Merge pull request #1424 from alex/verify-interfaces
Fixes #1024 -- a utility function for checking an implementor against an ABC
diff --git a/cryptography/utils.py b/cryptography/utils.py
index 1deb3d1..03c8c0e 100644
--- a/cryptography/utils.py
+++ b/cryptography/utils.py
@@ -13,6 +13,8 @@
from __future__ import absolute_import, division, print_function
+import abc
+import inspect
import sys
@@ -21,6 +23,7 @@
def register_interface(iface):
def register_decorator(klass):
+ verify_interface(iface, klass)
iface.register(klass)
return klass
return register_decorator
@@ -30,6 +33,30 @@
return property(lambda self: getattr(self, name))
+class InterfaceNotImplemented(Exception):
+ pass
+
+
+def verify_interface(iface, klass):
+ for method in iface.__abstractmethods__:
+ if not hasattr(klass, method):
+ raise InterfaceNotImplemented(
+ "{0} is missing a {1!r} method".format(klass, method)
+ )
+ if isinstance(getattr(iface, method), abc.abstractproperty):
+ # Can't properly verify these yet.
+ continue
+ spec = inspect.getargspec(getattr(iface, method))
+ actual = inspect.getargspec(getattr(klass, method))
+ if spec != actual:
+ raise InterfaceNotImplemented(
+ "{0}.{1}'s signature differs from the expected. Expected: "
+ "{2!r}. Received: {3!r}".format(
+ klass, method, spec, actual
+ )
+ )
+
+
def bit_length(x):
if sys.version_info >= (2, 7):
return x.bit_length()
diff --git a/tests/test_interfaces.py b/tests/test_interfaces.py
new file mode 100644
index 0000000..b988abe
--- /dev/null
+++ b/tests/test_interfaces.py
@@ -0,0 +1,63 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import abc
+
+import pytest
+
+import six
+
+from cryptography.utils import InterfaceNotImplemented, verify_interface
+
+
+class TestVerifyInterface(object):
+ def test_verify_missing_method(self):
+ @six.add_metaclass(abc.ABCMeta)
+ class SimpleInterface(object):
+ @abc.abstractmethod
+ def method(self):
+ """A simple method"""
+
+ class NonImplementer(object):
+ pass
+
+ with pytest.raises(InterfaceNotImplemented):
+ verify_interface(SimpleInterface, NonImplementer)
+
+ def test_different_arguments(self):
+ @six.add_metaclass(abc.ABCMeta)
+ class SimpleInterface(object):
+ @abc.abstractmethod
+ def method(self, a):
+ """Method with one argument"""
+
+ class NonImplementer(object):
+ def method(self):
+ """Method with no arguments"""
+
+ with pytest.raises(InterfaceNotImplemented):
+ verify_interface(SimpleInterface, NonImplementer)
+
+ def test_handles_abstract_property(self):
+ @six.add_metaclass(abc.ABCMeta)
+ class SimpleInterface(object):
+ @abc.abstractproperty
+ def property(self):
+ """An abstract property"""
+
+ class NonImplementer(object):
+ @property
+ def property(self):
+ """A concrete property"""
+
+ verify_interface(SimpleInterface, NonImplementer)