Improve @containers.copy to replace subcontainer providers

src/dependency_injector/containers.pyx

@@ -541,16 +541,25 @@ def copy(object container):
     :return: Declarative container's copying decorator.
     :rtype: callable(:py:class:`DeclarativeContainer`)
     """
-    def _decorator(copied_container):
-        cdef dict memo = dict()
-        for name, provider in six.iteritems(copied_container.cls_providers):
+    def _get_providers_memo(from_providers, source_providers):
+        memo = dict()
+
+        for name, provider in from_providers.items():
             try:
-                source_provider = getattr(container, name)
-            except AttributeError:
-                pass
+                source_provider = source_providers[name]
+            except KeyError:
+                ...
             else:
                 memo[id(source_provider)] = provider
 
+                if hasattr(provider, 'providers') and hasattr(source_provider, 'providers'):
+                    sub_memo = _get_providers_memo(provider.providers, source_provider.providers)
+                    memo.update(sub_memo)
+        return memo
+
+    def _decorator(copied_container):
+        memo = _get_providers_memo(copied_container.cls_providers, container.providers)
+
         providers_copy = deepcopy(container.providers, memo)
         for name, provider in six.iteritems(providers_copy):
             setattr(copied_container, name, provider)

tests/unit/containers/test_declarative_py2_py3.py

@@ -296,6 +296,26 @@ class DeclarativeContainerTests(unittest.TestCase):
         self.assertEqual(_Container1.p13(), 11)
         self.assertEqual(_Container2.p13(), 22)
 
+    def test_copy_with_replacing_subcontainer_providers(self):
+        # See: https://github.com/ets-labs/python-dependency-injector/issues/374
+        class X(containers.DeclarativeContainer):
+            foo = providers.Dependency(instance_of=str)
+
+        def build_x():
+            return X(foo='1')
+
+        class A(containers.DeclarativeContainer):
+            x = providers.DependenciesContainer(**X.providers)
+            y = x.foo
+
+        @containers.copy(A)
+        class B1(A):
+            x = providers.Container(build_x)
+
+        b1 = B1()
+
+        self.assertEqual(b1.y(), '1')
+
     def test_containers_attribute(self):
         class Container(containers.DeclarativeContainer):
             class Container1(containers.DeclarativeContainer):