Providers traversal (#385)

* Implement providers traversal in first precision

* Implement traversal for all providers

* Update traverse interface + add some tests

* Refactor tests

* Add tests for callable provider

* Add configuration tests

* Add Factory tests

* Add FactoryAggrefate tests

* Add .provides attribute to singleton providers

* Add singleton provider tests

* Add list and dict provider tests

* Add resource tests

* Add Container provider tests

* Add Selector provider tests

* Add ProvidedInstance provider tests

* Add AttributeGetter provider tests

* Add ItemGetter provider tests

* Add MethodCaller provider tests

* Refactor container interface

* Update resource provider string representation

* Add .initializer attribute to Resource provider

* Add docs and examples

* Remove not needed EOL in the tests

* Make cosmetic refactoring

* Ignore flake8 line width error in traverse example

docs/containers/index.rst

@@ -23,3 +23,4 @@ Containers module API docs - :py:mod:`dependency_injector.containers`.
     dynamic
     specialization
     overriding
+    traversal

docs/containers/traversal.rst

@@ -0,0 +1,33 @@
+Container providers traversal
+-----------------------------
+
+To traverse container providers use method ``.traverse()``.
+
+.. literalinclude:: ../../examples/containers/traverse.py
+   :language: python
+   :lines: 3-
+   :emphasize-lines: 38
+
+Method ``.traverse()`` returns a generator. Traversal generator visits all container providers.
+This includes nested providers even if they are not present on the root level of the container.
+
+Traversal generator guarantees that each container provider will be visited only once.
+It can traverse cyclic provider graphs.
+
+Traversal generator does not guarantee traversal order.
+
+You can use ``types=[...]`` argument to filter providers. Traversal generator will only return
+providers matching specified types.
+
+.. code-block:: python
+   :emphasize-lines: 3
+
+   container = Container()
+
+   for provider in container.traverse(types=[providers.Resource]):
+       print(provider)
+
+    # <dependency_injector.providers.Resource(<function init_database at 0x10bd2cb80>) at 0x10d346b40>
+    # <dependency_injector.providers.Resource(<function init_cache at 0x10be373a0>) at 0x10d346bc0>
+
+.. disqus::

docs/main/changelog.rst

@@ -7,6 +7,15 @@ that were made in every particular version.
 From version 0.7.6 *Dependency Injector* framework strictly 
 follows `Semantic versioning`_
 
+Development version
+-------------------
+- Add container providers traversal.
+- Add ``.provides`` attribute to ``Singleton`` and its subclasses.
+  It's a consistency change to make ``Singleton`` match ``Callable``
+  and ``Factory`` interfaces.
+- Add ``.initializer`` attribute to ``Resource`` provider.
+- Update string representation of ``Resource`` provider.
+
 4.13.2
 ------
 - Fix PyCharm typing warning "Expected type 'Optional[Iterable[ModuleType]]',

examples/containers/traverse.py

@@ -0,0 +1,48 @@
+"""Container traversal example."""
+
+from dependency_injector import containers, providers
+
+
+def init_database():
+    return ...
+
+
+def init_cache():
+    return ...
+
+
+class Service:
+    def __init__(self, database, cache):
+        self.database = database
+        self.cache = cache
+
+
+class Container(containers.DeclarativeContainer):
+
+    config = providers.Configuration()
+
+    service = providers.Factory(
+        Service,
+        database=providers.Resource(
+            init_database,
+            url=config.database_url,
+        ),
+        cache=providers.Resource(
+            init_cache,
+            hosts=config.cache_hosts,
+        ),
+    )
+
+
+if __name__ == '__main__':
+    container = Container()
+
+    for provider in container.traverse():
+        print(provider)
+
+    # <dependency_injector.providers.Configuration('config') at 0x10d37d200>
+    # <dependency_injector.providers.Factory(<class '__main__.Service'>) at 0x10d3a2820>
+    # <dependency_injector.providers.Resource(<function init_database at 0x10bd2cb80>) at 0x10d346b40>
+    # <dependency_injector.providers.ConfigurationOption('config.cache_hosts') at 0x10d37d350>
+    # <dependency_injector.providers.Resource(<function init_cache at 0x10be373a0>) at 0x10d346bc0>
+    # <dependency_injector.providers.ConfigurationOption('config.database_url') at 0x10d37d2e0>

setup.cfg

@@ -4,6 +4,7 @@ max_complexity = 10
 exclude = types.py
 per-file-ignores =
     examples/demo/*: F841
+    examples/containers/traverse.py: E501
     examples/providers/async.py: F841
     examples/providers/async_overriding.py: F841
     examples/wiring/*: F841

src/dependency_injector/containers.pyi

@@ -7,9 +7,12 @@ from typing import (
     Union,
     ClassVar,
     Callable as _Callable,
+    Sequence,
     Iterable,
+    Iterator,
     TypeVar,
     Awaitable,
+    overload,
 )
 
 from .providers import Provider
@@ -40,6 +43,11 @@ class Container:
     def unwire(self) -> None: ...
     def init_resources(self) -> Optional[Awaitable]: ...
     def shutdown_resources(self) -> Optional[Awaitable]: ...
+    @overload
+    def traverse(self, types: Optional[Sequence[Type]] = None) -> Iterator[Provider]: ...
+    @classmethod
+    @overload
+    def traverse(cls, types: Optional[Sequence[Type]] = None) -> Iterator[Provider]: ...
 
 
 class DynamicContainer(Container): ...

src/dependency_injector/containers.pyx

@@ -10,16 +10,7 @@ except ImportError:
 
 import six
 
-from .errors import Error
+from . import providers, errors
-from .providers cimport (
-    Provider,
-    Object,
-    Resource,
-    Dependency,
-    DependenciesContainer,
-    Container as ContainerProvider,
-    deepcopy,
-)
 
 
 if sys.version_info[:2] >= (3, 6):
@@ -68,13 +59,13 @@ class DynamicContainer(object):
 
         :rtype: None
         """
-        self.provider_type = Provider
+        self.provider_type = providers.Provider
         self.providers = {}
         self.overridden = tuple()
         self.declarative_parent = None
         self.wired_to_modules = []
         self.wired_to_packages = []
-        self.__self__ = Object(self)
+        self.__self__ = providers.Object(self)
         super(DynamicContainer, self).__init__()
 
     def __deepcopy__(self, memo):
@@ -84,11 +75,11 @@ class DynamicContainer(object):
             return copied
 
         copied = self.__class__()
-        copied.provider_type = Provider
+        copied.provider_type = providers.Provider
-        copied.overridden = deepcopy(self.overridden, memo)
+        copied.overridden = providers.deepcopy(self.overridden, memo)
         copied.declarative_parent = self.declarative_parent
 
-        for name, provider in deepcopy(self.providers, memo).items():
+        for name, provider in providers.deepcopy(self.providers, memo).items():
             setattr(copied, name, provider)
 
         return copied
@@ -107,7 +98,7 @@ class DynamicContainer(object):
 
         :rtype: None
         """
-        if isinstance(value, Provider) and name != '__self__':
+        if isinstance(value, providers.Provider) and name != '__self__':
             _check_provider_type(self, value)
             self.providers[name] = value
         super(DynamicContainer, self).__setattr__(name, value)
@@ -140,9 +131,13 @@ class DynamicContainer(object):
         return {
             name: provider
             for name, provider in self.providers.items()
-            if isinstance(provider, (Dependency, DependenciesContainer))
+            if isinstance(provider, (providers.Dependency, providers.DependenciesContainer))
         }
 
+    def traverse(self, types=None):
+        """Return providers traversal generator."""
+        yield from providers.traverse(*self.providers.values(), types=types)
+
     def set_providers(self, **providers):
         """Set container providers.
 
@@ -167,7 +162,7 @@ class DynamicContainer(object):
         :rtype: None
         """
         if overriding is self:
-            raise Error('Container {0} could not be overridden '
+            raise errors.Error('Container {0} could not be overridden '
                                'with itself'.format(self))
 
         self.overridden += (overriding,)
@@ -197,7 +192,7 @@ class DynamicContainer(object):
         :rtype: None
         """
         if not self.overridden:
-            raise Error('Container {0} is not overridden'.format(self))
+            raise errors.Error('Container {0} is not overridden'.format(self))
 
         self.overridden = self.overridden[:-1]
 
@@ -245,7 +240,7 @@ class DynamicContainer(object):
         """Initialize all container resources."""
         futures = []
         for provider in self.providers.values():
-            if not isinstance(provider, Resource):
+            if not isinstance(provider, providers.Resource):
                 continue
 
             resource = provider.init()
@@ -260,7 +255,7 @@ class DynamicContainer(object):
         """Shutdown all container resources."""
         futures = []
         for provider in self.providers.values():
-            if not isinstance(provider, Resource):
+            if not isinstance(provider, providers.Resource):
                 continue
 
             shutdown = provider.shutdown()
@@ -274,7 +269,7 @@ class DynamicContainer(object):
     def apply_container_providers_overridings(self):
         """Apply container providers' overridings."""
         for provider in self.providers.values():
-            if not isinstance(provider, ContainerProvider):
+            if not isinstance(provider, providers.Container):
                 continue
             provider.apply_overridings()
 
@@ -293,7 +288,7 @@ class DeclarativeContainerMetaClass(type):
         cls_providers = {
             name: provider
             for name, provider in six.iteritems(attributes)
-            if isinstance(provider, Provider)
+            if isinstance(provider, providers.Provider)
         }
 
         inherited_providers = {
@@ -303,18 +298,18 @@ class DeclarativeContainerMetaClass(type):
             for name, provider in six.iteritems(base.providers)
         }
 
-        providers = {}
+        all_providers = {}
-        providers.update(inherited_providers)
+        all_providers.update(inherited_providers)
-        providers.update(cls_providers)
+        all_providers.update(cls_providers)
 
         attributes['containers'] = containers
         attributes['inherited_providers'] = inherited_providers
         attributes['cls_providers'] = cls_providers
-        attributes['providers'] = providers
+        attributes['providers'] = all_providers
 
         cls = <type>type.__new__(mcs, class_name, bases, attributes)
 
-        cls.__self__ = Object(cls)
+        cls.__self__ = providers.Object(cls)
 
         for provider in six.itervalues(cls.providers):
             _check_provider_type(cls, provider)
@@ -335,7 +330,7 @@ class DeclarativeContainerMetaClass(type):
 
         :rtype: None
         """
-        if isinstance(value, Provider) and name != '__self__':
+        if isinstance(value, providers.Provider) and name != '__self__':
             _check_provider_type(cls, value)
             cls.providers[name] = value
             cls.cls_providers[name] = value
@@ -370,9 +365,13 @@ class DeclarativeContainerMetaClass(type):
         return {
             name: provider
             for name, provider in cls.providers.items()
-            if isinstance(provider, (Dependency, DependenciesContainer))
+            if isinstance(provider, (providers.Dependency, providers.DependenciesContainer))
         }
 
+    def traverse(cls, types=None):
+        """Return providers traversal generator."""
+        yield from providers.traverse(*cls.providers.values(), types=types)
+
 
 @six.add_metaclass(DeclarativeContainerMetaClass)
 class DeclarativeContainer(object):
@@ -388,7 +387,7 @@ class DeclarativeContainer(object):
 
     __IS_CONTAINER__ = True
 
-    provider_type = Provider
+    provider_type = providers.Provider
     """Type of providers that could be placed in container.
 
     :type: type
@@ -446,7 +445,7 @@ class DeclarativeContainer(object):
         container = cls.instance_type()
         container.provider_type = cls.provider_type
         container.declarative_parent = cls
-        container.set_providers(**deepcopy(cls.providers))
+        container.set_providers(**providers.deepcopy(cls.providers))
         container.override_providers(**overriding_providers)
         container.apply_container_providers_overridings()
         return container
@@ -464,7 +463,7 @@ class DeclarativeContainer(object):
         :rtype: None
         """
         if issubclass(cls, overriding):
-            raise Error('Container {0} could not be overridden '
+            raise errors.Error('Container {0} could not be overridden '
                                'with itself or its subclasses'.format(cls))
 
         cls.overridden += (overriding,)
@@ -482,7 +481,7 @@ class DeclarativeContainer(object):
         :rtype: None
         """
         if not cls.overridden:
-            raise Error('Container {0} is not overridden'.format(cls))
+            raise errors.Error('Container {0} is not overridden'.format(cls))
 
         cls.overridden = cls.overridden[:-1]
 
@@ -559,7 +558,7 @@ def copy(object container):
     def _decorator(copied_container):
         memo = _get_providers_memo(copied_container.cls_providers, container.providers)
 
-        providers_copy = deepcopy(container.providers, memo)
+        providers_copy = providers.deepcopy(container.providers, memo)
         for name, provider in six.iteritems(providers_copy):
             setattr(copied_container, name, provider)
 
@@ -580,7 +579,7 @@ cpdef bint is_container(object instance):
 
 cpdef object _check_provider_type(object container, object provider):
     if not isinstance(provider, container.provider_type):
-        raise Error('{0} can contain only {1} '
+        raise errors.Error('{0} can contain only {1} '
                            'instances'.format(container, container.provider_type))
 
 

src/dependency_injector/providers.pyi

@@ -14,6 +14,7 @@ from typing import (
     Optional,
     Union,
     Coroutine as _Coroutine,
+    Iterable as _Iterable,
     Iterator as _Iterator,
     AsyncIterator as _AsyncIterator,
     Generator as _Generator,
@@ -68,6 +69,9 @@ class Provider(Generic[T]):
     def is_async_mode_enabled(self) -> bool: ...
     def is_async_mode_disabled(self) -> bool: ...
     def is_async_mode_undefined(self) -> bool: ...
+    @property
+    def related(self) -> _Iterator[Provider]: ...
+    def traverse(self, types: Optional[_Iterable[Type]] = None) -> _Iterator[Provider]: ...
     def _copy_overridings(self, copied: Provider, memo: Optional[_Dict[Any, Any]]) -> None: ...
 
 
@@ -238,6 +242,8 @@ class BaseSingleton(Provider[T]):
     @property
     def cls(self) -> T: ...
     @property
+    def provides(self) -> T: ...
+    @property
     def args(self) -> Tuple[Injection]: ...
     def add_args(self, *args: Injection) -> BaseSingleton[T]: ...
     def set_args(self, *args: Injection) -> BaseSingleton[T]: ...
@@ -313,6 +319,8 @@ class Resource(Provider[T]):
     @overload
     def __init__(self, initializer: _Callable[..., T], *args: Injection, **kwargs: Injection) -> None: ...
     @property
+    def initializer(self) -> _Callable[..., Any]: ...
+    @property
     def args(self) -> Tuple[Injection]: ...
     def add_args(self, *args: Injection) -> Resource[T]: ...
     def set_args(self, *args: Injection) -> Resource[T]: ...
@@ -382,6 +390,9 @@ def deepcopy(instance: Any, memo: Optional[_Dict[Any, Any]] = None): Any: ...
 def merge_dicts(dict1: _Dict[Any, Any], dict2: _Dict[Any, Any]) -> _Dict[Any, Any]: ...
 
 
+def traverse(*providers: Provider, types: Optional[_Iterable[Type]]=None) -> _Iterator[Provider]: ...
+
+
 if yaml:
     class YamlLoader(yaml.SafeLoader): ...
 else:

src/dependency_injector/providers.pyx

@@ -363,6 +363,15 @@ cdef class Provider(object):
         """Check if async mode is undefined."""
         return self.__async_mode == ASYNC_MODE_UNDEFINED
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from self.overridden
+
+    def traverse(self, types=None):
+        """Return providers traversal generator."""
+        return traverse(*self.related, types=types)
+
     cpdef object _provide(self, tuple args, dict kwargs):
         """Providing strategy implementation.
 
@@ -423,6 +432,13 @@ cdef class Object(Provider):
         """
         return self.__str__()
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        if isinstance(self.__provides, Provider):
+            yield self.__provides
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         """Return provided instance.
 
@@ -487,6 +503,12 @@ cdef class Delegate(Provider):
         """Return provider."""
         return self.__provides
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield self.__provides
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         """Return provided instance.
 
@@ -619,6 +641,13 @@ cdef class Dependency(Provider):
         """Return default provider."""
         return self.__default
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        if self.__default is not UNDEFINED:
+            yield self.__default
+        yield from super().related
+
     def provided_by(self, provider):
         """Set external dependency provider.
 
@@ -790,6 +819,12 @@ cdef class DependenciesContainer(Object):
             child.reset_override()
         super(DependenciesContainer, self).reset_override()
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from self.providers.values()
+        yield from super().related
+
     cpdef object _override_providers(self, object container):
         """Override providers with providers from provided container."""
         for name, dependency_provider in container.providers.items():
@@ -998,6 +1033,14 @@ cdef class Callable(Provider):
         self.__kwargs_len = len(self.__kwargs)
         return self
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from filter(is_provider, [self.provides])
+        yield from filter(is_provider, self.args)
+        yield from filter(is_provider, self.kwargs.values())
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         """Return result of provided callable's call."""
         return __callable_call(self, args, kwargs)
@@ -1442,6 +1485,13 @@ cdef class ConfigurationOption(Provider):
 
         self.override(value)
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from filter(is_provider, self.__name)
+        yield from self.__children.values()
+        yield from super().related
+
     def _is_strict_mode_enabled(self):
         return self.__root.__strict
 
@@ -1763,6 +1813,12 @@ cdef class Configuration(Object):
 
         self.override(value)
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from self.__children.values()
+        yield from super().related
+
     def _is_strict_mode_enabled(self):
         return self.__strict
 
@@ -1979,6 +2035,15 @@ cdef class Factory(Provider):
         self.__attributes_len = len(self.__attributes)
         return self
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from filter(is_provider, [self.provides])
+        yield from filter(is_provider, self.args)
+        yield from filter(is_provider, self.kwargs.values())
+        yield from filter(is_provider, self.attributes.values())
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         """Return new instance."""
         return __factory_call(self, args, kwargs)
@@ -2141,6 +2206,12 @@ cdef class FactoryAggregate(Provider):
         raise Error(
             '{0} providers could not be overridden'.format(self.__class__))
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from self.__factories.values()
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         try:
             factory_name = args[0]
@@ -2212,7 +2283,12 @@ cdef class BaseSingleton(Provider):
     @property
     def cls(self):
         """Return provided type."""
-        return self.__instantiator.cls
+        return self.provides
+
+    @property
+    def provides(self):
+        """Return provided type."""
+        return self.__instantiator.provides
 
     @property
     def args(self):
@@ -2314,6 +2390,15 @@ cdef class BaseSingleton(Provider):
         """
         raise NotImplementedError()
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from filter(is_provider, [self.__instantiator.provides])
+        yield from filter(is_provider, self.args)
+        yield from filter(is_provider, self.kwargs.values())
+        yield from filter(is_provider, self.attributes.values())
+        yield from super().related
+
     def _async_init_instance(self, future_result, result):
         try:
             instance = result.result()
@@ -2741,6 +2826,12 @@ cdef class List(Provider):
         self.__args_len = len(self.__args)
         return self
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from filter(is_provider, self.args)
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         """Return result of provided callable's call."""
         return list(__provide_positional_args(args, self.__args, self.__args_len))
@@ -2853,6 +2944,12 @@ cdef class Dict(Provider):
         self.__kwargs_len = len(self.__kwargs)
         return self
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from filter(is_provider, self.kwargs.values())
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         """Return result of provided callable's call."""
         return __provide_keyword_args(kwargs, self.__kwargs, self.__kwargs_len)
@@ -2895,11 +2992,17 @@ cdef class Resource(Provider):
 
         return copied
 
-    def __repr__(self):
+    def __str__(self):
-        return (
+        """Return string representation of provider.
-            f'{self.__class__.__name__}({self.__initializer}, '
+
-            f'initialized={self.__initialized})'
+        :rtype: str
-        )
+        """
+        return represent_provider(provider=self, provides=self.__initializer)
+
+    @property
+    def initializer(self):
+        """Return initializer."""
+        return self.__initializer
 
     @property
     def args(self):
@@ -3021,6 +3124,14 @@ cdef class Resource(Provider):
             result.set_result(None)
             return result
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from filter(is_provider, [self.__initializer])
+        yield from filter(is_provider, self.args)
+        yield from filter(is_provider, self.kwargs.values())
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         if self.__initialized:
             return self.__resource
@@ -3246,6 +3357,12 @@ cdef class Container(Provider):
         declarative container initialization."""
         self.__container.override_providers(**self.__overriding_providers)
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from self.providers.values()
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         """Return single instance."""
         return self.__container
@@ -3335,6 +3452,13 @@ cdef class Selector(Provider):
         """Return providers."""
         return dict(self.__providers)
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield from filter(is_provider, [self.__selector])
+        yield from self.providers.values()
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         """Return single instance."""
         selector_value = self.__selector()
@@ -3411,6 +3535,12 @@ cdef class ProvidedInstance(Provider):
     def call(self, *args, **kwargs):
         return MethodCaller(self, *args, **kwargs)
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield self.__provider
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         return self.__provider(*args, **kwargs)
 
@@ -3460,6 +3590,12 @@ cdef class AttributeGetter(Provider):
     def call(self, *args, **kwargs):
         return MethodCaller(self, *args, **kwargs)
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield self.__provider
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         provided = self.__provider(*args, **kwargs)
         if __isawaitable(provided):
@@ -3520,6 +3656,12 @@ cdef class ItemGetter(Provider):
     def call(self, *args, **kwargs):
         return MethodCaller(self, *args, **kwargs)
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield self.__provider
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         provided = self.__provider(*args, **kwargs)
         if __isawaitable(provided):
@@ -3612,6 +3754,14 @@ cdef class MethodCaller(Provider):
     def call(self, *args, **kwargs):
         return MethodCaller(self, *args, **kwargs)
 
+    @property
+    def related(self):
+        """Return related providers generator."""
+        yield self.__provider
+        yield from filter(is_provider, self.args)
+        yield from filter(is_provider, self.kwargs.values())
+        yield from super().related
+
     cpdef object _provide(self, tuple args, dict kwargs):
         call = self.__provider()
         if __isawaitable(call):
@@ -3846,6 +3996,29 @@ def merge_dicts(dict1, dict2):
     return result
 
 
+def traverse(*providers, types=None):
+    """Return providers traversal generator."""
+    visited = set()
+    to_visit = set(providers)
+
+    if types:
+        types = tuple(types)
+
+    while len(to_visit) > 0:
+        visiting = to_visit.pop()
+        visited.add(visiting)
+
+        for child in visiting.related:
+            if child in visited:
+                continue
+            to_visit.add(child)
+
+        if types and not isinstance(visiting, types):
+            continue
+
+        yield visiting
+
+
 def isawaitable(obj):
     """Check if object is a coroutine function.
 

tests/unit/containers/test_traversal_py3.py

@@ -0,0 +1,93 @@
+import unittest
+
+from dependency_injector import containers, providers
+
+
+class TraverseProviderTests(unittest.TestCase):
+
+    def test_nested_providers(self):
+        class Container(containers.DeclarativeContainer):
+            obj_factory = providers.DelegatedFactory(
+                dict,
+                foo=providers.Resource(
+                    dict,
+                    foo='bar'
+                ),
+                bar=providers.Resource(
+                    dict,
+                    foo='bar'
+                )
+            )
+
+        container = Container()
+        all_providers = list(container.traverse())
+
+        self.assertIn(container.obj_factory, all_providers)
+        self.assertIn(container.obj_factory.kwargs['foo'], all_providers)
+        self.assertIn(container.obj_factory.kwargs['bar'], all_providers)
+        self.assertEqual(len(all_providers), 3)
+
+    def test_nested_providers_with_filtering(self):
+        class Container(containers.DeclarativeContainer):
+            obj_factory = providers.DelegatedFactory(
+                dict,
+                foo=providers.Resource(
+                    dict,
+                    foo='bar'
+                ),
+                bar=providers.Resource(
+                    dict,
+                    foo='bar'
+                )
+            )
+
+        container = Container()
+        all_providers = list(container.traverse(types=[providers.Resource]))
+
+        self.assertIn(container.obj_factory.kwargs['foo'], all_providers)
+        self.assertIn(container.obj_factory.kwargs['bar'], all_providers)
+        self.assertEqual(len(all_providers), 2)
+
+
+class TraverseProviderDeclarativeTests(unittest.TestCase):
+
+    def test_nested_providers(self):
+        class Container(containers.DeclarativeContainer):
+            obj_factory = providers.DelegatedFactory(
+                dict,
+                foo=providers.Resource(
+                    dict,
+                    foo='bar'
+                ),
+                bar=providers.Resource(
+                    dict,
+                    foo='bar'
+                )
+            )
+
+        all_providers = list(Container.traverse())
+
+        self.assertIn(Container.obj_factory, all_providers)
+        self.assertIn(Container.obj_factory.kwargs['foo'], all_providers)
+        self.assertIn(Container.obj_factory.kwargs['bar'], all_providers)
+        self.assertEqual(len(all_providers), 3)
+
+    def test_nested_providers_with_filtering(self):
+        class Container(containers.DeclarativeContainer):
+            obj_factory = providers.DelegatedFactory(
+                dict,
+                foo=providers.Resource(
+                    dict,
+                    foo='bar'
+                ),
+                bar=providers.Resource(
+                    dict,
+                    foo='bar'
+                )
+            )
+
+        all_providers = list(Container.traverse(types=[providers.Resource]))
+
+        self.assertIn(Container.obj_factory.kwargs['foo'], all_providers)
+        self.assertIn(Container.obj_factory.kwargs['bar'], all_providers)
+        self.assertEqual(len(all_providers), 2)

tests/unit/providers/test_resource_py35.py

@@ -337,9 +337,9 @@ class ResourceTests(unittest.TestCase):
 
         self.assertEqual(
             repr(provider),
-            'Resource({0}, initialized={1})'.format(
+            '<dependency_injector.providers.Resource({0}) at {1}>'.format(
-                init_fn,
+                repr(init_fn),
-                provider.initialized,
+                hex(id(provider)),
             )
         )
 

tests/unit/providers/test_traversal_py3.py

@@ -0,0 +1,875 @@
+import unittest
+
+from dependency_injector import containers, providers
+
+
+class TraverseTests(unittest.TestCase):
+
+    def test_traverse_cycled_graph(self):
+        provider1 = providers.Provider()
+
+        provider2 = providers.Provider()
+        provider2.override(provider1)
+
+        provider3 = providers.Provider()
+        provider3.override(provider2)
+
+        provider1.override(provider3)  # Cycle: provider3 -> provider2 -> provider1 -> provider3
+
+        all_providers = list(providers.traverse(provider1))
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provider3, all_providers)
+
+    def test_traverse_types_filtering(self):
+        provider1 = providers.Resource(dict)
+        provider2 = providers.Resource(dict)
+        provider3 = providers.Provider()
+
+        provider = providers.Provider()
+
+        provider.override(provider1)
+        provider.override(provider2)
+        provider.override(provider3)
+
+        all_providers = list(providers.traverse(provider, types=[providers.Resource]))
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+
+class ProviderTests(unittest.TestCase):
+
+    def test_traversal_overriding(self):
+        provider1 = providers.Provider()
+        provider2 = providers.Provider()
+        provider3 = providers.Provider()
+
+        provider = providers.Provider()
+
+        provider.override(provider1)
+        provider.override(provider2)
+        provider.override(provider3)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provider3, all_providers)
+
+    def test_traversal_overriding_nested(self):
+        provider1 = providers.Provider()
+
+        provider2 = providers.Provider()
+        provider2.override(provider1)
+
+        provider3 = providers.Provider()
+        provider3.override(provider2)
+
+        provider = providers.Provider()
+        provider.override(provider3)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provider3, all_providers)
+
+    def test_traverse_types_filtering(self):
+        provider1 = providers.Resource(dict)
+        provider2 = providers.Resource(dict)
+        provider3 = providers.Provider()
+
+        provider = providers.Provider()
+
+        provider.override(provider1)
+        provider.override(provider2)
+        provider.override(provider3)
+
+        all_providers = list(provider.traverse(types=[providers.Resource]))
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+
+class ObjectTests(unittest.TestCase):
+
+    def test_traversal(self):
+        provider = providers.Object('string')
+        all_providers = list(provider.traverse())
+        self.assertEqual(len(all_providers), 0)
+
+    def test_traversal_provider(self):
+        another_provider = providers.Provider()
+        provider = providers.Object(another_provider)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 1)
+        self.assertIn(another_provider, all_providers)
+
+    def test_traversal_provider_and_overriding(self):
+        another_provider_1 = providers.Provider()
+        another_provider_2 = providers.Provider()
+        another_provider_3 = providers.Provider()
+
+        provider = providers.Object(another_provider_1)
+
+        provider.override(another_provider_2)
+        provider.override(another_provider_3)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(another_provider_1, all_providers)
+        self.assertIn(another_provider_2, all_providers)
+        self.assertIn(another_provider_3, all_providers)
+
+
+class DelegateTests(unittest.TestCase):
+
+    def test_traversal_provider(self):
+        another_provider = providers.Provider()
+        provider = providers.Delegate(another_provider)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 1)
+        self.assertIn(another_provider, all_providers)
+
+    def test_traversal_provider_and_overriding(self):
+        provider1 = providers.Provider()
+        provider2 = providers.Provider()
+
+        provider3 = providers.Provider()
+        provider3.override(provider2)
+
+        provider = providers.Delegate(provider1)
+
+        provider.override(provider3)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provider3, all_providers)
+
+
+class DependencyTests(unittest.TestCase):
+
+    def test_traversal(self):
+        provider = providers.Dependency()
+        all_providers = list(provider.traverse())
+        self.assertEqual(len(all_providers), 0)
+
+    def test_traversal_default(self):
+        another_provider = providers.Provider()
+        provider = providers.Dependency(default=another_provider)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 1)
+        self.assertIn(another_provider, all_providers)
+
+    def test_traversal_overriding(self):
+        provider1 = providers.Provider()
+
+        provider2 = providers.Provider()
+        provider2.override(provider1)
+
+        provider = providers.Dependency()
+        provider.override(provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+
+class DependenciesContainerTests(unittest.TestCase):
+
+    def test_traversal(self):
+        provider = providers.DependenciesContainer()
+        all_providers = list(provider.traverse())
+        self.assertEqual(len(all_providers), 0)
+
+    def test_traversal_default(self):
+        another_provider = providers.Provider()
+        provider = providers.DependenciesContainer(default=another_provider)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 1)
+        self.assertIn(another_provider, all_providers)
+
+    def test_traversal_fluent_interface(self):
+        provider = providers.DependenciesContainer()
+        provider1 = provider.provider1
+        provider2 = provider.provider2
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traversal_overriding(self):
+        provider1 = providers.Provider()
+        provider2 = providers.Provider()
+        provider3 = providers.DependenciesContainer(
+            provider1=provider1,
+            provider2=provider2,
+        )
+
+        provider = providers.DependenciesContainer()
+        provider.override(provider3)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 5)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provider3, all_providers)
+        self.assertIn(provider.provider1, all_providers)
+        self.assertIn(provider.provider2, all_providers)
+
+
+class CallableTests(unittest.TestCase):
+
+    def test_traverse(self):
+        provider = providers.Callable(dict)
+        all_providers = list(provider.traverse())
+        self.assertEqual(len(all_providers), 0)
+
+    def test_traverse_args(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.Callable(list, 'foo', provider1, provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_kwargs(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.Callable(dict, foo='foo', bar=provider1, baz=provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+
+        provider = providers.Callable(dict, 'foo')
+        provider.override(provider1)
+        provider.override(provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_provides(self):
+        provider1 = providers.Callable(list)
+        provider2 = providers.Object('bar')
+        provider3 = providers.Object('baz')
+
+        provider = providers.Callable(provider1, provider2)
+        provider.override(provider3)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provider3, all_providers)
+
+
+class ConfigurationTests(unittest.TestCase):
+
+    def test_traverse(self):
+        config = providers.Configuration(default={'option1': {'option2': 'option2'}})
+        option1 = config.option1
+        option2 = config.option1.option2
+        option3 = config.option1[config.option1.option2]
+
+        all_providers = list(config.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(option1, all_providers)
+        self.assertIn(option2, all_providers)
+        self.assertIn(option3, all_providers)
+
+    def test_traverse_typed(self):
+        config = providers.Configuration()
+        option = config.option
+        typed_option = config.option.as_int()
+
+        all_providers = list(typed_option.traverse())
+
+        self.assertEqual(len(all_providers), 1)
+        self.assertIn(option, all_providers)
+
+    def test_traverse_overridden(self):
+        options = {'option1': {'option2': 'option2'}}
+        config = providers.Configuration()
+        config.from_dict(options)
+
+        all_providers = list(config.traverse())
+
+        self.assertEqual(len(all_providers), 1)
+        overridden, = all_providers
+        self.assertEqual(overridden(), options)
+        self.assertIs(overridden, config.last_overriding)
+
+    def test_traverse_overridden_option_1(self):
+        options = {'option2': 'option2'}
+        config = providers.Configuration()
+        config.option1.from_dict(options)
+
+        all_providers = list(config.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(config.option1, all_providers)
+        self.assertIn(config.last_overriding, all_providers)
+
+    def test_traverse_overridden_option_2(self):
+        options = {'option2': 'option2'}
+        config = providers.Configuration()
+        config.option1.from_dict(options)
+
+        all_providers = list(config.option1.traverse())
+
+        self.assertEqual(len(all_providers), 0)
+
+
+class FactoryTests(unittest.TestCase):
+
+    def test_traverse(self):
+        provider = providers.Factory(dict)
+        all_providers = list(provider.traverse())
+        self.assertEqual(len(all_providers), 0)
+
+    def test_traverse_args(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.Factory(list, 'foo', provider1, provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_kwargs(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.Factory(dict, foo='foo', bar=provider1, baz=provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_attributes(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.Factory(dict)
+        provider.add_attributes(foo='foo', bar=provider1, baz=provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+
+        provider = providers.Factory(dict, 'foo')
+        provider.override(provider1)
+        provider.override(provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_provides(self):
+        provider1 = providers.Callable(list)
+        provider2 = providers.Object('bar')
+        provider3 = providers.Object('baz')
+
+        provider = providers.Factory(provider1, provider2)
+        provider.override(provider3)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provider3, all_providers)
+
+
+class FactoryAggregateTests(unittest.TestCase):
+
+    def test_traverse(self):
+        factory1 = providers.Factory(dict)
+        factory2 = providers.Factory(list)
+        provider = providers.FactoryAggregate(factory1=factory1, factory2=factory2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(factory1, all_providers)
+        self.assertIn(factory2, all_providers)
+
+
+class BaseSingletonTests(unittest.TestCase):
+
+    def test_traverse(self):
+        provider = providers.Singleton(dict)
+        all_providers = list(provider.traverse())
+        self.assertEqual(len(all_providers), 0)
+
+    def test_traverse_args(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.Singleton(list, 'foo', provider1, provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_kwargs(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.Singleton(dict, foo='foo', bar=provider1, baz=provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_attributes(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.Singleton(dict)
+        provider.add_attributes(foo='foo', bar=provider1, baz=provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+
+        provider = providers.Singleton(dict, 'foo')
+        provider.override(provider1)
+        provider.override(provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_provides(self):
+        provider1 = providers.Callable(list)
+        provider2 = providers.Object('bar')
+        provider3 = providers.Object('baz')
+
+        provider = providers.Singleton(provider1, provider2)
+        provider.override(provider3)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provider3, all_providers)
+
+
+class ListTests(unittest.TestCase):
+
+    def test_traverse_args(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.List('foo', provider1, provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider3 = providers.List(provider1, provider2)
+
+        provider = providers.List('foo')
+        provider.override(provider3)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provider3, all_providers)
+
+
+class DictTests(unittest.TestCase):
+
+    def test_traverse_kwargs(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.Dict(foo='foo', bar=provider1, baz=provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider3 = providers.Dict(bar=provider1, baz=provider2)
+
+        provider = providers.Dict(foo='foo')
+        provider.override(provider3)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provider3, all_providers)
+
+
+class ResourceTests(unittest.TestCase):
+
+    def test_traverse(self):
+        provider = providers.Resource(dict)
+        all_providers = list(provider.traverse())
+        self.assertEqual(len(all_providers), 0)
+
+    def test_traverse_args(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.Resource(list, 'foo', provider1, provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_kwargs(self):
+        provider1 = providers.Object('bar')
+        provider2 = providers.Object('baz')
+        provider = providers.Resource(dict, foo='foo', bar=provider1, baz=provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Resource(list)
+        provider2 = providers.Resource(tuple)
+
+        provider = providers.Resource(dict, 'foo')
+        provider.override(provider1)
+        provider.override(provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_provides(self):
+        provider1 = providers.Callable(list)
+
+        provider = providers.Resource(provider1)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 1)
+        self.assertIn(provider1, all_providers)
+
+
+class ContainerTests(unittest.TestCase):
+
+    def test_traverse(self):
+        class Container(containers.DeclarativeContainer):
+            provider1 = providers.Callable(list)
+            provider2 = providers.Callable(dict)
+
+        provider = providers.Container(Container)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertEqual(
+            {provider.provides for provider in all_providers},
+            {list,  dict},
+        )
+
+    def test_traverse_overridden(self):
+        class Container1(containers.DeclarativeContainer):
+            provider1 = providers.Callable(list)
+            provider2 = providers.Callable(dict)
+
+        class Container2(containers.DeclarativeContainer):
+            provider1 = providers.Callable(tuple)
+            provider2 = providers.Callable(str)
+
+        container2 = Container2()
+
+        provider = providers.Container(Container1)
+        provider.override(container2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 5)
+        self.assertEqual(
+            {
+                provider.provides
+                for provider in all_providers
+                if isinstance(provider, providers.Callable)
+            },
+            {list, dict, tuple, str},
+        )
+        self.assertIn(provider.last_overriding, all_providers)
+        self.assertIs(provider.last_overriding(), container2)
+
+
+class SelectorTests(unittest.TestCase):
+
+    def test_traverse(self):
+        switch = lambda: 'provider1'
+        provider1 = providers.Callable(list)
+        provider2 = providers.Callable(dict)
+
+        provider = providers.Selector(
+            switch,
+            provider1=provider1,
+            provider2=provider2,
+        )
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_switch(self):
+        switch = providers.Callable(lambda: 'provider1')
+        provider1 = providers.Callable(list)
+        provider2 = providers.Callable(dict)
+
+        provider = providers.Selector(
+            switch,
+            provider1=provider1,
+            provider2=provider2,
+        )
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(switch, all_providers)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Callable(list)
+        provider2 = providers.Callable(dict)
+        selector1 = providers.Selector(lambda: 'provider1', provider1=provider1)
+
+        provider = providers.Selector(
+            lambda: 'provider2',
+            provider2=provider2,
+        )
+        provider.override(selector1)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(selector1, all_providers)
+
+
+class ProvidedInstanceTests(unittest.TestCase):
+
+    def test_traverse(self):
+        provider1 = providers.Provider()
+        provider = provider1.provided
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 1)
+        self.assertIn(provider1, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Provider()
+        provider2 = providers.Provider()
+
+        provider = provider1.provided
+        provider.override(provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+
+
+class AttributeGetterTests(unittest.TestCase):
+
+    def test_traverse(self):
+        provider1 = providers.Provider()
+        provided = provider1.provided
+        provider = provided.attr
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provided, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Provider()
+        provided = provider1.provided
+        provider2 = providers.Provider()
+
+        provider = provided.attr
+        provider.override(provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provided, all_providers)
+
+
+class ItemGetterTests(unittest.TestCase):
+
+    def test_traverse(self):
+        provider1 = providers.Provider()
+        provided = provider1.provided
+        provider = provided['item']
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 2)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provided, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Provider()
+        provided = provider1.provided
+        provider2 = providers.Provider()
+
+        provider = provided['item']
+        provider.override(provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provided, all_providers)
+
+
+class MethodCallerTests(unittest.TestCase):
+
+    def test_traverse(self):
+        provider1 = providers.Provider()
+        provided = provider1.provided
+        method = provided.method
+        provider = method.call()
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 3)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provided, all_providers)
+        self.assertIn(method, all_providers)
+
+    def test_traverse_args(self):
+        provider1 = providers.Provider()
+        provided = provider1.provided
+        method = provided.method
+        provider2 = providers.Provider()
+        provider = method.call('foo', provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 4)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provided, all_providers)
+        self.assertIn(method, all_providers)
+
+    def test_traverse_kwargs(self):
+        provider1 = providers.Provider()
+        provided = provider1.provided
+        method = provided.method
+        provider2 = providers.Provider()
+        provider = method.call(foo='foo', bar=provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 4)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provided, all_providers)
+        self.assertIn(method, all_providers)
+
+    def test_traverse_overridden(self):
+        provider1 = providers.Provider()
+        provided = provider1.provided
+        method = provided.method
+        provider2 = providers.Provider()
+
+        provider = method.call()
+        provider.override(provider2)
+
+        all_providers = list(provider.traverse())
+
+        self.assertEqual(len(all_providers), 4)
+        self.assertIn(provider1, all_providers)
+        self.assertIn(provider2, all_providers)
+        self.assertIn(provided, all_providers)
+        self.assertIn(method, all_providers)