Fix delete on instances using nested ModelMocker managers

Author: Nicolás Fantone

django_mock_queries/mocks.py

@@ -13,7 +13,6 @@
 
 from types import MethodType
 
-from .constants import DjangoModelDeletionCollector, DjangoDbRouter
 from .query import MockSet
 
 # noinspection PyUnresolvedReferences
@@ -330,10 +329,6 @@ class Mocker:
     A decorator that patches multiple class methods with a magic mock instance that does nothing.
     """
 
-    shared_mocks = {}
-    shared_patchers = {}
-    shared_original = {}
-
     def __init__(self, cls, *methods, **kwargs):
         self.cls = cls
         self.methods = methods
@@ -342,8 +337,6 @@ def __init__(self, cls, *methods, **kwargs):
         self.inst_patchers = {}
         self.inst_original = {}
 
-        self.outer = kwargs.get('outer', True)
-
     def __enter__(self):
         self._patch_object_methods(self.cls, *self.methods)
         return self
@@ -359,11 +352,8 @@ def decorated(*args, **kwargs):
         return decorated
 
     def __exit__(self, exc_type, exc_val, exc_tb):
-        for key, patcher in self.inst_patchers.items():
+        for patcher in self.inst_patchers.values():
             patcher.stop()
-        if self.outer:
-            for key, patcher in self.shared_patchers.items():
-                patcher.stop()
 
     def _key(self, method, obj=None):
         return '{}.{}'.format(obj or self.cls, method)
@@ -374,10 +364,10 @@ def _method_obj(self, name, obj, *sources):
         return d[self._key(name, obj=obj)]
 
     def method(self, name, obj=None):
-        return self._method_obj(name, obj, self.shared_mocks, self.inst_mocks)
+        return self._method_obj(name, obj, self.inst_mocks)
 
     def original_method(self, name, obj=None):
-        return self._method_obj(name, obj, self.shared_original, self.inst_original)
+        return self._method_obj(name, obj, self.inst_original)
 
     def _get_source_method(self, obj, method):
         source_obj = obj
@@ -406,28 +396,28 @@ def _patch_method(self, method_name, source_obj, source_method):
         return patch_object(source_obj, source_method, **mock_args)
 
     def _patch_object_methods(self, obj, *methods, **kwargs):
-        if kwargs.get('shared', False):
-            original, patchers, mocks = self.shared_original, self.shared_patchers, self.shared_mocks
-        else:
-            original, patchers, mocks = self.inst_original, self.inst_patchers, self.inst_mocks
+        original, patchers, mocks = self.inst_original, self.inst_patchers, self.inst_mocks
 
         for method in methods:
             key = self._key(method, obj=obj)
 
             source_obj, source_method = self._get_source_method(obj, method)
-            original[key] = original.get(key, None) or getattr(source_obj, source_method)
 
-            patcher = self._patch_method(method, source_obj, source_method)
-            patchers[key] = patcher
-            mocks[key] = patcher.start()
+            if key not in original:
+                original[key] = getattr(source_obj, source_method)
+
+            if key not in patchers:
+                patcher = self._patch_method(method, source_obj, source_method)
+                patchers[key] = patcher
+                mocks[key] = patcher.start()
 
 
 class ModelMocker(Mocker):
     """
     A decorator that patches django base model's db read/write methods and wires them to a MockSet.
     """
 
-    default_methods = ['objects', '_do_update']
+    default_methods = ['objects', '_do_update', 'delete']
 
     if django.VERSION[0] >= 3:
         default_methods += ['_base_manager._insert', ]
@@ -442,11 +432,8 @@ def __init__(self, cls, *methods, **kwargs):
         self.objects = MockSet(model=self.cls)
         self.objects.on('added', self._on_added)
 
-        self.state = {}
-
     def __enter__(self):
         result = super(ModelMocker, self).__enter__()
-        self._patch_object_methods(DjangoModelDeletionCollector, 'collect', 'delete', shared=True)
         return result
 
     def _obj_pk(self, obj):
@@ -482,23 +469,11 @@ def _do_update(self, *args, **_):
         else:
             return False
 
-    def collect(self, objects, *args, **kwargs):
-        model = getattr(objects, 'model', None) or objects[0]
-
-        if not (model is self.cls or isinstance(model, self.cls)):
-            using = getattr(objects, 'db', None) or DjangoDbRouter.db_for_write(model._meta.model, instance=model)
-            self.state['collector'] = DjangoModelDeletionCollector(using=using)
-
-            collect = self.original_method('collect', obj=DjangoModelDeletionCollector)
-            collect(self.state['collector'], objects, *args, **kwargs)
-
-        self.state['model'] = model
-
-    def delete(self, *args, **kwargs):
-        model = self.state.pop('model')
-
-        if not (model is self.cls or isinstance(model, self.cls)):
-            delete = self.original_method('delete', obj=DjangoModelDeletionCollector)
-            return delete(self.state.pop('collector'), *args, **kwargs)
-        else:
-            return self.objects.filter(pk=getattr(model, self.cls._meta.pk.attname)).delete()
+    def delete(self, *_args, **_kwargs):
+        pk = self._obj_pk(self.objects[0])
+        if not pk:
+            raise ValueError(
+                f"{self.cls._meta.object_name} object can't be deleted because "
+                f'its {self.cls._meta.pk.attname} attribute is set to None.'
+            )
+        return self.objects.filter(pk=pk).delete()

tests/test_mocks.py

@@ -486,6 +486,27 @@ def car_added(obj):
         self.assertIsInstance(objects['added'], Car)
         self.assertEqual(objects['added'], objects['car'])
 
+    def test_model_mocker_delete_from_instance_with_nested_context_manager(self):
+
+        def create_delete_models():
+            car = Car.objects.create(speed=10)
+            car.delete()
+
+            manufacturer = Manufacturer.objects.create(name='foo')
+            manufacturer.delete()
+
+        def models_exist():
+            return Manufacturer.objects.exists() or Car.objects.exists()
+
+        with ModelMocker(Manufacturer), ModelMocker(Car):
+            create_delete_models()
+            assert not models_exist()
+
+        # Test same scenario with reversed context manager order
+        with ModelMocker(Car), ModelMocker(Manufacturer):
+            create_delete_models()
+            assert not models_exist()
+
     def test_model_mocker_event_updated_from_manager(self):
         objects = {}