Add mediaType, artifactType, and subject to Index per the specification

opencontainers/image/v1/descriptor.py

@@ -6,6 +6,7 @@
 
 from opencontainers.struct import Struct
 from opencontainers.digest import Digest
+from opencontainers.mediatype import RFC6838
 
 
 class Descriptor(Struct):
@@ -28,12 +29,11 @@ def __init__(
         super().__init__()
 
         # MediaType is the media type of the object this schema refers to.
-        regexp = "^[A-Za-z0-9][A-Za-z0-9!#$&-^_.+]{0,126}/[A-Za-z0-9][A-Za-z0-9!#$&-^_.+]{0,126}$"
         self.newAttr(
             name="MediaType",
             attType=str,
             jsonName="mediaType",
-            regexp=regexp,
+            regexp=RFC6838,
             required=True,
         )
 

opencontainers/image/v1/index.py

@@ -7,6 +7,7 @@
 from opencontainers.struct import Struct
 from opencontainers.image.specs import Versioned
 from opencontainers.logger import bot
+from opencontainers.mediatype import RFC6838
 from .mediatype import MediaTypeImageIndex, MediaTypeImageManifest
 from .descriptor import Descriptor
 import re
@@ -20,22 +21,44 @@ class Index(Struct):
     mediatype when marshalled to JSON.
     """
 
-    def __init__(self, manifests=None, schemaVersion=None, annotations=None):
+    def __init__(self, manifests=None, schemaVersion=None, annotations=None,
+                 mediaType=None, artifactType=None, subject=None):
         super().__init__()
 
         self.newAttr(name="schemaVersion", attType=Versioned, required=True)
 
+        # MediaType must be "application/vnd.oci.image.index.v1+json" if given
+        self.newAttr(
+            name="MediaType",
+            attType=str,
+            jsonName="mediaType",
+        )
+
+        # ArtifactType must be a valid media type according to RFC6838
+        self.newAttr(
+            name="ArtifactType",
+            attType=str,
+            jsonName="artifactType",
+            regexp=RFC6838,
+        )
+
         # Manifests references platform specific manifests.
         self.newAttr(
             name="Manifests", attType=[Descriptor], jsonName="manifests", required=True
         )
 
+        # Subject is a descriptor of another manifest
+        self.newAttr(name="Subject", attType=Descriptor, jsonName="subject")
+
         # Annotations contains arbitrary metadata for the image index.
         self.newAttr(name="Annotations", attType=dict, jsonName="annotations")
 
+        self.add("schemaVersion", schemaVersion)
+        self.add("MediaType", mediaType)
+        self.add("ArtifactType", artifactType)
         self.add("Manifests", manifests)
+        self.add("Subject", subject)
         self.add("Annotations", annotations)
-        self.add("schemaVersion", schemaVersion)
 
     def _validate(self):
         """
@@ -44,8 +67,16 @@ def _validate(self):
         custom validation function to ensure that Manifests mediaTypes
         are valid.
         """
+        valid = True
+
         valid_types = [MediaTypeImageManifest, MediaTypeImageIndex]
 
+        mediaType = self.attrs.get("MediaType")
+        if mediaType.value and mediaType.value != MediaTypeImageIndex:
+            bot.error("%s must be %s" % (mediaType, MediaTypeImageIndex))
+            valid = False
+
+
         manifests = self.attrs.get("Manifests").value
         if manifests:
             for manifest in manifests:
@@ -61,6 +92,6 @@ def _validate(self):
                     # Case 2: not valid and doesn't match regular expression
                     else:
                         bot.error("%s is not valid for index manifest." % mediaType)
-                        return False
+                        valid = False
 
-        return True
+        return valid

opencontainers/mediatype.py

@@ -0,0 +1,2 @@
+# RFC6838 specifies a regexp string for validating media types.
+RFC6838 = "^[A-Za-z0-9][A-Za-z0-9!#$&-^_.+]{0,126}/[A-Za-z0-9][A-Za-z0-9!#$&-^_.+]{0,126}$"

opencontainers/tests/test_imageindex.py

@@ -125,6 +125,30 @@
     ],
 }
 
+root_mediatype_valid = {
+    "schemaVersion": 2,
+    "mediaType": "application/vnd.oci.image.index.v1+json",
+    "manifests": [
+        {
+            "mediaType": "application/vnd.oci.image.manifest.v1+json",
+            "size": 7143,
+            "digest": "sha256:e692418e4cbaf90ca69d05a66403747baa33ee08806650b51fab815ad7fc331f",
+        }
+    ],
+}
+
+root_mediatype_invalid = {
+    "schemaVersion": 2,
+    "mediaType": "something/else",
+    "manifests": [
+        {
+            "mediaType": "application/vnd.oci.image.manifest.v1+json",
+            "size": 7143,
+            "digest": "sha256:e692418e4cbaf90ca69d05a66403747baa33ee08806650b51fab815ad7fc331f",
+        }
+    ],
+}
+
 
 def test_imageindex(tmp_path):
     """test creation of an opencontainers Index"""
@@ -162,3 +186,10 @@ def test_imageindex(tmp_path):
 
     # valid image index, with customized media type of referenced manifest
     index.load(index_with_custom)
+
+    # expected failure: invalid root media type
+    with pytest.raises(SystemExit):
+        index.load(root_mediatype_invalid)
+
+    # valid root media type
+    index.load(root_mediatype_valid)