From 67dad877e35ea984f8d9fe648af30662034012eb Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 18 Mar 2024 09:56:03 +0000
Subject: [PATCH 01/36] feat: support `--format` in `manifest fetch` command

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/handler.go          |  4 ++
 .../internal/display/metadata/interface.go    |  5 ++
 .../display/metadata/model/mappable.go        | 55 ++++++++++++++++
 .../metadata/template/manifest_fetch.go       | 41 ++++++++++++
 cmd/oras/internal/option/pretty.go            |  6 +-
 cmd/oras/internal/option/pretty_test.go       |  8 +--
 cmd/oras/root/manifest/fetch.go               | 63 +++++++++++++++----
 .../e2e/internal/testdata/multi_arch/const.go |  1 +
 test/e2e/suite/command/manifest.go            | 21 +++++++
 9 files changed, 186 insertions(+), 18 deletions(-)
 create mode 100644 cmd/oras/internal/display/metadata/model/mappable.go
 create mode 100644 cmd/oras/internal/display/metadata/template/manifest_fetch.go

diff --git a/cmd/oras/internal/display/handler.go b/cmd/oras/internal/display/handler.go
index 56e05ae63..836f43f3e 100644
--- a/cmd/oras/internal/display/handler.go
+++ b/cmd/oras/internal/display/handler.go
@@ -72,3 +72,7 @@ func NewAttachHandler(format string, tty *os.File, verbose bool) (status.AttachH
 
 	return statusHandler, metadataHandler
 }
+
+func NewManifestFetchHandler(format string) metadata.ManifestFetchHandler {
+	return template.NewManifestFetchHandler(format)
+}
diff --git a/cmd/oras/internal/display/metadata/interface.go b/cmd/oras/internal/display/metadata/interface.go
index 577f9eb2e..c8ba1b41f 100644
--- a/cmd/oras/internal/display/metadata/interface.go
+++ b/cmd/oras/internal/display/metadata/interface.go
@@ -30,3 +30,8 @@ type PushHandler interface {
 type AttachHandler interface {
 	OnCompleted(opts *option.Target, root, subject ocispec.Descriptor) error
 }
+
+// ManifestFetchHandler handles metadata output for manifest fetch events.
+type ManifestFetchHandler interface {
+	OnFetched(manifest ocispec.Manifest) error
+}
diff --git a/cmd/oras/internal/display/metadata/model/mappable.go b/cmd/oras/internal/display/metadata/model/mappable.go
new file mode 100644
index 000000000..ca2ab686c
--- /dev/null
+++ b/cmd/oras/internal/display/metadata/model/mappable.go
@@ -0,0 +1,55 @@
+/*
+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 model
+
+import (
+	"reflect"
+	"strings"
+)
+
+// ToMappable converts an reflect value into a map[string]any with json tags as
+// key.
+func ToMappable(v reflect.Value) any {
+	switch v.Kind() {
+	case reflect.Struct:
+		t := v.Type()
+		numField := t.NumField()
+		ret := make(map[string]any)
+		for i := 0; i < numField; i++ {
+			fv := v.Field(i)
+			tag := t.Field(i).Tag.Get("json")
+			if tag == "" {
+				continue
+			}
+			key, _, _ := strings.Cut(tag, ",")
+			ret[key] = ToMappable(fv)
+		}
+		return ret
+	case reflect.Slice, reflect.Array:
+		ret := make([]any, v.Len())
+		for i := 0; i < v.Len(); i++ {
+			ret[i] = ToMappable(v.Index(i))
+		}
+		return ret
+	case reflect.Ptr, reflect.Interface:
+		if v.IsNil() {
+			return nil
+		}
+		elem := ToMappable(v.Elem())
+		return &elem
+	}
+	return v.Interface()
+}
diff --git a/cmd/oras/internal/display/metadata/template/manifest_fetch.go b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
new file mode 100644
index 000000000..256193974
--- /dev/null
+++ b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
@@ -0,0 +1,41 @@
+/*
+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 template
+
+import (
+	"reflect"
+
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"oras.land/oras/cmd/oras/internal/display/metadata"
+	"oras.land/oras/cmd/oras/internal/display/metadata/model"
+)
+
+// ManifestFetchHandler handles JSON metadata output for manifest fetch events.
+type ManifestFetchHandler struct {
+	template string
+}
+
+// NewManifestFetchHandler creates a new handler for manifest fetch events.
+func NewManifestFetchHandler(template string) metadata.ManifestFetchHandler {
+	return &ManifestFetchHandler{
+		template: template,
+	}
+}
+
+// OnFetched is called after the manifest fetch is completed.
+func (ph *ManifestFetchHandler) OnFetched(manifest ocispec.Manifest) error {
+	return parseAndWrite(model.ToMappable(reflect.ValueOf(manifest)), ph.template)
+}
diff --git a/cmd/oras/internal/option/pretty.go b/cmd/oras/internal/option/pretty.go
index 0e7524473..de889522e 100644
--- a/cmd/oras/internal/option/pretty.go
+++ b/cmd/oras/internal/option/pretty.go
@@ -26,18 +26,18 @@ import (
 
 // Pretty option struct.
 type Pretty struct {
-	pretty bool
+	Pretty bool
 }
 
 // ApplyFlags applies flags to a command flag set.
 func (opts *Pretty) ApplyFlags(fs *pflag.FlagSet) {
-	fs.BoolVarP(&opts.pretty, "pretty", "", false, "prettify JSON objects printed to stdout")
+	fs.BoolVarP(&opts.Pretty, "pretty", "", false, "prettify JSON objects printed to stdout")
 }
 
 // Output outputs the prettified content if `--pretty` flag is used. Otherwise
 // outputs the original content.
 func (opts *Pretty) Output(w io.Writer, content []byte) error {
-	if opts.pretty {
+	if opts.Pretty {
 		buf := bytes.NewBuffer(nil)
 		if err := json.Indent(buf, content, "", "  "); err != nil {
 			return fmt.Errorf("failed to prettify: %w", err)
diff --git a/cmd/oras/internal/option/pretty_test.go b/cmd/oras/internal/option/pretty_test.go
index 75aedd804..f42aa22d9 100644
--- a/cmd/oras/internal/option/pretty_test.go
+++ b/cmd/oras/internal/option/pretty_test.go
@@ -28,8 +28,8 @@ import (
 func TestPretty_ApplyFlags(t *testing.T) {
 	var test struct{ Pretty }
 	ApplyFlags(&test, pflag.NewFlagSet("oras-test", pflag.ExitOnError))
-	if test.Pretty.pretty != false {
-		t.Fatalf("expecting pretty to be false but got: %v", test.Pretty.pretty)
+	if test.Pretty.Pretty != false {
+		t.Fatalf("expecting pretty to be false but got: %v", test.Pretty.Pretty)
 	}
 }
 
@@ -49,7 +49,7 @@ func TestPretty_Output(t *testing.T) {
 
 	// test unprettified content
 	opts := Pretty{
-		pretty: false,
+		Pretty: false,
 	}
 	err = opts.Output(fp, raw)
 	if err != nil {
@@ -76,7 +76,7 @@ func TestPretty_Output(t *testing.T) {
 
 	// test prettified content
 	opts = Pretty{
-		pretty: true,
+		Pretty: true,
 	}
 	err = opts.Output(fp, raw)
 	if err != nil {
diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 5726552a4..2a43a7659 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -17,7 +17,6 @@ package manifest
 
 import (
 	"encoding/json"
-	"errors"
 	"fmt"
 	"os"
 
@@ -26,8 +25,10 @@ import (
 	"oras.land/oras-go/v2"
 	"oras.land/oras-go/v2/registry/remote"
 	"oras.land/oras/cmd/oras/internal/argument"
+	"oras.land/oras/cmd/oras/internal/display"
 	oerrors "oras.land/oras/cmd/oras/internal/errors"
 	"oras.land/oras/cmd/oras/internal/option"
+	"oras.land/oras/internal/docker"
 )
 
 type fetchOptions struct {
@@ -37,6 +38,7 @@ type fetchOptions struct {
 	option.Platform
 	option.Pretty
 	option.Target
+	option.Format
 
 	mediaTypes []string
 	outputPath string
@@ -72,9 +74,22 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 `,
 		Args: oerrors.CheckArgs(argument.Exactly(1), "the manifest to fetch"),
 		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)
 		},
@@ -86,6 +101,9 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 
 	cmd.Flags().StringSliceVarP(&opts.mediaTypes, "media-type", "", nil, "accepted media types")
 	cmd.Flags().StringVarP(&opts.outputPath, "output", "o", "", "file `path` to write the fetched manifest to, use - for stdout")
+	cmd.Flags().StringVar(&opts.Template, "format", "", `Format output using a custom template:
+'json':       Print manifest in prettified JSON format
+'$TEMPLATE':  Print output using the given Go template.`)
 	option.ApplyFlags(&opts, cmd.Flags())
 	return oerrors.Command(cmd, &opts.Target)
 }
@@ -110,6 +128,7 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 	if err != nil {
 		return err
 	}
+	handler := display.NewManifestFetchHandler(opts.Template)
 
 	var desc ocispec.Descriptor
 	if opts.OutputDescriptor && opts.outputPath == "" {
@@ -130,14 +149,37 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 			return fmt.Errorf("failed to fetch the content of %q: %w", opts.RawReference, err)
 		}
 
-		if opts.outputPath == "" || opts.outputPath == "-" {
-			// output manifest content
-			return opts.Output(os.Stdout, content)
+		if opts.Template != "" {
+			if opts.Template == "json" {
+				// output prettified json manifest content
+				opts.Pretty.Pretty = true
+				if err := opts.Output(os.Stdout, content); err != nil {
+					return err
+				}
+			} else {
+				// 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 = handler.OnFetched(manifest); err != nil {
+						return err
+					}
+				default:
+					return fmt.Errorf("cannot apply template to %q: unsupported media type %s", opts.RawReference, desc.MediaType)
+				}
+			}
 		}
-
-		// save manifest content into the local file if the output path is provided
-		if err = os.WriteFile(opts.outputPath, content, 0666); err != nil {
-			return err
+		if opts.outputPath != "" && opts.outputPath != "-" {
+			// save manifest content into the local file if the output path is provided
+			if err = os.WriteFile(opts.outputPath, content, 0666); err != nil {
+				return err
+			}
+		} else if opts.Template == "" {
+			// output raw manifest content
+			return opts.Output(os.Stdout, content)
 		}
 	}
 
@@ -149,6 +191,5 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 		}
 		return opts.Output(os.Stdout, descBytes)
 	}
-
 	return nil
 }
diff --git a/test/e2e/internal/testdata/multi_arch/const.go b/test/e2e/internal/testdata/multi_arch/const.go
index 5915b5942..d4a3ae380 100644
--- a/test/e2e/internal/testdata/multi_arch/const.go
+++ b/test/e2e/internal/testdata/multi_arch/const.go
@@ -64,6 +64,7 @@ var (
 		Size:         482,
 	}
 	LayerName                        = "hello.tar"
+	LayerDigest                      = "sha256:2ef548696ac7dd66ef38aab5cc8fc5cc1fb637dfaedb3a9afc89bf16db9277e1"
 	LinuxAMD64ReferrerStateKey       = match.StateKey{Digest: "c5e00045954a", Name: "application/vnd.oci.image.manifest.v1+json"}
 	LinuxAMD64ReferrerConfigStateKey = match.StateKey{Digest: "44136fa355b3", Name: "referrer/image"}
 	LinuxAMD64StateKeys              = []match.StateKey{
diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index f7e52ad01..5e227c91e 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -97,6 +97,15 @@ var _ = Describe("ORAS beginners:", func() {
 			It("should fail with suggestion if no tag or digest is provided", func() {
 				ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, "")).ExpectFailure().MatchErrKeyWords("Error:", "no tag or digest specified", "oras manifest fetch [flags] <name>{:<tag>|@<digest>}", "Please specify a reference").Exec()
 			})
+
+			It("should fail if stdout is used inpropriately", func() {
+				ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, foobar.Tag), "--output", "-", "--format", "test").
+					ExpectFailure().Exec()
+				ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, foobar.Tag), "--descriptor", "--format", "test").
+					ExpectFailure().Exec()
+				ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, foobar.Tag), "--output", "-", "--descriptor").
+					ExpectFailure().Exec()
+			})
 		})
 
 		When("running `manifest delete`", func() {
@@ -229,6 +238,18 @@ var _ = Describe("1.1 registry users:", func() {
 				MatchContent(multi_arch.LinuxAMD64Manifest).Exec()
 		})
 
+		It("should fetch manifest with platform validation and output json", func() {
+			out := ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.Tag), "--platform", "linux/amd64", "--format", "json").
+				Exec().Out.Contents()
+			Expect(out).To(MatchJSON(multi_arch.LinuxAMD64Manifest))
+		})
+
+		It("should fetch manifest and format output", func() {
+			ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.LinuxAMD64.Digest.String()), "--format", "{{(first .layers).digest}}").
+				MatchContent(multi_arch.LayerDigest).
+				Exec()
+		})
+
 		It("should fetch descriptor via digest", func() {
 			ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.Digest), "--descriptor").
 				MatchContent(multi_arch.Descriptor).Exec()

From fa0f2a1b7549dcb7b4e8316849e6ab1b835415e8 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 18 Mar 2024 10:03:22 +0000
Subject: [PATCH 02/36] add comment

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/handler.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/cmd/oras/internal/display/handler.go b/cmd/oras/internal/display/handler.go
index 836f43f3e..3a92622f5 100644
--- a/cmd/oras/internal/display/handler.go
+++ b/cmd/oras/internal/display/handler.go
@@ -73,6 +73,7 @@ func NewAttachHandler(format string, tty *os.File, verbose bool) (status.AttachH
 	return statusHandler, metadataHandler
 }
 
+// NewManifestFetchHandler returns a manifest fetch handler.
 func NewManifestFetchHandler(format string) metadata.ManifestFetchHandler {
 	return template.NewManifestFetchHandler(format)
 }

From e9c122680d06c2cc750fbb7a39fd39624017f49a Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 1 Apr 2024 04:59:18 +0000
Subject: [PATCH 03/36] refactor

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/root/manifest/fetch.go | 22 +++++++---------------
 1 file changed, 7 insertions(+), 15 deletions(-)

diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 2a43a7659..4173cccfb 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -74,22 +74,14 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 `,
 		Args: oerrors.CheckArgs(argument.Exactly(1), "the manifest to fetch"),
 		PreRunE: func(cmd *cobra.Command, args []string) error {
-			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 }},
+			switch {
+			case opts.outputPath == "-" && opts.Template != "":
+				return fmt.Errorf("`--output -` cannot be used with `--format` at the same time")
+			case opts.OutputDescriptor && opts.Template != "":
+				return fmt.Errorf("`--descriptor` cannot be used with `--format` at the same time")
+			case opts.OutputDescriptor && opts.outputPath != "":
+				return fmt.Errorf("`--descriptor` cannot be used with `--output` at the same time")
 			}
-			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)
 		},

From 6614c9287dff40b6fdfdda11304e998883464454 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 1 Apr 2024 05:06:18 +0000
Subject: [PATCH 04/36] use new printer

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/handler.go                     | 4 ++--
 .../internal/display/metadata/template/manifest_fetch.go | 9 ++++++---
 cmd/oras/root/manifest/fetch.go                          | 2 +-
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/cmd/oras/internal/display/handler.go b/cmd/oras/internal/display/handler.go
index f694be28c..49e961ac8 100644
--- a/cmd/oras/internal/display/handler.go
+++ b/cmd/oras/internal/display/handler.go
@@ -75,6 +75,6 @@ func NewAttachHandler(format string, tty *os.File, out io.Writer, verbose bool)
 }
 
 // NewManifestFetchHandler returns a manifest fetch handler.
-func NewManifestFetchHandler(format string) metadata.ManifestFetchHandler {
-	return template.NewManifestFetchHandler(format)
+func NewManifestFetchHandler(out io.Writer, format string) metadata.ManifestFetchHandler {
+	return template.NewManifestFetchHandler(out, format)
 }
diff --git a/cmd/oras/internal/display/metadata/template/manifest_fetch.go b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
index 256193974..5f999e70c 100644
--- a/cmd/oras/internal/display/metadata/template/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
@@ -16,6 +16,7 @@ limitations under the License.
 package template
 
 import (
+	"io"
 	"reflect"
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
@@ -26,16 +27,18 @@ import (
 // ManifestFetchHandler handles JSON metadata output for manifest fetch events.
 type ManifestFetchHandler struct {
 	template string
+	out      io.Writer
 }
 
 // NewManifestFetchHandler creates a new handler for manifest fetch events.
-func NewManifestFetchHandler(template string) metadata.ManifestFetchHandler {
+func NewManifestFetchHandler(out io.Writer, template string) metadata.ManifestFetchHandler {
 	return &ManifestFetchHandler{
 		template: template,
+		out:      out,
 	}
 }
 
 // OnFetched is called after the manifest fetch is completed.
-func (ph *ManifestFetchHandler) OnFetched(manifest ocispec.Manifest) error {
-	return parseAndWrite(model.ToMappable(reflect.ValueOf(manifest)), ph.template)
+func (h *ManifestFetchHandler) OnFetched(manifest ocispec.Manifest) error {
+	return parseAndWrite(h.out, model.ToMappable(reflect.ValueOf(manifest)), h.template)
 }
diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 5cbe23406..e3a5d0ddf 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -120,7 +120,7 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 	if err != nil {
 		return err
 	}
-	handler := display.NewManifestFetchHandler(opts.Template)
+	handler := display.NewManifestFetchHandler(cmd.OutOrStdout(), opts.Template)
 
 	var desc ocispec.Descriptor
 	if opts.OutputDescriptor && opts.outputPath == "" {

From eb5f62d9f19759e3a857b0bb6542da6a03dc2805 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 1 Apr 2024 05:31:26 +0000
Subject: [PATCH 05/36] bug fix

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/root/manifest/fetch.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index e3a5d0ddf..9d5e5f5f1 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -79,8 +79,8 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 				return fmt.Errorf("`--output -` cannot be used with `--format` at the same time")
 			case opts.OutputDescriptor && opts.Template != "":
 				return fmt.Errorf("`--descriptor` cannot be used with `--format` at the same time")
-			case opts.OutputDescriptor && opts.outputPath != "":
-				return fmt.Errorf("`--descriptor` cannot be used with `--output` at the same time")
+			case opts.OutputDescriptor && opts.outputPath == "-":
+				return fmt.Errorf("`--descriptor` cannot be used with `--output -` at the same time")
 			}
 			opts.RawReference = args[0]
 			return option.Parse(cmd, &opts)

From ce6bc89ce5a6cc92001aad3ddc1cc043a95ffbb9 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Tue, 2 Apr 2024 08:28:43 +0000
Subject: [PATCH 06/36] fix struct fields with json tags

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/handler.go          | 18 +++-
 cmd/oras/internal/display/metadata/discard.go | 28 +++++++
 .../internal/display/metadata/interface.go    |  3 +-
 .../display/metadata/json/manifest_fetch.go   | 54 ++++++++++++
 .../display/metadata/model/mappable.go        | 28 ++++---
 .../metadata/template/manifest_fetch.go       | 16 +++-
 cmd/oras/internal/display/raw/discard.go      | 33 ++++++++
 cmd/oras/internal/display/raw/interface.go    | 29 +++++++
 .../internal/display/raw/manifest_fetch.go    | 76 +++++++++++++++++
 cmd/oras/root/manifest/fetch.go               | 84 +++++--------------
 test/e2e/suite/command/manifest.go            |  2 +-
 11 files changed, 290 insertions(+), 81 deletions(-)
 create mode 100644 cmd/oras/internal/display/metadata/discard.go
 create mode 100644 cmd/oras/internal/display/metadata/json/manifest_fetch.go
 create mode 100644 cmd/oras/internal/display/raw/discard.go
 create mode 100644 cmd/oras/internal/display/raw/interface.go
 create mode 100644 cmd/oras/internal/display/raw/manifest_fetch.go

diff --git a/cmd/oras/internal/display/handler.go b/cmd/oras/internal/display/handler.go
index 49e961ac8..e2dba6654 100644
--- a/cmd/oras/internal/display/handler.go
+++ b/cmd/oras/internal/display/handler.go
@@ -23,6 +23,7 @@ import (
 	"oras.land/oras/cmd/oras/internal/display/metadata/json"
 	"oras.land/oras/cmd/oras/internal/display/metadata/template"
 	"oras.land/oras/cmd/oras/internal/display/metadata/text"
+	"oras.land/oras/cmd/oras/internal/display/raw"
 	"oras.land/oras/cmd/oras/internal/display/status"
 )
 
@@ -75,6 +76,19 @@ func NewAttachHandler(format string, tty *os.File, out io.Writer, verbose bool)
 }
 
 // NewManifestFetchHandler returns a manifest fetch handler.
-func NewManifestFetchHandler(out io.Writer, format string) metadata.ManifestFetchHandler {
-	return template.NewManifestFetchHandler(out, format)
+func NewManifestFetchHandler(out io.Writer, outputPath string, format string, pretty bool) (metadata.ManifestFetchHandler, raw.ManifestFetchHandler) {
+	var metadataHandler metadata.ManifestFetchHandler
+	var rawContentHandler raw.ManifestFetchHandler
+	switch format {
+	case "raw":
+		metadataHandler = metadata.NewDiscardHandler()
+		rawContentHandler = raw.NewManifestFetchHandler(out, pretty)
+	case "json":
+		metadataHandler = json.NewManifestFetchHandler(out)
+		rawContentHandler = raw.NewDiscardHandler()
+	default:
+		metadataHandler = template.NewManifestFetchHandler(out, format)
+		rawContentHandler = raw.NewDiscardHandler()
+	}
+	return metadataHandler, rawContentHandler
 }
diff --git a/cmd/oras/internal/display/metadata/discard.go b/cmd/oras/internal/display/metadata/discard.go
new file mode 100644
index 000000000..89f0f2d69
--- /dev/null
+++ b/cmd/oras/internal/display/metadata/discard.go
@@ -0,0 +1,28 @@
+/*
+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 metadata
+
+import ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+
+type discard struct{}
+
+// NewDiscardHandler creates a new handler that discards output for all events.
+func NewDiscardHandler() ManifestFetchHandler {
+	return discard{}
+}
+
+// OnFetched implements ManifestFetchHandler.
+func (discard) OnFetched([]byte, ocispec.Descriptor) error { return nil }
diff --git a/cmd/oras/internal/display/metadata/interface.go b/cmd/oras/internal/display/metadata/interface.go
index c8ba1b41f..c95c5eb12 100644
--- a/cmd/oras/internal/display/metadata/interface.go
+++ b/cmd/oras/internal/display/metadata/interface.go
@@ -33,5 +33,6 @@ type AttachHandler interface {
 
 // ManifestFetchHandler handles metadata output for manifest fetch events.
 type ManifestFetchHandler interface {
-	OnFetched(manifest ocispec.Manifest) error
+	// OnFetched is called after the manifest content is fetched.
+	OnFetched([]byte, ocispec.Descriptor) error
 }
diff --git a/cmd/oras/internal/display/metadata/json/manifest_fetch.go b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
new file mode 100644
index 000000000..01d4ba82a
--- /dev/null
+++ b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
@@ -0,0 +1,54 @@
+/*
+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 json
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"reflect"
+
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"oras.land/oras/cmd/oras/internal/display/metadata"
+	"oras.land/oras/cmd/oras/internal/display/metadata/model"
+	"oras.land/oras/internal/docker"
+)
+
+// ManifestFetchHandler handles JSON metadata output for manifest fetch events.
+type ManifestFetchHandler struct {
+	out io.Writer
+}
+
+// NewManifestFetchHandler creates a new handler for manifest fetch events.
+func NewManifestFetchHandler(out io.Writer) metadata.ManifestFetchHandler {
+	return &ManifestFetchHandler{
+		out: out,
+	}
+}
+
+// OnFetched is called after the manifest fetch is completed.
+func (h *ManifestFetchHandler) OnFetched(content []byte, desc ocispec.Descriptor) error {
+	switch desc.MediaType {
+	case ocispec.MediaTypeImageManifest, docker.MediaTypeManifest:
+		var manifest ocispec.Manifest
+		if err := json.Unmarshal(content, &manifest); err != nil {
+			return err
+		}
+		return printJSON(h.out, model.ToMappable(reflect.ValueOf(manifest)))
+	default:
+		return fmt.Errorf("cannot apply template: unsupported media type %s", desc.MediaType)
+	}
+}
diff --git a/cmd/oras/internal/display/metadata/model/mappable.go b/cmd/oras/internal/display/metadata/model/mappable.go
index ca2ab686c..dca57fb01 100644
--- a/cmd/oras/internal/display/metadata/model/mappable.go
+++ b/cmd/oras/internal/display/metadata/model/mappable.go
@@ -25,18 +25,8 @@ import (
 func ToMappable(v reflect.Value) any {
 	switch v.Kind() {
 	case reflect.Struct:
-		t := v.Type()
-		numField := t.NumField()
 		ret := make(map[string]any)
-		for i := 0; i < numField; i++ {
-			fv := v.Field(i)
-			tag := t.Field(i).Tag.Get("json")
-			if tag == "" {
-				continue
-			}
-			key, _, _ := strings.Cut(tag, ",")
-			ret[key] = ToMappable(fv)
-		}
+		addToMap(ret, v)
 		return ret
 	case reflect.Slice, reflect.Array:
 		ret := make([]any, v.Len())
@@ -53,3 +43,19 @@ func ToMappable(v reflect.Value) any {
 	}
 	return v.Interface()
 }
+
+func addToMap(ret map[string]any, v reflect.Value) {
+	t := v.Type()
+	numField := t.NumField()
+	for i := 0; i < numField; i++ {
+		fv := v.Field(i)
+		ft := t.Field(i)
+		tag := ft.Tag.Get("json")
+		if tag == "" {
+			addToMap(ret, fv)
+		} else {
+			key, _, _ := strings.Cut(tag, ",")
+			ret[key] = ToMappable(fv)
+		}
+	}
+}
diff --git a/cmd/oras/internal/display/metadata/template/manifest_fetch.go b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
index 5f999e70c..c2bdf8b32 100644
--- a/cmd/oras/internal/display/metadata/template/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
@@ -16,12 +16,15 @@ limitations under the License.
 package template
 
 import (
+	"encoding/json"
+	"fmt"
 	"io"
 	"reflect"
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"oras.land/oras/cmd/oras/internal/display/metadata"
 	"oras.land/oras/cmd/oras/internal/display/metadata/model"
+	"oras.land/oras/internal/docker"
 )
 
 // ManifestFetchHandler handles JSON metadata output for manifest fetch events.
@@ -39,6 +42,15 @@ func NewManifestFetchHandler(out io.Writer, template string) metadata.ManifestFe
 }
 
 // OnFetched is called after the manifest fetch is completed.
-func (h *ManifestFetchHandler) OnFetched(manifest ocispec.Manifest) error {
-	return parseAndWrite(h.out, model.ToMappable(reflect.ValueOf(manifest)), h.template)
+func (h *ManifestFetchHandler) OnFetched(content []byte, desc ocispec.Descriptor) error {
+	switch desc.MediaType {
+	case ocispec.MediaTypeImageManifest, docker.MediaTypeManifest:
+		var manifest ocispec.Manifest
+		if err := json.Unmarshal(content, &manifest); err != nil {
+			return err
+		}
+		return parseAndWrite(h.out, model.ToMappable(reflect.ValueOf(manifest)), h.template)
+	default:
+		return fmt.Errorf("cannot apply template: unsupported media type %s", desc.MediaType)
+	}
 }
diff --git a/cmd/oras/internal/display/raw/discard.go b/cmd/oras/internal/display/raw/discard.go
new file mode 100644
index 000000000..17eeab434
--- /dev/null
+++ b/cmd/oras/internal/display/raw/discard.go
@@ -0,0 +1,33 @@
+/*
+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 raw
+
+import (
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+type discard struct{}
+
+// OnContentFetched implements ManifestFetchHandler.
+func (discard) OnContentFetched(string, []byte) error { return nil }
+
+// OnDescriptorFetched implements ManifestFetchHandler.
+func (discard) OnDescriptorFetched(desc ocispec.Descriptor) error { return nil }
+
+// NewManifestFetchHandler creates a new handler.
+func NewDiscardHandler() ManifestFetchHandler {
+	return discard{}
+}
diff --git a/cmd/oras/internal/display/raw/interface.go b/cmd/oras/internal/display/raw/interface.go
new file mode 100644
index 000000000..a2476fcef
--- /dev/null
+++ b/cmd/oras/internal/display/raw/interface.go
@@ -0,0 +1,29 @@
+/*
+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 raw
+
+import (
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// ManifestFetchHandler handles raw output for manifest fetch events.
+type ManifestFetchHandler interface {
+	// OnFetched is called after the manifest content is fetched.
+	OnContentFetched(outputPath string, content []byte) error
+	// OnDescriptorFetched is called after the manifest descriptor is
+	// fetched.
+	OnDescriptorFetched(desc ocispec.Descriptor) error
+}
diff --git a/cmd/oras/internal/display/raw/manifest_fetch.go b/cmd/oras/internal/display/raw/manifest_fetch.go
new file mode 100644
index 000000000..c24ac2fe0
--- /dev/null
+++ b/cmd/oras/internal/display/raw/manifest_fetch.go
@@ -0,0 +1,76 @@
+/*
+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 raw
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// RawManifestFetch handles raw content output.
+type RawManifestFetch struct {
+	pretty bool
+	stdout io.Writer
+}
+
+// OnContentFetched implements ManifestFetchHandler.
+func (h *RawManifestFetch) OnContentFetched(outputPath string, manifest []byte) error {
+	out := h.stdout
+	if outputPath != "-" && outputPath != "" {
+		f, err := os.OpenFile(outputPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
+		if err != nil {
+			return fmt.Errorf("failed to open %q: %w", outputPath, err)
+		}
+		defer f.Close()
+	}
+	return h.output(out, manifest)
+}
+
+// OnDescriptorFetched implements ManifestFetchHandler.
+func (h *RawManifestFetch) OnDescriptorFetched(desc ocispec.Descriptor) error {
+	descBytes, err := json.Marshal(desc)
+	if err != nil {
+		return fmt.Errorf("invalid descriptor: %w", err)
+	}
+	return h.output(h.stdout, descBytes)
+}
+
+// NewManifestFetchHandler creates a new handler.
+func NewManifestFetchHandler(out io.Writer, pretty bool) ManifestFetchHandler {
+	return &RawManifestFetch{
+		pretty: pretty,
+		stdout: out,
+	}
+}
+
+// OnFetched is called after the content is fetched.
+func (h *RawManifestFetch) output(out io.Writer, data []byte) error {
+	if h.pretty {
+		buf := bytes.NewBuffer(nil)
+		if err := json.Indent(buf, data, "", "  "); err != nil {
+			return fmt.Errorf("failed to prettify: %w", err)
+		}
+		buf.WriteByte('\n')
+		data = buf.Bytes()
+	}
+	_, err := out.Write(data)
+	return err
+}
diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 9d5e5f5f1..7f98623d7 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -16,11 +16,8 @@ limitations under the License.
 package manifest
 
 import (
-	"encoding/json"
 	"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"
@@ -28,7 +25,6 @@ import (
 	"oras.land/oras/cmd/oras/internal/display"
 	oerrors "oras.land/oras/cmd/oras/internal/errors"
 	"oras.land/oras/cmd/oras/internal/option"
-	"oras.land/oras/internal/docker"
 )
 
 type fetchOptions struct {
@@ -75,10 +71,10 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 		Args: oerrors.CheckArgs(argument.Exactly(1), "the manifest to fetch"),
 		PreRunE: func(cmd *cobra.Command, args []string) error {
 			switch {
-			case opts.outputPath == "-" && opts.Template != "":
-				return fmt.Errorf("`--output -` cannot be used with `--format` at the same time")
-			case opts.OutputDescriptor && opts.Template != "":
-				return fmt.Errorf("`--descriptor` cannot be used with `--format` at the same time")
+			case opts.outputPath == "-" && opts.Template != "raw":
+				return fmt.Errorf("`--output -` cannot be used with `--format %s` at the same time", opts.Template)
+			case opts.OutputDescriptor && opts.Template != "raw":
+				return fmt.Errorf("`--descriptor` cannot be used with `--format %s` at the same time", opts.Template)
 			case opts.OutputDescriptor && opts.outputPath == "-":
 				return fmt.Errorf("`--descriptor` cannot be used with `--output -` at the same time")
 			}
@@ -93,7 +89,8 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 
 	cmd.Flags().StringSliceVarP(&opts.mediaTypes, "media-type", "", nil, "accepted media types")
 	cmd.Flags().StringVarP(&opts.outputPath, "output", "o", "", "file `path` to write the fetched manifest to, use - for stdout")
-	cmd.Flags().StringVar(&opts.Template, "format", "", `Format output using a custom template:
+	cmd.Flags().StringVar(&opts.Template, "format", "raw", `Format output using a custom template:
+'raw':       Print raw manifest content
 'json':       Print manifest in prettified JSON format
 '$TEMPLATE':  Print output using the given Go template.`)
 	option.ApplyFlags(&opts, cmd.Flags())
@@ -120,68 +117,27 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 	if err != nil {
 		return err
 	}
-	handler := display.NewManifestFetchHandler(cmd.OutOrStdout(), opts.Template)
+	metadataHandler, contentHandler := display.NewManifestFetchHandler(cmd.OutOrStdout(), opts.outputPath, opts.Template, opts.Pretty.Pretty)
 
-	var desc ocispec.Descriptor
-	if opts.OutputDescriptor && opts.outputPath == "" {
+	if opts.OutputDescriptor {
 		// fetch manifest descriptor only
 		fetchOpts := oras.DefaultResolveOptions
 		fetchOpts.TargetPlatform = opts.Platform.Platform
-		desc, err = oras.Resolve(ctx, src, opts.Reference, fetchOpts)
+		desc, err := oras.Resolve(ctx, src, opts.Reference, fetchOpts)
 		if err != nil {
 			return fmt.Errorf("failed to find %q: %w", opts.RawReference, err)
 		}
-	} else {
-		// fetch manifest content
-		var content []byte
-		fetchOpts := oras.DefaultFetchBytesOptions
-		fetchOpts.TargetPlatform = opts.Platform.Platform
-		desc, content, err = oras.FetchBytes(ctx, src, opts.Reference, fetchOpts)
-		if err != nil {
-			return fmt.Errorf("failed to fetch the content of %q: %w", opts.RawReference, err)
-		}
-
-		if opts.Template != "" {
-			if opts.Template == "json" {
-				// output prettified json manifest content
-				opts.Pretty.Pretty = true
-				if err := opts.Output(os.Stdout, content); err != nil {
-					return err
-				}
-			} else {
-				// 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 = handler.OnFetched(manifest); err != nil {
-						return err
-					}
-				default:
-					return fmt.Errorf("cannot apply template to %q: unsupported media type %s", opts.RawReference, desc.MediaType)
-				}
-			}
-		}
-		if opts.outputPath != "" && opts.outputPath != "-" {
-			// save manifest content into the local file if the output path is provided
-			if err = os.WriteFile(opts.outputPath, content, 0666); err != nil {
-				return err
-			}
-		} else if opts.Template == "" {
-			// output raw manifest content
-			return opts.Output(os.Stdout, content)
-		}
+		return contentHandler.OnDescriptorFetched(desc)
 	}
-
-	// output manifest's descriptor if `--descriptor` is used
-	if opts.OutputDescriptor {
-		descBytes, err := json.Marshal(desc)
-		if err != nil {
-			return err
-		}
-		return opts.Output(os.Stdout, descBytes)
+	// fetch manifest content
+	fetchOpts := oras.DefaultFetchBytesOptions
+	fetchOpts.TargetPlatform = opts.Platform.Platform
+	desc, content, err := oras.FetchBytes(ctx, src, opts.Reference, fetchOpts)
+	if err != nil {
+		return fmt.Errorf("failed to fetch the content of %q: %w", opts.RawReference, err)
+	}
+	if err = metadataHandler.OnFetched(content, desc); err != nil {
+		return nil
 	}
-	return nil
+	return contentHandler.OnContentFetched(opts.outputPath, content)
 }
diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index 5e227c91e..8b0108e70 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -198,7 +198,7 @@ var _ = Describe("ORAS beginners:", func() {
 	})
 })
 
-var _ = Describe("1.1 registry users:", func() {
+var _ = Describe("1.1 registry users:", Focus, func() {
 	repoFmt := fmt.Sprintf("command/manifest/%%s/%d/%%s", GinkgoRandomSeed())
 	When("running `manifest fetch`", func() {
 		It("should fetch manifest list with digest", func() {

From c13ee29ea1ea3cd83f74cf196ca626532e40cf3d Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 3 Apr 2024 08:46:27 +0000
Subject: [PATCH 07/36] remove raw discarder

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/handler.go          |  8 ++---
 cmd/oras/internal/display/raw/discard.go      | 33 -------------------
 .../internal/display/raw/manifest_fetch.go    |  1 +
 cmd/oras/root/manifest/fetch.go               |  4 +--
 test/e2e/suite/command/manifest.go            |  4 ++-
 5 files changed, 8 insertions(+), 42 deletions(-)
 delete mode 100644 cmd/oras/internal/display/raw/discard.go

diff --git a/cmd/oras/internal/display/handler.go b/cmd/oras/internal/display/handler.go
index e2dba6654..d3c0e4cd3 100644
--- a/cmd/oras/internal/display/handler.go
+++ b/cmd/oras/internal/display/handler.go
@@ -76,19 +76,15 @@ func NewAttachHandler(format string, tty *os.File, out io.Writer, verbose bool)
 }
 
 // NewManifestFetchHandler returns a manifest fetch handler.
-func NewManifestFetchHandler(out io.Writer, outputPath string, format string, pretty bool) (metadata.ManifestFetchHandler, raw.ManifestFetchHandler) {
+func NewManifestFetchHandler(out io.Writer, format string, pretty bool) (metadata.ManifestFetchHandler, raw.ManifestFetchHandler) {
 	var metadataHandler metadata.ManifestFetchHandler
-	var rawContentHandler raw.ManifestFetchHandler
 	switch format {
 	case "raw":
 		metadataHandler = metadata.NewDiscardHandler()
-		rawContentHandler = raw.NewManifestFetchHandler(out, pretty)
 	case "json":
 		metadataHandler = json.NewManifestFetchHandler(out)
-		rawContentHandler = raw.NewDiscardHandler()
 	default:
 		metadataHandler = template.NewManifestFetchHandler(out, format)
-		rawContentHandler = raw.NewDiscardHandler()
 	}
-	return metadataHandler, rawContentHandler
+	return metadataHandler, raw.NewManifestFetchHandler(out, pretty)
 }
diff --git a/cmd/oras/internal/display/raw/discard.go b/cmd/oras/internal/display/raw/discard.go
deleted file mode 100644
index 17eeab434..000000000
--- a/cmd/oras/internal/display/raw/discard.go
+++ /dev/null
@@ -1,33 +0,0 @@
-/*
-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 raw
-
-import (
-	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
-)
-
-type discard struct{}
-
-// OnContentFetched implements ManifestFetchHandler.
-func (discard) OnContentFetched(string, []byte) error { return nil }
-
-// OnDescriptorFetched implements ManifestFetchHandler.
-func (discard) OnDescriptorFetched(desc ocispec.Descriptor) error { return nil }
-
-// NewManifestFetchHandler creates a new handler.
-func NewDiscardHandler() ManifestFetchHandler {
-	return discard{}
-}
diff --git a/cmd/oras/internal/display/raw/manifest_fetch.go b/cmd/oras/internal/display/raw/manifest_fetch.go
index c24ac2fe0..6c9fd6cc0 100644
--- a/cmd/oras/internal/display/raw/manifest_fetch.go
+++ b/cmd/oras/internal/display/raw/manifest_fetch.go
@@ -40,6 +40,7 @@ func (h *RawManifestFetch) OnContentFetched(outputPath string, manifest []byte)
 			return fmt.Errorf("failed to open %q: %w", outputPath, err)
 		}
 		defer f.Close()
+		out = f
 	}
 	return h.output(out, manifest)
 }
diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 7f98623d7..7ba05d836 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -117,7 +117,7 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 	if err != nil {
 		return err
 	}
-	metadataHandler, contentHandler := display.NewManifestFetchHandler(cmd.OutOrStdout(), opts.outputPath, opts.Template, opts.Pretty.Pretty)
+	metadataHandler, contentHandler := display.NewManifestFetchHandler(cmd.OutOrStdout(), opts.Template, opts.Pretty.Pretty)
 
 	if opts.OutputDescriptor {
 		// fetch manifest descriptor only
@@ -137,7 +137,7 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 		return fmt.Errorf("failed to fetch the content of %q: %w", opts.RawReference, err)
 	}
 	if err = metadataHandler.OnFetched(content, desc); err != nil {
-		return nil
+		return err
 	}
 	return contentHandler.OnContentFetched(opts.outputPath, content)
 }
diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index 8b0108e70..7d5808b5f 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -241,7 +241,9 @@ var _ = Describe("1.1 registry users:", Focus, func() {
 		It("should fetch manifest with platform validation and output json", func() {
 			out := ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.Tag), "--platform", "linux/amd64", "--format", "json").
 				Exec().Out.Contents()
-			Expect(out).To(MatchJSON(multi_arch.LinuxAMD64Manifest))
+			var manifest ocispec.Manifest
+			Expect(json.Unmarshal(out, &manifest)).ShouldNot(HaveOccurred())
+			Expect(manifest.MediaType).To(Equal(multi_arch.LinuxAMD64.MediaType))
 		})
 
 		It("should fetch manifest and format output", func() {

From 4b1e2f9c969e434e81b016c4fedc53895b929667 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 3 Apr 2024 08:51:55 +0000
Subject: [PATCH 08/36] fix e2e

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/root/manifest/fetch.go | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 7ba05d836..c5691914f 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -119,7 +119,7 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 	}
 	metadataHandler, contentHandler := display.NewManifestFetchHandler(cmd.OutOrStdout(), opts.Template, opts.Pretty.Pretty)
 
-	if opts.OutputDescriptor {
+	if opts.OutputDescriptor && opts.outputPath == "" {
 		// fetch manifest descriptor only
 		fetchOpts := oras.DefaultResolveOptions
 		fetchOpts.TargetPlatform = opts.Platform.Platform
@@ -136,8 +136,11 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 	if err != nil {
 		return fmt.Errorf("failed to fetch the content of %q: %w", opts.RawReference, err)
 	}
-	if err = metadataHandler.OnFetched(content, desc); err != nil {
+	if err = contentHandler.OnDescriptorFetched(desc); err != nil {
 		return err
 	}
-	return contentHandler.OnContentFetched(opts.outputPath, content)
+	if err = contentHandler.OnContentFetched(opts.outputPath, content); err != nil {
+		return err
+	}
+	return metadataHandler.OnFetched(content, desc)
 }

From c7488d6e5696f7177647454535c9437b2f4f6224 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Sun, 7 Apr 2024 10:40:53 +0000
Subject: [PATCH 09/36] fix e2e

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/root/manifest/fetch.go | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index c5691914f..0af5ec1f1 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -136,8 +136,10 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 	if err != nil {
 		return fmt.Errorf("failed to fetch the content of %q: %w", opts.RawReference, err)
 	}
-	if err = contentHandler.OnDescriptorFetched(desc); err != nil {
-		return err
+	if opts.OutputDescriptor {
+		if err = contentHandler.OnDescriptorFetched(desc); err != nil {
+			return err
+		}
 	}
 	if err = contentHandler.OnContentFetched(opts.outputPath, content); err != nil {
 		return err

From 42ab0a363102014cfe491f5b94943cb6d6ab52a4 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Sun, 7 Apr 2024 10:48:43 +0000
Subject: [PATCH 10/36] refactor

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/handler.go          |  4 +--
 cmd/oras/internal/display/raw/interface.go    |  4 +--
 .../internal/display/raw/manifest_fetch.go    | 27 +++++++++++++------
 cmd/oras/root/manifest/fetch.go               |  9 ++-----
 4 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/cmd/oras/internal/display/handler.go b/cmd/oras/internal/display/handler.go
index d3c0e4cd3..021b6ffb3 100644
--- a/cmd/oras/internal/display/handler.go
+++ b/cmd/oras/internal/display/handler.go
@@ -76,7 +76,7 @@ func NewAttachHandler(format string, tty *os.File, out io.Writer, verbose bool)
 }
 
 // NewManifestFetchHandler returns a manifest fetch handler.
-func NewManifestFetchHandler(out io.Writer, format string, pretty bool) (metadata.ManifestFetchHandler, raw.ManifestFetchHandler) {
+func NewManifestFetchHandler(out io.Writer, format string, outputDescriptor bool, pretty bool, outputPath string) (metadata.ManifestFetchHandler, raw.ManifestFetchHandler) {
 	var metadataHandler metadata.ManifestFetchHandler
 	switch format {
 	case "raw":
@@ -86,5 +86,5 @@ func NewManifestFetchHandler(out io.Writer, format string, pretty bool) (metadat
 	default:
 		metadataHandler = template.NewManifestFetchHandler(out, format)
 	}
-	return metadataHandler, raw.NewManifestFetchHandler(out, pretty)
+	return metadataHandler, raw.NewManifestFetchHandler(out, outputDescriptor, pretty, outputPath)
 }
diff --git a/cmd/oras/internal/display/raw/interface.go b/cmd/oras/internal/display/raw/interface.go
index a2476fcef..44653d212 100644
--- a/cmd/oras/internal/display/raw/interface.go
+++ b/cmd/oras/internal/display/raw/interface.go
@@ -21,9 +21,9 @@ import (
 
 // ManifestFetchHandler handles raw output for manifest fetch events.
 type ManifestFetchHandler interface {
-	// OnFetched is called after the manifest content is fetched.
-	OnContentFetched(outputPath string, content []byte) error
 	// OnDescriptorFetched is called after the manifest descriptor is
 	// fetched.
 	OnDescriptorFetched(desc ocispec.Descriptor) error
+	// OnContentFetched is called after the manifest content is fetched.
+	OnContentFetched(desc ocispec.Descriptor, content []byte) error
 }
diff --git a/cmd/oras/internal/display/raw/manifest_fetch.go b/cmd/oras/internal/display/raw/manifest_fetch.go
index 6c9fd6cc0..e8a96d990 100644
--- a/cmd/oras/internal/display/raw/manifest_fetch.go
+++ b/cmd/oras/internal/display/raw/manifest_fetch.go
@@ -27,12 +27,22 @@ import (
 
 // RawManifestFetch handles raw content output.
 type RawManifestFetch struct {
-	pretty bool
-	stdout io.Writer
+	pretty           bool
+	stdout           io.Writer
+	outputDescriptor bool
+	outputPath       string
 }
 
-// OnContentFetched implements ManifestFetchHandler.
-func (h *RawManifestFetch) OnContentFetched(outputPath string, manifest []byte) error {
+func (h *RawManifestFetch) OnContentFetched(desc ocispec.Descriptor, manifest []byte) error {
+	if h.outputDescriptor {
+		if err := h.OnDescriptorFetched(desc); err != nil {
+			return err
+		}
+	}
+	return h.onContentFetched(h.outputPath, manifest)
+}
+
+func (h *RawManifestFetch) onContentFetched(outputPath string, manifest []byte) error {
 	out := h.stdout
 	if outputPath != "-" && outputPath != "" {
 		f, err := os.OpenFile(outputPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
@@ -45,7 +55,6 @@ func (h *RawManifestFetch) OnContentFetched(outputPath string, manifest []byte)
 	return h.output(out, manifest)
 }
 
-// OnDescriptorFetched implements ManifestFetchHandler.
 func (h *RawManifestFetch) OnDescriptorFetched(desc ocispec.Descriptor) error {
 	descBytes, err := json.Marshal(desc)
 	if err != nil {
@@ -55,10 +64,12 @@ func (h *RawManifestFetch) OnDescriptorFetched(desc ocispec.Descriptor) error {
 }
 
 // NewManifestFetchHandler creates a new handler.
-func NewManifestFetchHandler(out io.Writer, pretty bool) ManifestFetchHandler {
+func NewManifestFetchHandler(out io.Writer, outputDescriptor bool, pretty bool, outputPath string) ManifestFetchHandler {
 	return &RawManifestFetch{
-		pretty: pretty,
-		stdout: out,
+		pretty:           pretty,
+		stdout:           out,
+		outputDescriptor: outputDescriptor,
+		outputPath:       outputPath,
 	}
 }
 
diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 0af5ec1f1..0c758c7ab 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -117,7 +117,7 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 	if err != nil {
 		return err
 	}
-	metadataHandler, contentHandler := display.NewManifestFetchHandler(cmd.OutOrStdout(), opts.Template, opts.Pretty.Pretty)
+	metadataHandler, contentHandler := display.NewManifestFetchHandler(cmd.OutOrStdout(), opts.Template, opts.OutputDescriptor, opts.Pretty.Pretty, opts.outputPath)
 
 	if opts.OutputDescriptor && opts.outputPath == "" {
 		// fetch manifest descriptor only
@@ -136,12 +136,7 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 	if err != nil {
 		return fmt.Errorf("failed to fetch the content of %q: %w", opts.RawReference, err)
 	}
-	if opts.OutputDescriptor {
-		if err = contentHandler.OnDescriptorFetched(desc); err != nil {
-			return err
-		}
-	}
-	if err = contentHandler.OnContentFetched(opts.outputPath, content); err != nil {
+	if err = contentHandler.OnContentFetched(desc, content); err != nil {
 		return err
 	}
 	return metadataHandler.OnFetched(content, desc)

From d954405de69451f3376d800771df08937cd6c685 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Sun, 7 Apr 2024 10:56:56 +0000
Subject: [PATCH 11/36] add discard handler for raw output

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/handler.go     |  9 +++---
 cmd/oras/internal/display/raw/discard.go | 35 ++++++++++++++++++++++++
 2 files changed, 39 insertions(+), 5 deletions(-)
 create mode 100644 cmd/oras/internal/display/raw/discard.go

diff --git a/cmd/oras/internal/display/handler.go b/cmd/oras/internal/display/handler.go
index 021b6ffb3..8adfec53e 100644
--- a/cmd/oras/internal/display/handler.go
+++ b/cmd/oras/internal/display/handler.go
@@ -77,14 +77,13 @@ func NewAttachHandler(format string, tty *os.File, out io.Writer, verbose bool)
 
 // NewManifestFetchHandler returns a manifest fetch handler.
 func NewManifestFetchHandler(out io.Writer, format string, outputDescriptor bool, pretty bool, outputPath string) (metadata.ManifestFetchHandler, raw.ManifestFetchHandler) {
-	var metadataHandler metadata.ManifestFetchHandler
+	discardHandler := raw.NewDiscardHandler()
 	switch format {
 	case "raw":
-		metadataHandler = metadata.NewDiscardHandler()
+		return metadata.NewDiscardHandler(), raw.NewManifestFetchHandler(out, outputDescriptor, pretty, outputPath)
 	case "json":
-		metadataHandler = json.NewManifestFetchHandler(out)
+		return json.NewManifestFetchHandler(out), discardHandler
 	default:
-		metadataHandler = template.NewManifestFetchHandler(out, format)
+		return template.NewManifestFetchHandler(out, format), discardHandler
 	}
-	return metadataHandler, raw.NewManifestFetchHandler(out, outputDescriptor, pretty, outputPath)
 }
diff --git a/cmd/oras/internal/display/raw/discard.go b/cmd/oras/internal/display/raw/discard.go
new file mode 100644
index 000000000..ff40a0e93
--- /dev/null
+++ b/cmd/oras/internal/display/raw/discard.go
@@ -0,0 +1,35 @@
+/*
+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 raw
+
+import v1 "github.com/opencontainers/image-spec/specs-go/v1"
+
+type discardHandler struct{}
+
+// OnContentFetched implements ManifestFetchHandler.
+func (discardHandler) OnContentFetched(v1.Descriptor, []byte) error {
+	return nil
+}
+
+// OnDescriptorFetched implements ManifestFetchHandler.
+func (discardHandler) OnDescriptorFetched(v1.Descriptor) error {
+	return nil
+}
+
+// NewDiscardHandler returns a new discard handler.
+func NewDiscardHandler() ManifestFetchHandler {
+	return discardHandler{}
+}

From 74600606b16cb9fa0156cfb19aaf9fb7d69a74e9 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Sun, 7 Apr 2024 11:01:32 +0000
Subject: [PATCH 12/36] revert focus

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 test/e2e/suite/command/manifest.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index 7d5808b5f..8c4fad3c0 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -198,7 +198,7 @@ var _ = Describe("ORAS beginners:", func() {
 	})
 })
 
-var _ = Describe("1.1 registry users:", Focus, func() {
+var _ = Describe("1.1 registry users:", func() {
 	repoFmt := fmt.Sprintf("command/manifest/%%s/%d/%%s", GinkgoRandomSeed())
 	When("running `manifest fetch`", func() {
 		It("should fetch manifest list with digest", func() {

From de6acf1c686a1f3ecec5fec1baa20e17bd64140c Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Sun, 7 Apr 2024 11:14:57 +0000
Subject: [PATCH 13/36] rename to content handler

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 .../display/{raw => content}/discard.go         |  2 +-
 .../display/{raw => content}/interface.go       |  2 +-
 .../display/{raw => content}/manifest_fetch.go  |  2 +-
 cmd/oras/internal/display/handler.go            | 17 +++++++++++------
 4 files changed, 14 insertions(+), 9 deletions(-)
 rename cmd/oras/internal/display/{raw => content}/discard.go (98%)
 rename cmd/oras/internal/display/{raw => content}/interface.go (98%)
 rename cmd/oras/internal/display/{raw => content}/manifest_fetch.go (99%)

diff --git a/cmd/oras/internal/display/raw/discard.go b/cmd/oras/internal/display/content/discard.go
similarity index 98%
rename from cmd/oras/internal/display/raw/discard.go
rename to cmd/oras/internal/display/content/discard.go
index ff40a0e93..f62e879a1 100644
--- a/cmd/oras/internal/display/raw/discard.go
+++ b/cmd/oras/internal/display/content/discard.go
@@ -13,7 +13,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package raw
+package content
 
 import v1 "github.com/opencontainers/image-spec/specs-go/v1"
 
diff --git a/cmd/oras/internal/display/raw/interface.go b/cmd/oras/internal/display/content/interface.go
similarity index 98%
rename from cmd/oras/internal/display/raw/interface.go
rename to cmd/oras/internal/display/content/interface.go
index 44653d212..815d1c346 100644
--- a/cmd/oras/internal/display/raw/interface.go
+++ b/cmd/oras/internal/display/content/interface.go
@@ -13,7 +13,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package raw
+package content
 
 import (
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
diff --git a/cmd/oras/internal/display/raw/manifest_fetch.go b/cmd/oras/internal/display/content/manifest_fetch.go
similarity index 99%
rename from cmd/oras/internal/display/raw/manifest_fetch.go
rename to cmd/oras/internal/display/content/manifest_fetch.go
index e8a96d990..ad35a2792 100644
--- a/cmd/oras/internal/display/raw/manifest_fetch.go
+++ b/cmd/oras/internal/display/content/manifest_fetch.go
@@ -13,7 +13,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package raw
+package content
 
 import (
 	"bytes"
diff --git a/cmd/oras/internal/display/handler.go b/cmd/oras/internal/display/handler.go
index 7df177361..5a8f4962c 100644
--- a/cmd/oras/internal/display/handler.go
+++ b/cmd/oras/internal/display/handler.go
@@ -19,11 +19,11 @@ import (
 	"io"
 	"os"
 
+	"oras.land/oras/cmd/oras/internal/display/content"
 	"oras.land/oras/cmd/oras/internal/display/metadata"
 	"oras.land/oras/cmd/oras/internal/display/metadata/json"
 	"oras.land/oras/cmd/oras/internal/display/metadata/template"
 	"oras.land/oras/cmd/oras/internal/display/metadata/text"
-	"oras.land/oras/cmd/oras/internal/display/raw"
 	"oras.land/oras/cmd/oras/internal/display/status"
 )
 
@@ -97,14 +97,19 @@ func NewPullHandler(format string, path string, tty *os.File, out io.Writer, ver
 }
 
 // NewManifestFetchHandler returns a manifest fetch handler.
-func NewManifestFetchHandler(out io.Writer, format string, outputDescriptor bool, pretty bool, outputPath string) (metadata.ManifestFetchHandler, raw.ManifestFetchHandler) {
-	discardHandler := raw.NewDiscardHandler()
+func NewManifestFetchHandler(out io.Writer, format string, outputDescriptor bool, pretty bool, outputPath string) (metadata.ManifestFetchHandler, content.ManifestFetchHandler) {
+	var metadataHandler metadata.ManifestFetchHandler
+	var contentHandler content.ManifestFetchHandler = content.NewDiscardHandler()
+	if outputPath != "" {
+		contentHandler = content.NewManifestFetchHandler(out, outputDescriptor, pretty, outputPath)
+	}
 	switch format {
 	case "raw":
-		return metadata.NewDiscardHandler(), raw.NewManifestFetchHandler(out, outputDescriptor, pretty, outputPath)
+		metadataHandler = metadata.NewDiscardHandler()
 	case "json":
-		return json.NewManifestFetchHandler(out), discardHandler
+		metadataHandler = json.NewManifestFetchHandler(out)
 	default:
-		return template.NewManifestFetchHandler(out, format), discardHandler
+		metadataHandler = template.NewManifestFetchHandler(out, format)
 	}
+	return metadataHandler, contentHandler
 }

From 4709b62ab7768d654d46337dc5365c10b4daa492 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Sun, 7 Apr 2024 11:20:39 +0000
Subject: [PATCH 14/36] fix e2e

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/handler.go | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/cmd/oras/internal/display/handler.go b/cmd/oras/internal/display/handler.go
index 5a8f4962c..207392bf2 100644
--- a/cmd/oras/internal/display/handler.go
+++ b/cmd/oras/internal/display/handler.go
@@ -99,17 +99,22 @@ func NewPullHandler(format string, path string, tty *os.File, out io.Writer, ver
 // NewManifestFetchHandler returns a manifest fetch handler.
 func NewManifestFetchHandler(out io.Writer, format string, outputDescriptor bool, pretty bool, outputPath string) (metadata.ManifestFetchHandler, content.ManifestFetchHandler) {
 	var metadataHandler metadata.ManifestFetchHandler
-	var contentHandler content.ManifestFetchHandler = content.NewDiscardHandler()
-	if outputPath != "" {
-		contentHandler = content.NewManifestFetchHandler(out, outputDescriptor, pretty, outputPath)
-	}
+	var contentHandler content.ManifestFetchHandler = content.NewManifestFetchHandler(out, outputDescriptor, pretty, outputPath)
+	var discardHandler = content.NewDiscardHandler()
+
 	switch format {
 	case "raw":
 		metadataHandler = metadata.NewDiscardHandler()
 	case "json":
 		metadataHandler = json.NewManifestFetchHandler(out)
+		if outputPath == "" {
+			contentHandler = discardHandler
+		}
 	default:
 		metadataHandler = template.NewManifestFetchHandler(out, format)
+		if outputPath == "" {
+			contentHandler = discardHandler
+		}
 	}
 	return metadataHandler, contentHandler
 }

From 3fcab699c625bca9a3f9550422460ead1f74bc59 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Sun, 7 Apr 2024 11:27:36 +0000
Subject: [PATCH 15/36] add e2e

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 test/e2e/suite/command/manifest.go | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index 8c4fad3c0..9b5ab26f3 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -223,6 +223,15 @@ var _ = Describe("1.1 registry users:", func() {
 			MatchFile(fetchPath, multi_arch.Manifest, DefaultTimeout)
 		})
 
+		It("should fetch manifest to file and output full ref", func() {
+			fetchPath := filepath.Join(GinkgoT().TempDir(), "fetchedImage")
+			digest := multi_arch.LinuxAMD64.Digest.String()
+			ref := RegistryRef(ZOTHost, ImageRepo, digest)
+			ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "{{.digest}}").
+				MatchContent(digest).Exec()
+			MatchFile(fetchPath, multi_arch.LinuxAMD64Manifest, DefaultTimeout)
+		})
+
 		It("should fetch manifest via tag with platform selection", func() {
 			ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.Tag), "--platform", "linux/amd64").
 				MatchContent(multi_arch.LinuxAMD64Manifest).Exec()

From f8c2dbfcbb39816eb4011ebe6fda27eb3cb70bfd Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Sun, 7 Apr 2024 11:28:40 +0000
Subject: [PATCH 16/36] fix e2e

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 test/e2e/suite/command/manifest.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index 9b5ab26f3..6e5be1a72 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -227,8 +227,8 @@ var _ = Describe("1.1 registry users:", func() {
 			fetchPath := filepath.Join(GinkgoT().TempDir(), "fetchedImage")
 			digest := multi_arch.LinuxAMD64.Digest.String()
 			ref := RegistryRef(ZOTHost, ImageRepo, digest)
-			ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "{{.digest}}").
-				MatchContent(digest).Exec()
+			ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "{{.mediaType}}").
+				MatchContent("application/vnd.oci.image.manifest.v1+json").Exec()
 			MatchFile(fetchPath, multi_arch.LinuxAMD64Manifest, DefaultTimeout)
 		})
 

From 90a31417bc9eece6adc375e38cad3979291aa6f8 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 8 Apr 2024 02:42:21 +0000
Subject: [PATCH 17/36] use unmarshal and enhance e2e

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 .../display/metadata/json/manifest_fetch.go   | 17 ++----
 .../display/metadata/model/mappable.go        | 61 -------------------
 .../metadata/template/manifest_fetch.go       | 18 ++----
 test/e2e/suite/command/manifest.go            | 10 ++-
 4 files changed, 13 insertions(+), 93 deletions(-)
 delete mode 100644 cmd/oras/internal/display/metadata/model/mappable.go

diff --git a/cmd/oras/internal/display/metadata/json/manifest_fetch.go b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
index 01d4ba82a..4d717e666 100644
--- a/cmd/oras/internal/display/metadata/json/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
@@ -17,14 +17,10 @@ package json
 
 import (
 	"encoding/json"
-	"fmt"
 	"io"
-	"reflect"
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"oras.land/oras/cmd/oras/internal/display/metadata"
-	"oras.land/oras/cmd/oras/internal/display/metadata/model"
-	"oras.land/oras/internal/docker"
 )
 
 // ManifestFetchHandler handles JSON metadata output for manifest fetch events.
@@ -41,14 +37,9 @@ func NewManifestFetchHandler(out io.Writer) metadata.ManifestFetchHandler {
 
 // OnFetched is called after the manifest fetch is completed.
 func (h *ManifestFetchHandler) OnFetched(content []byte, desc ocispec.Descriptor) error {
-	switch desc.MediaType {
-	case ocispec.MediaTypeImageManifest, docker.MediaTypeManifest:
-		var manifest ocispec.Manifest
-		if err := json.Unmarshal(content, &manifest); err != nil {
-			return err
-		}
-		return printJSON(h.out, model.ToMappable(reflect.ValueOf(manifest)))
-	default:
-		return fmt.Errorf("cannot apply template: unsupported media type %s", desc.MediaType)
+	var manifest map[string]any
+	if err := json.Unmarshal(content, &manifest); err != nil {
+		return err
 	}
+	return printJSON(h.out, manifest)
 }
diff --git a/cmd/oras/internal/display/metadata/model/mappable.go b/cmd/oras/internal/display/metadata/model/mappable.go
deleted file mode 100644
index dca57fb01..000000000
--- a/cmd/oras/internal/display/metadata/model/mappable.go
+++ /dev/null
@@ -1,61 +0,0 @@
-/*
-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 model
-
-import (
-	"reflect"
-	"strings"
-)
-
-// ToMappable converts an reflect value into a map[string]any with json tags as
-// key.
-func ToMappable(v reflect.Value) any {
-	switch v.Kind() {
-	case reflect.Struct:
-		ret := make(map[string]any)
-		addToMap(ret, v)
-		return ret
-	case reflect.Slice, reflect.Array:
-		ret := make([]any, v.Len())
-		for i := 0; i < v.Len(); i++ {
-			ret[i] = ToMappable(v.Index(i))
-		}
-		return ret
-	case reflect.Ptr, reflect.Interface:
-		if v.IsNil() {
-			return nil
-		}
-		elem := ToMappable(v.Elem())
-		return &elem
-	}
-	return v.Interface()
-}
-
-func addToMap(ret map[string]any, v reflect.Value) {
-	t := v.Type()
-	numField := t.NumField()
-	for i := 0; i < numField; i++ {
-		fv := v.Field(i)
-		ft := t.Field(i)
-		tag := ft.Tag.Get("json")
-		if tag == "" {
-			addToMap(ret, fv)
-		} else {
-			key, _, _ := strings.Cut(tag, ",")
-			ret[key] = ToMappable(fv)
-		}
-	}
-}
diff --git a/cmd/oras/internal/display/metadata/template/manifest_fetch.go b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
index c2bdf8b32..6934d7825 100644
--- a/cmd/oras/internal/display/metadata/template/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
@@ -17,14 +17,10 @@ package template
 
 import (
 	"encoding/json"
-	"fmt"
 	"io"
-	"reflect"
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"oras.land/oras/cmd/oras/internal/display/metadata"
-	"oras.land/oras/cmd/oras/internal/display/metadata/model"
-	"oras.land/oras/internal/docker"
 )
 
 // ManifestFetchHandler handles JSON metadata output for manifest fetch events.
@@ -43,14 +39,10 @@ func NewManifestFetchHandler(out io.Writer, template string) metadata.ManifestFe
 
 // OnFetched is called after the manifest fetch is completed.
 func (h *ManifestFetchHandler) OnFetched(content []byte, desc ocispec.Descriptor) error {
-	switch desc.MediaType {
-	case ocispec.MediaTypeImageManifest, docker.MediaTypeManifest:
-		var manifest ocispec.Manifest
-		if err := json.Unmarshal(content, &manifest); err != nil {
-			return err
-		}
-		return parseAndWrite(h.out, model.ToMappable(reflect.ValueOf(manifest)), h.template)
-	default:
-		return fmt.Errorf("cannot apply template: unsupported media type %s", desc.MediaType)
+	var manifest map[string]any
+	if err := json.Unmarshal(content, &manifest); err != nil {
+		return err
 	}
+	// return parseAndWrite(h.out, model.ToMappable(reflect.ValueOf(manifest)), h.template)
+	return parseAndWrite(h.out, manifest, h.template)
 }
diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index 6e5be1a72..2b74b2ad9 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -223,12 +223,12 @@ var _ = Describe("1.1 registry users:", func() {
 			MatchFile(fetchPath, multi_arch.Manifest, DefaultTimeout)
 		})
 
-		It("should fetch manifest to file and output full ref", func() {
+		It("should fetch manifest to file and output json", func() {
 			fetchPath := filepath.Join(GinkgoT().TempDir(), "fetchedImage")
 			digest := multi_arch.LinuxAMD64.Digest.String()
 			ref := RegistryRef(ZOTHost, ImageRepo, digest)
-			ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "{{.mediaType}}").
-				MatchContent("application/vnd.oci.image.manifest.v1+json").Exec()
+			out := ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "json").Exec().Out.Contents()
+			Expect(out).To(MatchJSON(multi_arch.LinuxAMD64Manifest))
 			MatchFile(fetchPath, multi_arch.LinuxAMD64Manifest, DefaultTimeout)
 		})
 
@@ -250,9 +250,7 @@ var _ = Describe("1.1 registry users:", func() {
 		It("should fetch manifest with platform validation and output json", func() {
 			out := ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.Tag), "--platform", "linux/amd64", "--format", "json").
 				Exec().Out.Contents()
-			var manifest ocispec.Manifest
-			Expect(json.Unmarshal(out, &manifest)).ShouldNot(HaveOccurred())
-			Expect(manifest.MediaType).To(Equal(multi_arch.LinuxAMD64.MediaType))
+			Expect(out).To(MatchJSON(multi_arch.LinuxAMD64Manifest))
 		})
 
 		It("should fetch manifest and format output", func() {

From ca0f082173a7d1a8aa8a656a75ef5fceadddd642 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 8 Apr 2024 06:29:27 +0000
Subject: [PATCH 18/36] code clean

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/content/manifest_fetch.go | 1 -
 1 file changed, 1 deletion(-)

diff --git a/cmd/oras/internal/display/content/manifest_fetch.go b/cmd/oras/internal/display/content/manifest_fetch.go
index ad35a2792..d99c46e92 100644
--- a/cmd/oras/internal/display/content/manifest_fetch.go
+++ b/cmd/oras/internal/display/content/manifest_fetch.go
@@ -73,7 +73,6 @@ func NewManifestFetchHandler(out io.Writer, outputDescriptor bool, pretty bool,
 	}
 }
 
-// OnFetched is called after the content is fetched.
 func (h *RawManifestFetch) output(out io.Writer, data []byte) error {
 	if h.pretty {
 		buf := bytes.NewBuffer(nil)

From a1addb43f845af4ec7a79bdc0da339bec8c97421 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 8 Apr 2024 08:37:19 +0000
Subject: [PATCH 19/36] resolve comments

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/content/discard.go  |  6 +-
 .../internal/display/content/interface.go     |  3 -
 .../display/content/manifest_fetch.go         | 57 ++++---------------
 cmd/oras/internal/display/handler.go          | 19 +++++--
 .../display/metadata/descriptor/interface.go  | 24 ++++++++
 .../metadata/descriptor/manifest_fetch.go     | 49 ++++++++++++++++
 cmd/oras/internal/display/metadata/discard.go |  2 +-
 .../internal/display/metadata/interface.go    |  2 +-
 .../display/metadata/json/manifest_fetch.go   |  2 +-
 .../metadata/template/manifest_fetch.go       |  2 +-
 cmd/oras/internal/display/utils/utils.go      | 23 +++++++-
 cmd/oras/root/manifest/fetch.go               | 32 ++++++-----
 12 files changed, 144 insertions(+), 77 deletions(-)
 create mode 100644 cmd/oras/internal/display/metadata/descriptor/interface.go
 create mode 100644 cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go

diff --git a/cmd/oras/internal/display/content/discard.go b/cmd/oras/internal/display/content/discard.go
index f62e879a1..3c08fb695 100644
--- a/cmd/oras/internal/display/content/discard.go
+++ b/cmd/oras/internal/display/content/discard.go
@@ -15,17 +15,17 @@ limitations under the License.
 
 package content
 
-import v1 "github.com/opencontainers/image-spec/specs-go/v1"
+import ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 
 type discardHandler struct{}
 
 // OnContentFetched implements ManifestFetchHandler.
-func (discardHandler) OnContentFetched(v1.Descriptor, []byte) error {
+func (discardHandler) OnContentFetched(ocispec.Descriptor, []byte) error {
 	return nil
 }
 
 // OnDescriptorFetched implements ManifestFetchHandler.
-func (discardHandler) OnDescriptorFetched(v1.Descriptor) error {
+func (discardHandler) OnDescriptorFetched(ocispec.Descriptor) error {
 	return nil
 }
 
diff --git a/cmd/oras/internal/display/content/interface.go b/cmd/oras/internal/display/content/interface.go
index 815d1c346..2c35fc552 100644
--- a/cmd/oras/internal/display/content/interface.go
+++ b/cmd/oras/internal/display/content/interface.go
@@ -21,9 +21,6 @@ import (
 
 // ManifestFetchHandler handles raw output for manifest fetch events.
 type ManifestFetchHandler interface {
-	// OnDescriptorFetched is called after the manifest descriptor is
-	// fetched.
-	OnDescriptorFetched(desc ocispec.Descriptor) error
 	// OnContentFetched is called after the manifest content is fetched.
 	OnContentFetched(desc ocispec.Descriptor, content []byte) error
 }
diff --git a/cmd/oras/internal/display/content/manifest_fetch.go b/cmd/oras/internal/display/content/manifest_fetch.go
index d99c46e92..6da0172b1 100644
--- a/cmd/oras/internal/display/content/manifest_fetch.go
+++ b/cmd/oras/internal/display/content/manifest_fetch.go
@@ -16,72 +16,39 @@ limitations under the License.
 package content
 
 import (
-	"bytes"
-	"encoding/json"
 	"fmt"
 	"io"
 	"os"
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"oras.land/oras/cmd/oras/internal/display/utils"
 )
 
 // RawManifestFetch handles raw content output.
 type RawManifestFetch struct {
-	pretty           bool
-	stdout           io.Writer
-	outputDescriptor bool
-	outputPath       string
+	pretty     bool
+	stdout     io.Writer
+	outputPath string
 }
 
 func (h *RawManifestFetch) OnContentFetched(desc ocispec.Descriptor, manifest []byte) error {
-	if h.outputDescriptor {
-		if err := h.OnDescriptorFetched(desc); err != nil {
-			return err
-		}
-	}
-	return h.onContentFetched(h.outputPath, manifest)
-}
-
-func (h *RawManifestFetch) onContentFetched(outputPath string, manifest []byte) error {
 	out := h.stdout
-	if outputPath != "-" && outputPath != "" {
-		f, err := os.OpenFile(outputPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
+	if h.outputPath != "-" && h.outputPath != "" {
+		f, err := os.OpenFile(h.outputPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
 		if err != nil {
-			return fmt.Errorf("failed to open %q: %w", outputPath, err)
+			return fmt.Errorf("failed to open %q: %w", h.outputPath, err)
 		}
 		defer f.Close()
 		out = f
 	}
-	return h.output(out, manifest)
-}
-
-func (h *RawManifestFetch) OnDescriptorFetched(desc ocispec.Descriptor) error {
-	descBytes, err := json.Marshal(desc)
-	if err != nil {
-		return fmt.Errorf("invalid descriptor: %w", err)
-	}
-	return h.output(h.stdout, descBytes)
+	return utils.Output(out, manifest, h.pretty)
 }
 
 // NewManifestFetchHandler creates a new handler.
-func NewManifestFetchHandler(out io.Writer, outputDescriptor bool, pretty bool, outputPath string) ManifestFetchHandler {
+func NewManifestFetchHandler(out io.Writer, pretty bool, outputPath string) ManifestFetchHandler {
 	return &RawManifestFetch{
-		pretty:           pretty,
-		stdout:           out,
-		outputDescriptor: outputDescriptor,
-		outputPath:       outputPath,
-	}
-}
-
-func (h *RawManifestFetch) output(out io.Writer, data []byte) error {
-	if h.pretty {
-		buf := bytes.NewBuffer(nil)
-		if err := json.Indent(buf, data, "", "  "); err != nil {
-			return fmt.Errorf("failed to prettify: %w", err)
-		}
-		buf.WriteByte('\n')
-		data = buf.Bytes()
+		pretty:     pretty,
+		stdout:     out,
+		outputPath: outputPath,
 	}
-	_, err := out.Write(data)
-	return err
 }
diff --git a/cmd/oras/internal/display/handler.go b/cmd/oras/internal/display/handler.go
index 207392bf2..29cc2d921 100644
--- a/cmd/oras/internal/display/handler.go
+++ b/cmd/oras/internal/display/handler.go
@@ -21,6 +21,7 @@ import (
 
 	"oras.land/oras/cmd/oras/internal/display/content"
 	"oras.land/oras/cmd/oras/internal/display/metadata"
+	"oras.land/oras/cmd/oras/internal/display/metadata/descriptor"
 	"oras.land/oras/cmd/oras/internal/display/metadata/json"
 	"oras.land/oras/cmd/oras/internal/display/metadata/template"
 	"oras.land/oras/cmd/oras/internal/display/metadata/text"
@@ -99,21 +100,27 @@ func NewPullHandler(format string, path string, tty *os.File, out io.Writer, ver
 // NewManifestFetchHandler returns a manifest fetch handler.
 func NewManifestFetchHandler(out io.Writer, format string, outputDescriptor bool, pretty bool, outputPath string) (metadata.ManifestFetchHandler, content.ManifestFetchHandler) {
 	var metadataHandler metadata.ManifestFetchHandler
-	var contentHandler content.ManifestFetchHandler = content.NewManifestFetchHandler(out, outputDescriptor, pretty, outputPath)
-	var discardHandler = content.NewDiscardHandler()
+	var contentHandler content.ManifestFetchHandler = content.NewManifestFetchHandler(out, pretty, outputPath)
 
 	switch format {
-	case "raw":
-		metadataHandler = metadata.NewDiscardHandler()
+	case "":
+		// raw
+		if outputDescriptor {
+			metadataHandler = descriptor.NewManifestFetchHandler(out, pretty)
+		} else {
+			metadataHandler = metadata.NewDiscardHandler()
+		}
 	case "json":
+		// json
 		metadataHandler = json.NewManifestFetchHandler(out)
 		if outputPath == "" {
-			contentHandler = discardHandler
+			contentHandler = content.NewDiscardHandler()
 		}
 	default:
+		// go template
 		metadataHandler = template.NewManifestFetchHandler(out, format)
 		if outputPath == "" {
-			contentHandler = discardHandler
+			contentHandler = content.NewDiscardHandler()
 		}
 	}
 	return metadataHandler, contentHandler
diff --git a/cmd/oras/internal/display/metadata/descriptor/interface.go b/cmd/oras/internal/display/metadata/descriptor/interface.go
new file mode 100644
index 000000000..94958f7f4
--- /dev/null
+++ b/cmd/oras/internal/display/metadata/descriptor/interface.go
@@ -0,0 +1,24 @@
+/*
+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 descriptor
+
+import ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+
+// ManifestFetchHandler handles metadata output for manifest fetch events.
+type ManifestFetchHandler interface {
+	// OnFetched is called after the manifest content is fetched.
+	OnFetched(ocispec.Descriptor) error
+}
diff --git a/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go b/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go
new file mode 100644
index 000000000..2a55b503d
--- /dev/null
+++ b/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go
@@ -0,0 +1,49 @@
+/*
+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 descriptor
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"oras.land/oras/cmd/oras/internal/display/metadata"
+	"oras.land/oras/cmd/oras/internal/display/utils"
+)
+
+// ManifestFetchHandler handles metadata descriptor output.
+type ManifestFetch struct {
+	pretty bool
+	out    io.Writer
+}
+
+// OnFetched implements ManifestFetchHandler.
+func (h *ManifestFetch) OnFetched(desc ocispec.Descriptor, _ []byte) error {
+	descBytes, err := json.Marshal(desc)
+	if err != nil {
+		return fmt.Errorf("invalid descriptor: %w", err)
+	}
+	return utils.Output(h.out, descBytes, h.pretty)
+}
+
+// NewManifestFetchHandler creates a new handler.
+func NewManifestFetchHandler(out io.Writer, pretty bool) metadata.ManifestFetchHandler {
+	return &ManifestFetch{
+		pretty: pretty,
+		out:    out,
+	}
+}
diff --git a/cmd/oras/internal/display/metadata/discard.go b/cmd/oras/internal/display/metadata/discard.go
index 89f0f2d69..dc31bae0f 100644
--- a/cmd/oras/internal/display/metadata/discard.go
+++ b/cmd/oras/internal/display/metadata/discard.go
@@ -25,4 +25,4 @@ func NewDiscardHandler() ManifestFetchHandler {
 }
 
 // OnFetched implements ManifestFetchHandler.
-func (discard) OnFetched([]byte, ocispec.Descriptor) error { return nil }
+func (discard) OnFetched(ocispec.Descriptor, []byte) error { return nil }
diff --git a/cmd/oras/internal/display/metadata/interface.go b/cmd/oras/internal/display/metadata/interface.go
index fdeedfaf6..7a06b8635 100644
--- a/cmd/oras/internal/display/metadata/interface.go
+++ b/cmd/oras/internal/display/metadata/interface.go
@@ -34,7 +34,7 @@ type AttachHandler interface {
 // ManifestFetchHandler handles metadata output for manifest fetch events.
 type ManifestFetchHandler interface {
 	// OnFetched is called after the manifest content is fetched.
-	OnFetched([]byte, ocispec.Descriptor) error
+	OnFetched(ocispec.Descriptor, []byte) error
 }
 
 // PullHandler handles metadata output for pull events.
diff --git a/cmd/oras/internal/display/metadata/json/manifest_fetch.go b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
index 4d717e666..42bf6ebb4 100644
--- a/cmd/oras/internal/display/metadata/json/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
@@ -36,7 +36,7 @@ func NewManifestFetchHandler(out io.Writer) metadata.ManifestFetchHandler {
 }
 
 // OnFetched is called after the manifest fetch is completed.
-func (h *ManifestFetchHandler) OnFetched(content []byte, desc ocispec.Descriptor) error {
+func (h *ManifestFetchHandler) OnFetched(desc ocispec.Descriptor, content []byte) error {
 	var manifest map[string]any
 	if err := json.Unmarshal(content, &manifest); err != nil {
 		return err
diff --git a/cmd/oras/internal/display/metadata/template/manifest_fetch.go b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
index 6934d7825..3c777670d 100644
--- a/cmd/oras/internal/display/metadata/template/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
@@ -38,7 +38,7 @@ func NewManifestFetchHandler(out io.Writer, template string) metadata.ManifestFe
 }
 
 // OnFetched is called after the manifest fetch is completed.
-func (h *ManifestFetchHandler) OnFetched(content []byte, desc ocispec.Descriptor) error {
+func (h *ManifestFetchHandler) OnFetched(desc ocispec.Descriptor, content []byte) error {
 	var manifest map[string]any
 	if err := json.Unmarshal(content, &manifest); err != nil {
 		return err
diff --git a/cmd/oras/internal/display/utils/utils.go b/cmd/oras/internal/display/utils/utils.go
index 6a88c7c02..b8463bef6 100644
--- a/cmd/oras/internal/display/utils/utils.go
+++ b/cmd/oras/internal/display/utils/utils.go
@@ -15,7 +15,14 @@ limitations under the License.
 
 package utils
 
-import v1 "github.com/opencontainers/image-spec/specs-go/v1"
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+
+	v1 "github.com/opencontainers/image-spec/specs-go/v1"
+)
 
 // GenerateContentKey generates a unique key for each content descriptor, using
 // its digest and name if applicable.
@@ -31,3 +38,17 @@ const (
 	PullPromptRestored    = "Restored   "
 	PullPromptDownloaded  = "Downloaded "
 )
+
+// Output writes the data to the output stream, optionally prettifying it.
+func Output(out io.Writer, data []byte, pretty bool) error {
+	if pretty {
+		buf := bytes.NewBuffer(nil)
+		if err := json.Indent(buf, data, "", "  "); err != nil {
+			return fmt.Errorf("failed to prettify: %w", err)
+		}
+		buf.WriteByte('\n')
+		data = buf.Bytes()
+	}
+	_, err := out.Write(data)
+	return err
+}
diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 0c758c7ab..ff0ffbb86 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -18,6 +18,7 @@ package manifest
 import (
 	"fmt"
 
+	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"
@@ -89,8 +90,7 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 
 	cmd.Flags().StringSliceVarP(&opts.mediaTypes, "media-type", "", nil, "accepted media types")
 	cmd.Flags().StringVarP(&opts.outputPath, "output", "o", "", "file `path` to write the fetched manifest to, use - for stdout")
-	cmd.Flags().StringVar(&opts.Template, "format", "raw", `Format output using a custom template:
-'raw':       Print raw manifest content
+	cmd.Flags().StringVar(&opts.Template, "format", "", `Format output using a custom template:
 'json':       Print manifest in prettified JSON format
 '$TEMPLATE':  Print output using the given Go template.`)
 	option.ApplyFlags(&opts, cmd.Flags())
@@ -119,25 +119,27 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 	}
 	metadataHandler, contentHandler := display.NewManifestFetchHandler(cmd.OutOrStdout(), opts.Template, opts.OutputDescriptor, opts.Pretty.Pretty, opts.outputPath)
 
+	var desc ocispec.Descriptor
+	var content []byte
 	if opts.OutputDescriptor && opts.outputPath == "" {
 		// fetch manifest descriptor only
 		fetchOpts := oras.DefaultResolveOptions
 		fetchOpts.TargetPlatform = opts.Platform.Platform
-		desc, err := oras.Resolve(ctx, src, opts.Reference, fetchOpts)
+		desc, err = oras.Resolve(ctx, src, opts.Reference, fetchOpts)
 		if err != nil {
 			return fmt.Errorf("failed to find %q: %w", opts.RawReference, err)
 		}
-		return contentHandler.OnDescriptorFetched(desc)
-	}
-	// fetch manifest content
-	fetchOpts := oras.DefaultFetchBytesOptions
-	fetchOpts.TargetPlatform = opts.Platform.Platform
-	desc, content, err := oras.FetchBytes(ctx, src, opts.Reference, fetchOpts)
-	if err != nil {
-		return fmt.Errorf("failed to fetch the content of %q: %w", opts.RawReference, err)
-	}
-	if err = contentHandler.OnContentFetched(desc, content); err != nil {
-		return err
+	} else {
+		// fetch manifest descriptor and content
+		fetchOpts := oras.DefaultFetchBytesOptions
+		fetchOpts.TargetPlatform = opts.Platform.Platform
+		desc, content, err = oras.FetchBytes(ctx, src, opts.Reference, fetchOpts)
+		if err != nil {
+			return fmt.Errorf("failed to fetch the content of %q: %w", opts.RawReference, err)
+		}
+		if err = contentHandler.OnContentFetched(desc, content); err != nil {
+			return err
+		}
 	}
-	return metadataHandler.OnFetched(content, desc)
+	return metadataHandler.OnFetched(desc, content)
 }

From 998ad767950ae64a5f4db8484e853685f5496a52 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 8 Apr 2024 08:39:51 +0000
Subject: [PATCH 20/36] fix e2e

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/root/manifest/fetch.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index ff0ffbb86..585f4fb55 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -72,9 +72,9 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 		Args: oerrors.CheckArgs(argument.Exactly(1), "the manifest to fetch"),
 		PreRunE: func(cmd *cobra.Command, args []string) error {
 			switch {
-			case opts.outputPath == "-" && opts.Template != "raw":
+			case opts.outputPath == "-" && opts.Template != "":
 				return fmt.Errorf("`--output -` cannot be used with `--format %s` at the same time", opts.Template)
-			case opts.OutputDescriptor && opts.Template != "raw":
+			case opts.OutputDescriptor && opts.Template != "":
 				return fmt.Errorf("`--descriptor` cannot be used with `--format %s` at the same time", opts.Template)
 			case opts.OutputDescriptor && opts.outputPath == "-":
 				return fmt.Errorf("`--descriptor` cannot be used with `--output -` at the same time")

From f93ba89b6be93aaf039e37ad3e443d929a0bb1be Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 8 Apr 2024 08:40:41 +0000
Subject: [PATCH 21/36] code clean

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/content/discard.go | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/cmd/oras/internal/display/content/discard.go b/cmd/oras/internal/display/content/discard.go
index 3c08fb695..cdf543797 100644
--- a/cmd/oras/internal/display/content/discard.go
+++ b/cmd/oras/internal/display/content/discard.go
@@ -24,11 +24,6 @@ func (discardHandler) OnContentFetched(ocispec.Descriptor, []byte) error {
 	return nil
 }
 
-// OnDescriptorFetched implements ManifestFetchHandler.
-func (discardHandler) OnDescriptorFetched(ocispec.Descriptor) error {
-	return nil
-}
-
 // NewDiscardHandler returns a new discard handler.
 func NewDiscardHandler() ManifestFetchHandler {
 	return discardHandler{}

From b54a2e6686842ec85f7827869da3cf0fc90be335 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 8 Apr 2024 11:38:06 +0000
Subject: [PATCH 22/36] code clean

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/content/manifest_fetch.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/cmd/oras/internal/display/content/manifest_fetch.go b/cmd/oras/internal/display/content/manifest_fetch.go
index 6da0172b1..b6c9b5d81 100644
--- a/cmd/oras/internal/display/content/manifest_fetch.go
+++ b/cmd/oras/internal/display/content/manifest_fetch.go
@@ -24,14 +24,14 @@ import (
 	"oras.land/oras/cmd/oras/internal/display/utils"
 )
 
-// RawManifestFetch handles raw content output.
-type RawManifestFetch struct {
+// manifestFetch handles raw content output.
+type manifestFetch struct {
 	pretty     bool
 	stdout     io.Writer
 	outputPath string
 }
 
-func (h *RawManifestFetch) OnContentFetched(desc ocispec.Descriptor, manifest []byte) error {
+func (h *manifestFetch) OnContentFetched(desc ocispec.Descriptor, manifest []byte) error {
 	out := h.stdout
 	if h.outputPath != "-" && h.outputPath != "" {
 		f, err := os.OpenFile(h.outputPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
@@ -46,7 +46,7 @@ func (h *RawManifestFetch) OnContentFetched(desc ocispec.Descriptor, manifest []
 
 // NewManifestFetchHandler creates a new handler.
 func NewManifestFetchHandler(out io.Writer, pretty bool, outputPath string) ManifestFetchHandler {
-	return &RawManifestFetch{
+	return &manifestFetch{
 		pretty:     pretty,
 		stdout:     out,
 		outputPath: outputPath,

From e682458b661ae1e5deb30e15b8dae29ec20d0648 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 8 Apr 2024 11:38:52 +0000
Subject: [PATCH 23/36] code clean

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 .../display/metadata/descriptor/interface.go  | 24 -------------------
 1 file changed, 24 deletions(-)
 delete mode 100644 cmd/oras/internal/display/metadata/descriptor/interface.go

diff --git a/cmd/oras/internal/display/metadata/descriptor/interface.go b/cmd/oras/internal/display/metadata/descriptor/interface.go
deleted file mode 100644
index 94958f7f4..000000000
--- a/cmd/oras/internal/display/metadata/descriptor/interface.go
+++ /dev/null
@@ -1,24 +0,0 @@
-/*
-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 descriptor
-
-import ocispec "github.com/opencontainers/image-spec/specs-go/v1"
-
-// ManifestFetchHandler handles metadata output for manifest fetch events.
-type ManifestFetchHandler interface {
-	// OnFetched is called after the manifest content is fetched.
-	OnFetched(ocispec.Descriptor) error
-}

From faa8c636ac88c81752415b18f91fb893e5020db6 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Mon, 8 Apr 2024 12:32:53 +0000
Subject: [PATCH 24/36] code clean

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 .../display/metadata/descriptor/manifest_fetch.go         | 8 ++++----
 .../internal/display/metadata/template/manifest_fetch.go  | 8 ++++----
 cmd/oras/internal/display/utils/utils.go                  | 6 +++---
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go b/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go
index 2a55b503d..bbdedc2e7 100644
--- a/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go
@@ -25,14 +25,14 @@ import (
 	"oras.land/oras/cmd/oras/internal/display/utils"
 )
 
-// ManifestFetchHandler handles metadata descriptor output.
-type ManifestFetch struct {
+// manifestFetchHandler handles metadata descriptor output.
+type manifestFetchHandler struct {
 	pretty bool
 	out    io.Writer
 }
 
 // OnFetched implements ManifestFetchHandler.
-func (h *ManifestFetch) OnFetched(desc ocispec.Descriptor, _ []byte) error {
+func (h *manifestFetchHandler) OnFetched(desc ocispec.Descriptor, _ []byte) error {
 	descBytes, err := json.Marshal(desc)
 	if err != nil {
 		return fmt.Errorf("invalid descriptor: %w", err)
@@ -42,7 +42,7 @@ func (h *ManifestFetch) OnFetched(desc ocispec.Descriptor, _ []byte) error {
 
 // NewManifestFetchHandler creates a new handler.
 func NewManifestFetchHandler(out io.Writer, pretty bool) metadata.ManifestFetchHandler {
-	return &ManifestFetch{
+	return &manifestFetchHandler{
 		pretty: pretty,
 		out:    out,
 	}
diff --git a/cmd/oras/internal/display/metadata/template/manifest_fetch.go b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
index 3c777670d..186d63eca 100644
--- a/cmd/oras/internal/display/metadata/template/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
@@ -23,22 +23,22 @@ import (
 	"oras.land/oras/cmd/oras/internal/display/metadata"
 )
 
-// ManifestFetchHandler handles JSON metadata output for manifest fetch events.
-type ManifestFetchHandler struct {
+// manifestFetchHandler handles JSON metadata output for manifest fetch events.
+type manifestFetchHandler struct {
 	template string
 	out      io.Writer
 }
 
 // NewManifestFetchHandler creates a new handler for manifest fetch events.
 func NewManifestFetchHandler(out io.Writer, template string) metadata.ManifestFetchHandler {
-	return &ManifestFetchHandler{
+	return &manifestFetchHandler{
 		template: template,
 		out:      out,
 	}
 }
 
 // OnFetched is called after the manifest fetch is completed.
-func (h *ManifestFetchHandler) OnFetched(desc ocispec.Descriptor, content []byte) error {
+func (h *manifestFetchHandler) OnFetched(desc ocispec.Descriptor, content []byte) error {
 	var manifest map[string]any
 	if err := json.Unmarshal(content, &manifest); err != nil {
 		return err
diff --git a/cmd/oras/internal/display/utils/utils.go b/cmd/oras/internal/display/utils/utils.go
index b8463bef6..8cde3dd43 100644
--- a/cmd/oras/internal/display/utils/utils.go
+++ b/cmd/oras/internal/display/utils/utils.go
@@ -21,13 +21,13 @@ import (
 	"fmt"
 	"io"
 
-	v1 "github.com/opencontainers/image-spec/specs-go/v1"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
 // GenerateContentKey generates a unique key for each content descriptor, using
 // its digest and name if applicable.
-func GenerateContentKey(desc v1.Descriptor) string {
-	return desc.Digest.String() + desc.Annotations[v1.AnnotationTitle]
+func GenerateContentKey(desc ocispec.Descriptor) string {
+	return desc.Digest.String() + desc.Annotations[ocispec.AnnotationTitle]
 }
 
 const (

From 4eb5b9f5895b3e23e7af3dd3fd1908f3081eec99 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 01:38:30 +0000
Subject: [PATCH 25/36] add fetched model

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 .../metadata/descriptor/manifest_fetch.go     |  2 +-
 cmd/oras/internal/display/metadata/discard.go |  2 +-
 .../internal/display/metadata/interface.go    |  2 +-
 .../display/metadata/json/manifest_fetch.go   | 11 ++++---
 .../display/metadata/model/fetched.go         | 31 +++++++++++++++++++
 .../metadata/template/manifest_fetch.go       |  5 +--
 cmd/oras/root/manifest/fetch.go               |  2 +-
 test/e2e/suite/command/manifest.go            |  4 +--
 8 files changed, 46 insertions(+), 13 deletions(-)
 create mode 100644 cmd/oras/internal/display/metadata/model/fetched.go

diff --git a/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go b/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go
index bbdedc2e7..db7f9ede8 100644
--- a/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go
@@ -32,7 +32,7 @@ type manifestFetchHandler struct {
 }
 
 // OnFetched implements ManifestFetchHandler.
-func (h *manifestFetchHandler) OnFetched(desc ocispec.Descriptor, _ []byte) error {
+func (h *manifestFetchHandler) OnFetched(_ string, desc ocispec.Descriptor, _ []byte) error {
 	descBytes, err := json.Marshal(desc)
 	if err != nil {
 		return fmt.Errorf("invalid descriptor: %w", err)
diff --git a/cmd/oras/internal/display/metadata/discard.go b/cmd/oras/internal/display/metadata/discard.go
index dc31bae0f..2e2f0a382 100644
--- a/cmd/oras/internal/display/metadata/discard.go
+++ b/cmd/oras/internal/display/metadata/discard.go
@@ -25,4 +25,4 @@ func NewDiscardHandler() ManifestFetchHandler {
 }
 
 // OnFetched implements ManifestFetchHandler.
-func (discard) OnFetched(ocispec.Descriptor, []byte) error { return nil }
+func (discard) OnFetched(string, ocispec.Descriptor, []byte) error { return nil }
diff --git a/cmd/oras/internal/display/metadata/interface.go b/cmd/oras/internal/display/metadata/interface.go
index 7a06b8635..c7815aa12 100644
--- a/cmd/oras/internal/display/metadata/interface.go
+++ b/cmd/oras/internal/display/metadata/interface.go
@@ -34,7 +34,7 @@ type AttachHandler interface {
 // ManifestFetchHandler handles metadata output for manifest fetch events.
 type ManifestFetchHandler interface {
 	// OnFetched is called after the manifest content is fetched.
-	OnFetched(ocispec.Descriptor, []byte) error
+	OnFetched(path string, desc ocispec.Descriptor, content []byte) error
 }
 
 // PullHandler handles metadata output for pull events.
diff --git a/cmd/oras/internal/display/metadata/json/manifest_fetch.go b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
index 42bf6ebb4..081d7d827 100644
--- a/cmd/oras/internal/display/metadata/json/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
@@ -21,25 +21,26 @@ import (
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"oras.land/oras/cmd/oras/internal/display/metadata"
+	"oras.land/oras/cmd/oras/internal/display/metadata/model"
 )
 
-// ManifestFetchHandler handles JSON metadata output for manifest fetch events.
-type ManifestFetchHandler struct {
+// manifestFetchHandler handles JSON metadata output for manifest fetch events.
+type manifestFetchHandler struct {
 	out io.Writer
 }
 
 // NewManifestFetchHandler creates a new handler for manifest fetch events.
 func NewManifestFetchHandler(out io.Writer) metadata.ManifestFetchHandler {
-	return &ManifestFetchHandler{
+	return &manifestFetchHandler{
 		out: out,
 	}
 }
 
 // OnFetched is called after the manifest fetch is completed.
-func (h *ManifestFetchHandler) OnFetched(desc ocispec.Descriptor, content []byte) error {
+func (h *manifestFetchHandler) OnFetched(path string, desc ocispec.Descriptor, content []byte) error {
 	var manifest map[string]any
 	if err := json.Unmarshal(content, &manifest); err != nil {
 		return err
 	}
-	return printJSON(h.out, manifest)
+	return printJSON(h.out, model.NewFetched(path, desc, manifest))
 }
diff --git a/cmd/oras/internal/display/metadata/model/fetched.go b/cmd/oras/internal/display/metadata/model/fetched.go
new file mode 100644
index 000000000..be764839f
--- /dev/null
+++ b/cmd/oras/internal/display/metadata/model/fetched.go
@@ -0,0 +1,31 @@
+/*
+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 model
+
+import ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+
+type fetched struct {
+	Descriptor
+	Content any
+}
+
+// NewFetched creates a new fetched metadata.
+func NewFetched(path string, desc ocispec.Descriptor, content any) any {
+	return &fetched{
+		Descriptor: FromDescriptor(path, desc),
+		Content:    content,
+	}
+}
diff --git a/cmd/oras/internal/display/metadata/template/manifest_fetch.go b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
index 186d63eca..2a42d53fd 100644
--- a/cmd/oras/internal/display/metadata/template/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
@@ -21,6 +21,7 @@ import (
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"oras.land/oras/cmd/oras/internal/display/metadata"
+	"oras.land/oras/cmd/oras/internal/display/metadata/model"
 )
 
 // manifestFetchHandler handles JSON metadata output for manifest fetch events.
@@ -38,11 +39,11 @@ func NewManifestFetchHandler(out io.Writer, template string) metadata.ManifestFe
 }
 
 // OnFetched is called after the manifest fetch is completed.
-func (h *manifestFetchHandler) OnFetched(desc ocispec.Descriptor, content []byte) error {
+func (h *manifestFetchHandler) OnFetched(path string, desc ocispec.Descriptor, content []byte) error {
 	var manifest map[string]any
 	if err := json.Unmarshal(content, &manifest); err != nil {
 		return err
 	}
 	// return parseAndWrite(h.out, model.ToMappable(reflect.ValueOf(manifest)), h.template)
-	return parseAndWrite(h.out, manifest, h.template)
+	return parseAndWrite(h.out, model.NewFetched(path, desc, manifest), h.template)
 }
diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 585f4fb55..690bdeb0c 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -141,5 +141,5 @@ func fetchManifest(cmd *cobra.Command, opts *fetchOptions) (fetchErr error) {
 			return err
 		}
 	}
-	return metadataHandler.OnFetched(desc, content)
+	return metadataHandler.OnFetched(opts.Path, desc, content)
 }
diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index 2b74b2ad9..03e764ae8 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -227,7 +227,7 @@ var _ = Describe("1.1 registry users:", func() {
 			fetchPath := filepath.Join(GinkgoT().TempDir(), "fetchedImage")
 			digest := multi_arch.LinuxAMD64.Digest.String()
 			ref := RegistryRef(ZOTHost, ImageRepo, digest)
-			out := ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "json").Exec().Out.Contents()
+			out := ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "{{.Content}}").Exec().Out.Contents()
 			Expect(out).To(MatchJSON(multi_arch.LinuxAMD64Manifest))
 			MatchFile(fetchPath, multi_arch.LinuxAMD64Manifest, DefaultTimeout)
 		})
@@ -248,7 +248,7 @@ var _ = Describe("1.1 registry users:", func() {
 		})
 
 		It("should fetch manifest with platform validation and output json", func() {
-			out := ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.Tag), "--platform", "linux/amd64", "--format", "json").
+			out := ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.Tag), "--platform", "linux/amd64", "--format", "{{.Content}}").
 				Exec().Out.Contents()
 			Expect(out).To(MatchJSON(multi_arch.LinuxAMD64Manifest))
 		})

From 3cbbf9b84cdb63c37442e9db34c7bae0a944e4ed Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 01:43:39 +0000
Subject: [PATCH 26/36] add experimental mark

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/root/manifest/fetch.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 690bdeb0c..0e2103619 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -90,7 +90,7 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 
 	cmd.Flags().StringSliceVarP(&opts.mediaTypes, "media-type", "", nil, "accepted media types")
 	cmd.Flags().StringVarP(&opts.outputPath, "output", "o", "", "file `path` to write the fetched manifest to, use - for stdout")
-	cmd.Flags().StringVar(&opts.Template, "format", "", `Format output using a custom template:
+	cmd.Flags().StringVar(&opts.Template, "format", "", `[Experimental] Format fetched manifest using a custom template:
 'json':       Print manifest in prettified JSON format
 '$TEMPLATE':  Print output using the given Go template.`)
 	option.ApplyFlags(&opts, cmd.Flags())

From 7b09792a0ba46a3f7285d7d715ee11f79c8c1467 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 01:49:48 +0000
Subject: [PATCH 27/36] fix e2e

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 test/e2e/suite/command/manifest.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index 03e764ae8..6c3f21bcc 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -227,7 +227,7 @@ var _ = Describe("1.1 registry users:", func() {
 			fetchPath := filepath.Join(GinkgoT().TempDir(), "fetchedImage")
 			digest := multi_arch.LinuxAMD64.Digest.String()
 			ref := RegistryRef(ZOTHost, ImageRepo, digest)
-			out := ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "{{.Content}}").Exec().Out.Contents()
+			out := ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "{{toJson .Content}}").Exec().Out.Contents()
 			Expect(out).To(MatchJSON(multi_arch.LinuxAMD64Manifest))
 			MatchFile(fetchPath, multi_arch.LinuxAMD64Manifest, DefaultTimeout)
 		})
@@ -248,7 +248,7 @@ var _ = Describe("1.1 registry users:", func() {
 		})
 
 		It("should fetch manifest with platform validation and output json", func() {
-			out := ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.Tag), "--platform", "linux/amd64", "--format", "{{.Content}}").
+			out := ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.Tag), "--platform", "linux/amd64", "--format", "{{toJson .Content}}").
 				Exec().Out.Contents()
 			Expect(out).To(MatchJSON(multi_arch.LinuxAMD64Manifest))
 		})

From cb98a26ed8d7037455fb6ee27cb9a9db6a689e44 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 01:53:52 +0000
Subject: [PATCH 28/36] fix e2e

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 test/e2e/suite/command/manifest.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index 6c3f21bcc..b657d37ca 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -254,7 +254,7 @@ var _ = Describe("1.1 registry users:", func() {
 		})
 
 		It("should fetch manifest and format output", func() {
-			ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.LinuxAMD64.Digest.String()), "--format", "{{(first .layers).digest}}").
+			ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.LinuxAMD64.Digest.String()), "--format", "{{(first .Content.layers).digest}}").
 				MatchContent(multi_arch.LayerDigest).
 				Exec()
 		})

From 6615478377234df3ae7afae893590d9d9ce82ef8 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 02:06:57 +0000
Subject: [PATCH 29/36] resolve comments

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 .../internal/display/content/manifest_fetch.go   |  2 +-
 cmd/oras/internal/display/handler.go             |  8 ++++++--
 .../metadata/descriptor/manifest_fetch.go        |  2 +-
 cmd/oras/internal/display/metadata/discard.go    |  4 +++-
 cmd/oras/internal/display/utils/utils.go         |  4 ++--
 cmd/oras/internal/option/pretty.go               | 16 ++--------------
 6 files changed, 15 insertions(+), 21 deletions(-)

diff --git a/cmd/oras/internal/display/content/manifest_fetch.go b/cmd/oras/internal/display/content/manifest_fetch.go
index b6c9b5d81..8a826337e 100644
--- a/cmd/oras/internal/display/content/manifest_fetch.go
+++ b/cmd/oras/internal/display/content/manifest_fetch.go
@@ -41,7 +41,7 @@ func (h *manifestFetch) OnContentFetched(desc ocispec.Descriptor, manifest []byt
 		defer f.Close()
 		out = f
 	}
-	return utils.Output(out, manifest, h.pretty)
+	return utils.PrintJSON(out, manifest, h.pretty)
 }
 
 // NewManifestFetchHandler creates a new handler.
diff --git a/cmd/oras/internal/display/handler.go b/cmd/oras/internal/display/handler.go
index 29cc2d921..884b7427e 100644
--- a/cmd/oras/internal/display/handler.go
+++ b/cmd/oras/internal/display/handler.go
@@ -98,9 +98,9 @@ func NewPullHandler(format string, path string, tty *os.File, out io.Writer, ver
 }
 
 // NewManifestFetchHandler returns a manifest fetch handler.
-func NewManifestFetchHandler(out io.Writer, format string, outputDescriptor bool, pretty bool, outputPath string) (metadata.ManifestFetchHandler, content.ManifestFetchHandler) {
+func NewManifestFetchHandler(out io.Writer, format string, outputDescriptor, pretty bool, outputPath string) (metadata.ManifestFetchHandler, content.ManifestFetchHandler) {
 	var metadataHandler metadata.ManifestFetchHandler
-	var contentHandler content.ManifestFetchHandler = content.NewManifestFetchHandler(out, pretty, outputPath)
+	var contentHandler content.ManifestFetchHandler
 
 	switch format {
 	case "":
@@ -123,5 +123,9 @@ func NewManifestFetchHandler(out io.Writer, format string, outputDescriptor bool
 			contentHandler = content.NewDiscardHandler()
 		}
 	}
+
+	if contentHandler == nil {
+		contentHandler = content.NewManifestFetchHandler(out, pretty, outputPath)
+	}
 	return metadataHandler, contentHandler
 }
diff --git a/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go b/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go
index db7f9ede8..a55407494 100644
--- a/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/descriptor/manifest_fetch.go
@@ -37,7 +37,7 @@ func (h *manifestFetchHandler) OnFetched(_ string, desc ocispec.Descriptor, _ []
 	if err != nil {
 		return fmt.Errorf("invalid descriptor: %w", err)
 	}
-	return utils.Output(h.out, descBytes, h.pretty)
+	return utils.PrintJSON(h.out, descBytes, h.pretty)
 }
 
 // NewManifestFetchHandler creates a new handler.
diff --git a/cmd/oras/internal/display/metadata/discard.go b/cmd/oras/internal/display/metadata/discard.go
index 2e2f0a382..4b1941f59 100644
--- a/cmd/oras/internal/display/metadata/discard.go
+++ b/cmd/oras/internal/display/metadata/discard.go
@@ -25,4 +25,6 @@ func NewDiscardHandler() ManifestFetchHandler {
 }
 
 // OnFetched implements ManifestFetchHandler.
-func (discard) OnFetched(string, ocispec.Descriptor, []byte) error { return nil }
+func (discard) OnFetched(string, ocispec.Descriptor, []byte) error {
+	return nil
+}
diff --git a/cmd/oras/internal/display/utils/utils.go b/cmd/oras/internal/display/utils/utils.go
index 8cde3dd43..776be54df 100644
--- a/cmd/oras/internal/display/utils/utils.go
+++ b/cmd/oras/internal/display/utils/utils.go
@@ -39,8 +39,8 @@ const (
 	PullPromptDownloaded  = "Downloaded "
 )
 
-// Output writes the data to the output stream, optionally prettifying it.
-func Output(out io.Writer, data []byte, pretty bool) error {
+// PrintJSON writes the data to the output stream, optionally prettifying it.
+func PrintJSON(out io.Writer, data []byte, pretty bool) error {
 	if pretty {
 		buf := bytes.NewBuffer(nil)
 		if err := json.Indent(buf, data, "", "  "); err != nil {
diff --git a/cmd/oras/internal/option/pretty.go b/cmd/oras/internal/option/pretty.go
index de889522e..6013be141 100644
--- a/cmd/oras/internal/option/pretty.go
+++ b/cmd/oras/internal/option/pretty.go
@@ -16,12 +16,10 @@ limitations under the License.
 package option
 
 import (
-	"bytes"
-	"encoding/json"
-	"fmt"
 	"io"
 
 	"github.com/spf13/pflag"
+	"oras.land/oras/cmd/oras/internal/display/utils"
 )
 
 // Pretty option struct.
@@ -37,15 +35,5 @@ func (opts *Pretty) ApplyFlags(fs *pflag.FlagSet) {
 // Output outputs the prettified content if `--pretty` flag is used. Otherwise
 // outputs the original content.
 func (opts *Pretty) Output(w io.Writer, content []byte) error {
-	if opts.Pretty {
-		buf := bytes.NewBuffer(nil)
-		if err := json.Indent(buf, content, "", "  "); err != nil {
-			return fmt.Errorf("failed to prettify: %w", err)
-		}
-		buf.WriteByte('\n')
-		content = buf.Bytes()
-	}
-
-	_, err := w.Write(content)
-	return err
+	return utils.PrintJSON(w, content, opts.Pretty)
 }

From a8c3de8d0ac2f23e8a9fe303bf3930509414c6a9 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 02:20:02 +0000
Subject: [PATCH 30/36] add json test

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 test/e2e/suite/command/manifest.go | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index b657d37ca..6e55d7aae 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -227,8 +227,11 @@ var _ = Describe("1.1 registry users:", func() {
 			fetchPath := filepath.Join(GinkgoT().TempDir(), "fetchedImage")
 			digest := multi_arch.LinuxAMD64.Digest.String()
 			ref := RegistryRef(ZOTHost, ImageRepo, digest)
-			out := ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "{{toJson .Content}}").Exec().Out.Contents()
-			Expect(out).To(MatchJSON(multi_arch.LinuxAMD64Manifest))
+			// test
+			out := ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "{{json}}").Exec().Out.Contents()
+			// validate
+			var content = struct{ Content any }{}
+			Expect(json.Unmarshal(out, &content)).ShouldNot(HaveOccurred())
 			MatchFile(fetchPath, multi_arch.LinuxAMD64Manifest, DefaultTimeout)
 		})
 
@@ -247,7 +250,7 @@ var _ = Describe("1.1 registry users:", func() {
 				MatchContent(multi_arch.LinuxAMD64Manifest).Exec()
 		})
 
-		It("should fetch manifest with platform validation and output json", func() {
+		It("should fetch manifest with platform validation and output content", func() {
 			out := ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.Tag), "--platform", "linux/amd64", "--format", "{{toJson .Content}}").
 				Exec().Out.Contents()
 			Expect(out).To(MatchJSON(multi_arch.LinuxAMD64Manifest))

From 1dfd284770a01e4438df8699c6cafd937ae8b077 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 02:35:17 +0000
Subject: [PATCH 31/36] fix e2e

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 test/e2e/suite/command/manifest.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index 6e55d7aae..0e96113ba 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -228,7 +228,7 @@ var _ = Describe("1.1 registry users:", func() {
 			digest := multi_arch.LinuxAMD64.Digest.String()
 			ref := RegistryRef(ZOTHost, ImageRepo, digest)
 			// test
-			out := ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "{{json}}").Exec().Out.Contents()
+			out := ORAS("manifest", "fetch", ref, "--output", fetchPath, "--format", "json").Exec().Out.Contents()
 			// validate
 			var content = struct{ Content any }{}
 			Expect(json.Unmarshal(out, &content)).ShouldNot(HaveOccurred())

From dfb8dce7d15b4fbf4d4f6e7cf443f5292427a66f Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 06:00:39 +0000
Subject: [PATCH 32/36] resolve comments

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/metadata/json/manifest_fetch.go   | 4 +---
 .../internal/display/metadata/template/manifest_fetch.go    | 5 +----
 cmd/oras/root/manifest/fetch.go                             | 6 +++---
 3 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/cmd/oras/internal/display/metadata/json/manifest_fetch.go b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
index 081d7d827..993a1a054 100644
--- a/cmd/oras/internal/display/metadata/json/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
@@ -39,8 +39,6 @@ func NewManifestFetchHandler(out io.Writer) metadata.ManifestFetchHandler {
 // OnFetched is called after the manifest fetch is completed.
 func (h *manifestFetchHandler) OnFetched(path string, desc ocispec.Descriptor, content []byte) error {
 	var manifest map[string]any
-	if err := json.Unmarshal(content, &manifest); err != nil {
-		return err
-	}
+	_ = json.Unmarshal(content, &manifest)
 	return printJSON(h.out, model.NewFetched(path, desc, manifest))
 }
diff --git a/cmd/oras/internal/display/metadata/template/manifest_fetch.go b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
index 2a42d53fd..dee02a4ba 100644
--- a/cmd/oras/internal/display/metadata/template/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
@@ -41,9 +41,6 @@ func NewManifestFetchHandler(out io.Writer, template string) metadata.ManifestFe
 // OnFetched is called after the manifest fetch is completed.
 func (h *manifestFetchHandler) OnFetched(path string, desc ocispec.Descriptor, content []byte) error {
 	var manifest map[string]any
-	if err := json.Unmarshal(content, &manifest); err != nil {
-		return err
-	}
-	// return parseAndWrite(h.out, model.ToMappable(reflect.ValueOf(manifest)), h.template)
+	_ = json.Unmarshal(content, &manifest)
 	return parseAndWrite(h.out, model.NewFetched(path, desc, manifest), h.template)
 }
diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 0e2103619..2eab3c2ff 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -90,9 +90,9 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 
 	cmd.Flags().StringSliceVarP(&opts.mediaTypes, "media-type", "", nil, "accepted media types")
 	cmd.Flags().StringVarP(&opts.outputPath, "output", "o", "", "file `path` to write the fetched manifest to, use - for stdout")
-	cmd.Flags().StringVar(&opts.Template, "format", "", `[Experimental] Format fetched manifest using a custom template:
-'json':       Print manifest in prettified JSON format
-'$TEMPLATE':  Print output using the given Go template.`)
+	cmd.Flags().StringVar(&opts.Template, "format", "", `[Experimental] Format operation metadata using a custom template:
+'json':       Print in prettified JSON format
+'$TEMPLATE':  Print using the given Go template.`)
 	option.ApplyFlags(&opts, cmd.Flags())
 	return oerrors.Command(cmd, &opts.Target)
 }

From 6c5e2cfbcf437ac8229af914bf8a7e318ec99caf Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 07:11:30 +0000
Subject: [PATCH 33/36] resolve comments

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/metadata/json/manifest_fetch.go     | 4 +++-
 cmd/oras/internal/display/metadata/template/manifest_fetch.go | 4 +++-
 cmd/oras/root/manifest/fetch.go                               | 2 +-
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/cmd/oras/internal/display/metadata/json/manifest_fetch.go b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
index 993a1a054..01fe57a02 100644
--- a/cmd/oras/internal/display/metadata/json/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/json/manifest_fetch.go
@@ -39,6 +39,8 @@ func NewManifestFetchHandler(out io.Writer) metadata.ManifestFetchHandler {
 // OnFetched is called after the manifest fetch is completed.
 func (h *manifestFetchHandler) OnFetched(path string, desc ocispec.Descriptor, content []byte) error {
 	var manifest map[string]any
-	_ = json.Unmarshal(content, &manifest)
+	if err := json.Unmarshal(content, &manifest); err != nil {
+		manifest = nil
+	}
 	return printJSON(h.out, model.NewFetched(path, desc, manifest))
 }
diff --git a/cmd/oras/internal/display/metadata/template/manifest_fetch.go b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
index dee02a4ba..8148f13d6 100644
--- a/cmd/oras/internal/display/metadata/template/manifest_fetch.go
+++ b/cmd/oras/internal/display/metadata/template/manifest_fetch.go
@@ -41,6 +41,8 @@ func NewManifestFetchHandler(out io.Writer, template string) metadata.ManifestFe
 // OnFetched is called after the manifest fetch is completed.
 func (h *manifestFetchHandler) OnFetched(path string, desc ocispec.Descriptor, content []byte) error {
 	var manifest map[string]any
-	_ = json.Unmarshal(content, &manifest)
+	if err := json.Unmarshal(content, &manifest); err != nil {
+		manifest = nil
+	}
 	return parseAndWrite(h.out, model.NewFetched(path, desc, manifest), h.template)
 }
diff --git a/cmd/oras/root/manifest/fetch.go b/cmd/oras/root/manifest/fetch.go
index 2eab3c2ff..abe211c8f 100644
--- a/cmd/oras/root/manifest/fetch.go
+++ b/cmd/oras/root/manifest/fetch.go
@@ -90,7 +90,7 @@ Example - Fetch raw manifest from an OCI layout archive file 'layout.tar':
 
 	cmd.Flags().StringSliceVarP(&opts.mediaTypes, "media-type", "", nil, "accepted media types")
 	cmd.Flags().StringVarP(&opts.outputPath, "output", "o", "", "file `path` to write the fetched manifest to, use - for stdout")
-	cmd.Flags().StringVar(&opts.Template, "format", "", `[Experimental] Format operation metadata using a custom template:
+	cmd.Flags().StringVar(&opts.Template, "format", "", `[Experimental] Format metadata using a custom template:
 'json':       Print in prettified JSON format
 '$TEMPLATE':  Print using the given Go template.`)
 	option.ApplyFlags(&opts, cmd.Flags())

From bb69b393944cd0230f29eb748156ce1d8beb719b Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 08:01:09 +0000
Subject: [PATCH 34/36] add e2e coverage

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 test/e2e/suite/command/manifest.go | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/test/e2e/suite/command/manifest.go b/test/e2e/suite/command/manifest.go
index 0e96113ba..bf644acb1 100644
--- a/test/e2e/suite/command/manifest.go
+++ b/test/e2e/suite/command/manifest.go
@@ -235,6 +235,15 @@ var _ = Describe("1.1 registry users:", func() {
 			MatchFile(fetchPath, multi_arch.LinuxAMD64Manifest, DefaultTimeout)
 		})
 
+		It("should fetch manifest and output json", func() {
+			ref := RegistryRef(ZOTHost, ImageRepo, multi_arch.LinuxAMD64.Digest.String())
+			// test
+			out := ORAS("manifest", "fetch", ref, "--format", "json").Exec().Out.Contents()
+			// validate
+			var content = struct{ Content any }{}
+			Expect(json.Unmarshal(out, &content)).ShouldNot(HaveOccurred())
+		})
+
 		It("should fetch manifest via tag with platform selection", func() {
 			ORAS("manifest", "fetch", RegistryRef(ZOTHost, ImageRepo, multi_arch.Tag), "--platform", "linux/amd64").
 				MatchContent(multi_arch.LinuxAMD64Manifest).Exec()

From 57d2078dae55c683324673da2715166982e34299 Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 08:03:22 +0000
Subject: [PATCH 35/36] remove used code

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/utils/utils.go | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/cmd/oras/internal/display/utils/utils.go b/cmd/oras/internal/display/utils/utils.go
index 776be54df..2f3205067 100644
--- a/cmd/oras/internal/display/utils/utils.go
+++ b/cmd/oras/internal/display/utils/utils.go
@@ -20,16 +20,9 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-
-	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 )
 
-// GenerateContentKey generates a unique key for each content descriptor, using
-// its digest and name if applicable.
-func GenerateContentKey(desc ocispec.Descriptor) string {
-	return desc.Digest.String() + desc.Annotations[ocispec.AnnotationTitle]
-}
-
+// Prompt constants for pull.
 const (
 	PullPromptDownloading = "Downloading"
 	PullPromptPulled      = "Pulled     "

From 4ec65f97eb380c6609fe7d394f30a9b0d802548b Mon Sep 17 00:00:00 2001
From: Billy Zha <jinzha1@microsoft.com>
Date: Wed, 10 Apr 2024 08:10:41 +0000
Subject: [PATCH 36/36] use create file instead of open file

Signed-off-by: Billy Zha <jinzha1@microsoft.com>
---
 cmd/oras/internal/display/content/manifest_fetch.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cmd/oras/internal/display/content/manifest_fetch.go b/cmd/oras/internal/display/content/manifest_fetch.go
index 8a826337e..20707b04b 100644
--- a/cmd/oras/internal/display/content/manifest_fetch.go
+++ b/cmd/oras/internal/display/content/manifest_fetch.go
@@ -34,7 +34,7 @@ type manifestFetch struct {
 func (h *manifestFetch) OnContentFetched(desc ocispec.Descriptor, manifest []byte) error {
 	out := h.stdout
 	if h.outputPath != "-" && h.outputPath != "" {
-		f, err := os.OpenFile(h.outputPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0666)
+		f, err := os.Create(h.outputPath)
 		if err != nil {
 			return fmt.Errorf("failed to open %q: %w", h.outputPath, err)
 		}