tests.unity.service: Make sure volumes order is preserved.

Signed-off-by: Antony MECHIN <antony.mechin@docker.com>

compose/service.py

@@ -56,6 +56,7 @@ from .utils import json_hash
 from .utils import parse_bytes
 from .utils import parse_seconds_float
 from .utils import truncate_id
+from .utils import unique_everseen
 
 
 log = logging.getLogger(__name__)
@@ -940,8 +941,9 @@ class Service(object):
                 override_options['mounts'] = override_options.get('mounts') or []
                 override_options['mounts'].extend([build_mount(v) for v in secret_volumes])
 
-        # Remove possible duplicates (see e.g. https://github.com/docker/compose/issues/5885)
-        override_options['binds'] = list(set(binds))
+        # Remove possible duplicates (see e.g. https://github.com/docker/compose/issues/5885).
+        # unique_everseen preserves order. (see https://github.com/docker/compose/issues/6091).
+        override_options['binds'] = list(unique_everseen(binds))
         return container_options, override_options
 
     def _get_container_host_config(self, override_options, one_off=False):

tests/unit/service_test.py

@@ -1037,6 +1037,23 @@ class ServiceTest(unittest.TestCase):
         assert len(override_opts['binds']) == 1
         assert override_opts['binds'][0] == 'vol:/data:rw'
 
+    def test_volumes_order_is_preserved(self):
+        service = Service('foo', client=self.mock_client)
+        volumes = [
+            VolumeSpec.parse(cfg) for cfg in [
+                '/v{0}:/v{0}:rw'.format(i) for i in range(6)
+            ]
+        ]
+        ctnr_opts, override_opts = service._build_container_volume_options(
+            previous_container=None,
+            container_options={
+                'volumes': volumes,
+                'environment': {},
+            },
+            override_options={},
+        )
+        assert override_opts['binds'] == [vol.repr() for vol in volumes]
+
 
 class TestServiceNetwork(unittest.TestCase):
     def setUp(self):