Add validation of provided type for Factory provider

dependency_injector/providers.py

@@ -246,6 +246,16 @@ class Factory(Provider):
         some_object = factory()
     """
 
+    provided_type = None
+    """Provided type.
+
+    If provided type is defined, :py:class:`Factory` checks that
+    :py:attr:`Factory.provides` is subclass of
+    :py:attr:`Factory.provided_type`.
+
+    :type: type | None
+    """
+
     __slots__ = ('provides', 'args', 'kwargs', 'attributes', 'methods')
 
     def __init__(self, provides, *args, **kwargs):
@@ -261,10 +271,7 @@ class Factory(Provider):
         :param kwargs: Dictionary of injections.
         :type kwargs: dict
         """
-        if not callable(provides):
-            raise Error('Factory provider expects to get callable, ' +
-                        'got {0} instead'.format(str(provides)))
-        self.provides = provides
+        self.provides = self._ensure_provides_type(provides)
         """Class or other callable that provides object for creation.
 
         :type: type | callable
@@ -328,6 +335,31 @@ class Factory(Provider):
 
         return instance
 
+    def _ensure_provides_type(self, provides):
+        """Check if provided type is valid type for this factory.
+
+        :param provides: Factory provided type
+        :type provides: type
+
+        :raise: :py:exc:`dependency_injector.errors.Error` if ``provides``
+                is not callable
+        :raise: :py:exc:`dependency_injector.errors.Error` if ``provides``
+                doesn't meet factory provided type
+
+        :return: validated ``provides``
+        :rtype: type
+        """
+        if not callable(provides):
+            raise Error('Factory provider expects to get callable, ' +
+                        'got {0} instead'.format(str(provides)))
+        if (self.__class__.provided_type and
+                not issubclass(provides, self.__class__.provided_type)):
+            raise Error('{0} can provide only {1} instances'.format(
+                '.'.join((self.__class__.__module__,
+                          self.__class__.__name__)),
+                self.__class__.provided_type))
+        return provides
+
     def __str__(self):
         """Return string representation of provider.
 

docs/main/changelog.rst

@@ -9,7 +9,8 @@ follows `Semantic versioning`_
 
 Development version
 -------------------
-- No features.
+- Add possibility to validate ``Factory`` provided type on ``Factory`` 
+  initialization.
 
 1.11.2
 ------

tests/test_providers.py

@@ -176,6 +176,41 @@ class FactoryTests(unittest.TestCase):
         """Test creation of provider with a callable."""
         self.assertTrue(providers.Factory(credits))
 
+    def test_init_with_valid_provided_type(self):
+        """Test creation with not valid provided type."""
+        class ExampleFactory(providers.Factory):
+            """Example factory."""
+
+            provided_type = Example
+
+        example_factory = ExampleFactory(Example, 1, 2)
+
+        self.assertIsInstance(example_factory(), Example)
+
+    def test_init_with_valid_provided_subtype(self):
+        """Test creation with not valid provided type."""
+        class ExampleFactory(providers.Factory):
+            """Example factory."""
+
+            provided_type = Example
+
+        class NewExampe(Example):
+            """Example class subclass."""
+
+        example_factory = ExampleFactory(NewExampe, 1, 2)
+
+        self.assertIsInstance(example_factory(), NewExampe)
+
+    def test_init_with_invalid_provided_type(self):
+        """Test creation with not valid provided type."""
+        class ExampleFactory(providers.Factory):
+            """Example factory."""
+
+            provided_type = Example
+
+        with self.assertRaises(errors.Error):
+            ExampleFactory(list)
+
     def test_init_with_not_callable(self):
         """Test creation of provider with not a callable."""
         self.assertRaises(errors.Error, providers.Factory, 123)