531 Provider import from string (#555)

* Implement string imports for Factory, Callable, Singletons, and Resource

* Refactor the implementation

* Add tests

* Update tests to pass on Python 2

* Update typing and add typing tests

* Update changelog

* Update docs

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.
+- Add string imports for ``Factory``, ``Singleton``, ``Callable``, ``Resource``, and ``Coroutine``
+  providers, e.g. ``Factory("module.Class")``.
+  See issue `#531 <https://github.com/ets-labs/python-dependency-injector/issues/531>`_.
+  Thanks to `@al-stefanitsky-mozdor <https://github.com/al-stefanitsky-mozdor>`_ for suggesting the feature.
 - 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

docs/providers/factory.rst

@@ -110,6 +110,45 @@ attribute of the provider that you're going to inject.
 
 .. note:: Any provider has a ``.provider`` attribute.
 
+.. _factory-string-imports:
+
+String imports
+--------------
+
+``Factory`` provider can handle string imports:
+
+.. code-block:: python
+
+   class Container(containers.DeclarativeContainer):
+
+       service = providers.Factory("myapp.mypackage.mymodule.Service")
+
+You can also make a relative import:
+
+.. code-block:: python
+
+   # in myapp/container.py
+
+   class Container(containers.DeclarativeContainer):
+
+       service = providers.Factory(".mypackage.mymodule.Service")
+
+or import a member of the current module just specifying its name:
+
+.. code-block:: python
+
+   class Service:
+       ...
+
+
+   class Container(containers.DeclarativeContainer):
+
+       service = providers.Factory("Service")
+
+.. note::
+   ``Singleton``, ``Callable``, ``Resource``, and ``Coroutine`` providers handle string imports
+   the same way as a ``Factory`` provider.
+
 .. _factory-specialize-provided-type:
 
 Specializing the provided type

src/dependency_injector/providers.pyi

@@ -158,10 +158,10 @@ class DependenciesContainer(Object):
 
 
 class Callable(Provider[T]):
-    def __init__(self, provides: Optional[_Callable[..., T]] = None, *args: Injection, **kwargs: Injection) -> None: ...
+    def __init__(self, provides: Optional[Union[_Callable[..., T], str]] = None, *args: Injection, **kwargs: Injection) -> None: ...
     @property
     def provides(self) -> Optional[_Callable[..., T]]: ...
-    def set_provides(self, provides: Optional[_Callable[..., T]]) -> Callable[T]: ...
+    def set_provides(self, provides: Optional[Union[_Callable[..., T], str]]) -> Callable[T]: ...
     @property
     def args(self) -> Tuple[Injection]: ...
     def add_args(self, *args: Injection) -> Callable[T]: ...
@@ -283,12 +283,12 @@ class Configuration(Object[Any]):
 
 class Factory(Provider[T]):
     provided_type: Optional[Type]
-    def __init__(self, provides: Optional[_Callable[..., T]] = None, *args: Injection, **kwargs: Injection) -> None: ...
+    def __init__(self, provides: Optional[Union[_Callable[..., T], str]] = None, *args: Injection, **kwargs: Injection) -> None: ...
     @property
     def cls(self) -> Type[T]: ...
     @property
     def provides(self) -> Optional[_Callable[..., T]]: ...
-    def set_provides(self, provides: Optional[_Callable[..., T]]) -> Factory[T]: ...
+    def set_provides(self, provides: Optional[Union[_Callable[..., T], str]]) -> Factory[T]: ...
     @property
     def args(self) -> Tuple[Injection]: ...
     def add_args(self, *args: Injection) -> Factory[T]: ...
@@ -326,12 +326,12 @@ class FactoryAggregate(Aggregate[T]):
 
 class BaseSingleton(Provider[T]):
     provided_type = Optional[Type]
-    def __init__(self, provides: Optional[_Callable[..., T]] = None, *args: Injection, **kwargs: Injection) -> None: ...
+    def __init__(self, provides: Optional[Union[_Callable[..., T], str]] = None, *args: Injection, **kwargs: Injection) -> None: ...
     @property
     def cls(self) -> Type[T]: ...
     @property
     def provides(self) -> Optional[_Callable[..., T]]: ...
-    def set_provides(self, provides: Optional[_Callable[..., T]]) -> BaseSingleton[T]: ...
+    def set_provides(self, provides: Optional[Union[_Callable[..., T], str]]) -> BaseSingleton[T]: ...
     @property
     def args(self) -> Tuple[Injection]: ...
     def add_args(self, *args: Injection) -> BaseSingleton[T]: ...
@@ -377,7 +377,7 @@ class AbstractSingleton(BaseSingleton[T]):
 
 
 class SingletonDelegate(Delegate):
-    def __init__(self, factory: BaseSingleton): ...
+    def __init__(self, singleton: BaseSingleton): ...
 
 
 class List(Provider[_List]):
@@ -410,7 +410,7 @@ class Resource(Provider[T]):
     @overload
     def __init__(self, provides: Optional[_Callable[..., _Coroutine[Injection, Injection, T]]] = None, *args: Injection, **kwargs: Injection) -> None: ...
     @overload
-    def __init__(self, provides: Optional[_Callable[..., T]] = None, *args: Injection, **kwargs: Injection) -> None: ...
+    def __init__(self, provides: Optional[Union[_Callable[..., T], str]] = None, *args: Injection, **kwargs: Injection) -> None: ...
     @property
     def provides(self) -> Optional[_Callable[..., Any]]: ...
     def set_provides(self, provides: Optional[Any]) -> Resource[T]: ...

src/dependency_injector/providers.pyx

@@ -6,6 +6,7 @@ import copy
 import errno
 import functools
 import inspect
+import importlib
 import os
 import re
 import sys
@@ -18,6 +19,11 @@ try:
 except ImportError:
     contextvars = None
 
+try:
+    import builtins
+except ImportError:
+    # Python 2.7
+    import __builtin__ as builtins
 
 try:
     import asyncio
@@ -1221,6 +1227,7 @@ cdef class Callable(Provider):
 
     def set_provides(self, provides):
         """Set provider provides."""
+        provides = _resolve_provides(provides)
         if provides and not callable(provides):
             raise Error(
                 "Provider {0} expected to get callable, got {1} instead".format(
@@ -1426,9 +1433,10 @@ cdef class Coroutine(Callable):
     _is_coroutine = _is_coroutine_marker
 
     def set_provides(self, provides):
-        """Set provider"s provides."""
+        """Set provider provides."""
         if not asyncio:
             raise Error("Package asyncio is not available")
+        provides = _resolve_provides(provides)
         if provides and not asyncio.iscoroutinefunction(provides):
             raise Error(f"Provider {_class_qualname(self)} expected to get coroutine function, "
                         f"got {provides} instead")
@@ -2452,6 +2460,7 @@ cdef class Factory(Provider):
 
     def set_provides(self, provides):
         """Set provider provides."""
+        provides = _resolve_provides(provides)
         if (provides
                 and self.__class__.provided_type and
                 not issubclass(provides, self.__class__.provided_type)):
@@ -2742,6 +2751,7 @@ cdef class BaseSingleton(Provider):
 
     def set_provides(self, provides):
         """Set provider provides."""
+        provides = _resolve_provides(provides)
         if (provides
                 and self.__class__.provided_type and
                 not issubclass(provides, self.__class__.provided_type)):
@@ -3580,6 +3590,7 @@ cdef class Resource(Provider):
 
     def set_provides(self, provides):
         """Set provider provides."""
+        provides = _resolve_provides(provides)
         self.__provides = provides
         return self
 
@@ -4882,6 +4893,44 @@ def isasyncgenfunction(obj):
         return False
 
 
+def _resolve_provides(provides):
+    if provides is None:
+        return provides
+
+    if not isinstance(provides, str):
+        return provides
+
+    segments = provides.split(".")
+    member_name = segments[-1]
+
+    if len(segments) == 1:
+        if  member_name in dir(builtins):
+            module = builtins
+        else:
+            module = _resolve_calling_module()
+        return getattr(module, member_name)
+
+    module_name = ".".join(segments[:-1])
+
+    package_name = _resolve_calling_package_name()
+    if module_name.startswith(".") and package_name is None:
+        raise ImportError("Attempted relative import with no known parent package")
+
+    module = importlib.import_module(module_name, package=package_name)
+    return getattr(module, member_name)
+
+
+def _resolve_calling_module():
+    stack = inspect.stack()
+    pre_last_frame = stack[0]
+    return inspect.getmodule(pre_last_frame[0])
+
+
+def _resolve_calling_package_name():
+    module = _resolve_calling_module()
+    return module.__package__
+
+
 cpdef _copy_parent(object from_, object to, dict memo):
     """Copy and assign provider parent."""
     copied_parent = (

tests/typing/callable.py

@@ -66,3 +66,7 @@ assert provides10 is Cat
 provider11 = providers.Callable[Animal](Cat)
 provides11: Optional[Callable[..., Animal]] = provider11.provides
 assert provides11 is Cat
+
+# Test 12: to check string imports
+provider12: providers.Callable[dict] = providers.Callable("builtins.dict")
+provider12.set_provides("builtins.dict")

tests/typing/coroutine.py

@@ -9,3 +9,7 @@ async def _coro() -> None:
 # Test 1: to check the return type
 provider1 = providers.Coroutine(_coro)
 var1: Coroutine = provider1()
+
+# Test 2: to check string imports
+provider2: providers.Coroutine[None] = providers.Coroutine("_coro")
+provider2.set_provides("_coro")

tests/typing/factory.py

@@ -99,3 +99,7 @@ provided_cls13: Type[Animal] = provider13.cls
 assert issubclass(provided_cls13, Animal)
 provided_provides13: Optional[Callable[..., Animal]] = provider13.provides
 assert provided_provides13 is not None and provided_provides13() == Cat()
+
+# Test 14: to check string imports
+provider14: providers.Factory[dict] = providers.Factory("builtins.dict")
+provider14.set_provides("builtins.dict")

tests/typing/resource.py

@@ -97,3 +97,8 @@ provider8 = providers.Resource(MyResource8)
 async def _provide8() -> None:
     var1: List[int] = await provider8()  # type: ignore
     var2: List[int] = await provider8.async_()
+
+
+# Test 9: to check string imports
+provider9: providers.Resource[dict] = providers.Resource("builtins.dict")
+provider9.set_provides("builtins.dict")

tests/typing/singleton.py

@@ -89,3 +89,7 @@ provided_cls15: Type[Animal] = provider15.cls
 assert issubclass(provided_cls15, Animal)
 provided_provides15: Optional[Callable[..., Animal]] = provider15.provides
 assert provided_provides15 is not None and provided_provides15() == Cat()
+
+# Test 16: to check string imports
+provider16: providers.Singleton[dict] = providers.Singleton("builtins.dict")
+provider16.set_provides("builtins.dict")

tests/unit/providers/callables/test_callable_py2_py3.py

@@ -1,9 +1,10 @@
 """Callable provider tests."""
 
+import decimal
 import sys
 
 from dependency_injector import providers, errors
-from pytest import raises
+from pytest import raises, mark
 
 from .common import example
 
@@ -29,6 +30,20 @@ def test_set_provides_returns_():
     assert provider.set_provides(object) is provider
 
 
+@mark.parametrize(
+    "str_name,cls",
+    [
+        ("dependency_injector.providers.Factory", providers.Factory),
+        ("decimal.Decimal", decimal.Decimal),
+        ("list", list),
+        (".common.example", example),
+        ("test_is_provider", test_is_provider),
+    ],
+)
+def test_set_provides_string_imports(str_name, cls):
+    assert providers.Callable(str_name).provides is cls
+
+
 def test_provided_instance_provider():
     provider = providers.Callable(example)
     assert isinstance(provider.provided, providers.ProvidedInstance)

tests/unit/providers/coroutines/test_coroutine_py35.py

@@ -31,6 +31,17 @@ def test_set_provides_returns_self():
     assert provider.set_provides(example) is provider
 
 
+@mark.parametrize(
+    "str_name,cls",
+    [
+        (".common.example", example),
+        ("example", example),
+    ],
+)
+def test_set_provides_string_imports(str_name, cls):
+    assert providers.Coroutine(str_name).provides is cls
+
+
 @mark.asyncio
 async def test_call_with_positional_args():
     provider = providers.Coroutine(example, 1, 2, 3, 4)

tests/unit/providers/factories/test_factory_py2_py3.py

@@ -1,9 +1,10 @@
 """Factory provider tests."""
 
+import decimal
 import sys
 
 from dependency_injector import providers, errors
-from pytest import raises
+from pytest import raises, mark
 
 from .common import Example
 
@@ -29,6 +30,20 @@ def test_set_provides_returns_():
     assert provider.set_provides(object) is provider
 
 
+@mark.parametrize(
+    "str_name,cls",
+    [
+        ("dependency_injector.providers.Factory", providers.Factory),
+        ("decimal.Decimal", decimal.Decimal),
+        ("list", list),
+        (".common.Example", Example),
+        ("test_is_provider", test_is_provider),
+    ],
+)
+def test_set_provides_string_imports(str_name, cls):
+    assert providers.Factory(str_name).provides is cls
+
+
 def test_init_with_valid_provided_type():
     class ExampleProvider(providers.Factory):
         provided_type = Example

tests/unit/providers/resource/test_resource_py35.py

@@ -1,10 +1,11 @@
 """Resource provider tests."""
 
+import decimal
 import sys
 from typing import Any
 
 from dependency_injector import containers, providers, resources, errors
-from pytest import raises
+from pytest import raises, mark
 
 
 def init_fn(*args, **kwargs):
@@ -27,6 +28,20 @@ def test_set_provides_returns_():
     assert provider.set_provides(init_fn) is provider
 
 
+@mark.parametrize(
+    "str_name,cls",
+    [
+        ("dependency_injector.providers.Factory", providers.Factory),
+        ("decimal.Decimal", decimal.Decimal),
+        ("list", list),
+        (".test_resource_py35.test_is_provider", test_is_provider),
+        ("test_is_provider", test_is_provider),
+    ],
+)
+def test_set_provides_string_imports(str_name, cls):
+    assert providers.Resource(str_name).provides is cls
+
+
 def test_provided_instance_provider():
     provider = providers.Resource(init_fn)
     assert isinstance(provider.provided, providers.ProvidedInstance)

tests/unit/providers/singleton/test_singleton_py2_py3.py

@@ -1,9 +1,9 @@
 """Singleton provider tests."""
-
+import decimal
 import sys
 
 from dependency_injector import providers, errors
-from pytest import fixture, raises
+from pytest import fixture, raises, mark
 
 from .common import Example
 
@@ -49,6 +49,20 @@ def test_set_provides_returns_self(provider):
     assert provider.set_provides(object) is provider
 
 
+@mark.parametrize(
+    "str_name,cls",
+    [
+        ("dependency_injector.providers.Factory", providers.Factory),
+        ("decimal.Decimal", decimal.Decimal),
+        ("list", list),
+        (".common.Example", Example),
+        ("test_is_provider", test_is_provider),
+    ],
+)
+def test_set_provides_string_imports(str_name, cls):
+    assert providers.Singleton(str_name).provides is cls
+
+
 def test_init_with_valid_provided_type(singleton_cls):
     class ExampleProvider(singleton_cls):
         provided_type = Example