Fix ets-labs#550

Author: rmk135

docs/main/changelog.rst

@@ -21,6 +21,10 @@ Development version
   ``FactoryAggregate.factories`` attribute.
 - Add ``.set_providers()`` method to the ``FactoryAggregate`` provider. It is an alias for
   ``FactoryAggregate.set_factories()`` method.
+- Fix ``Dependency`` provider to don't raise "Dependency is not defined" error when the ``default``
+  is a falsy value of proper type.
+  See issue `#550 <https://github.com/ets-labs/python-dependency-injector/issues/550>`_. Thanks to
+  `@approxit <https://github.com/approxit>`_ for reporting the issue.
 - Refactor ``FactoryAggregate`` provider internals.
 - Update logo on Github and in docs to support dark themes and remove some imperfections.
 

src/dependency_injector/providers.c

@@ -879,7 +879,7 @@ cdef class Dependency(Provider):
 
     def set_default(self, default):
         """Set type."""
-        if default and not isinstance(default, Provider):
+        if default is not None and not isinstance(default, Provider):
             default = Object(default)
         self.__default = default
         return self

src/dependency_injector/providers.pyx

@@ -77,6 +77,22 @@ def test_default_attribute_provider():
     assert provider.default is default
 
 
+def test_default_with_empty_dict():
+    # See: https://github.com/ets-labs/python-dependency-injector/issues/550
+    default = {}
+    provider = providers.Dependency(instance_of=dict, default=default)
+    assert provider() == default
+    assert provider.default() == default
+
+
+def test_default_with_empty_string():
+    # See: https://github.com/ets-labs/python-dependency-injector/issues/550
+    default = ""
+    provider = providers.Dependency(instance_of=str, default=default)
+    assert provider() == default
+    assert provider.default() == default
+
+
 def test_is_defined(provider):
     assert provider.is_defined is False