Configuration option typed injections (#284)

* Add implementation and tests

* Add docs page and examples

* Revert the api_client miniapp accidental changes

docs/providers/configuration.rst

@@ -96,4 +96,34 @@ where ``examples/providers/configuration/config.local.yml`` is:
 .. literalinclude:: ../../examples/providers/configuration/config.local.yml
    :language: ini
 
+Specifying value type
+~~~~~~~~~~~~~~~~~~~~~
+
+You can specify the type of the injected configuration value explicitly.
+
+This helps when you read the value from the ini file or the environment variable and need to
+convert it into an ``int`` or a ``float``.
+
+.. literalinclude:: ../../examples/providers/configuration/configuration_type.py
+   :language: python
+   :lines: 3-
+   :emphasize-lines: 17
+
+:py:class:`Configuration` provider has next helper methods:
+
+- ``.as_int()``
+- ``.as_float()``
+- ``.as_(callback, *args, **kwargs)``
+
+The last method ``.as_(callback, *args, **kwargs)`` helps to implement a other conversions.
+
+.. literalinclude:: ../../examples/providers/configuration/configuration_type_custom.py
+   :language: python
+   :lines: 3-
+   :emphasize-lines: 16
+
+With the ``.as_(callback, *args, **kwargs)`` you can specify the function that will be called
+before the injection. The value from the config will be passed as a first argument. The returned
+value will be injected. Parameters ``*args`` and ``**kwargs`` are handled as any other injections.
+
 .. disqus::

docs/providers/provided_instance.rst

@@ -62,3 +62,5 @@ should use the :py:class:`ProvidedInstance` provider.
 In all other cases you should not use :py:class:`ProvidedInstance`, :py:class:`AttributeGetter`,
 :py:class:`ItemGetter`, or :py:class:`MethodCaller` providers directly. Use the ``.provided``
 attribute of the injected provider instead.
+
+.. disqus::

examples/providers/configuration/configuration_type.py

@@ -0,0 +1,34 @@
+"""`Configuration` provider type specification example."""
+
+import os
+
+from dependency_injector import providers
+
+
+class ApiClient:
+    def __init__(self, api_key: str, timeout: int):
+        self.api_key = api_key
+        self.timeout = timeout
+
+
+config = providers.Configuration()
+
+api_client_factory = providers.Factory(
+    ApiClient,
+    api_key=config.api.key,
+    timeout=config.api.timeout.as_int(),
+)
+
+
+if __name__ == '__main__':
+    # Emulate environment variables
+    os.environ['API_KEY'] = 'secret'
+    os.environ['API_TIMEOUT'] = '5'
+
+    config.api.key.from_env('API_KEY')
+    config.api.timeout.from_env('API_TIMEOUT')
+
+    api_client = api_client_factory()
+
+    assert api_client.api_key == 'secret'
+    assert api_client.timeout == 5

examples/providers/configuration/configuration_type_custom.py

@@ -0,0 +1,30 @@
+"""`Configuration` provider custom type specification example."""
+
+import os
+import decimal
+
+from dependency_injector import providers
+
+
+class Calculator:
+    def __init__(self, pi: decimal.Decimal):
+        self.pi = pi
+
+
+config = providers.Configuration()
+
+calculator_factory = providers.Factory(
+    Calculator,
+    pi=config.pi.as_(decimal.Decimal),
+)
+
+
+if __name__ == '__main__':
+    # Emulate environment variables
+    os.environ['PI'] = '3.1415926535897932384626433832'
+
+    config.pi.from_env('PI')
+
+    calculator = calculator_factory()
+
+    assert calculator.pi == decimal.Decimal('3.1415926535897932384626433832')

src/dependency_injector/providers.pyx

@@ -1140,6 +1140,15 @@ cdef class ConfigurationOption(Provider):
         root = self.__root_ref()
         return '.'.join((root.get_name(), self._get_self_name()))
 
+    def as_int(self):
+        return Callable(int, self)
+
+    def as_float(self):
+        return Callable(float, self)
+
+    def as_(self, callback, *args, **kwargs):
+        return Callable(callback, self, *args, **kwargs)
+
     def override(self, value):
         if isinstance(value, Provider):
             raise Error('Configuration option can only be overridden by a value')

tests/unit/providers/test_configuration_py2_py3.py

@@ -1,6 +1,7 @@
 """Dependency injector config providers unit tests."""
 
 import contextlib
+import decimal
 import os
 import sys
 import tempfile
@@ -69,6 +70,33 @@ class ConfigTests(unittest.TestCase):
         self.assertEqual(abc(), 1)
         self.assertEqual(abd(), 2)
 
+    def test_as_int(self):
+        value_provider = providers.Callable(lambda value: value, self.config.test.as_int())
+        self.config.from_dict({'test': '123'})
+
+        value = value_provider()
+
+        self.assertEqual(value, 123)
+
+    def test_as_float(self):
+        value_provider = providers.Callable(lambda value: value, self.config.test.as_float())
+        self.config.from_dict({'test': '123.123'})
+
+        value = value_provider()
+
+        self.assertEqual(value, 123.123)
+
+    def test_as_(self):
+        value_provider = providers.Callable(
+            lambda value: value,
+            self.config.test.as_(decimal.Decimal),
+        )
+        self.config.from_dict({'test': '123.123'})
+
+        value = value_provider()
+
+        self.assertEqual(value, decimal.Decimal('123.123'))
+
     def test_providers_value_override(self):
         a = self.config.a
         ab = self.config.a.b
@@ -358,7 +386,6 @@ class ConfigFromIniWithEnvInterpolationTests(unittest.TestCase):
         self.assertEqual(self.config.section1.value1(), 'test-value')
 
 
-
 class ConfigFromYamlTests(unittest.TestCase):
 
     def setUp(self):