Add support of overriding for container provider

src/dependency_injector/providers.pyx

@@ -3069,13 +3069,21 @@ cdef class Container(Provider):
                                               attribute_name=name))
         return getattr(self.__container, name)
 
+    @property
+    def providers(self):
+        return self.__container.providers
+
     @property
     def container(self):
         return self.__container
 
     def override(self, provider):
         """Override provider with another provider."""
-        raise Error('Provider {0} can not be overridden'.format(self))
+        if not hasattr(provider, 'providers'):
+            raise Error('Container provider {0} can be overridden only by providers container'.format(self))
+
+        self.__container.override_providers = provider.providers
+        super().override(provider)
 
     cpdef object _provide(self, tuple args, dict kwargs):
         """Return single instance."""

tests/unit/providers/test_container_py2_py3.py

@@ -4,7 +4,7 @@ import copy
 
 import unittest2 as unittest
 
-from dependency_injector import containers, providers
+from dependency_injector import containers, providers, errors
 
 
 TEST_VALUE_1 = 'core_section_value1'
@@ -52,3 +52,27 @@ class ContainerTests(unittest.TestCase):
         application.config.override(_copied(TEST_CONFIG_1))
         application.config.override(_copied(TEST_CONFIG_2))
         self.assertEqual(application.dict_factory(), {'value': TEST_VALUE_2})
+
+    def test_override(self):
+        class D(containers.DeclarativeContainer):
+            foo = providers.Object('foo')
+
+        class A(containers.DeclarativeContainer):
+            d = providers.DependenciesContainer()
+            bar = providers.Callable(lambda f: f + '++', d.foo.provided)
+
+        class B(containers.DeclarativeContainer):
+            d = providers.Container(D)
+
+            a = providers.Container(A, d=d)
+
+        b = B(d=D())
+        result = b.a().bar()
+        self.assertEqual(result, 'foo++')
+        # See: https://github.com/ets-labs/python-dependency-injector/issues/354
+
+    def test_override_by_not_a_container(self):
+        provider = providers.Container(TestCore)
+
+        with self.assertRaises(errors.Error):
+            provider.override(providers.Object('foo'))