VMware: Make DatastorePath hashable

Make DatastorePath work properly when used as a key value in a dict or
set.

This change specifically enables a subsequent change in the fake
driver, which stores DatastorePath objects in a set. However, it's
probably a good idea in general as I spent quite some time trying to
work out why it didn't work when I hit it.

Change-Id: Ia5519b84bc47ea1e0a5a70f9368806f762d12db5

nova/tests/virt/vmwareapi/test_ds_util.py

@@ -17,6 +17,7 @@
 
 import mock
 from oslo.vmware import exceptions as vexc
+from testtools import matchers
 
 from nova import exception
 from nova.i18n import _
@@ -447,6 +448,14 @@ def test_ds_path_non_equivalence(self):
             p = ds_util.DatastorePath(t[0], *t[1])
             self.assertNotEqual(str(canonical_p), str(p))
 
+    def test_ds_path_hashable(self):
+        ds1 = ds_util.DatastorePath('dsname', 'path')
+        ds2 = ds_util.DatastorePath('dsname', 'path')
+
+        # If the above objects have the same hash, they will only be added to
+        # the set once
+        self.assertThat(set([ds1, ds2]), matchers.HasLength(1))
+
     def test_equal(self):
         a = ds_util.DatastorePath('ds_name', 'a')
         b = ds_util.DatastorePath('ds_name', 'a')

nova/virt/vmwareapi/ds_util.py

@@ -161,6 +161,9 @@ def __eq__(self, other):
                 self._datastore_name == other._datastore_name and
                 self._rel_path == other._rel_path)
 
+    def __hash__(self):
+        return str(self).__hash__()
+
     @classmethod
     def parse(cls, datastore_path):
         """Constructs a DatastorePath object given a datastore path string."""