[virt-tools-list] [virt-bootstrap] [PATCH 1/1] docker-source: Get list of layers without `--raw`

[Radostin Stoyanov]

When `skopeo inspect --raw docker://feodra` is used the returned
manifest content contains a list with manifests for specific
platforms [1] rather than a list with layers.

By using `skopeo inpect docker://fedora` the correct manifest
content is retrieved and a list with layers is provided. In addition,
skopeo handles the difference between schemaVersion 1 and 2.

[1] https://docs.docker.com/registry/spec/manifest-v2-2/#manifest-list-field-descriptions
---
 src/virtBootstrap/sources/docker_source.py | 29 ++++++-------
 tests/docker_source.py                     | 66 +++++-------------------------
 2 files changed, 22 insertions(+), 73 deletions(-)

diff --git a/src/virtBootstrap/sources/docker_source.py b/src/virtBootstrap/sources/docker_source.py
index ec1a812..0eace81 100644
--- a/src/virtBootstrap/sources/docker_source.py
+++ b/src/virtBootstrap/sources/docker_source.py
@@ -77,7 +77,7 @@ class DockerSource(object):
         self.no_cache = kwargs.get('no_cache', False)
         self.progress = kwargs['progress'].update_progress
         self.images_dir = utils.get_image_dir(self.no_cache)
-        self.manifest = None
+        self.image_details = None
         self.layers = []
         self.checksums = []
 
@@ -91,30 +91,25 @@ class DockerSource(object):
         Retrive manifest from registry and get layers' digest,
         sum_type, size and file_path in a list.
         """
-        self.manifest = utils.get_image_details(self.url, raw=True,
+        image_details = utils.get_image_details(self.url, raw=False,
                                                 insecure=self.insecure,
                                                 username=self.username,
                                                 password=self.password)
 
-        if self.manifest['schemaVersion'] == 1:
-            layers_list = self.manifest['fsLayers'][::-1]
-            digest_field = 'blobSum'
-        elif self.manifest['schemaVersion'] == 2:
-            layers_list = self.manifest['layers']
-            digest_field = 'digest'
-        else:
-            raise ValueError('Unsupported manifest schema.')
+        if not 'Layers' in image_details or not image_details['Layers']:
+            raise ValueError('No image layers.')
 
-        for layer in layers_list:
-            # Store checksums of layers
-            layer_digest = layer[digest_field]
+        # Layers are in order:
+        # - root layer first, and then successive layered layers
+        # Ref: https://github.com/containers/image/blob/master/image/oci.go
+        for layer_digest in image_details['Layers']:
             sum_type, layer_sum = layer_digest.split(':')
-            self.checksums.append([sum_type, layer_sum])
+            self.checksums.append([sum_type, layer_sum]) # Store checksums
 
-            # Store file path and size of each layer
+            # Layers are tar files with hashsum used as name
             file_path = os.path.join(self.images_dir, layer_sum + '.tar')
-            layer_size = layer.get('size', None)
-            self.layers.append([file_path, layer_size])
+            # Store 'file path' and set placeholder for 'size'
+            self.layers.append([file_path, None])
 
     def gen_valid_uri(self, uri):
         """
diff --git a/tests/docker_source.py b/tests/docker_source.py
index 9090988..c8f4e08 100644
--- a/tests/docker_source.py
+++ b/tests/docker_source.py
@@ -90,11 +90,8 @@ class CreateLayers(object):
         """
         return {
             "schemaVersion": 2,
-            "layers": [
-                {
-                    "digest":
-                    "sha256:" + os.path.basename(layer).split('.')[0]
-                }
+            "Layers": [
+                "sha256:" + os.path.basename(layer).split('.')[0]
                 for layer in self.layers
             ]
         }
@@ -340,7 +337,7 @@ class TestDockerSource(unittest.TestCase):
             'progress': mock.Mock()
         }
 
-        manifest = {'schemaVersion': 2, 'layers': []}
+        manifest = {'schemaVersion': 2, 'Layers': ['sha256:a7050fc1']}
         (src_instance,
          m_uri, m_utils) = self._mock_retrieve_layers_info(manifest,
                                                            src_kwargs)
@@ -349,7 +346,7 @@ class TestDockerSource(unittest.TestCase):
             'insecure': src_instance.insecure,
             'username': src_instance.username,
             'password': src_instance.password,
-            'raw': True
+            'raw': False
         }
         m_utils['get_image_details'].assert_called_once_with(m_uri(), **kwargs)
 
@@ -365,11 +362,11 @@ class TestDockerSource(unittest.TestCase):
         }
 
         manifest = {
-            'schemaVersion': 1,
-            'fsLayers': [
-                {'blobSum': 'sha256:75c416ea'},
-                {'blobSum': 'sha256:c6ff40b6'},
-                {'blobSum': 'sha256:a7050fc1'}
+            'schemaVersion': 2,
+            'Layers': [
+                'sha256:a7050fc1',
+                'sha256:c6ff40b6',
+                'sha256:75c416ea'
             ]
         }
 
@@ -382,47 +379,4 @@ class TestDockerSource(unittest.TestCase):
         with mock.patch('os.path.getsize') as m_getsize:
             m_getsize.return_value = None
             src_instance = self._mock_retrieve_layers_info(manifest, kwargs)[0]
-        self.assertEqual(src_instance.layers, expected_result)
-
-    def test_retrieve_layers_info_schema_version_2(self):
-        """
-        Ensures that retrieve_layers_info() extracts the layers' information
-        from manifest with schema version 2 a list with format:
-            ["digest", "sum_type", "file_path", "size"].
-        """
-        kwargs = {
-            'uri': '',
-            'progress': mock.Mock()
-        }
-
-        manifest = {
-            'schemaVersion': 2,
-            "layers": [
-                {"size": 47103294, "digest": "sha256:75c416ea"},
-                {"size": 814, "digest": "sha256:c6ff40b6"},
-                {"size": 513, "digest": "sha256:a7050fc1"}
-            ]
-        }
-
-        expected_result = [
-            ['/images_path/75c416ea.tar', 47103294],
-            ['/images_path/c6ff40b6.tar', 814],
-            ['/images_path/a7050fc1.tar', 513]
-        ]
-
-        src_instance = self._mock_retrieve_layers_info(manifest, kwargs)[0]
-        self.assertEqual(src_instance.layers, expected_result)
-
-    def test_retrieve_layers_info_raise_error_on_invalid_schema_version(self):
-        """
-        Ensures that retrieve_layers_info() calls get_image_details()
-        with all passed arguments.
-        """
-        kwargs = {
-            'uri': '',
-            'progress': mock.Mock()
-        }
-
-        manifest = {'schemaVersion': 3}
-        with self.assertRaises(ValueError):
-            self._mock_retrieve_layers_info(manifest, kwargs)
+        self.assertEqual(src_instance.layers, expected_result)
\ No newline at end of file
-- 
2.13.6