Config linking (#255)

* Add config linking test

* Add provider linking

* Update changelog

docs/main/changelog.rst

@@ -7,6 +7,10 @@ that were made in every particular version.
 From version 0.7.6 *Dependency Injector* framework strictly 
 follows `Semantic versioning`_
 
+Development version
+-------------------
+- Add ``Configuration`` providers linking.
+
 3.16.1
 ------
 - Update ``singleton_thread_locals.py`` to support Python 3 (thanks to

src/dependency_injector/providers.pxd

@@ -92,6 +92,7 @@ cdef class CoroutineDelegate(Delegate):
 cdef class Configuration(Object):
     cdef str __name
     cdef dict __children
+    cdef tuple __linked
 
 
 # Factory providers

src/dependency_injector/providers.pyx

@@ -1029,6 +1029,7 @@ cdef class Configuration(Object):
 
         self.__name = name
         self.__children = self._create_children(default)
+        self.__linked = tuple()
 
     def __deepcopy__(self, memo):
         """Create and return full copy of provider."""
@@ -1041,6 +1042,7 @@ cdef class Configuration(Object):
         copied = self.__class__(self.__name)
         copied.__provides = deepcopy(self.__provides, memo)
         copied.__children = deepcopy(self.__children, memo)
+        copied.__linked = deepcopy(self.__linked, memo)
 
         self._copy_overridings(copied, memo)
 
@@ -1093,11 +1095,17 @@ cdef class Configuration(Object):
         """
         overriding_context = super(Configuration, self).override(provider)
 
+        for linked in self.__linked:
+            linked.override(provider)
+
+        if isinstance(provider, Configuration):
+            provider.link_provider(self)
+
         value = self.__call__()
         if not isinstance(value, dict):
             return
 
-        for name in value:
+        for name in value.keys():
             child_provider = self.__children.get(name)
             if child_provider is None:
                 continue
@@ -1129,6 +1137,10 @@ cdef class Configuration(Object):
             child.reset_override()
         super(Configuration, self).reset_override()
 
+    def link_provider(self, provider):
+        """Configuration link two configuration providers."""
+        self.__linked += (<Configuration?>provider,)
+
     def update(self, value):
         """Set configuration options.
 

tests/unit/providers/test_configuration_py2_py3.py

@@ -2,7 +2,7 @@
 
 import unittest2 as unittest
 
-from dependency_injector import providers
+from dependency_injector import containers, providers
 
 
 class ConfigTests(unittest.TestCase):
@@ -177,3 +177,72 @@ class ConfigTests(unittest.TestCase):
                          'Configuration({0}) at {1}>'.format(
                              repr('config.a.b.c'),
                              hex(id(self.config.a.b.c))))
+
+
+class ConfigLinkingTests(unittest.TestCase):
+
+    class TestCore(containers.DeclarativeContainer):
+        config = providers.Configuration('core')
+        value_getter = providers.Callable(lambda _: _, config.value)
+
+    class TestServices(containers.DeclarativeContainer):
+        config = providers.Configuration('services')
+        value_getter = providers.Callable(lambda _: _, config.value)
+
+    def test(self):
+        root_config = providers.Configuration('main')
+        core = self.TestCore(config=root_config.core)
+        services = self.TestServices(config=root_config.services)
+
+        root_config.override(
+            {
+                'core': {
+                    'value': 'core',
+                },
+                'services': {
+                    'value': 'services',
+                },
+            },
+        )
+
+        self.assertEqual(core.config(), {'value': 'core'})
+        self.assertEqual(core.config.value(), 'core')
+        self.assertEqual(core.value_getter(), 'core')
+
+        self.assertEqual(services.config(), {'value': 'services'})
+        self.assertEqual(services.config.value(), 'services')
+        self.assertEqual(services.value_getter(), 'services')
+
+    def test_double_override(self):
+        root_config = providers.Configuration('main')
+        core = self.TestCore(config=root_config.core)
+        services = self.TestServices(config=root_config.services)
+
+        root_config.override(
+            {
+                'core': {
+                    'value': 'core1',
+                },
+                'services': {
+                    'value': 'services1',
+                },
+            },
+        )
+        root_config.override(
+            {
+                'core': {
+                    'value': 'core2',
+                },
+                'services': {
+                    'value': 'services2',
+                },
+            },
+        )
+
+        self.assertEqual(core.config(), {'value': 'core2'})
+        self.assertEqual(core.config.value(), 'core2')
+        self.assertEqual(core.value_getter(), 'core2')
+
+        self.assertEqual(services.config(), {'value': 'services2'})
+        self.assertEqual(services.config.value(), 'services2')
+        self.assertEqual(services.value_getter(), 'services2')