Implement 'labels' option

Signed-off-by: Aanand Prasad <aanand.prasad@gmail.com>

tests/integration/service_test.py

@@ -584,3 +584,30 @@ class ServiceTest(DockerClientTestCase):
         env = create_and_start_container(service).environment
         for k, v in {'FILE_DEF': 'F1', 'FILE_DEF_EMPTY': '', 'ENV_DEF': 'E3', 'NO_DEF': ''}.items():
             self.assertEqual(env[k], v)
+
+    def test_labels(self):
+        labels_dict = {
+            'com.example.description': "Accounting webapp",
+            'com.example.department': "Finance",
+            'com.example.label-with-empty-value': "",
+        }
+
+        service = self.create_service('web', labels=labels_dict)
+        labels = create_and_start_container(service).labels.items()
+        for pair in labels_dict.items():
+            self.assertIn(pair, labels)
+
+        labels_list = ["%s=%s" % pair for pair in labels_dict.items()]
+
+        service = self.create_service('web', labels=labels_list)
+        labels = create_and_start_container(service).labels.items()
+        for pair in labels_dict.items():
+            self.assertIn(pair, labels)
+
+    def test_empty_labels(self):
+        labels_list = ['foo', 'bar']
+
+        service = self.create_service('web', labels=labels_list)
+        labels = create_and_start_container(service).labels.items()
+        for name in labels_list:
+            self.assertIn((name, ''), labels)

tests/unit/config_test.py

@@ -185,6 +185,47 @@ class MergeStringsOrListsTest(unittest.TestCase):
         self.assertEqual(set(service_dict['dns']), set(['8.8.8.8', '9.9.9.9']))
 
 
+class MergeLabelsTest(unittest.TestCase):
+    def test_empty(self):
+        service_dict = config.merge_service_dicts({}, {})
+        self.assertNotIn('labels', service_dict)
+
+    def test_no_override(self):
+        service_dict = config.merge_service_dicts(
+            config.make_service_dict('foo', {'labels': ['foo=1', 'bar']}),
+            config.make_service_dict('foo', {}),
+        )
+        self.assertEqual(service_dict['labels'], {'foo': '1', 'bar': ''})
+
+    def test_no_base(self):
+        service_dict = config.merge_service_dicts(
+            config.make_service_dict('foo', {}),
+            config.make_service_dict('foo', {'labels': ['foo=2']}),
+        )
+        self.assertEqual(service_dict['labels'], {'foo': '2'})
+
+    def test_override_explicit_value(self):
+        service_dict = config.merge_service_dicts(
+            config.make_service_dict('foo', {'labels': ['foo=1', 'bar']}),
+            config.make_service_dict('foo', {'labels': ['foo=2']}),
+        )
+        self.assertEqual(service_dict['labels'], {'foo': '2', 'bar': ''})
+
+    def test_add_explicit_value(self):
+        service_dict = config.merge_service_dicts(
+            config.make_service_dict('foo', {'labels': ['foo=1', 'bar']}),
+            config.make_service_dict('foo', {'labels': ['bar=2']}),
+        )
+        self.assertEqual(service_dict['labels'], {'foo': '1', 'bar': '2'})
+
+    def test_remove_explicit_value(self):
+        service_dict = config.merge_service_dicts(
+            config.make_service_dict('foo', {'labels': ['foo=1', 'bar=2']}),
+            config.make_service_dict('foo', {'labels': ['bar']}),
+        )
+        self.assertEqual(service_dict['labels'], {'foo': '1', 'bar': ''})
+
+
 class EnvTest(unittest.TestCase):
     def test_parse_environment_as_list(self):
         environment = [