Remove AppCache state handling, replace with swappable caches

django/db/backends/sqlite3/schema.py

@@ -1,5 +1,5 @@
 from django.db.backends.schema import BaseDatabaseSchemaEditor
-from django.db.models.loading import cache
+from django.db.models.loading import cache, default_cache, AppCache
 from django.db.models.fields.related import ManyToManyField
 
 
@@ -46,10 +46,12 @@ class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
         }
         meta = type("Meta", tuple(), meta_contents)
         body['Meta'] = meta
-        body['__module__'] = "__fake__"
-        with cache.temporary_state():
-            del cache.app_models[model._meta.app_label][model._meta.object_name.lower()]
-            temp_model = type(model._meta.object_name, model.__bases__, body)
+        body['__module__'] = model.__module__
+        self.app_cache = AppCache()
+        cache.set_cache(self.app_cache)
+        cache.copy_from(default_cache)
+        temp_model = type(model._meta.object_name, model.__bases__, body)
+        cache.set_cache(default_cache)
         # Create a new table with that format
         self.create_model(temp_model)
         # Copy data from the old table

django/db/models/base.py

@@ -228,14 +228,17 @@ class ModelBase(type):
             return new_class
 
         new_class._prepare()
-        register_models(new_class._meta.app_label, new_class)
         
-        # Because of the way imports happen (recursively), we may or may not be
-        # the first time this model tries to register with the framework. There
-        # should only be one class for each model, so we always return the
-        # registered version.
-        return get_model(new_class._meta.app_label, name,
-                         seed_cache=False, only_installed=False)
+        if new_class._meta.auto_register:
+            register_models(new_class._meta.app_label, new_class)
+            # Because of the way imports happen (recursively), we may or may not be
+            # the first time this model tries to register with the framework. There
+            # should only be one class for each model, so we always return the
+            # registered version.
+            return get_model(new_class._meta.app_label, name,
+                             seed_cache=False, only_installed=False)
+        else:
+            return new_class
 
     def copy_managers(cls, base_managers):
         # This is in-place sorting of an Options attribute, but that's fine.

django/db/models/loading.py

@@ -236,69 +236,49 @@ class AppCache(object):
             model_dict[model_name] = model
         self._get_models_cache.clear()
 
-    def save_state(self):
-        """
-        Returns an object that contains the current AppCache state.
-        Can be provided to restore_state to undo actions.
-        """
-        return {
-            "app_store": SortedDict(self.app_store.items()),
-            "app_labels": dict(self.app_labels.items()),
-            "app_models": SortedDict((k, SortedDict(v.items())) for k, v in self.app_models.items()),
-            "app_errors": dict(self.app_errors.items()),
-        }
-
-    def restore_state(self, state):
-        """
-        Restores the AppCache to a previous state from save_state.
-        Note that the state is used by reference, not copied in.
-        """
-        self.app_store = state['app_store']
-        self.app_labels = state['app_labels']
-        self.app_models = state['app_models']
-        self.app_errors = state['app_errors']
-        self._get_models_cache.clear()
-
-    def temporary_state(self):
-        "Returns a context manager that restores the state on exit"
-        return StateContextManager(self)
-
-    def unregister_all(self):
-        """
-        Wipes the AppCache clean of all registered models.
-        Used for things like migration libraries' fake ORMs.
-        """
-        self.app_store = SortedDict()
-        self.app_labels = {}
-        self.app_models = SortedDict()
-        self.app_errors = {}
+    def copy_from(self, other):
+        "Registers all models from the other cache into this one"
+        cache._populate()
+        for app_label, models in other.app_models.items():
+            self.register_models(app_label, *models.values())
 
 
-class StateContextManager(object):
+class AppCacheWrapper(object):
     """
-    Context manager for locking cache state.
-    Useful for making temporary models you don't want to stay in the cache.
+    As AppCache can be changed at runtime, this class wraps it so any
+    imported references to 'cache' are changed along with it.
     """
 
     def __init__(self, cache):
-        self.cache = cache
+        self._cache = cache
 
-    def __enter__(self):
-        self.state = self.cache.save_state()
+    def set_cache(self, cache):
+        self._cache = cache
 
-    def __exit__(self, type, value, traceback):
-        self.cache.restore_state(self.state)
+    def __getattr__(self, attr):
+        if attr in ("_cache", "set_cache"):
+            return self.__dict__[attr]
+        return getattr(self._cache, attr)
+
+    def __setattr__(self, attr, value):
+        if attr in ("_cache", "set_cache"):
+            self.__dict__[attr] = value
+            return
+        return setattr(self._cache, attr, value)
 
 
-cache = AppCache()
+default_cache = AppCache()
+cache = AppCacheWrapper(default_cache)
+
 
 # These methods were always module level, so are kept that way for backwards
-# compatibility.
-get_apps = cache.get_apps
-get_app = cache.get_app
-get_app_errors = cache.get_app_errors
-get_models = cache.get_models
-get_model = cache.get_model
-register_models = cache.register_models
-load_app = cache.load_app
-app_cache_ready = cache.app_cache_ready
+# compatibility. These are wrapped with lambdas to stop the attribute
+# access resolving directly to a method on a single cache instance.
+get_apps = lambda *x, **y: cache.get_apps(*x, **y)
+get_app = lambda *x, **y: cache.get_app(*x, **y)
+get_app_errors = lambda *x, **y: cache.get_app_errors(*x, **y)
+get_models = lambda *x, **y: cache.get_models(*x, **y)
+get_model = lambda *x, **y: cache.get_model(*x, **y)
+register_models = lambda *x, **y: cache.register_models(*x, **y)
+load_app = lambda *x, **y: cache.load_app(*x, **y)
+app_cache_ready = lambda *x, **y: cache.app_cache_ready(*x, **y)

django/db/models/options.py

@@ -21,7 +21,7 @@ get_verbose_name = lambda class_name: re.sub('(((?<=[a-z])[A-Z])|([A-Z](?![A-Z]|
 DEFAULT_NAMES = ('verbose_name', 'verbose_name_plural', 'db_table', 'ordering',
                  'unique_together', 'permissions', 'get_latest_by',
                  'order_with_respect_to', 'app_label', 'db_tablespace',
-                 'abstract', 'managed', 'proxy', 'auto_created')
+                 'abstract', 'managed', 'proxy', 'auto_created', 'auto_register')
 
 @python_2_unicode_compatible
 class Options(object):
@@ -68,6 +68,9 @@ class Options(object):
         # from *other* models. Needed for some admin checks. Internal use only.
         self.related_fkey_lookups = []
 
+        # If we should auto-register with the AppCache
+        self.auto_register = True
+
     def contribute_to_class(self, cls, name):
         from django.db import connection
         from django.db.backends.util import truncate_name

tests/modeltests/schema/models.py

@@ -10,14 +10,14 @@ class Author(models.Model):
     height = models.PositiveIntegerField(null=True, blank=True)
 
     class Meta:
-        managed = False
+        auto_register = False
 
 
 class AuthorWithM2M(models.Model):
     name = models.CharField(max_length=255)
 
     class Meta:
-        managed = False
+        auto_register = False
 
 
 class Book(models.Model):
@@ -27,7 +27,7 @@ class Book(models.Model):
     #tags = models.ManyToManyField("Tag", related_name="books")
 
     class Meta:
-        managed = False
+        auto_register = False
 
 
 class BookWithM2M(models.Model):
@@ -37,7 +37,7 @@ class BookWithM2M(models.Model):
     tags = models.ManyToManyField("Tag", related_name="books")
 
     class Meta:
-        managed = False
+        auto_register = False
 
 
 class BookWithSlug(models.Model):
@@ -47,7 +47,7 @@ class BookWithSlug(models.Model):
     slug = models.CharField(max_length=20, unique=True)
 
     class Meta:
-        managed = False
+        auto_register = False
         db_table = "schema_book"
 
 
@@ -56,7 +56,7 @@ class Tag(models.Model):
     slug = models.SlugField(unique=True)
 
     class Meta:
-        managed = False
+        auto_register = False
 
 
 class TagUniqueRename(models.Model):
@@ -64,7 +64,7 @@ class TagUniqueRename(models.Model):
     slug2 = models.SlugField(unique=True)
 
     class Meta:
-        managed = False
+        auto_register = False
         db_table = "schema_tag"
 
 
@@ -73,5 +73,5 @@ class UniqueTest(models.Model):
     slug = models.SlugField(unique=False)
 
     class Meta:
-        managed = False
+        auto_register = False
         unique_together = ["year", "slug"]

tests/modeltests/schema/tests.py

@@ -6,7 +6,7 @@ from django.utils.unittest import skipUnless
 from django.db import connection, DatabaseError, IntegrityError
 from django.db.models.fields import IntegerField, TextField, CharField, SlugField
 from django.db.models.fields.related import ManyToManyField, ForeignKey
-from django.db.models.loading import cache
+from django.db.models.loading import cache, default_cache, AppCache
 from .models import Author, AuthorWithM2M, Book, BookWithSlug, BookWithM2M, Tag, TagUniqueRename, UniqueTest
 
 
@@ -30,9 +30,12 @@ class SchemaTests(TestCase):
         connection.managed(True)
         # The unmanaged models need to be removed after the test in order to
         # prevent bad interactions with the flush operation in other tests.
-        self.cache_state = cache.save_state()
+        self.app_cache = AppCache()
+        cache.set_cache(self.app_cache)
+        cache.copy_from(default_cache)
         for model in self.models:
-            model._meta.managed = True
+            cache.register_models("schema", model)
+            model._prepare()
 
     def tearDown(self):
         # Delete any tables made for our models
@@ -40,10 +43,8 @@ class SchemaTests(TestCase):
         # Rollback anything that may have happened
         connection.rollback()
         connection.leave_transaction_management()
-        # Unhook our models
-        for model in self.models:
-            model._meta.managed = False
-        cache.restore_state(self.cache_state)
+        cache.set_cache(default_cache)
+        cache.app_models['schema'] = {}  # One M2M gets left in the old cache
 
     def delete_tables(self):
         "Deletes all model tables for our models for a clean test environment"