Pass volume snapshot size to volume create

When creating a volume from a snapshot, the size parameter is required
and type is checked. Since we have to pass something and it needs to be
a valid data type (None is not acceptable) grab the size from the
snapshot object and pass it.

Change-Id: Ie23e3d23828919234e40336b5c65b22e140d337c

Author: emonty

openstackclient/tests/unit/volume/v2/test_volume.py

@@ -430,7 +430,7 @@ def test_volume_create_with_snapshot(self):
         columns, data = self.cmd.take_action(parsed_args)
 
         self.volumes_mock.create.assert_called_once_with(
-            size=None,
+            size=snapshot.size,
             snapshot_id=snapshot.id,
             name=self.new_volume.name,
             description=None,

openstackclient/volume/v2/volume.py

@@ -186,11 +186,21 @@ def take_action(self, parsed_args):
                 image_client.images,
                 parsed_args.image).id
 
+        size = parsed_args.size
+
         snapshot = None
         if parsed_args.snapshot:
-            snapshot = utils.find_resource(
+            snapshot_obj = utils.find_resource(
                 volume_client.volume_snapshots,
-                parsed_args.snapshot).id
+                parsed_args.snapshot)
+            snapshot = snapshot_obj.id
+            # Cinder requires a value for size when creating a volume
+            # even if creating from a snapshot. Cinder will create the
+            # volume with at least the same size as the snapshot anyway,
+            # so since we have the object here, just override the size
+            # value if it's either not given or is smaller than the
+            # snapshot size.
+            size = max(size or 0, snapshot_obj.size)
 
         project = None
         if parsed_args.project:
@@ -205,7 +215,7 @@ def take_action(self, parsed_args):
                 parsed_args.user).id
 
         volume = volume_client.volumes.create(
-            size=parsed_args.size,
+            size=size,
             snapshot_id=snapshot,
             name=parsed_args.name,
             description=parsed_args.description,