Add subclasshook for CacheMutex

Also restore python-memcached to test suite

Change-Id: If4cd5e4604a0c5b51e1b34ba5a1a397ec1ef15cf

4 files changed, 44 insertions, 0 deletions

diff --git a/dogpile/cache/api.py b/dogpile/cache/api.py
index dd16252..d89ac56 100644
--- a/dogpile/cache/api.py
+++ b/dogpile/cache/api.py
@@ -85,6 +85,10 @@ class CacheMutex(abc.ABC):
 
         raise NotImplementedError()
 
+    @classmethod
+    def __subclasshook__(cls, C):
+        return hasattr(C, "acquire") and hasattr(C, "release")
+
 
 class CachedValue(NamedTuple):
     """Represent a value stored in the cache.
diff --git a/tests/cache/_fixtures.py b/tests/cache/_fixtures.py
index e55c471..1be5a2c 100644
--- a/tests/cache/_fixtures.py
+++ b/tests/cache/_fixtures.py
@@ -12,6 +12,7 @@ import pytest
 from dogpile.cache import CacheRegion
 from dogpile.cache import register_backend
 from dogpile.cache.api import CacheBackend
+from dogpile.cache.api import CacheMutex
 from dogpile.cache.api import NO_VALUE
 from dogpile.cache.region import _backend_loader
 from . import assert_raises_message
@@ -395,6 +396,12 @@ class _GenericMutexTest(_GenericBackendFixture, TestCase):
         assert ac3
         mutex.release()
 
+    def test_subclass_match(self):
+        backend = self._backend()
+        mutex = backend.get_mutex("foo")
+
+        assert isinstance(mutex, CacheMutex)
+
     @pytest.mark.time_intensive
     def test_mutex_threaded(self):
         backend = self._backend()
diff --git a/tests/cache/test_region.py b/tests/cache/test_region.py
index 7168433..087d533 100644
--- a/tests/cache/test_region.py
+++ b/tests/cache/test_region.py
@@ -13,6 +13,7 @@ from dogpile.cache import make_region
 from dogpile.cache import util
 from dogpile.cache.api import CacheBackend
 from dogpile.cache.api import CachedValue
+from dogpile.cache.api import CacheMutex
 from dogpile.cache.api import NO_VALUE
 from dogpile.cache.proxy import ProxyBackend
 from dogpile.cache.region import _backend_loader
@@ -605,6 +606,37 @@ class TestProxyValue(object):
         self.value = value
 
 
+class MutexAPITest(TestCase):
+    def test_mutex_non_match(self):
+        assert not isinstance(5, CacheMutex)
+        assert not isinstance("some string", CacheMutex)
+
+        class Foo:
+            def release(self):
+                pass
+
+        assert not isinstance(Foo(), CacheMutex)
+
+        class Bar:
+            def acquire(self):
+                pass
+
+        assert not isinstance(Bar(), CacheMutex)
+
+    def test_mutex_match(self):
+        class Foo:
+            def acquire(self):
+                # note we are missing the "wait" parameter.  not sure
+                # how ABCs are supposed to efficiently test these
+                # things.
+                pass
+
+            def release(self):
+                pass
+
+        assert isinstance(Foo(), CacheMutex)
+
+
 class AsyncCreatorTest(TestCase):
     def _fixture(self):
         def async_creation_runner(cache, somekey, creator, mutex):
diff --git a/tox.ini b/tox.ini
index 2c11621..61c6d19 100644
--- a/tox.ini
+++ b/tox.ini
@@ -35,6 +35,7 @@ deps=
 
     # the py3k python-memcached fails for multiple
     # delete
+    {memcached}: python-memcached
     {memcached}: python-binary-memcached>=0.29.0
     {memcached}: pifpaf>=2.5.0
     {redis}: redis