export manifest on push

Signed-off-by: Shiwei Zhang <[email protected]>

cmd/oras/push.go

@@ -28,6 +28,7 @@ type pushOptions struct {
 	fileRefs               []string
 	manifestConfigRef      string
 	manifestAnnotations    string
+	manifestExport         string
 	artifactType           string
 	artifactRefs           []string
 	pathValidationDisabled bool
@@ -76,6 +77,7 @@ Example - Push file to the HTTP registry:
 
 	cmd.Flags().StringVarP(&opts.manifestConfigRef, "manifest-config", "", "", "manifest config file")
 	cmd.Flags().StringVarP(&opts.manifestAnnotations, "manifest-annotations", "", "", "manifest annotation file")
+	cmd.Flags().StringVarP(&opts.manifestExport, "export-manifest", "", "", "export the pushed manifest")
 	cmd.Flags().StringVarP(&opts.artifactType, "artifact-type", "", "", "artifact type")
 	cmd.Flags().StringArrayVarP(&opts.artifactRefs, "artifact-reference", "", nil, "artifact reference")
 	cmd.Flags().BoolVarP(&opts.pathValidationDisabled, "disable-path-validation", "", false, "skip path validation")
@@ -145,6 +147,16 @@ func runPush(opts pushOptions) error {
 		fmt.Println("Uploading empty artifact")
 	}
 
+	// export manifest
+	if opts.manifestExport != "" {
+		manifestFile, err := os.Create(opts.manifestExport)
+		if err != nil {
+			return err
+		}
+		defer manifestFile.Close()
+		pushOpts = append(pushOpts, oras.WithManifestWriter(manifestFile))
+	}
+
 	// ready to push
 	pushOpts = append(pushOpts, oras.WithPushStatusTrack(os.Stdout))
 	desc, err := oras.Push(ctx, resolver, opts.targetRef, store, files, pushOpts...)

pkg/oras/push.go

@@ -87,8 +87,8 @@ func pack(provider content.Provider, descriptors []ocispec.Descriptor, opts *pus
 	}
 
 	// Manifest
-	var desc ocispec.Descriptor
-	var err error
+	var mediaType string
+	var content interface{}
 	if opts.artifact != nil {
 		artifact := *opts.artifact
 		if config != nil {
@@ -97,20 +97,28 @@ func pack(provider content.Provider, descriptors []ocispec.Descriptor, opts *pus
 		}
 		artifact.Blobs = convertV1DescriptorsToV2(descriptors)
 		artifact.Annotations = opts.manifestAnnotations
-		desc, err = store.SetObject(artifact.MediaType, artifact)
+		mediaType = artifact.MediaType
+		content = artifact
 	} else {
-		desc, err = store.SetObject(ocispec.MediaTypeImageManifest, ocispec.Manifest{
+		mediaType = ocispec.MediaTypeImageManifest
+		content = ocispec.Manifest{
 			Versioned: specs.Versioned{
 				SchemaVersion: 2, // historical value. does not pertain to OCI or docker version
 			},
 			Config:      *config,
 			Layers:      descriptors,
 			Annotations: opts.manifestAnnotations,
-		})
+		}
 	}
+	desc, contentBytes, err := store.SetObject(mediaType, content)
 	if err != nil {
 		return ocispec.Descriptor{}, nil, err
 	}
+	if opts.manifestWriter != nil {
+		if _, err := opts.manifestWriter.Write(contentBytes); err != nil {
+			return ocispec.Descriptor{}, nil, err
+		}
+	}
 
 	return desc, store, nil
 }

pkg/oras/push_opts.go

@@ -23,6 +23,7 @@ type pushOpts struct {
 	configAnnotations   map[string]string
 	manifest            *ocispec.Descriptor
 	manifestAnnotations map[string]string
+	manifestWriter      io.Writer
 	validateName        func(desc ocispec.Descriptor) error
 	baseHandlers        []images.Handler
 	artifact            *artifactspec.Artifact
@@ -77,6 +78,14 @@ func WithManifestAnnotations(annotations map[string]string) PushOpt {
 	}
 }
 
+// WithManifestWriter exports the pushed manifest
+func WithManifestWriter(writer io.Writer) PushOpt {
+	return func(o *pushOpts) error {
+		o.manifestWriter = writer
+		return nil
+	}
+}
+
 // WithNameValidation validates the image title in the descriptor.
 // Pass nil to disable name validation.
 func WithNameValidation(validate func(desc ocispec.Descriptor) error) PushOpt {

pkg/oras/store.go

@@ -47,18 +47,18 @@ func (s *hybridStore) Set(desc ocispec.Descriptor, content []byte) {
 	s.cache.Set(desc, content)
 }
 
-func (s *hybridStore) SetObject(mediaType string, object interface{}) (ocispec.Descriptor, error) {
+func (s *hybridStore) SetObject(mediaType string, object interface{}) (ocispec.Descriptor, []byte, error) {
 	content, err := json.Marshal(object)
 	if err != nil {
-		return ocispec.Descriptor{}, err
+		return ocispec.Descriptor{}, nil, err
 	}
 	desc := ocispec.Descriptor{
 		MediaType: mediaType,
 		Digest:    digest.FromBytes(content),
 		Size:      int64(len(content)),
 	}
 	s.Set(desc, content)
-	return desc, nil
+	return desc, content, nil
 }
 
 // ReaderAt provides contents