Use VolumeSpec instead of re-parsing the volume string.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

compose/service.py

@@ -911,14 +911,15 @@ def merge_volume_bindings(volumes_option, previous_container):
     """Return a list of volume bindings for a container. Container data volumes
     are replaced by those from the previous container.
     """
+    volumes = [parse_volume_spec(volume) for volume in volumes_option or []]
     volume_bindings = dict(
-        build_volume_binding(parse_volume_spec(volume))
-        for volume in volumes_option or []
-        if ':' in volume)
+        build_volume_binding(volume)
+        for volume in volumes
+        if volume.external)
 
     if previous_container:
         volume_bindings.update(
-            get_container_data_volumes(previous_container, volumes_option))
+            get_container_data_volumes(previous_container, volumes))
 
     return list(volume_bindings.values())
 
@@ -929,12 +930,14 @@ def get_container_data_volumes(container, volumes_option):
     """
     volumes = []
 
-    volumes_option = volumes_option or []
     container_volumes = container.get('Volumes') or {}
-    image_volumes = container.image_config['ContainerConfig'].get('Volumes') or {}
+    image_volumes = [
+        parse_volume_spec(volume)
+        for volume in
+        container.image_config['ContainerConfig'].get('Volumes') or {}
+    ]
 
-    for volume in set(volumes_option + list(image_volumes)):
-        volume = parse_volume_spec(volume)
+    for volume in set(volumes_option + image_volumes):
         # No need to preserve host volumes
         if volume.external:
             continue

tests/unit/service_test.py

@@ -593,11 +593,11 @@ class ServiceVolumesTest(unittest.TestCase):
         self.assertEqual(binding, ('/inside', '/outside:/inside:rw'))
 
     def test_get_container_data_volumes(self):
-        options = [
+        options = [parse_volume_spec(v) for v in [
             '/host/volume:/host/volume:ro',
             '/new/volume',
             '/existing/volume',
-        ]
+        ]]
 
         self.mock_client.inspect_image.return_value = {
             'ContainerConfig': {