Emit a DeprecationWarning rather than log a message

When used as a library we really don't know how logging will be
configured in the calling application so we shouldn't be logging our own
messages. Instead the standard way to signal deprecation is via a
DeprecationWarning.

Change the WARN enforcement to emit a warning instead of logging.

Resolves: #1

README.rst

@@ -126,8 +126,8 @@ This behaviour will work with the `positional.method` and
     >>> MyClass.my_method(10, kwonly1=20)  # Ok.
 
 For compatibility reasons you may wish to not always raise an exception so
-a WARN mode is available. Rather than raise an exception a warning message
-will be logged:
+a WARN mode is available. Rather than raise an exception a warning will be
+emitted.
 
 .. code:: python
 
@@ -138,7 +138,7 @@ will be logged:
 Available modes are:
 
 - positional.EXCEPT - the default, raise an exception.
-- positional.WARN - log a warning on mistake.
+- positional.WARN - emit a warning.
 
 
 .. |Build Status| image:: https://travis-ci.org/morganfainberg/positional.svg?branch=master

positional/__init__.py

@@ -12,12 +12,11 @@
 
 import functools
 import inspect
-import logging
+import warnings
 
 import pbr.version
 
 __version__ = pbr.version.VersionInfo('python-keystoneclient').version_string()
-_logger = logging.getLogger(__name__)
 
 
 class positional(object):
@@ -43,7 +42,7 @@ class positional(object):
 
     :param enforcement: defines the way incorrect usage is reported. Currenlty
         accepts :py:attr:`positional.EXCEPT` to raise a TypeError or
-        :py:attr:`positional.WARN` to print a warning. A warning can be useful
+        :py:attr:`positional.WARN` to show a warning. A warning can be useful
         for applying to functions that are already public as a deprecation
         notice. Defaults to :py:attr:`positional.EXCEPT`.
     """
@@ -90,7 +89,7 @@ class positional(object):
                 if self._enforcement == self.EXCEPT:
                     raise TypeError(message)
                 elif self._enforcement == self.WARN:
-                    _logger.warning(message)
+                    warnings.warn(message, DeprecationWarning, stacklevel=2)
 
             return func(*args, **kwargs)
 

positional/tests/test_positional.py

@@ -10,9 +10,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import logging
+import warnings
 
-import six
 import testtools
 
 from positional import positional
@@ -46,21 +45,15 @@ class TestPositional(testtools.TestCase):
         self.assertRaises(TypeError, self.mixed_except, 1, 2, 3)
 
     def test_mixed_warn(self):
-        logger_message = six.moves.cStringIO()
-        handler = logging.StreamHandler(logger_message)
-        handler.setLevel(logging.DEBUG)
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
 
-        logger = logging.getLogger(positional.__name__)
-        level = logger.getEffectiveLevel()
-        logger.setLevel(logging.DEBUG)
-        logger.addHandler(handler)
+            self.mixed_warn(1, 2, 3)
 
-        self.addCleanup(logger.removeHandler, handler)
-        self.addCleanup(logger.setLevel, level)
+        self.assertEqual(1, len(w))
 
-        self.mixed_warn(1, 2, 3)
-
-        self.assertIn('takes at most 3 positional', logger_message.getvalue())
+        self.assertTrue(issubclass(w[0].category, DeprecationWarning))
+        self.assertIn('takes at most 3 positional', str(w[0].message))
 
     @positional(enforcement=positional.EXCEPT)
     def inspect_func(self, arg, kwarg=None):

requirements.txt

@@ -2,5 +2,3 @@
 # of appearance.
 
 pbr>=1.6
-
-six>=1.9.0