Implement container.check_dependencies() (#396)

* Add implementation, typing stubs, and tests

* Add docs and example

* Update changelog

Author: rmk135

docs/containers/check_dependencies.rst

@@ -0,0 +1,18 @@
+.. _check-container-dependencies:
+
+Check container dependencies
+----------------------------
+
+To check container dependencies use method ``.check_dependencies()``.
+
+.. literalinclude:: ../../examples/containers/check_dependencies.py
+   :language: python
+   :lines: 3-
+   :emphasize-lines: 12
+
+Method ``.check_dependencies()`` raises an error if container has any undefined dependencies.
+If all dependencies are provided or have defaults, no error is raised.
+
+See also: :ref:`dependency-provider`.
+
+.. disqus::

docs/containers/index.rst

@@ -24,4 +24,5 @@ Containers module API docs - :py:mod:`dependency_injector.containers`.
     specialization
     overriding
     reset_singletons
+    check_dependencies
     traversal

docs/main/changelog.rst

@@ -7,6 +7,13 @@ that were made in every particular version.
 From version 0.7.6 *Dependency Injector* framework strictly 
 follows `Semantic versioning`_
 
+Development version
+-------------------
+- Add method ``container.check_dependencies()`` to check if all container dependencies
+  are defined.
+  See issue: `#383 <https://github.com/ets-labs/python-dependency-injector/issues/383>`_.
+  Thanks to `@shaunc <https://github.com/shaunc>`_ for suggesting the feature.
+
 4.21.0
 ------
 - Improve ``Dependency`` provider error message: when dependency is undefined,

docs/providers/dependency.rst

@@ -1,3 +1,5 @@
+.. _dependency-provider:
+
 Dependency provider
 ===================
 
@@ -31,4 +33,6 @@ dependency provider will wrap it into the ``Object`` provider.
    :lines: 16-23
    :emphasize-lines: 3
 
+See also: :ref:`check-container-dependencies`.
+
 .. disqus::

examples/containers/check_dependencies.py

@@ -0,0 +1,15 @@
+"""Container dependencies check example."""
+
+from dependency_injector import containers, providers
+
+
+class Container(containers.DeclarativeContainer):
+
+    service1 = providers.Dependency()
+    service2 = providers.Dependency()
+
+
+if __name__ == '__main__':
+    container = Container()
+    container.check_dependencies()  # <-- raises error:
+    # Container has undefined dependencies: "Container.service1", "Container.service2"

src/dependency_injector/containers.c

@@ -45,6 +45,7 @@ class Container:
     def shutdown_resources(self) -> Optional[Awaitable]: ...
     def apply_container_providers_overridings(self) -> None: ...
     def reset_singletons(self) -> None: ...
+    def check_dependencies(self) -> None: ...
     @overload
     def resolve_provider_name(self, provider: Provider) -> str: ...
     @classmethod

src/dependency_injector/containers.pyi

@@ -305,6 +305,30 @@ class DynamicContainer(Container):
         for provider in self.traverse(types=[providers.BaseSingleton]):
             provider.reset()
 
+    def check_dependencies(self):
+        """Check if container dependencies are defined.
+
+        If any dependency is undefined, raises an error.
+        """
+        undefined = [
+            dependency
+            for dependency in self.traverse(types=[providers.Dependency])
+            if not dependency.is_defined
+        ]
+
+        if not undefined:
+            return
+
+        container_name = self.parent_name if self.parent_name else self.__class__.__name__
+        undefined_names = [
+            f'"{dependency.parent_name if dependency.parent_name else dependency}"'
+            for dependency in undefined
+        ]
+        raise errors.Error(
+            f'Container "{container_name}" has undefined dependencies: '
+            f'{", ".join(undefined_names)}',
+        )
+
     def resolve_provider_name(self, provider):
         """Try to resolve provider name."""
         for provider_name, container_provider in self.providers.items():