Fix config hash consistency with unprioritized networks

Signed-off-by: Joffrey F <joffrey@docker.com>

compose/network.py

@@ -323,7 +323,12 @@ def get_networks(service_dict, network_definitions):
                 'Service "{}" uses an undefined network "{}"'
                 .format(service_dict['name'], name))
 
-    return OrderedDict(sorted(
+    if any([v.get('priority') for v in networks.values()]):
-        networks.items(),
+        return OrderedDict(sorted(
-        key=lambda t: t[1].get('priority') or 0, reverse=True
+            networks.items(),
-    ))
+            key=lambda t: t[1].get('priority') or 0, reverse=True
+        ))
+    else:
+        # Ensure Compose will pick a consistent primary network if no
+        # priority is set
+        return OrderedDict(sorted(networks.items(), key=lambda t: t[0]))

tests/unit/service_test.py

@@ -701,9 +701,11 @@ class ServiceTest(unittest.TestCase):
             image='example.com/foo',
             client=self.mock_client,
             network_mode=NetworkMode('bridge'),
-            networks={'bridge': {}},
+            networks={'bridge': {}, 'net2': {}},
             links=[(Service('one', client=self.mock_client), 'one')],
-            volumes_from=[VolumeFromSpec(Service('two', client=self.mock_client), 'rw', 'service')]
+            volumes_from=[VolumeFromSpec(Service('two', client=self.mock_client), 'rw', 'service')],
+            volumes=[VolumeSpec('/ext', '/int', 'ro')],
+            build={'context': 'some/random/path'},
         )
         config_hash = service.config_hash