Fixed #24351, #24346 -- Changed the signature of allow_migrate().

The new signature enables better support for routing RunPython and
RunSQL operations, especially w.r.t. reusable and third-party apps.

This commit also takes advantage of the deprecation cycle for the old
signature to remove the backward incompatibility introduced in #22583;
RunPython and RunSQL won't call allow_migrate() when when the router
has the old signature.

Thanks Aymeric Augustin and Tim Graham for helping shape up the patch.

Refs 22583.

15 files changed, 67 insertions, 38 deletions

diff --git a/django/contrib/auth/management/__init__.py b/django/contrib/auth/management/__init__.py
index 44d8563c14..ea05d2b497 100644
--- a/django/contrib/auth/management/__init__.py
+++ b/django/contrib/auth/management/__init__.py
@@ -66,7 +66,7 @@ def create_permissions(app_config, verbosity=2, interactive=True, using=DEFAULT_
     except LookupError:
         return
 
-    if not router.allow_migrate(using, Permission):
+    if not router.allow_migrate_model(using, Permission):
         return
 
     from django.contrib.contenttypes.models import ContentType
diff --git a/django/contrib/contenttypes/management.py b/django/contrib/contenttypes/management.py
index 6364c752d2..bfc25b3405 100644
--- a/django/contrib/contenttypes/management.py
+++ b/django/contrib/contenttypes/management.py
@@ -17,7 +17,7 @@ def update_contenttypes(app_config, verbosity=2, interactive=True, using=DEFAULT
     except LookupError:
         return
 
-    if not router.allow_migrate(using, ContentType):
+    if not router.allow_migrate_model(using, ContentType):
         return
 
     ContentType.objects.clear_cache()
diff --git a/django/contrib/contenttypes/migrations/0002_remove_content_type_name.py b/django/contrib/contenttypes/migrations/0002_remove_content_type_name.py
index 044fb615cf..8bd8032b41 100644
--- a/django/contrib/contenttypes/migrations/0002_remove_content_type_name.py
+++ b/django/contrib/contenttypes/migrations/0002_remove_content_type_name.py
@@ -33,6 +33,7 @@ class Migration(migrations.Migration):
         migrations.RunPython(
             migrations.RunPython.noop,
             add_legacy_name,
+            hints={'model_name': 'contenttype'},
         ),
         migrations.RemoveField(
             model_name='contenttype',
diff --git a/django/contrib/sites/management.py b/django/contrib/sites/management.py
index 7c6c32d95b..5647b6a304 100644
--- a/django/contrib/sites/management.py
+++ b/django/contrib/sites/management.py
@@ -14,7 +14,7 @@ def create_default_site(app_config, verbosity=2, interactive=True, using=DEFAULT
     except LookupError:
         return
 
-    if not router.allow_migrate(using, Site):
+    if not router.allow_migrate_model(using, Site):
         return
 
     if not Site.objects.using(using).exists():
diff --git a/django/core/cache/backends/db.py b/django/core/cache/backends/db.py
index f016179491..a41b611d5b 100644
--- a/django/core/cache/backends/db.py
+++ b/django/core/cache/backends/db.py
@@ -30,6 +30,7 @@ class Options(object):
         self.abstract = False
         self.managed = True
         self.proxy = False
+        self.swapped = False
 
 
 class BaseDatabaseCache(BaseCache):
diff --git a/django/core/management/commands/createcachetable.py b/django/core/management/commands/createcachetable.py
index 750e787200..4c014c88fd 100644
--- a/django/core/management/commands/createcachetable.py
+++ b/django/core/management/commands/createcachetable.py
@@ -38,7 +38,7 @@ class Command(BaseCommand):
 
     def create_table(self, database, tablename):
         cache = BaseDatabaseCache(tablename, {})
-        if not router.allow_migrate(database, cache.cache_model_class):
+        if not router.allow_migrate_model(database, cache.cache_model_class):
             return
         connection = connections[database]
 
diff --git a/django/core/management/commands/dumpdata.py b/django/core/management/commands/dumpdata.py
index a7c8bd7615..da1584d561 100644
--- a/django/core/management/commands/dumpdata.py
+++ b/django/core/management/commands/dumpdata.py
@@ -132,7 +132,7 @@ class Command(BaseCommand):
             for model in serializers.sort_dependencies(app_list.items()):
                 if model in excluded_models:
                     continue
-                if not model._meta.proxy and router.allow_migrate(using, model):
+                if not model._meta.proxy and router.allow_migrate_model(using, model):
                     if use_base_manager:
                         objects = model._base_manager
                     else:
diff --git a/django/core/management/commands/loaddata.py b/django/core/management/commands/loaddata.py
index a07f6b7300..464e19ce0c 100644
--- a/django/core/management/commands/loaddata.py
+++ b/django/core/management/commands/loaddata.py
@@ -139,7 +139,7 @@ class Command(BaseCommand):
 
                 for obj in objects:
                     objects_in_fixture += 1
-                    if router.allow_migrate(self.using, obj.object.__class__):
+                    if router.allow_migrate_model(self.using, obj.object.__class__):
                         loaded_objects_in_fixture += 1
                         self.models.add(obj.object.__class__)
                         try:
diff --git a/django/db/backends/base/creation.py b/django/db/backends/base/creation.py
index 854e17b6c2..a5e69ceedb 100644
--- a/django/db/backends/base/creation.py
+++ b/django/db/backends/base/creation.py
@@ -107,7 +107,7 @@ class BaseDatabaseCreation(object):
         def get_objects():
             for model in serializers.sort_dependencies(app_list):
                 if (not model._meta.proxy and model._meta.managed and
-                        router.allow_migrate(self.connection.alias, model)):
+                        router.allow_migrate_model(self.connection.alias, model)):
                     queryset = model._default_manager.using(self.connection.alias).order_by(model._meta.pk.name)
                     for obj in queryset.iterator():
                         yield obj
diff --git a/django/db/migrations/operations/base.py b/django/db/migrations/operations/base.py
index 557c956732..b750a1e4be 100644
--- a/django/db/migrations/operations/base.py
+++ b/django/db/migrations/operations/base.py
@@ -99,15 +99,17 @@ class Operation(object):
         """
         return self.references_model(model_name, app_label)
 
-    def allowed_to_migrate(self, connection_alias, model, hints=None):
+    def allow_migrate_model(self, connection_alias, model):
         """
         Returns if we're allowed to migrate the model.
+
+        This is a thin wrapper around router.allow_migrate_model() that
+        preemptively rejects any proxy, swapped out, or unmanaged model.
         """
-        # Always skip if proxy, swapped out, or unmanaged.
-        if model and (model._meta.proxy or model._meta.swapped or not model._meta.managed):
+        if model._meta.proxy or model._meta.swapped or not model._meta.managed:
             return False
 
-        return router.allow_migrate(connection_alias, model, **(hints or {}))
+        return router.allow_migrate_model(connection_alias, model)
 
     def __repr__(self):
         return "<%s %s%s>" % (
diff --git a/django/db/migrations/operations/fields.py b/django/db/migrations/operations/fields.py
index 70e7a0f296..e00cfa66e2 100644
--- a/django/db/migrations/operations/fields.py
+++ b/django/db/migrations/operations/fields.py
@@ -52,7 +52,7 @@ class AddField(Operation):
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.model_name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, to_model):
             from_model = from_state.apps.get_model(app_label, self.model_name)
             field = to_model._meta.get_field(self.name)
             if not self.preserve_default:
@@ -66,7 +66,7 @@ class AddField(Operation):
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
         from_model = from_state.apps.get_model(app_label, self.model_name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, from_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, from_model):
             schema_editor.remove_field(from_model, from_model._meta.get_field(self.name))
 
     def describe(self):
@@ -117,12 +117,12 @@ class RemoveField(Operation):
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         from_model = from_state.apps.get_model(app_label, self.model_name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, from_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, from_model):
             schema_editor.remove_field(from_model, from_model._meta.get_field(self.name))
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.model_name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, to_model):
             from_model = from_state.apps.get_model(app_label, self.model_name)
             schema_editor.add_field(from_model, to_model._meta.get_field(self.name))
 
@@ -184,7 +184,7 @@ class AlterField(Operation):
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.model_name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, to_model):
             from_model = from_state.apps.get_model(app_label, self.model_name)
             from_field = from_model._meta.get_field(self.name)
             to_field = to_model._meta.get_field(self.name)
@@ -267,7 +267,7 @@ class RenameField(Operation):
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.model_name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, to_model):
             from_model = from_state.apps.get_model(app_label, self.model_name)
             schema_editor.alter_field(
                 from_model,
@@ -277,7 +277,7 @@ class RenameField(Operation):
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.model_name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, to_model):
             from_model = from_state.apps.get_model(app_label, self.model_name)
             schema_editor.alter_field(
                 from_model,
diff --git a/django/db/migrations/operations/models.py b/django/db/migrations/operations/models.py
index 99df8a073e..efd35f0501 100644
--- a/django/db/migrations/operations/models.py
+++ b/django/db/migrations/operations/models.py
@@ -55,12 +55,12 @@ class CreateModel(Operation):
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         model = to_state.apps.get_model(app_label, self.name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, model):
+        if self.allow_migrate_model(schema_editor.connection.alias, model):
             schema_editor.create_model(model)
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
         model = from_state.apps.get_model(app_label, self.name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, model):
+        if self.allow_migrate_model(schema_editor.connection.alias, model):
             schema_editor.delete_model(model)
 
     def describe(self):
@@ -111,12 +111,12 @@ class DeleteModel(Operation):
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         model = from_state.apps.get_model(app_label, self.name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, model):
+        if self.allow_migrate_model(schema_editor.connection.alias, model):
             schema_editor.delete_model(model)
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
         model = to_state.apps.get_model(app_label, self.name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, model):
+        if self.allow_migrate_model(schema_editor.connection.alias, model):
             schema_editor.create_model(model)
 
     def references_model(self, name, app_label=None):
@@ -189,7 +189,7 @@ class RenameModel(Operation):
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         new_model = to_state.apps.get_model(app_label, self.new_name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, new_model):
             old_model = from_state.apps.get_model(app_label, self.old_name)
             # Move the main table
             schema_editor.alter_db_table(
@@ -287,7 +287,7 @@ class AlterModelTable(Operation):
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         new_model = to_state.apps.get_model(app_label, self.name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, new_model):
             old_model = from_state.apps.get_model(app_label, self.name)
             schema_editor.alter_db_table(
                 new_model,
@@ -347,7 +347,7 @@ class AlterUniqueTogether(Operation):
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         new_model = to_state.apps.get_model(app_label, self.name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, new_model):
             old_model = from_state.apps.get_model(app_label, self.name)
             schema_editor.alter_unique_together(
                 new_model,
@@ -399,7 +399,7 @@ class AlterIndexTogether(Operation):
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         new_model = to_state.apps.get_model(app_label, self.name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, new_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, new_model):
             old_model = from_state.apps.get_model(app_label, self.name)
             schema_editor.alter_index_together(
                 new_model,
@@ -448,7 +448,7 @@ class AlterOrderWithRespectTo(Operation):
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_model = to_state.apps.get_model(app_label, self.name)
-        if self.allowed_to_migrate(schema_editor.connection.alias, to_model):
+        if self.allow_migrate_model(schema_editor.connection.alias, to_model):
             from_model = from_state.apps.get_model(app_label, self.name)
             # Remove a field if we need to
             if from_model._meta.order_with_respect_to and not to_model._meta.order_with_respect_to:
diff --git a/django/db/migrations/operations/special.py b/django/db/migrations/operations/special.py
index 91261f724f..2c995c54ac 100644
--- a/django/db/migrations/operations/special.py
+++ b/django/db/migrations/operations/special.py
@@ -1,5 +1,7 @@
 from __future__ import unicode_literals
 
+from django.db import router
+
 from .base import Operation
 
 
@@ -94,13 +96,13 @@ class RunSQL(Operation):
             state_operation.state_forwards(app_label, state)
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        if self.allowed_to_migrate(schema_editor.connection.alias, None, hints=self.hints):
+        if router.allow_migrate(schema_editor.connection.alias, app_label, **self.hints):
             self._run_sql(schema_editor, self.sql)
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
         if self.reverse_sql is None:
             raise NotImplementedError("You cannot reverse this operation")
-        if self.allowed_to_migrate(schema_editor.connection.alias, None, hints=self.hints):
+        if router.allow_migrate(schema_editor.connection.alias, app_label, **self.hints):
             self._run_sql(schema_editor, self.reverse_sql)
 
     def describe(self):
@@ -171,7 +173,7 @@ class RunPython(Operation):
         pass
 
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
-        if self.allowed_to_migrate(schema_editor.connection.alias, None, hints=self.hints):
+        if router.allow_migrate(schema_editor.connection.alias, app_label, **self.hints):
             # We now execute the Python code in a context that contains a 'models'
             # object, representing the versioned models as an app registry.
             # We could try to override the global cache, but then people will still
@@ -181,7 +183,7 @@ class RunPython(Operation):
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
         if self.reverse_code is None:
             raise NotImplementedError("You cannot reverse this operation")
-        if self.allowed_to_migrate(schema_editor.connection.alias, None, hints=self.hints):
+        if router.allow_migrate(schema_editor.connection.alias, app_label, **self.hints):
             self.reverse_code(from_state.apps, schema_editor)
 
     def describe(self):
diff --git a/django/db/models/base.py b/django/db/models/base.py
index d906f2e461..60daa105b2 100644
--- a/django/db/models/base.py
+++ b/django/db/models/base.py
@@ -1549,7 +1549,7 @@ class Model(six.with_metaclass(ModelBase)):
         # Find the minimum max allowed length among all specified db_aliases.
         for db in settings.DATABASES.keys():
             # skip databases where the model won't be created
-            if not router.allow_migrate(db, cls):
+            if not router.allow_migrate_model(db, cls):
                 continue
             connection = connections[db]
             max_name_length = connection.ops.max_name_length()
diff --git a/django/db/utils.py b/django/db/utils.py
index 0480adf2dc..d038c20368 100644
--- a/django/db/utils.py
+++ b/django/db/utils.py
@@ -1,5 +1,7 @@
+import inspect
 import os
 import pkgutil
+import warnings
 from importlib import import_module
 from threading import local
 
@@ -7,6 +9,7 @@ from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
 from django.utils import six
 from django.utils._os import upath
+from django.utils.deprecation import RemovedInDjango20Warning
 from django.utils.functional import cached_property
 from django.utils.module_loading import import_string
 
@@ -276,22 +279,42 @@ class ConnectionRouter(object):
                     return allow
         return obj1._state.db == obj2._state.db
 
-    def allow_migrate(self, db, model, **hints):
+    def allow_migrate(self, db, app_label, **hints):
         for router in self.routers:
             try:
                 method = router.allow_migrate
             except AttributeError:
                 # If the router doesn't have a method, skip to the next one.
-                pass
+                continue
+
+            argspec = inspect.getargspec(router.allow_migrate)
+            if len(argspec.args) == 3 and not argspec.keywords:
+                warnings.warn(
+                    "The signature of allow_migrate has changed from "
+                    "allow_migrate(self, db, model) to "
+                    "allow_migrate(self, db, app_label, model_name=None, **hints). "
+                    "Support for the old signature will be removed in Django 2.0.",
+                    RemovedInDjango20Warning)
+                model = hints.get('model')
+                allow = None if model is None else method(db, model)
             else:
-                allow = method(db, model, **hints)
-                if allow is not None:
-                    return allow
+                allow = method(db, app_label, **hints)
+
+            if allow is not None:
+                return allow
         return True
 
+    def allow_migrate_model(self, db, model):
+        return self.allow_migrate(
+            db,
+            model._meta.app_label,
+            model_name=model._meta.model_name,
+            model=model,
+        )
+
     def get_migratable_models(self, app_config, db, include_auto_created=False):
         """
         Return app models allowed to be synchronized on provided db.
         """
         models = app_config.get_models(include_auto_created=include_auto_created)
-        return [model for model in models if self.allow_migrate(db, model)]
+        return [model for model in models if self.allow_migrate_model(db, model)]