Readd support for decorating classes with @inject

As a bonus this provides dataclass support.

.travis.yml

@@ -15,7 +15,7 @@ matrix:
   include:
     - { python: "3.7", dist: xenial, sudo: true }
 install:
-  - pip install --upgrade coveralls pytest "typing$TYPING_VERSION" "pytest-cov>=2.5.1"
+  - pip install --upgrade coveralls pytest "typing$TYPING_VERSION" "pytest-cov>=2.5.1" dataclasses
   # mypy can't be installed on pypy
   - if [[ "${TRAVIS_PYTHON_VERSION}" != "pypy"* ]] ; then pip install mypy ; fi
   # Black is Python 3.6+-only

CHANGES

@@ -1,6 +1,13 @@
 Injector Change Log
 ===================
 
+0.16.2
+------
+
+- (Re)added support for decorating classes themselves with :func:`@inject <injector.inject>`. This is the same
+  as decorating their constructors. Among other things this gives us
+  `dataclasses <https://docs.python.org/3/library/dataclasses.html>`_ integration.
+
 0.16.1
 ------
 

README.md

@@ -50,6 +50,26 @@ A Quick Example
 
 ```
 
+Or with `dataclasses` if you like:
+
+```python
+from dataclasses import dataclass
+from injector import Injector, inject
+class Inner:
+    def __init__(self):
+        self.forty_two = 42
+
+@inject
+@dataclass
+class Outer:
+    inner: Inner
+
+injector = Injector()
+outer = injector.get(Outer)
+print(outer.inner.forty_two)  # Prints 42
+```
+
+
 A Full Example
 --------------
 

injector/__init__.py

@@ -899,7 +899,7 @@ def provider(function):
     return function
 
 
-def inject(function):
+def inject(constructor_or_class):
     """Decorator declaring parameters to be injected.
 
     eg.
@@ -923,15 +923,40 @@ def inject(function):
     >>> a = Injector(configure).get(A)
     [123, 'Bob', [1, 2, 3]]
 
+    As a convenience one can decorate a class itself:
+
+    >>> @inject
+    ... class B:
+    ...     def __init__(self, dependency: Dependency):
+    ...         self.dependency = dependency
+
+    This is equivalent to decorating its constructor. In particular this provides integration with
+    `dataclasses <https://docs.python.org/3/library/dataclasses.html>`_ (the order of decorator
+    application is important here):
+
+    >>> @inject
+    ... @dataclass
+    ... class C:
+    ...     dependency: Dependency
+
     .. note::
 
-        This decorator is to be used on class constructors. Using it on non-constructor
-        methods worked in the past but it was an implementation detail rather than
-        a design decision.
+        This decorator is to be used on class constructors (or, as a convenience, on classes).
+        Using it on non-constructor methods worked in the past but it was an implementation
+        detail rather than a design decision.
 
         Third party libraries may, however, provide support for injecting dependencies
         into non-constructor methods or free functions in one form or another.
+
+    .. versionchanged:: 0.16.2
+
+        (Re)added support for decorating classes with @inject.
     """
+    if isinstance(constructor_or_class, type) and hasattr(constructor_or_class, '__init__'):
+        inject(constructor_or_class.__init__)
+        return constructor_or_class
+
+    function = constructor_or_class
     try:
         bindings = _infer_injected_bindings(function)
     except _BindingNotYetAvailable:

injector_test.py

@@ -13,6 +13,7 @@
 from contextlib import contextmanager
 from typing import Any, NewType
 import abc
+import sys
 import threading
 import traceback
 import warnings
@@ -1393,3 +1394,26 @@ def test_newtype_integration_works():
 
     injector = Injector([configure])
     assert injector.get(UserID) == 123
+
+
+@pytest.mark.skipif(sys.version_info < (3, 6), reason="Requires Python 3.6+")
+def test_dataclass_integration_works():
+    import dataclasses
+
+    # Python 3.6+-only syntax below
+    exec(
+        """
+@inject
+@dataclasses.dataclass
+class Data:
+    name: str
+    """,
+        locals(),
+        globals(),
+    )
+
+    def configure(binder):
+        binder.bind(str, to='data')
+
+    injector = Injector([configure])
+    assert injector.get(Data).name == 'data'