Merge pull request #6406 from collin5/b5948

Error on duplicate mount points.

compose/config/config.py

@@ -8,6 +8,7 @@ import os
 import string
 import sys
 from collections import namedtuple
+from operator import attrgetter
 
 import six
 import yaml
@@ -835,6 +836,17 @@ def finalize_service_volumes(service_dict, environment):
                 finalized_volumes.append(MountSpec.parse(v, normalize, win_host))
             else:
                 finalized_volumes.append(VolumeSpec.parse(v, normalize, win_host))
+
+        duplicate_mounts = []
+        mounts = [v.as_volume_spec() if isinstance(v, MountSpec) else v for v in finalized_volumes]
+        for mount in mounts:
+            if list(map(attrgetter('internal'), mounts)).count(mount.internal) > 1:
+                duplicate_mounts.append(mount.repr())
+
+        if duplicate_mounts:
+            raise ConfigurationError("Duplicate mount points: [%s]" % (
+                ', '.join(duplicate_mounts)))
+
         service_dict['volumes'] = finalized_volumes
 
     return service_dict

tests/unit/config/config_test.py

@@ -3106,6 +3106,41 @@ class ConfigTest(unittest.TestCase):
         )
         config.load(config_details)
 
+    def test_config_duplicate_mount_points(self):
+        config1 = build_config_details(
+            {
+                'version': '3.5',
+                'services': {
+                    'web': {
+                        'image': 'busybox',
+                        'volumes': ['/tmp/foo:/tmp/foo', '/tmp/foo:/tmp/foo:rw']
+                    }
+                }
+            }
+        )
+
+        config2 = build_config_details(
+            {
+                'version': '3.5',
+                'services': {
+                    'web': {
+                        'image': 'busybox',
+                        'volumes': ['/x:/y', '/z:/y']
+                    }
+                }
+            }
+        )
+
+        with self.assertRaises(ConfigurationError) as e:
+            config.load(config1)
+        self.assertEquals(str(e.exception), 'Duplicate mount points: [%s]' % (
+            ', '.join(['/tmp/foo:/tmp/foo:rw']*2)))
+
+        with self.assertRaises(ConfigurationError) as e:
+            config.load(config2)
+        self.assertEquals(str(e.exception), 'Duplicate mount points: [%s]' % (
+            ', '.join(['/x:/y:rw', '/z:/y:rw'])))
+
 
 class NetworkModeTest(unittest.TestCase):