feat: support formatted output in manifest fetch

Signed-off-by: Billy Zha <[email protected]>

cmd/oras/internal/meta/manfiest_fetch.go

@@ -0,0 +1,37 @@
+/*
+Copyright The ORAS Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package meta
+
+import (
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+type manifestFetch struct {
+	DigestReference
+	Config Descriptor   `json:"config"`
+	Layers []Descriptor `json:"layers"`
+}
+
+// NewManifestFetch creates a new manifest fetch metadata for formatting.
+func NewManifestFetch(path string, digest string, manifest ocispec.Manifest) manifestFetch {
+	mf := manifestFetch{
+		DigestReference: ToDigestReference(path, digest),
+	}
+	for _, layer := range manifest.Layers {
+		mf.Layers = append(mf.Layers, ToDescriptor(path, layer))
+	}
+	return mf
+}

cmd/oras/internal/meta/type.go

@@ -22,6 +22,13 @@ type DigestReference struct {
 	Reference string `json:"reference"`
 }
 
+// ToDigestReference converts a name and digest to a digest reference.
+func ToDigestReference(name string, digest string) DigestReference {
+	return DigestReference{
+		Reference: name + "@" + digest,
+	}
+}
+
 // Descriptor is a descriptor with digest reference.
 type Descriptor struct {
 	DigestReference
@@ -31,9 +38,7 @@ type Descriptor struct {
 // ToDescriptor converts a descriptor to a descriptor with digest reference.
 func ToDescriptor(name string, desc ocispec.Descriptor) Descriptor {
 	return Descriptor{
-		DigestReference: DigestReference{
-			Reference: name + "@" + desc.Digest.String(),
-		},
-		Descriptor: desc,
+		DigestReference: ToDigestReference(name, desc.Digest.String()),
+		Descriptor:      desc,
 	}
 }

cmd/oras/root/manifest/fetch.go

@@ -18,15 +18,17 @@ package manifest
 import (
 	"context"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"os"
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"github.com/spf13/cobra"
 	"oras.land/oras-go/v2"
 	"oras.land/oras-go/v2/registry/remote"
+	"oras.land/oras/cmd/oras/internal/display"
+	"oras.land/oras/cmd/oras/internal/meta"
 	"oras.land/oras/cmd/oras/internal/option"
+	"oras.land/oras/internal/docker"
 )
 
 type fetchOptions struct {
@@ -36,6 +38,7 @@ type fetchOptions struct {
 	option.Platform
 	option.Pretty
 	option.Target
+	option.Format
 
 	mediaTypes []string
 	outputPath string
@@ -71,14 +74,27 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 `,
 		Args: cobra.ExactArgs(1),
 		PreRunE: func(cmd *cobra.Command, args []string) error {
-			if opts.outputPath == "-" && opts.OutputDescriptor {
-				return errors.New("`--output -` cannot be used with `--descriptor` at the same time")
+			toCheck := []struct {
+				name      string
+				isPresent func() bool
+			}{
+				{"--output -", func() bool { return opts.outputPath == "-" }},
+				{"--format", func() bool { return opts.Template != "" }},
+				{"--descriptor", func() bool { return opts.OutputDescriptor }},
+			}
+			for i := range toCheck {
+				for j := i + 1; j < len(toCheck); j++ {
+					if toCheck[i].isPresent() && toCheck[j].isPresent() {
+						return fmt.Errorf("`%s` cannot be used with `%s` at the same time", toCheck[i].name, toCheck[j].name)
+					}
+				}
 			}
 			opts.RawReference = args[0]
 			return option.Parse(&opts)
 		},
 		Aliases: []string{"get"},
 		RunE: func(cmd *cobra.Command, args []string) error {
+			display.Set(opts.Template, opts.TTY)
 			return fetchManifest(cmd.Context(), opts)
 		},
 	}
@@ -129,7 +145,24 @@ func fetchManifest(ctx context.Context, opts fetchOptions) (fetchErr error) {
 			return fmt.Errorf("failed to fetch the content of %q: %w", opts.RawReference, err)
 		}
 
-		if opts.outputPath == "" || opts.outputPath == "-" {
+		if opts.Template != "" {
+			// output formatted data
+			switch desc.MediaType {
+			case ocispec.MediaTypeImageManifest, docker.MediaTypeManifest:
+				var manifest ocispec.Manifest
+				if err := json.Unmarshal(content, &manifest); err != nil {
+					return err
+				}
+				if err := json.Unmarshal(content, &manifest); err != nil {
+					return err
+				}
+				if err = opts.WriteTo(os.Stdout, meta.NewManifestFetch(opts.outputPath, desc.Digest.String(), manifest)); err != nil {
+					return err
+				}
+			default:
+				return fmt.Errorf("cannot apply template to %q: unsupported media type %s", opts.RawReference, desc.MediaType)
+			}
+		} else if opts.outputPath == "" || opts.outputPath == "-" {
 			// output manifest content
 			return opts.Output(os.Stdout, content)
 		}
@@ -148,6 +181,5 @@ func fetchManifest(ctx context.Context, opts fetchOptions) (fetchErr error) {
 		}
 		return opts.Output(os.Stdout, descBytes)
 	}
-
 	return nil
 }

cmd/oras/root/pull.go

@@ -290,7 +290,7 @@ func doPull(ctx context.Context, src oras.ReadOnlyTarget, dst oras.GraphTarget,
 		for _, s := range successors {
 			if name, ok := s.Annotations[ocispec.AnnotationTitle]; ok {
 				result.filesLock.Lock()
-				result.files = append(result.files, meta.NewFile(name, po.Output, desc, fmt.Sprintf("%s@%s", po.Path, desc.Digest)))
+				result.files = append(result.files, meta.NewFile(name, po.Output, desc, po.Path))
 				result.filesLock.Unlock()
 				if err := printOnce(&printed, s, promptRestored, po.Verbose, tracked); err != nil {
 					return err