checks.txt b/docs/ref/checks.txt
index 55e4ca64b2..92278db659 100644
--- a/docs/ref/checks.txt
+++ b/docs/ref/checks.txt
@@ -83,7 +83,6 @@ Django's system checks are organized using the following tags:
   you specify configured database aliases using the ``--database`` option when
   calling the :djadmin:`check` command.
 * ``files``: Checks files related configuration.
-* ``migrations``: Checks of migration operations.
 * ``models``: Checks of model, field, and manager definitions.
 * ``security``: Checks security related configuration.
 * ``signals``: Checks on signal declarations and handler registrations.
@@ -95,10 +94,6 @@ Django's system checks are organized using the following tags:
 
 Some checks may be registered with multiple tags.
 
-.. versionchanged:: 4.2
-
-    The ``migrations`` tag was added.
-
 Core system checks
 ==================
 
diff --git a/docs/releases/4.2.txt b/docs/releases/4.2.txt
index 3b8ae5596c..24458cfc86 100644
--- a/docs/releases/4.2.txt
+++ b/docs/releases/4.2.txt
@@ -172,8 +172,7 @@ Management Commands
 Migrations
 ~~~~~~~~~~
 
-* The new :ref:`generic mechanism <migrations-removing-operation>` allows
-  handling the deprecation of migration operations.
+* ...
 
 Models
 ~~~~~~
diff --git a/docs/topics/checks.txt b/docs/topics/checks.txt
index 0864d6db38..9586466285 100644
--- a/docs/topics/checks.txt
+++ b/docs/topics/checks.txt
@@ -128,18 +128,18 @@ The code below is equivalent to the code above::
 
 .. _field-checking:
 
-Field, model, manager, migration, and database checks
------------------------------------------------------
+Field, model, manager, and database checks
+------------------------------------------
 
 In some cases, you won't need to register your check function -- you can
 piggyback on an existing registration.
 
-Fields, models, model managers, migrations, and database backends all implement
-a ``check()`` method that is already registered with the check framework. If
-you want to add extra checks, you can extend the implementation on the base
-class, perform any extra checks you need, and append any messages to those
-generated by the base class. It's recommended that you delegate each check to
-separate methods.
+Fields, models, model managers, and database backends all implement a
+``check()`` method that is already registered with the check framework. If you
+want to add extra checks, you can extend the implementation on the base class,
+perform any extra checks you need, and append any messages to those generated
+by the base class. It's recommended that you delegate each check to separate
+methods.
 
 Consider an example where you are implementing a custom field named
 ``RangedIntegerField``. This field adds ``min`` and ``max`` arguments to the
@@ -194,10 +194,6 @@ the only difference is that the check is a classmethod, not an instance method::
             # ... your own checks ...
             return errors
 
-.. versionchanged:: 4.2
-
-    Migration checks were added.
-
 Writing tests
 -------------
 
diff --git a/docs/topics/migrations.txt b/docs/topics/migrations.txt
index 2350ac756c..cf3451a782 100644
--- a/docs/topics/migrations.txt
+++ b/docs/topics/migrations.txt
@@ -503,56 +503,6 @@ database migrations such as ``__init__()``, ``deconstruct()``, and
 which reference the field exist. For example, after squashing migrations and
 removing the old ones, you should be able to remove the field completely.
 
-.. _migrations-removing-operation:
-
-Considerations when removing migration operations
-=================================================
-
-.. versionadded:: 4.2
-
-Removing custom operations from your project or third-party app will cause a
-problem if they are referenced in old migrations.
-
-To help with this situation, Django provides some operation attributes to
-assist with operation deprecation using the :doc:`system checks framework
-</topics/checks>`.
-
-Add the ``system_check_deprecated_details`` attribute to your operation similar
-to the following::
-
-    class MyCustomOperation(Operation):
-        system_check_deprecated_details = {
-            "msg": (
-                "MyCustomOperation has been deprecated. Support for it "
-                "(except in historical migrations) will be removed in "
-                "Django 5.1."
-            ),
-            "hint": "Use DifferentOperation instead.",  # optional
-            "id": "migrations.W900",  # pick a unique ID for your operation.
-        }
-
-After a deprecation period of your choosing (two or three feature releases for
-operations in Django itself), change the ``system_check_deprecated_details``
-attribute to ``system_check_removed_details`` and update the dictionary similar
-to::
-
-    class MyCustomOperation(Operation):
-        system_check_removed_details = {
-            "msg": (
-                "MyCustomOperation has been removed except for support in "
-                "historical migrations."
-            ),
-            "hint': "Use DifferentOperation instead.",
-            "id": "migrations.E900",  # pick a unique ID for your operation.
-        }
-
-You should keep the operation's methods that are required for it to operate in
-database migrations such as ``__init__()``, ``state_forwards()``,
-``database_forwards()``, and ``database_backwards()``. Keep this stub operation
-for as long as any migrations which reference the operation exist. For example,
-after squashing migrations and removing the old ones, you should be able to
-remove the operation completely.
-
 .. _data-migrations:
 
 Data Migrations
diff --git a/tests/check_framework/test_migrations.py b/tests/check_framework/test_migrations.py
deleted file mode 100644
index 0b00690e77..0000000000
--- a/tests/check_framework/test_migrations.py
+++ /dev/null
@@ -1,101 +0,0 @@
-from django.core import checks
-from django.db import migrations
-from django.db.migrations.operations.base import Operation
-from django.test import TestCase
-
-
-class DeprecatedMigrationOperationTests(TestCase):
-    def test_default_operation(self):
-        class MyOperation(Operation):
-            system_check_deprecated_details = {}
-
-        my_operation = MyOperation()
-
-        class Migration(migrations.Migration):
-            operations = [my_operation]
-
-        self.assertEqual(
-            Migration("name", "app_label").check(),
-            [
-                checks.Warning(
-                    msg="MyOperation has been deprecated.",
-                    obj=my_operation,
-                    id="migrations.WXXX",
-                )
-            ],
-        )
-
-    def test_user_specified_details(self):
-        class MyOperation(Operation):
-            system_check_deprecated_details = {
-                "msg": "This operation is deprecated and will be removed soon.",
-                "hint": "Use something else.",
-                "id": "migrations.W999",
-            }
-
-        my_operation = MyOperation()
-
-        class Migration(migrations.Migration):
-            operations = [my_operation]
-
-        self.assertEqual(
-            Migration("name", "app_label").check(),
-            [
-                checks.Warning(
-                    msg="This operation is deprecated and will be removed soon.",
-                    obj=my_operation,
-                    hint="Use something else.",
-                    id="migrations.W999",
-                )
-            ],
-        )
-
-
-class RemovedMigrationOperationTests(TestCase):
-    def test_default_operation(self):
-        class MyOperation(Operation):
-            system_check_removed_details = {}
-
-        my_operation = MyOperation()
-
-        class Migration(migrations.Migration):
-            operations = [my_operation]
-
-        self.assertEqual(
-            Migration("name", "app_label").check(),
-            [
-                checks.Error(
-                    msg=(
-                        "MyOperation has been removed except for support in historical "
-                        "migrations."
-                    ),
-                    obj=my_operation,
-                    id="migrations.EXXX",
-                )
-            ],
-        )
-
-    def test_user_specified_details(self):
-        class MyOperation(Operation):
-            system_check_removed_details = {
-                "msg": "Support for this operation is gone.",
-                "hint": "Use something else.",
-                "id": "migrations.E999",
-            }
-
-        my_operation = MyOperation()
-
-        class Migration(migrations.Migration):
-            operations = [my_operation]
-
-        self.assertEqual(
-            Migration("name", "app_label").check(),
-            [
-                checks.Error(
-                    msg="Support for this operation is gone.",
-                    obj=my_operation,
-                    hint="Use something else.",
-                    id="migrations.E999",
-                )
-            ],
-        )
diff --git a/tests/db_functions/migrations/0001_setup_extensions.py b/tests/db_functions/migrations/0001_setup_extensions.py
index 5909a96eb8..0289055499 100644
--- a/tests/db_functions/migrations/0001_setup_extensions.py
+++ b/tests/db_functions/migrations/0001_setup_extensions.py
@@ -1,22 +1,11 @@
-from django.db import migrations
-from django.db.migrations.operations.base import Operation
-
-
-class DummyOperation(Operation):
-    def state_forwards(self, app_label, state):
-        pass
-
-    def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        pass
-
-    def database_backwards(self, app_label, schema_editor, from_state, to_state):
-        pass
+from unittest import mock
 
+from django.db import migrations
 
 try:
     from django.contrib.postgres.operations import CryptoExtension
 except ImportError:
-    CryptoExtension = DummyOperation
+    CryptoExtension = mock.Mock()
 
 
 class Migration(migrations.Migration):
diff --git a/tests/postgres_tests/migrations/0001_setup_extensions.py b/tests/postgres_tests/migrations/0001_setup_extensions.py
index 3edeff7b82..090abf9649 100644
--- a/tests/postgres_tests/migrations/0001_setup_extensions.py
+++ b/tests/postgres_tests/migrations/0001_setup_extensions.py
@@ -1,17 +1,6 @@
-from django.db import connection, migrations
-from django.db.migrations.operations.base import Operation
-
-
-class DummyOperation(Operation):
-    def state_forwards(self, app_label, state):
-        pass
-
-    def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        pass
-
-    def database_backwards(self, app_label, schema_editor, from_state, to_state):
-        pass
+from unittest import mock
 
+from django.db import connection, migrations
 
 try:
     from django.contrib.postgres.operations import (
@@ -26,14 +15,14 @@ try:
         UnaccentExtension,
     )
 except ImportError:
-    BloomExtension = DummyOperation
-    BtreeGinExtension = DummyOperation
-    BtreeGistExtension = DummyOperation
-    CITextExtension = DummyOperation
-    CreateExtension = DummyOperation
-    HStoreExtension = DummyOperation
-    TrigramExtension = DummyOperation
-    UnaccentExtension = DummyOperation
+    BloomExtension = mock.Mock()
+    BtreeGinExtension = mock.Mock()
+    BtreeGistExtension = mock.Mock()
+    CITextExtension = mock.Mock()
+    CreateExtension = mock.Mock()
+    HStoreExtension = mock.Mock()
+    TrigramExtension = mock.Mock()
+    UnaccentExtension = mock.Mock()
     needs_crypto_extension = False
 else:
     needs_crypto_extension = (
@@ -52,7 +41,7 @@ class Migration(migrations.Migration):
         # dash in its name.
         CreateExtension("uuid-ossp"),
         # CryptoExtension is required for RandomUUID() on PostgreSQL < 13.
-        CryptoExtension() if needs_crypto_extension else DummyOperation(),
+        CryptoExtension() if needs_crypto_extension else mock.Mock(),
         HStoreExtension(),
         TrigramExtension(),
         UnaccentExtension(),