Optional field

go.mod

@@ -27,7 +27,7 @@ require (
 	github.com/ncw/swift v1.0.47
 	github.com/opencontainers/go-digest v1.0.0
 	github.com/opencontainers/image-spec v1.0.1
-	github.com/oras-project/artifacts-spec v1.0.0-rc.1
+	github.com/oras-project/artifacts-spec v1.0.0-rc.2
 	github.com/sirupsen/logrus v1.8.1
 	github.com/spf13/cobra v1.0.0
 	github.com/yvasiyarov/go-metrics v0.0.0-20140926110328-57bccd1ccd43 // indirect

go.sum

@@ -136,11 +136,8 @@ github.com/opencontainers/go-digest v1.0.0 h1:apOUWs51W5PlhuyGyz9FCeeBIOUDA/6nW8
 github.com/opencontainers/go-digest v1.0.0/go.mod h1:0JzlMkj0TRzQZfJkVvzbP0HBR3IKzErnv2BNG4W4MAM=
 github.com/opencontainers/image-spec v1.0.1 h1:JMemWkRwHx4Zj+fVxWoMCFm/8sYGGrUVojFA6h/TRcI=
 github.com/opencontainers/image-spec v1.0.1/go.mod h1:BtxoFyWECRxE4U/7sNtV5W15zMzWCbyJoFRP3s7yZA0=
-github.com/oras-project/artifacts-spec v1.0.0-draft.1 h1:AyD++MU8sif5eyyvPbT5qskkJA9VZynYVoroVFTXPLM=
-github.com/oras-project/artifacts-spec v1.0.0-draft.1/go.mod h1:Xch2aLzSwtkhbFFN6LUzTfLtukYvMMdXJ4oZ8O7BOdc=
-github.com/oras-project/artifacts-spec v1.0.0-rc.1 h1:bCHf9mPbrgiNwQFyVzBX79BYZVAl0OUrmvICZOCOwts=
-github.com/oras-project/artifacts-spec v1.0.0-rc.1/go.mod h1:Xch2aLzSwtkhbFFN6LUzTfLtukYvMMdXJ4oZ8O7BOdc=
-github.com/pelletier/go-toml v1.2.0 h1:T5zMGML61Wp+FlcbWjRDT7yAxhJNAiPPLOFECq181zc=
+github.com/oras-project/artifacts-spec v1.0.0-rc.2 h1:9SMCNSxkJEHqWGDiMCuy6TXHgvjgwXGdXZZGXLKQvVE=
+github.com/oras-project/artifacts-spec v1.0.0-rc.2/go.mod h1:Xch2aLzSwtkhbFFN6LUzTfLtukYvMMdXJ4oZ8O7BOdc=
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
 github.com/pkg/errors v0.8.0/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=

registry/extension/oras/artifactmanifest.go

@@ -61,8 +61,11 @@ func (a Manifest) References() []distribution.Descriptor {
 }
 
 // Subject returns the the subject manifest this artifact references.
-func (a Manifest) Subject() distribution.Descriptor {
-	return distribution.Descriptor{
+func (a Manifest) Subject() *distribution.Descriptor {
+	if a.inner.Subject == nil {
+		return nil
+	}
+	return &distribution.Descriptor{
 		MediaType: a.inner.Subject.MediaType,
 		Digest:    a.inner.Subject.Digest,
 		Size:      a.inner.Subject.Size,

registry/extension/oras/artifactmanifesthandler.go

@@ -119,11 +119,13 @@ func (amh *artifactManifestHandler) verifyManifest(ctx context.Context, dm Deser
 
 		// Validate subject manifest.
 		subject := dm.Subject()
-		exists, err := ms.Exists(ctx, subject.Digest)
-		if !exists || err == distribution.ErrBlobUnknown {
-			errs = append(errs, distribution.ErrManifestBlobUnknown{Digest: subject.Digest})
-		} else if err != nil {
-			errs = append(errs, err)
+		if subject != nil {
+			exists, err := ms.Exists(ctx, subject.Digest)
+			if !exists || err == distribution.ErrBlobUnknown {
+				errs = append(errs, distribution.ErrManifestBlobUnknown{Digest: subject.Digest})
+			} else if err != nil {
+				errs = append(errs, err)
+			}
 		}
 	}
 
@@ -136,6 +138,10 @@ func (amh *artifactManifestHandler) verifyManifest(ctx context.Context, dm Deser
 
 // indexReferrers indexes the subject of the given revision in its referrers index store.
 func (amh *artifactManifestHandler) indexReferrers(ctx context.Context, dm DeserializedManifest, revision digest.Digest) error {
+	if dm.Subject() == nil {
+		return nil
+	}
+
 	// [TODO] We can use artifact type in the link path to support filtering by artifact type
 	//  but need to consider the max path length in different os
 	//artifactType := dm.ArtifactType()

registry/extension/oras/artifactmanifesthandler_test.go

@@ -119,7 +119,7 @@ func TestVerifyArtifactManifestPut(t *testing.T) {
 			Blobs: []orasartifacts.Descriptor{
 				artifactBlobDescriptor,
 			},
-			Subject: orasartifacts.Descriptor{
+			Subject: &orasartifacts.Descriptor{
 				MediaType: dm.MediaType,
 				Size:      int64(len(dmPayload)),
 				Digest:    dg,
@@ -134,7 +134,7 @@ func TestVerifyArtifactManifestPut(t *testing.T) {
 		MediaType    string
 		ArtifactType string
 		Blobs        []orasartifacts.Descriptor
-		Subject      orasartifacts.Descriptor
+		Subject      *orasartifacts.Descriptor
 		Annotations  map[string]string
 		Err          error
 	}
@@ -166,12 +166,21 @@ func TestVerifyArtifactManifestPut(t *testing.T) {
 			template.Annotations(),
 			errInvalidArtifactType,
 		},
+		// no subject
+		{
+			orasartifacts.MediaTypeArtifactManifest,
+			template.inner.ArtifactType,
+			template.inner.Blobs,
+			nil,
+			template.Annotations(),
+			nil,
+		},
 		// invalid subject
 		{
 			orasartifacts.MediaTypeArtifactManifest,
 			template.inner.ArtifactType,
 			template.inner.Blobs,
-			orasartifacts.Descriptor{
+			&orasartifacts.Descriptor{
 				MediaType: dm.MediaType,
 				Size:      int64(len(dmPayload)),
 				Digest:    digest.FromString("sha256:invalid"),

registry/handlers/api_test.go

@@ -1464,7 +1464,7 @@ func TestReferrers(t *testing.T) {
 		Blobs: []orasartifacts.Descriptor{
 			artifactBlobDescriptor,
 		},
-		Subject: orasartifacts.Descriptor{
+		Subject: &orasartifacts.Descriptor{
 			MediaType: schema2.MediaTypeManifest,
 			Size:      int64(len(p)),
 			Digest:    dgst,

vendor/modules.txt

@@ -153,7 +153,7 @@ github.com/opencontainers/go-digest
 ## explicit
 github.com/opencontainers/image-spec/specs-go
 github.com/opencontainers/image-spec/specs-go/v1
-# github.com/oras-project/artifacts-spec v1.0.0-rc.1
+# github.com/oras-project/artifacts-spec v1.0.0-rc.2
 ## explicit
 github.com/oras-project/artifacts-spec/specs-go/v1
 # github.com/prometheus/client_golang v1.1.0