Add deprecation warning when @inject is used

dependency_injector/injections.py

@@ -1,5 +1,7 @@
 """Dependency injector injections module."""
 
+import warnings
+
 import six
 
 from dependency_injector.providers.base import (
@@ -41,6 +43,10 @@ def inject(*args, **kwargs):
             def __init__(self, arg1, arg2):
                 pass
 
+    .. deprecated:: 2.2.0
+        Usage of :py:func:`inject` decorator can lead to bad design and could
+        be considered as anti-pattern.
+
     :param args: Tuple of context positional arguments.
     :type args: tuple[object]
 
@@ -50,6 +56,11 @@ def inject(*args, **kwargs):
     :return: Class / callable decorator
     :rtype: (callable) -> (type | callable)
     """
+    warnings.warn(message='Call to a deprecated decorator - @{0}.{1}'
+                          .format(inject.__module__, inject.__name__),
+                  category=DeprecationWarning,
+                  stacklevel=2)
+
     arg_injections = _parse_positional_injections(args)
     kwarg_injections = _parse_keyword_injections(kwargs)
 

tests/test_injections.py

@@ -1,5 +1,7 @@
 """Dependency injector injections unittests."""
 
+import warnings
+
 import unittest2 as unittest
 
 from dependency_injector import injections
@@ -176,3 +178,25 @@ class InjectTests(unittest.TestCase):
             @injections.inject(arg1=123)
             class Test(object):
                 """Test class."""
+
+
+class InjectDeprecationTests(unittest.TestCase):
+    """Deprecation of `@inject()` tests."""
+
+    def test_deprecation_warning_on_usage(self):
+        """Test that DeprecationWarning is produced when `@inject` is used."""
+        with warnings.catch_warnings(record=True) as caught_warnings:
+            warnings.simplefilter('always')
+
+            @injections.inject(1)
+            def _example(arg):
+                pass
+
+            warnings.simplefilter('default')
+
+        self.assertEquals(len(caught_warnings), 1)
+        self.assertEquals(caught_warnings[-1].category, DeprecationWarning)
+        self.assertIn('Call to a deprecated decorator',
+                      str(caught_warnings[-1].message))
+        self.assertIn('@dependency_injector.injections.inject',
+                      str(caught_warnings[-1].message))