From 7d537e959da74875f2138dd3f5b6edda2369848d Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Fri, 15 Dec 2023 14:33:05 +0800
Subject: [PATCH 01/13] feat: Referrers support for oci.Store

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 content/oci/oci.go      |  78 ++++++++++++++++++
 content/oci/oci_test.go | 174 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 252 insertions(+)

diff --git a/content/oci/oci.go b/content/oci/oci.go
index 1deca875..92bb4652 100644
--- a/content/oci/oci.go
+++ b/content/oci/oci.go
@@ -36,6 +36,7 @@ import (
 	"oras.land/oras-go/v2/internal/descriptor"
 	"oras.land/oras-go/v2/internal/graph"
 	"oras.land/oras-go/v2/internal/resolver"
+	"oras.land/oras-go/v2/internal/spec"
 )
 
 // Store implements `oras.Target`, and represents a content store
@@ -398,6 +399,83 @@ func (s *Store) writeIndexFile() error {
 	return os.WriteFile(s.indexPath, indexJSON, 0666)
 }
 
+// Referrers lists the descriptors of image or artifact manifests directly
+// referencing the given manifest descriptor.
+//
+// fn is called on the referrer results. If artifactType is not empty, only
+// referrers of the same artifact type are fed to fn.
+//
+// Reference: https://github.com/opencontainers/distribution-spec/blob/v1.1.0-rc3/spec.md#listing-referrers
+func (s *Store) Referrers(ctx context.Context, desc ocispec.Descriptor, artifactType string, fn func(referrers []ocispec.Descriptor) error) error {
+	s.sync.RLock()
+	defer s.sync.RUnlock()
+
+	if !descriptor.IsManifest(desc) {
+		return fmt.Errorf("the descriptor %v is not a manifest", desc)
+	}
+	var results []ocispec.Descriptor
+	predecessors, err := s.Predecessors(ctx, desc)
+	if err != nil {
+		return err
+	}
+	for _, node := range predecessors {
+		switch node.MediaType {
+		case ocispec.MediaTypeImageManifest:
+			fetched, err := content.FetchAll(ctx, s, node)
+			if err != nil {
+				return err
+			}
+			var manifest ocispec.Manifest
+			if err := json.Unmarshal(fetched, &manifest); err != nil {
+				return err
+			}
+			if manifest.Subject == nil || !content.Equal(*manifest.Subject, desc) {
+				continue
+			}
+			if manifest.ArtifactType != "" {
+				node.ArtifactType = manifest.ArtifactType
+			} else {
+				node.ArtifactType = manifest.Config.MediaType
+			}
+			node.Annotations = manifest.Annotations
+		case ocispec.MediaTypeImageIndex:
+			fetched, err := content.FetchAll(ctx, s, node)
+			if err != nil {
+				return err
+			}
+			var index ocispec.Index
+			if err := json.Unmarshal(fetched, &index); err != nil {
+				return err
+			}
+			if index.Subject == nil || !content.Equal(*index.Subject, desc) {
+				continue
+			}
+			node.ArtifactType = index.ArtifactType
+			node.Annotations = index.Annotations
+		case spec.MediaTypeArtifactManifest:
+			fetched, err := content.FetchAll(ctx, s, node)
+			if err != nil {
+				return err
+			}
+			var artifact spec.Artifact
+			if err := json.Unmarshal(fetched, &artifact); err != nil {
+				return err
+			}
+			if artifact.Subject == nil || !content.Equal(*artifact.Subject, desc) {
+				continue
+			}
+			node.ArtifactType = artifact.ArtifactType
+			node.Annotations = artifact.Annotations
+		default:
+			continue
+		}
+		if artifactType == "" || artifactType == node.ArtifactType {
+			results = append(results, node)
+		}
+	}
+	return fn(results)
+}
+
 // validateReference validates ref.
 func validateReference(ref string) error {
 	if ref == "" {
diff --git a/content/oci/oci_test.go b/content/oci/oci_test.go
index bba9037a..bcdc0e4b 100644
--- a/content/oci/oci_test.go
+++ b/content/oci/oci_test.go
@@ -2378,6 +2378,180 @@ func TestStore_UntagErrorPath(t *testing.T) {
 	}
 }
 
+func TestStore_Referrers(t *testing.T) {
+	tempDir := t.TempDir()
+	s, err := New(tempDir)
+	if err != nil {
+		t.Fatal("New() error =", err)
+	}
+	ctx := context.Background()
+
+	// generate test content
+	var blobs [][]byte
+	var descs []ocispec.Descriptor
+	appendBlob := func(mediaType string, artifactType string, blob []byte) {
+		blobs = append(blobs, blob)
+		descs = append(descs, ocispec.Descriptor{
+			MediaType:    mediaType,
+			ArtifactType: artifactType,
+			Annotations:  map[string]string{"test": "content"},
+			Digest:       digest.FromBytes(blob),
+			Size:         int64(len(blob)),
+		})
+	}
+	generateImageManifest := func(config ocispec.Descriptor, subject *ocispec.Descriptor, layers ...ocispec.Descriptor) {
+		manifest := ocispec.Manifest{
+			MediaType:   ocispec.MediaTypeImageManifest,
+			Config:      config,
+			Subject:     subject,
+			Layers:      layers,
+			Annotations: map[string]string{"test": "content"},
+		}
+		manifestJSON, err := json.Marshal(manifest)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(ocispec.MediaTypeImageManifest, manifest.Config.MediaType, manifestJSON)
+	}
+	generateArtifactManifest := func(subject *ocispec.Descriptor, blobs ...ocispec.Descriptor) {
+		artifact := spec.Artifact{
+			MediaType:    spec.MediaTypeArtifactManifest,
+			ArtifactType: "artifact",
+			Subject:      subject,
+			Blobs:        blobs,
+			Annotations:  map[string]string{"test": "content"},
+		}
+		manifestJSON, err := json.Marshal(artifact)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(spec.MediaTypeArtifactManifest, artifact.ArtifactType, manifestJSON)
+	}
+	generateIndex := func(subject *ocispec.Descriptor, manifests ...ocispec.Descriptor) {
+		index := ocispec.Index{
+			MediaType:    ocispec.MediaTypeImageIndex,
+			ArtifactType: "index",
+			Subject:      subject,
+			Manifests:    manifests,
+			Annotations:  map[string]string{"test": "content"},
+		}
+		indexJSON, err := json.Marshal(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(ocispec.MediaTypeImageIndex, index.ArtifactType, indexJSON)
+	}
+
+	appendBlob("image manifest", "image config", []byte("config"))    // Blob 0
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("foo"))   // Blob 1
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("bar"))   // Blob 2
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("hello")) // Blob 3
+	generateImageManifest(descs[0], nil, descs[1])                    // Blob 4
+	generateArtifactManifest(&descs[4], descs[2])                     // Blob 5
+	generateImageManifest(descs[0], &descs[5], descs[3])              // Blob 6
+	generateIndex(&descs[6], descs[4:6]...)                           // Blob 7
+	generateIndex(&descs[4], descs[5:8]...)                           // Blob 8
+
+	eg, egCtx := errgroup.WithContext(ctx)
+	for i := range blobs {
+		eg.Go(func(i int) func() error {
+			return func() error {
+				err := s.Push(egCtx, descs[i], bytes.NewReader(blobs[i]))
+				if err != nil {
+					return fmt.Errorf("failed to push test content to src: %d: %v", i, err)
+				}
+				return nil
+			}
+		}(i))
+	}
+	if err := eg.Wait(); err != nil {
+		t.Fatal(err)
+	}
+
+	// verify predecessors
+	wantedPredecessors := [][]ocispec.Descriptor{
+		{descs[4], descs[6]},           // Blob 0
+		{descs[4]},                     // Blob 1
+		{descs[5]},                     // Blob 2
+		{descs[6]},                     // Blob 3
+		{descs[5], descs[7], descs[8]}, // Blob 4
+		{descs[6], descs[7], descs[8]}, // Blob 5
+		{descs[7], descs[8]},           // Blob 6
+		{descs[8]},                     // Blob 7
+		nil,                            // Blob 8
+	}
+	for i, want := range wantedPredecessors {
+		predecessors, err := s.Predecessors(ctx, descs[i])
+		if err != nil {
+			t.Errorf("Store.Predecessors(%d) error = %v", i, err)
+		}
+		if !equalDescriptorSet(predecessors, want) {
+			t.Errorf("Store.Predecessors(%d) = %v, want %v", i, predecessors, want)
+		}
+	}
+
+	// verify referrers
+	wantedReferrers := [][]ocispec.Descriptor{
+		nil,                  // Blob 0
+		nil,                  // Blob 1
+		nil,                  // Blob 2
+		nil,                  // Blob 3
+		{descs[5], descs[8]}, // Blob 4
+		{descs[6]},           // Blob 5
+		{descs[7]},           // Blob 6
+		nil,                  // Blob 7
+		nil,                  // Blob 8
+	}
+	for i := 4; i < len(wantedReferrers); i++ {
+		want := wantedReferrers[i]
+		var results []ocispec.Descriptor
+		err := s.Referrers(ctx, descs[i], "", func(referrers []ocispec.Descriptor) error {
+			results = append(results, referrers...)
+			return nil
+		})
+		if err != nil {
+			t.Errorf("Store.Referrers(%d) error = %v", i, err)
+		}
+		if !equalDescriptorSet(results, want) {
+			t.Errorf("Store.Predecessors(%d) = %v, want %v", i, results, want)
+		}
+	}
+
+	// test filtering on ArtifactType
+	wantedReferrers = [][]ocispec.Descriptor{
+		nil,        // Blob 0
+		nil,        // Blob 1
+		nil,        // Blob 2
+		nil,        // Blob 3
+		nil,        // Blob 4
+		{descs[6]}, // Blob 5
+		nil,        // Blob 6
+		nil,        // Blob 7
+		nil,        // Blob 8
+	}
+	for i := 4; i < len(wantedReferrers); i++ {
+		want := wantedReferrers[i]
+		var results []ocispec.Descriptor
+		err := s.Referrers(ctx, descs[i], "image manifest", func(referrers []ocispec.Descriptor) error {
+			results = append(results, referrers...)
+			return nil
+		})
+		if err != nil {
+			t.Errorf("Store.Referrers(%d) error = %v", i, err)
+		}
+		if !equalDescriptorSet(results, want) {
+			t.Errorf("Store.Predecessors(%d) = %v, want %v", i, results, want)
+		}
+	}
+}
+
+func TestStore_ReferrersInterface(t *testing.T) {
+	var store interface{} = &Store{}
+	if _, ok := store.(registry.ReferrerLister); !ok {
+		t.Error("&Store{} does not conform to registry.ReferrerLister")
+	}
+}
+
 func equalDescriptorSet(actual []ocispec.Descriptor, expected []ocispec.Descriptor) bool {
 	if len(actual) != len(expected) {
 		return false

From 7444a42093883c1557c37bfa5b16640c7fcc8ce4 Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Wed, 20 Dec 2023 12:43:28 +0800
Subject: [PATCH 02/13] generic implementation

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 content/oci/oci.go      | 78 ---------------------------------------
 content/oci/oci_test.go | 11 +-----
 registry/repository.go  | 82 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 84 insertions(+), 87 deletions(-)

diff --git a/content/oci/oci.go b/content/oci/oci.go
index 92bb4652..1deca875 100644
--- a/content/oci/oci.go
+++ b/content/oci/oci.go
@@ -36,7 +36,6 @@ import (
 	"oras.land/oras-go/v2/internal/descriptor"
 	"oras.land/oras-go/v2/internal/graph"
 	"oras.land/oras-go/v2/internal/resolver"
-	"oras.land/oras-go/v2/internal/spec"
 )
 
 // Store implements `oras.Target`, and represents a content store
@@ -399,83 +398,6 @@ func (s *Store) writeIndexFile() error {
 	return os.WriteFile(s.indexPath, indexJSON, 0666)
 }
 
-// Referrers lists the descriptors of image or artifact manifests directly
-// referencing the given manifest descriptor.
-//
-// fn is called on the referrer results. If artifactType is not empty, only
-// referrers of the same artifact type are fed to fn.
-//
-// Reference: https://github.com/opencontainers/distribution-spec/blob/v1.1.0-rc3/spec.md#listing-referrers
-func (s *Store) Referrers(ctx context.Context, desc ocispec.Descriptor, artifactType string, fn func(referrers []ocispec.Descriptor) error) error {
-	s.sync.RLock()
-	defer s.sync.RUnlock()
-
-	if !descriptor.IsManifest(desc) {
-		return fmt.Errorf("the descriptor %v is not a manifest", desc)
-	}
-	var results []ocispec.Descriptor
-	predecessors, err := s.Predecessors(ctx, desc)
-	if err != nil {
-		return err
-	}
-	for _, node := range predecessors {
-		switch node.MediaType {
-		case ocispec.MediaTypeImageManifest:
-			fetched, err := content.FetchAll(ctx, s, node)
-			if err != nil {
-				return err
-			}
-			var manifest ocispec.Manifest
-			if err := json.Unmarshal(fetched, &manifest); err != nil {
-				return err
-			}
-			if manifest.Subject == nil || !content.Equal(*manifest.Subject, desc) {
-				continue
-			}
-			if manifest.ArtifactType != "" {
-				node.ArtifactType = manifest.ArtifactType
-			} else {
-				node.ArtifactType = manifest.Config.MediaType
-			}
-			node.Annotations = manifest.Annotations
-		case ocispec.MediaTypeImageIndex:
-			fetched, err := content.FetchAll(ctx, s, node)
-			if err != nil {
-				return err
-			}
-			var index ocispec.Index
-			if err := json.Unmarshal(fetched, &index); err != nil {
-				return err
-			}
-			if index.Subject == nil || !content.Equal(*index.Subject, desc) {
-				continue
-			}
-			node.ArtifactType = index.ArtifactType
-			node.Annotations = index.Annotations
-		case spec.MediaTypeArtifactManifest:
-			fetched, err := content.FetchAll(ctx, s, node)
-			if err != nil {
-				return err
-			}
-			var artifact spec.Artifact
-			if err := json.Unmarshal(fetched, &artifact); err != nil {
-				return err
-			}
-			if artifact.Subject == nil || !content.Equal(*artifact.Subject, desc) {
-				continue
-			}
-			node.ArtifactType = artifact.ArtifactType
-			node.Annotations = artifact.Annotations
-		default:
-			continue
-		}
-		if artifactType == "" || artifactType == node.ArtifactType {
-			results = append(results, node)
-		}
-	}
-	return fn(results)
-}
-
 // validateReference validates ref.
 func validateReference(ref string) error {
 	if ref == "" {
diff --git a/content/oci/oci_test.go b/content/oci/oci_test.go
index bcdc0e4b..c948be3a 100644
--- a/content/oci/oci_test.go
+++ b/content/oci/oci_test.go
@@ -2505,7 +2505,7 @@ func TestStore_Referrers(t *testing.T) {
 	for i := 4; i < len(wantedReferrers); i++ {
 		want := wantedReferrers[i]
 		var results []ocispec.Descriptor
-		err := s.Referrers(ctx, descs[i], "", func(referrers []ocispec.Descriptor) error {
+		err := registry.Referrers(ctx, s, descs[i], "", func(referrers []ocispec.Descriptor) error {
 			results = append(results, referrers...)
 			return nil
 		})
@@ -2532,7 +2532,7 @@ func TestStore_Referrers(t *testing.T) {
 	for i := 4; i < len(wantedReferrers); i++ {
 		want := wantedReferrers[i]
 		var results []ocispec.Descriptor
-		err := s.Referrers(ctx, descs[i], "image manifest", func(referrers []ocispec.Descriptor) error {
+		err := registry.Referrers(ctx, s, descs[i], "image manifest", func(referrers []ocispec.Descriptor) error {
 			results = append(results, referrers...)
 			return nil
 		})
@@ -2545,13 +2545,6 @@ func TestStore_Referrers(t *testing.T) {
 	}
 }
 
-func TestStore_ReferrersInterface(t *testing.T) {
-	var store interface{} = &Store{}
-	if _, ok := store.(registry.ReferrerLister); !ok {
-		t.Error("&Store{} does not conform to registry.ReferrerLister")
-	}
-}
-
 func equalDescriptorSet(actual []ocispec.Descriptor, expected []ocispec.Descriptor) bool {
 	if len(actual) != len(expected) {
 		return false
diff --git a/registry/repository.go b/registry/repository.go
index b75b7b8e..36f73cba 100644
--- a/registry/repository.go
+++ b/registry/repository.go
@@ -17,10 +17,14 @@ package registry
 
 import (
 	"context"
+	"encoding/json"
+	"fmt"
 	"io"
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"oras.land/oras-go/v2/content"
+	"oras.land/oras-go/v2/internal/descriptor"
+	"oras.land/oras-go/v2/internal/spec"
 )
 
 // Repository is an ORAS target and an union of the blob and the manifest CASs.
@@ -134,3 +138,81 @@ func Tags(ctx context.Context, repo TagLister) ([]string, error) {
 	}
 	return res, nil
 }
+
+// Referrers lists the descriptors of image or artifact manifests directly
+// referencing the given manifest descriptor.
+//
+// fn is called on the referrer results. If artifactType is not empty, only
+// referrers of the same artifact type are fed to fn.
+//
+// Reference: https://github.com/opencontainers/distribution-spec/blob/v1.1.0-rc3/spec.md#listing-referrers
+func Referrers(ctx context.Context, store content.ReadOnlyGraphStorage, desc ocispec.Descriptor, artifactType string, fn func(referrers []ocispec.Descriptor) error) error {
+	if !descriptor.IsManifest(desc) {
+		return fmt.Errorf("the descriptor %v is not a manifest", desc)
+	}
+	// use the Referrer API if it is available
+	if rf, ok := store.(ReferrerLister); ok {
+		return rf.Referrers(ctx, desc, artifactType, fn)
+	}
+	var results []ocispec.Descriptor
+	predecessors, err := store.Predecessors(ctx, desc)
+	if err != nil {
+		return err
+	}
+	for _, node := range predecessors {
+		switch node.MediaType {
+		case ocispec.MediaTypeImageManifest:
+			fetched, err := content.FetchAll(ctx, store, node)
+			if err != nil {
+				return err
+			}
+			var manifest ocispec.Manifest
+			if err := json.Unmarshal(fetched, &manifest); err != nil {
+				return err
+			}
+			if manifest.Subject == nil || !content.Equal(*manifest.Subject, desc) {
+				continue
+			}
+			if manifest.ArtifactType != "" {
+				node.ArtifactType = manifest.ArtifactType
+			} else {
+				node.ArtifactType = manifest.Config.MediaType
+			}
+			node.Annotations = manifest.Annotations
+		case ocispec.MediaTypeImageIndex:
+			fetched, err := content.FetchAll(ctx, store, node)
+			if err != nil {
+				return err
+			}
+			var index ocispec.Index
+			if err := json.Unmarshal(fetched, &index); err != nil {
+				return err
+			}
+			if index.Subject == nil || !content.Equal(*index.Subject, desc) {
+				continue
+			}
+			node.ArtifactType = index.ArtifactType
+			node.Annotations = index.Annotations
+		case spec.MediaTypeArtifactManifest:
+			fetched, err := content.FetchAll(ctx, store, node)
+			if err != nil {
+				return err
+			}
+			var artifact spec.Artifact
+			if err := json.Unmarshal(fetched, &artifact); err != nil {
+				return err
+			}
+			if artifact.Subject == nil || !content.Equal(*artifact.Subject, desc) {
+				continue
+			}
+			node.ArtifactType = artifact.ArtifactType
+			node.Annotations = artifact.Annotations
+		default:
+			continue
+		}
+		if artifactType == "" || artifactType == node.ArtifactType {
+			results = append(results, node)
+		}
+	}
+	return fn(results)
+}

From b1205f4c1f53db8a08de44e2a7e17ef7aa36adee Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Wed, 20 Dec 2023 14:24:09 +0800
Subject: [PATCH 03/13] resolved comments

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 content/oci/oci_test.go | 167 ----------------------------------------
 registry/repository.go  |   3 +-
 2 files changed, 2 insertions(+), 168 deletions(-)

diff --git a/content/oci/oci_test.go b/content/oci/oci_test.go
index c948be3a..bba9037a 100644
--- a/content/oci/oci_test.go
+++ b/content/oci/oci_test.go
@@ -2378,173 +2378,6 @@ func TestStore_UntagErrorPath(t *testing.T) {
 	}
 }
 
-func TestStore_Referrers(t *testing.T) {
-	tempDir := t.TempDir()
-	s, err := New(tempDir)
-	if err != nil {
-		t.Fatal("New() error =", err)
-	}
-	ctx := context.Background()
-
-	// generate test content
-	var blobs [][]byte
-	var descs []ocispec.Descriptor
-	appendBlob := func(mediaType string, artifactType string, blob []byte) {
-		blobs = append(blobs, blob)
-		descs = append(descs, ocispec.Descriptor{
-			MediaType:    mediaType,
-			ArtifactType: artifactType,
-			Annotations:  map[string]string{"test": "content"},
-			Digest:       digest.FromBytes(blob),
-			Size:         int64(len(blob)),
-		})
-	}
-	generateImageManifest := func(config ocispec.Descriptor, subject *ocispec.Descriptor, layers ...ocispec.Descriptor) {
-		manifest := ocispec.Manifest{
-			MediaType:   ocispec.MediaTypeImageManifest,
-			Config:      config,
-			Subject:     subject,
-			Layers:      layers,
-			Annotations: map[string]string{"test": "content"},
-		}
-		manifestJSON, err := json.Marshal(manifest)
-		if err != nil {
-			t.Fatal(err)
-		}
-		appendBlob(ocispec.MediaTypeImageManifest, manifest.Config.MediaType, manifestJSON)
-	}
-	generateArtifactManifest := func(subject *ocispec.Descriptor, blobs ...ocispec.Descriptor) {
-		artifact := spec.Artifact{
-			MediaType:    spec.MediaTypeArtifactManifest,
-			ArtifactType: "artifact",
-			Subject:      subject,
-			Blobs:        blobs,
-			Annotations:  map[string]string{"test": "content"},
-		}
-		manifestJSON, err := json.Marshal(artifact)
-		if err != nil {
-			t.Fatal(err)
-		}
-		appendBlob(spec.MediaTypeArtifactManifest, artifact.ArtifactType, manifestJSON)
-	}
-	generateIndex := func(subject *ocispec.Descriptor, manifests ...ocispec.Descriptor) {
-		index := ocispec.Index{
-			MediaType:    ocispec.MediaTypeImageIndex,
-			ArtifactType: "index",
-			Subject:      subject,
-			Manifests:    manifests,
-			Annotations:  map[string]string{"test": "content"},
-		}
-		indexJSON, err := json.Marshal(index)
-		if err != nil {
-			t.Fatal(err)
-		}
-		appendBlob(ocispec.MediaTypeImageIndex, index.ArtifactType, indexJSON)
-	}
-
-	appendBlob("image manifest", "image config", []byte("config"))    // Blob 0
-	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("foo"))   // Blob 1
-	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("bar"))   // Blob 2
-	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("hello")) // Blob 3
-	generateImageManifest(descs[0], nil, descs[1])                    // Blob 4
-	generateArtifactManifest(&descs[4], descs[2])                     // Blob 5
-	generateImageManifest(descs[0], &descs[5], descs[3])              // Blob 6
-	generateIndex(&descs[6], descs[4:6]...)                           // Blob 7
-	generateIndex(&descs[4], descs[5:8]...)                           // Blob 8
-
-	eg, egCtx := errgroup.WithContext(ctx)
-	for i := range blobs {
-		eg.Go(func(i int) func() error {
-			return func() error {
-				err := s.Push(egCtx, descs[i], bytes.NewReader(blobs[i]))
-				if err != nil {
-					return fmt.Errorf("failed to push test content to src: %d: %v", i, err)
-				}
-				return nil
-			}
-		}(i))
-	}
-	if err := eg.Wait(); err != nil {
-		t.Fatal(err)
-	}
-
-	// verify predecessors
-	wantedPredecessors := [][]ocispec.Descriptor{
-		{descs[4], descs[6]},           // Blob 0
-		{descs[4]},                     // Blob 1
-		{descs[5]},                     // Blob 2
-		{descs[6]},                     // Blob 3
-		{descs[5], descs[7], descs[8]}, // Blob 4
-		{descs[6], descs[7], descs[8]}, // Blob 5
-		{descs[7], descs[8]},           // Blob 6
-		{descs[8]},                     // Blob 7
-		nil,                            // Blob 8
-	}
-	for i, want := range wantedPredecessors {
-		predecessors, err := s.Predecessors(ctx, descs[i])
-		if err != nil {
-			t.Errorf("Store.Predecessors(%d) error = %v", i, err)
-		}
-		if !equalDescriptorSet(predecessors, want) {
-			t.Errorf("Store.Predecessors(%d) = %v, want %v", i, predecessors, want)
-		}
-	}
-
-	// verify referrers
-	wantedReferrers := [][]ocispec.Descriptor{
-		nil,                  // Blob 0
-		nil,                  // Blob 1
-		nil,                  // Blob 2
-		nil,                  // Blob 3
-		{descs[5], descs[8]}, // Blob 4
-		{descs[6]},           // Blob 5
-		{descs[7]},           // Blob 6
-		nil,                  // Blob 7
-		nil,                  // Blob 8
-	}
-	for i := 4; i < len(wantedReferrers); i++ {
-		want := wantedReferrers[i]
-		var results []ocispec.Descriptor
-		err := registry.Referrers(ctx, s, descs[i], "", func(referrers []ocispec.Descriptor) error {
-			results = append(results, referrers...)
-			return nil
-		})
-		if err != nil {
-			t.Errorf("Store.Referrers(%d) error = %v", i, err)
-		}
-		if !equalDescriptorSet(results, want) {
-			t.Errorf("Store.Predecessors(%d) = %v, want %v", i, results, want)
-		}
-	}
-
-	// test filtering on ArtifactType
-	wantedReferrers = [][]ocispec.Descriptor{
-		nil,        // Blob 0
-		nil,        // Blob 1
-		nil,        // Blob 2
-		nil,        // Blob 3
-		nil,        // Blob 4
-		{descs[6]}, // Blob 5
-		nil,        // Blob 6
-		nil,        // Blob 7
-		nil,        // Blob 8
-	}
-	for i := 4; i < len(wantedReferrers); i++ {
-		want := wantedReferrers[i]
-		var results []ocispec.Descriptor
-		err := registry.Referrers(ctx, s, descs[i], "image manifest", func(referrers []ocispec.Descriptor) error {
-			results = append(results, referrers...)
-			return nil
-		})
-		if err != nil {
-			t.Errorf("Store.Referrers(%d) error = %v", i, err)
-		}
-		if !equalDescriptorSet(results, want) {
-			t.Errorf("Store.Predecessors(%d) = %v, want %v", i, results, want)
-		}
-	}
-}
-
 func equalDescriptorSet(actual []ocispec.Descriptor, expected []ocispec.Descriptor) bool {
 	if len(actual) != len(expected) {
 		return false
diff --git a/registry/repository.go b/registry/repository.go
index 36f73cba..7d22475b 100644
--- a/registry/repository.go
+++ b/registry/repository.go
@@ -23,6 +23,7 @@ import (
 
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"oras.land/oras-go/v2/content"
+	"oras.land/oras-go/v2/errdef"
 	"oras.land/oras-go/v2/internal/descriptor"
 	"oras.land/oras-go/v2/internal/spec"
 )
@@ -148,7 +149,7 @@ func Tags(ctx context.Context, repo TagLister) ([]string, error) {
 // Reference: https://github.com/opencontainers/distribution-spec/blob/v1.1.0-rc3/spec.md#listing-referrers
 func Referrers(ctx context.Context, store content.ReadOnlyGraphStorage, desc ocispec.Descriptor, artifactType string, fn func(referrers []ocispec.Descriptor) error) error {
 	if !descriptor.IsManifest(desc) {
-		return fmt.Errorf("the descriptor %v is not a manifest", desc)
+		return fmt.Errorf("the descriptor %v is not a manifest: %w", desc, errdef.ErrUnsupported)
 	}
 	// use the Referrer API if it is available
 	if rf, ok := store.(ReferrerLister); ok {

From 0b22ea74854dace01aad7a068a57146c843dfb34 Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Wed, 20 Dec 2023 15:46:55 +0800
Subject: [PATCH 04/13] added unit test

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 registry/repository_test.go | 238 ++++++++++++++++++++++++++++++++++++
 1 file changed, 238 insertions(+)
 create mode 100644 registry/repository_test.go

diff --git a/registry/repository_test.go b/registry/repository_test.go
new file mode 100644
index 00000000..d7642063
--- /dev/null
+++ b/registry/repository_test.go
@@ -0,0 +1,238 @@
+/*
+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 registry
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"reflect"
+	"testing"
+
+	"github.com/opencontainers/go-digest"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"golang.org/x/sync/errgroup"
+	"oras.land/oras-go/v2/content/memory"
+	"oras.land/oras-go/v2/internal/spec"
+)
+
+// testStorage implements content.ReadOnlyGraphStorage
+type testStorage struct {
+	store *memory.Store
+}
+
+func (s *testStorage) Push(ctx context.Context, expected ocispec.Descriptor, reader io.Reader) error {
+	return s.store.Push(ctx, expected, reader)
+}
+
+func (s *testStorage) Fetch(ctx context.Context, target ocispec.Descriptor) (io.ReadCloser, error) {
+	return s.store.Fetch(ctx, target)
+}
+
+func (s *testStorage) Exists(ctx context.Context, target ocispec.Descriptor) (bool, error) {
+	return s.store.Exists(ctx, target)
+}
+
+func (s *testStorage) Predecessors(ctx context.Context, node ocispec.Descriptor) ([]ocispec.Descriptor, error) {
+	return s.store.Predecessors(ctx, node)
+}
+
+func TestReferrers(t *testing.T) {
+	s := testStorage{
+		store: memory.New(),
+	}
+	ctx := context.Background()
+
+	// generate test content
+	var blobs [][]byte
+	var descs []ocispec.Descriptor
+	appendBlob := func(mediaType string, artifactType string, blob []byte) {
+		blobs = append(blobs, blob)
+		descs = append(descs, ocispec.Descriptor{
+			MediaType:    mediaType,
+			ArtifactType: artifactType,
+			Annotations:  map[string]string{"test": "content"},
+			Digest:       digest.FromBytes(blob),
+			Size:         int64(len(blob)),
+		})
+	}
+	generateImageManifest := func(config ocispec.Descriptor, subject *ocispec.Descriptor, layers ...ocispec.Descriptor) {
+		manifest := ocispec.Manifest{
+			MediaType:   ocispec.MediaTypeImageManifest,
+			Config:      config,
+			Subject:     subject,
+			Layers:      layers,
+			Annotations: map[string]string{"test": "content"},
+		}
+		manifestJSON, err := json.Marshal(manifest)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(ocispec.MediaTypeImageManifest, manifest.Config.MediaType, manifestJSON)
+	}
+	generateArtifactManifest := func(subject *ocispec.Descriptor, blobs ...ocispec.Descriptor) {
+		artifact := spec.Artifact{
+			MediaType:    spec.MediaTypeArtifactManifest,
+			ArtifactType: "artifact",
+			Subject:      subject,
+			Blobs:        blobs,
+			Annotations:  map[string]string{"test": "content"},
+		}
+		manifestJSON, err := json.Marshal(artifact)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(spec.MediaTypeArtifactManifest, artifact.ArtifactType, manifestJSON)
+	}
+	generateIndex := func(subject *ocispec.Descriptor, manifests ...ocispec.Descriptor) {
+		index := ocispec.Index{
+			MediaType:    ocispec.MediaTypeImageIndex,
+			ArtifactType: "index",
+			Subject:      subject,
+			Manifests:    manifests,
+			Annotations:  map[string]string{"test": "content"},
+		}
+		indexJSON, err := json.Marshal(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(ocispec.MediaTypeImageIndex, index.ArtifactType, indexJSON)
+	}
+
+	appendBlob("image manifest", "image config", []byte("config"))    // Blob 0
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("foo"))   // Blob 1
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("bar"))   // Blob 2
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("hello")) // Blob 3
+	generateImageManifest(descs[0], nil, descs[1])                    // Blob 4
+	generateArtifactManifest(&descs[4], descs[2])                     // Blob 5
+	generateImageManifest(descs[0], &descs[5], descs[3])              // Blob 6
+	generateIndex(&descs[6], descs[4:6]...)                           // Blob 7
+	generateIndex(&descs[4], descs[5:8]...)                           // Blob 8
+
+	eg, egCtx := errgroup.WithContext(ctx)
+	for i := range blobs {
+		eg.Go(func(i int) func() error {
+			return func() error {
+				err := s.Push(egCtx, descs[i], bytes.NewReader(blobs[i]))
+				if err != nil {
+					return fmt.Errorf("failed to push test content to src: %d: %v", i, err)
+				}
+				return nil
+			}
+		}(i))
+	}
+	if err := eg.Wait(); err != nil {
+		t.Fatal(err)
+	}
+
+	// verify predecessors
+	wantedPredecessors := [][]ocispec.Descriptor{
+		{descs[4], descs[6]},           // Blob 0
+		{descs[4]},                     // Blob 1
+		{descs[5]},                     // Blob 2
+		{descs[6]},                     // Blob 3
+		{descs[5], descs[7], descs[8]}, // Blob 4
+		{descs[6], descs[7], descs[8]}, // Blob 5
+		{descs[7], descs[8]},           // Blob 6
+		{descs[8]},                     // Blob 7
+		nil,                            // Blob 8
+	}
+	for i, want := range wantedPredecessors {
+		predecessors, err := s.Predecessors(ctx, descs[i])
+		if err != nil {
+			t.Errorf("Store.Predecessors(%d) error = %v", i, err)
+		}
+		if !equalDescriptorSet(predecessors, want) {
+			t.Errorf("Store.Predecessors(%d) = %v, want %v", i, predecessors, want)
+		}
+	}
+
+	// verify referrers
+	wantedReferrers := [][]ocispec.Descriptor{
+		nil,                  // Blob 0
+		nil,                  // Blob 1
+		nil,                  // Blob 2
+		nil,                  // Blob 3
+		{descs[5], descs[8]}, // Blob 4
+		{descs[6]},           // Blob 5
+		{descs[7]},           // Blob 6
+		nil,                  // Blob 7
+		nil,                  // Blob 8
+	}
+	for i := 4; i < len(wantedReferrers); i++ {
+		want := wantedReferrers[i]
+		var results []ocispec.Descriptor
+		err := Referrers(ctx, &s, descs[i], "", func(referrers []ocispec.Descriptor) error {
+			results = append(results, referrers...)
+			return nil
+		})
+		if err != nil {
+			t.Errorf("Store.Referrers(%d) error = %v", i, err)
+		}
+		if !equalDescriptorSet(results, want) {
+			t.Errorf("Store.Predecessors(%d) = %v, want %v", i, results, want)
+		}
+	}
+
+	// test filtering on ArtifactType
+	wantedReferrers = [][]ocispec.Descriptor{
+		nil,        // Blob 0
+		nil,        // Blob 1
+		nil,        // Blob 2
+		nil,        // Blob 3
+		nil,        // Blob 4
+		{descs[6]}, // Blob 5
+		nil,        // Blob 6
+		nil,        // Blob 7
+		nil,        // Blob 8
+	}
+	for i := 4; i < len(wantedReferrers); i++ {
+		want := wantedReferrers[i]
+		var results []ocispec.Descriptor
+		err := Referrers(ctx, &s, descs[i], "image manifest", func(referrers []ocispec.Descriptor) error {
+			results = append(results, referrers...)
+			return nil
+		})
+		if err != nil {
+			t.Errorf("Store.Referrers(%d) error = %v", i, err)
+		}
+		if !equalDescriptorSet(results, want) {
+			t.Errorf("Store.Predecessors(%d) = %v, want %v", i, results, want)
+		}
+	}
+}
+
+func equalDescriptorSet(actual []ocispec.Descriptor, expected []ocispec.Descriptor) bool {
+	if len(actual) != len(expected) {
+		return false
+	}
+	contains := func(node ocispec.Descriptor) bool {
+		for _, candidate := range actual {
+			if reflect.DeepEqual(candidate, node) {
+				return true
+			}
+		}
+		return false
+	}
+	for _, node := range expected {
+		if !contains(node) {
+			return false
+		}
+	}
+	return true
+}

From a0dccadffba562b31ed6a4d249e772f1fa3554c7 Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Sun, 24 Dec 2023 18:10:02 +0800
Subject: [PATCH 05/13] changed the function signature

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 registry/repository.go      | 44 ++++++++++++++++++++++---------------
 registry/repository_test.go | 12 ++--------
 2 files changed, 28 insertions(+), 28 deletions(-)

diff --git a/registry/repository.go b/registry/repository.go
index 7d22475b..d244f44d 100644
--- a/registry/repository.go
+++ b/registry/repository.go
@@ -143,51 +143,57 @@ func Tags(ctx context.Context, repo TagLister) ([]string, error) {
 // Referrers lists the descriptors of image or artifact manifests directly
 // referencing the given manifest descriptor.
 //
-// fn is called on the referrer results. If artifactType is not empty, only
-// referrers of the same artifact type are fed to fn.
-//
 // Reference: https://github.com/opencontainers/distribution-spec/blob/v1.1.0-rc3/spec.md#listing-referrers
-func Referrers(ctx context.Context, store content.ReadOnlyGraphStorage, desc ocispec.Descriptor, artifactType string, fn func(referrers []ocispec.Descriptor) error) error {
+
+func Referrers(ctx context.Context, store content.ReadOnlyGraphStorage, desc ocispec.Descriptor, artifactType string) ([]ocispec.Descriptor, error) {
 	if !descriptor.IsManifest(desc) {
-		return fmt.Errorf("the descriptor %v is not a manifest: %w", desc, errdef.ErrUnsupported)
+		return nil, fmt.Errorf("the descriptor %v is not a manifest: %w", desc, errdef.ErrUnsupported)
 	}
+
+	var results []ocispec.Descriptor
+
 	// use the Referrer API if it is available
 	if rf, ok := store.(ReferrerLister); ok {
-		return rf.Referrers(ctx, desc, artifactType, fn)
+		if err := rf.Referrers(ctx, desc, artifactType, func(referrers []ocispec.Descriptor) error {
+			results = append(results, referrers...)
+			return nil
+		}); err != nil {
+			return nil, err
+		}
+		return results, nil
 	}
-	var results []ocispec.Descriptor
+
 	predecessors, err := store.Predecessors(ctx, desc)
 	if err != nil {
-		return err
+		return nil, err
 	}
 	for _, node := range predecessors {
 		switch node.MediaType {
 		case ocispec.MediaTypeImageManifest:
 			fetched, err := content.FetchAll(ctx, store, node)
 			if err != nil {
-				return err
+				return nil, err
 			}
 			var manifest ocispec.Manifest
 			if err := json.Unmarshal(fetched, &manifest); err != nil {
-				return err
+				return nil, err
 			}
 			if manifest.Subject == nil || !content.Equal(*manifest.Subject, desc) {
 				continue
 			}
-			if manifest.ArtifactType != "" {
-				node.ArtifactType = manifest.ArtifactType
-			} else {
+			node.ArtifactType = manifest.ArtifactType
+			if node.ArtifactType == "" {
 				node.ArtifactType = manifest.Config.MediaType
 			}
 			node.Annotations = manifest.Annotations
 		case ocispec.MediaTypeImageIndex:
 			fetched, err := content.FetchAll(ctx, store, node)
 			if err != nil {
-				return err
+				return nil, err
 			}
 			var index ocispec.Index
 			if err := json.Unmarshal(fetched, &index); err != nil {
-				return err
+				return nil, err
 			}
 			if index.Subject == nil || !content.Equal(*index.Subject, desc) {
 				continue
@@ -197,11 +203,11 @@ func Referrers(ctx context.Context, store content.ReadOnlyGraphStorage, desc oci
 		case spec.MediaTypeArtifactManifest:
 			fetched, err := content.FetchAll(ctx, store, node)
 			if err != nil {
-				return err
+				return nil, err
 			}
 			var artifact spec.Artifact
 			if err := json.Unmarshal(fetched, &artifact); err != nil {
-				return err
+				return nil, err
 			}
 			if artifact.Subject == nil || !content.Equal(*artifact.Subject, desc) {
 				continue
@@ -212,8 +218,10 @@ func Referrers(ctx context.Context, store content.ReadOnlyGraphStorage, desc oci
 			continue
 		}
 		if artifactType == "" || artifactType == node.ArtifactType {
+			// the field artifactType in referrers descriptor is allowed to be empty
+			// https://github.com/opencontainers/distribution-spec/issues/458
 			results = append(results, node)
 		}
 	}
-	return fn(results)
+	return results, nil
 }
diff --git a/registry/repository_test.go b/registry/repository_test.go
index d7642063..8a138441 100644
--- a/registry/repository_test.go
+++ b/registry/repository_test.go
@@ -176,11 +176,7 @@ func TestReferrers(t *testing.T) {
 	}
 	for i := 4; i < len(wantedReferrers); i++ {
 		want := wantedReferrers[i]
-		var results []ocispec.Descriptor
-		err := Referrers(ctx, &s, descs[i], "", func(referrers []ocispec.Descriptor) error {
-			results = append(results, referrers...)
-			return nil
-		})
+		results, err := Referrers(ctx, &s, descs[i], "")
 		if err != nil {
 			t.Errorf("Store.Referrers(%d) error = %v", i, err)
 		}
@@ -203,11 +199,7 @@ func TestReferrers(t *testing.T) {
 	}
 	for i := 4; i < len(wantedReferrers); i++ {
 		want := wantedReferrers[i]
-		var results []ocispec.Descriptor
-		err := Referrers(ctx, &s, descs[i], "image manifest", func(referrers []ocispec.Descriptor) error {
-			results = append(results, referrers...)
-			return nil
-		})
+		results, err := Referrers(ctx, &s, descs[i], "image manifest")
 		if err != nil {
 			t.Errorf("Store.Referrers(%d) error = %v", i, err)
 		}

From 7ec19a16a840faddb95ef90a7e60f9d1e253a26f Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Sun, 24 Dec 2023 19:33:03 +0800
Subject: [PATCH 06/13] added test cases

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 registry/repository_test.go | 77 ++++++++++++++++++++++++++++++++-----
 1 file changed, 68 insertions(+), 9 deletions(-)

diff --git a/registry/repository_test.go b/registry/repository_test.go
index 8a138441..dcb71487 100644
--- a/registry/repository_test.go
+++ b/registry/repository_test.go
@@ -19,6 +19,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"reflect"
@@ -28,6 +29,8 @@ import (
 	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
 	"golang.org/x/sync/errgroup"
 	"oras.land/oras-go/v2/content/memory"
+	"oras.land/oras-go/v2/errdef"
+	"oras.land/oras-go/v2/internal/docker"
 	"oras.land/oras-go/v2/internal/spec"
 )
 
@@ -52,6 +55,16 @@ func (s *testStorage) Predecessors(ctx context.Context, node ocispec.Descriptor)
 	return s.store.Predecessors(ctx, node)
 }
 
+// TestReferrerLister implements content.ReadOnlyGraphStorage and registry.ReferrerLister
+type TestReferrerLister struct {
+	*testStorage
+}
+
+func (rl *TestReferrerLister) Referrers(ctx context.Context, desc ocispec.Descriptor, artifactType string, fn func(referrers []ocispec.Descriptor) error) error {
+	results := []ocispec.Descriptor{desc}
+	return fn(results)
+}
+
 func TestReferrers(t *testing.T) {
 	s := testStorage{
 		store: memory.New(),
@@ -113,6 +126,17 @@ func TestReferrers(t *testing.T) {
 		}
 		appendBlob(ocispec.MediaTypeImageIndex, index.ArtifactType, indexJSON)
 	}
+	generateManifestList := func(manifests ...ocispec.Descriptor) {
+		index := ocispec.Index{
+			ArtifactType: "manifest list",
+			Manifests:    manifests,
+		}
+		indexJSON, err := json.Marshal(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(docker.MediaTypeManifestList, index.ArtifactType, indexJSON)
+	}
 
 	appendBlob("image manifest", "image config", []byte("config"))    // Blob 0
 	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("foo"))   // Blob 1
@@ -123,6 +147,7 @@ func TestReferrers(t *testing.T) {
 	generateImageManifest(descs[0], &descs[5], descs[3])              // Blob 6
 	generateIndex(&descs[6], descs[4:6]...)                           // Blob 7
 	generateIndex(&descs[4], descs[5:8]...)                           // Blob 8
+	generateManifestList(descs[4:7]...)                               // blob 9
 
 	eg, egCtx := errgroup.WithContext(ctx)
 	for i := range blobs {
@@ -142,15 +167,16 @@ func TestReferrers(t *testing.T) {
 
 	// verify predecessors
 	wantedPredecessors := [][]ocispec.Descriptor{
-		{descs[4], descs[6]},           // Blob 0
-		{descs[4]},                     // Blob 1
-		{descs[5]},                     // Blob 2
-		{descs[6]},                     // Blob 3
-		{descs[5], descs[7], descs[8]}, // Blob 4
-		{descs[6], descs[7], descs[8]}, // Blob 5
-		{descs[7], descs[8]},           // Blob 6
-		{descs[8]},                     // Blob 7
-		nil,                            // Blob 8
+		{descs[4], descs[6]},                     // Blob 0
+		{descs[4]},                               // Blob 1
+		{descs[5]},                               // Blob 2
+		{descs[6]},                               // Blob 3
+		{descs[5], descs[7], descs[8], descs[9]}, // Blob 4
+		{descs[6], descs[7], descs[8], descs[9]}, // Blob 5
+		{descs[7], descs[8], descs[9]},           // Blob 6
+		{descs[8]},                               // Blob 7
+		nil,                                      // Blob 8
+		nil,                                      // Blob 9
 	}
 	for i, want := range wantedPredecessors {
 		predecessors, err := s.Predecessors(ctx, descs[i])
@@ -173,6 +199,13 @@ func TestReferrers(t *testing.T) {
 		{descs[7]},           // Blob 6
 		nil,                  // Blob 7
 		nil,                  // Blob 8
+		nil,                  // Blob 9
+	}
+	for i := 0; i <= 3; i++ {
+		_, err := Referrers(ctx, &s, descs[i], "")
+		if !errors.Is(err, errdef.ErrUnsupported) {
+			t.Errorf("Store.Referrers(%d) error = %v, want %v", i, err, errdef.ErrUnsupported)
+		}
 	}
 	for i := 4; i < len(wantedReferrers); i++ {
 		want := wantedReferrers[i]
@@ -196,6 +229,7 @@ func TestReferrers(t *testing.T) {
 		nil,        // Blob 6
 		nil,        // Blob 7
 		nil,        // Blob 8
+		nil,        // Blob 9
 	}
 	for i := 4; i < len(wantedReferrers); i++ {
 		want := wantedReferrers[i]
@@ -207,6 +241,31 @@ func TestReferrers(t *testing.T) {
 			t.Errorf("Store.Predecessors(%d) = %v, want %v", i, results, want)
 		}
 	}
+
+	// test ReferrerLister
+	rl := TestReferrerLister{testStorage: &s}
+	wantedReferrers = [][]ocispec.Descriptor{
+		nil,        // Blob 0
+		nil,        // Blob 1
+		nil,        // Blob 2
+		nil,        // Blob 3
+		{descs[4]}, // Blob 4
+		{descs[5]}, // Blob 5
+		{descs[6]}, // Blob 6
+		{descs[7]}, // Blob 7
+		{descs[8]}, // Blob 8
+		{descs[9]}, // Blob 9
+	}
+	for i := 4; i < len(wantedReferrers); i++ {
+		want := wantedReferrers[i]
+		results, err := Referrers(ctx, &rl, descs[i], "")
+		if err != nil {
+			t.Errorf("Store.Referrers(%d) error = %v", i, err)
+		}
+		if !equalDescriptorSet(results, want) {
+			t.Errorf("Store.Predecessors(%d) = %v, want %v", i, results, want)
+		}
+	}
 }
 
 func equalDescriptorSet(actual []ocispec.Descriptor, expected []ocispec.Descriptor) bool {

From 70afd23369014987eb347c18e595932a33b1ca93 Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Mon, 25 Dec 2023 10:03:19 +0800
Subject: [PATCH 07/13] removed empty line

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 registry/repository.go | 1 -
 1 file changed, 1 deletion(-)

diff --git a/registry/repository.go b/registry/repository.go
index d244f44d..394a9aa8 100644
--- a/registry/repository.go
+++ b/registry/repository.go
@@ -144,7 +144,6 @@ func Tags(ctx context.Context, repo TagLister) ([]string, error) {
 // referencing the given manifest descriptor.
 //
 // Reference: https://github.com/opencontainers/distribution-spec/blob/v1.1.0-rc3/spec.md#listing-referrers
-
 func Referrers(ctx context.Context, store content.ReadOnlyGraphStorage, desc ocispec.Descriptor, artifactType string) ([]ocispec.Descriptor, error) {
 	if !descriptor.IsManifest(desc) {
 		return nil, fmt.Errorf("the descriptor %v is not a manifest: %w", desc, errdef.ErrUnsupported)

From dea20f832dd06d801af07d866667a949aa8c2b5b Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Tue, 26 Dec 2023 13:48:29 +0800
Subject: [PATCH 08/13] increase coverage

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 registry/repository_test.go | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/registry/repository_test.go b/registry/repository_test.go
index dcb71487..18411893 100644
--- a/registry/repository_test.go
+++ b/registry/repository_test.go
@@ -148,6 +148,7 @@ func TestReferrers(t *testing.T) {
 	generateIndex(&descs[6], descs[4:6]...)                           // Blob 7
 	generateIndex(&descs[4], descs[5:8]...)                           // Blob 8
 	generateManifestList(descs[4:7]...)                               // blob 9
+	generateImageManifest(descs[0], nil, descs[4])                    // Blob 10
 
 	eg, egCtx := errgroup.WithContext(ctx)
 	for i := range blobs {
@@ -167,16 +168,16 @@ func TestReferrers(t *testing.T) {
 
 	// verify predecessors
 	wantedPredecessors := [][]ocispec.Descriptor{
-		{descs[4], descs[6]},                     // Blob 0
-		{descs[4]},                               // Blob 1
-		{descs[5]},                               // Blob 2
-		{descs[6]},                               // Blob 3
-		{descs[5], descs[7], descs[8], descs[9]}, // Blob 4
-		{descs[6], descs[7], descs[8], descs[9]}, // Blob 5
-		{descs[7], descs[8], descs[9]},           // Blob 6
-		{descs[8]},                               // Blob 7
-		nil,                                      // Blob 8
-		nil,                                      // Blob 9
+		{descs[4], descs[6], descs[10]}, // Blob 0
+		{descs[4]},                      // Blob 1
+		{descs[5]},                      // Blob 2
+		{descs[6]},                      // Blob 3
+		{descs[5], descs[7], descs[8], descs[9], descs[10]}, // Blob 4
+		{descs[6], descs[7], descs[8], descs[9]},            // Blob 5
+		{descs[7], descs[8], descs[9]},                      // Blob 6
+		{descs[8]},                                          // Blob 7
+		nil,                                                 // Blob 8
+		nil,                                                 // Blob 9
 	}
 	for i, want := range wantedPredecessors {
 		predecessors, err := s.Predecessors(ctx, descs[i])

From 4e6c66fba276edb167fff2733bfdcb293d2b740e Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Tue, 26 Dec 2023 13:54:06 +0800
Subject: [PATCH 09/13] increase converage

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 registry/repository_test.go | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/registry/repository_test.go b/registry/repository_test.go
index 18411893..1e1ca16e 100644
--- a/registry/repository_test.go
+++ b/registry/repository_test.go
@@ -149,6 +149,7 @@ func TestReferrers(t *testing.T) {
 	generateIndex(&descs[4], descs[5:8]...)                           // Blob 8
 	generateManifestList(descs[4:7]...)                               // blob 9
 	generateImageManifest(descs[0], nil, descs[4])                    // Blob 10
+	generateArtifactManifest(nil, descs[5])                           // Blob 11
 
 	eg, egCtx := errgroup.WithContext(ctx)
 	for i := range blobs {
@@ -173,7 +174,7 @@ func TestReferrers(t *testing.T) {
 		{descs[5]},                      // Blob 2
 		{descs[6]},                      // Blob 3
 		{descs[5], descs[7], descs[8], descs[9], descs[10]}, // Blob 4
-		{descs[6], descs[7], descs[8], descs[9]},            // Blob 5
+		{descs[6], descs[7], descs[8], descs[9], descs[11]}, // Blob 5
 		{descs[7], descs[8], descs[9]},                      // Blob 6
 		{descs[8]},                                          // Blob 7
 		nil,                                                 // Blob 8

From ba808c788810b66cf5a84b23f19fe19e2e59805e Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Tue, 26 Dec 2023 17:03:00 +0800
Subject: [PATCH 10/13] increase coverage

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 registry/repository_test.go | 138 ++++++++++++++++++++++++++++++++----
 1 file changed, 126 insertions(+), 12 deletions(-)

diff --git a/registry/repository_test.go b/registry/repository_test.go
index 1e1ca16e..8d025101 100644
--- a/registry/repository_test.go
+++ b/registry/repository_test.go
@@ -30,13 +30,17 @@ import (
 	"golang.org/x/sync/errgroup"
 	"oras.land/oras-go/v2/content/memory"
 	"oras.land/oras-go/v2/errdef"
+	"oras.land/oras-go/v2/internal/container/set"
 	"oras.land/oras-go/v2/internal/docker"
 	"oras.land/oras-go/v2/internal/spec"
 )
 
+var ErrBadFetch = errors.New("bad fetch error")
+
 // testStorage implements content.ReadOnlyGraphStorage
 type testStorage struct {
-	store *memory.Store
+	store     *memory.Store
+	badValues set.Set[digest.Digest]
 }
 
 func (s *testStorage) Push(ctx context.Context, expected ocispec.Descriptor, reader io.Reader) error {
@@ -44,6 +48,9 @@ func (s *testStorage) Push(ctx context.Context, expected ocispec.Descriptor, rea
 }
 
 func (s *testStorage) Fetch(ctx context.Context, target ocispec.Descriptor) (io.ReadCloser, error) {
+	if s.badValues.Contains(target.Digest) {
+		return nil, ErrBadFetch
+	}
 	return s.store.Fetch(ctx, target)
 }
 
@@ -67,7 +74,8 @@ func (rl *TestReferrerLister) Referrers(ctx context.Context, desc ocispec.Descri
 
 func TestReferrers(t *testing.T) {
 	s := testStorage{
-		store: memory.New(),
+		store:     memory.New(),
+		badValues: set.New[digest.Digest](),
 	}
 	ctx := context.Background()
 
@@ -179,6 +187,8 @@ func TestReferrers(t *testing.T) {
 		{descs[8]},                                          // Blob 7
 		nil,                                                 // Blob 8
 		nil,                                                 // Blob 9
+		nil,                                                 // Blob 10
+		nil,                                                 // Blob 11
 	}
 	for i, want := range wantedPredecessors {
 		predecessors, err := s.Predecessors(ctx, descs[i])
@@ -202,6 +212,8 @@ func TestReferrers(t *testing.T) {
 		nil,                  // Blob 7
 		nil,                  // Blob 8
 		nil,                  // Blob 9
+		nil,                  // Blob 10
+		nil,                  // Blob 11
 	}
 	for i := 0; i <= 3; i++ {
 		_, err := Referrers(ctx, &s, descs[i], "")
@@ -232,6 +244,8 @@ func TestReferrers(t *testing.T) {
 		nil,        // Blob 7
 		nil,        // Blob 8
 		nil,        // Blob 9
+		nil,        // Blob 10
+		nil,        // Blob 11
 	}
 	for i := 4; i < len(wantedReferrers); i++ {
 		want := wantedReferrers[i]
@@ -247,16 +261,18 @@ func TestReferrers(t *testing.T) {
 	// test ReferrerLister
 	rl := TestReferrerLister{testStorage: &s}
 	wantedReferrers = [][]ocispec.Descriptor{
-		nil,        // Blob 0
-		nil,        // Blob 1
-		nil,        // Blob 2
-		nil,        // Blob 3
-		{descs[4]}, // Blob 4
-		{descs[5]}, // Blob 5
-		{descs[6]}, // Blob 6
-		{descs[7]}, // Blob 7
-		{descs[8]}, // Blob 8
-		{descs[9]}, // Blob 9
+		nil,         // Blob 0
+		nil,         // Blob 1
+		nil,         // Blob 2
+		nil,         // Blob 3
+		{descs[4]},  // Blob 4
+		{descs[5]},  // Blob 5
+		{descs[6]},  // Blob 6
+		{descs[7]},  // Blob 7
+		{descs[8]},  // Blob 8
+		{descs[9]},  // Blob 9
+		{descs[10]}, // Blob 10
+		{descs[11]}, // Blob 11
 	}
 	for i := 4; i < len(wantedReferrers); i++ {
 		want := wantedReferrers[i]
@@ -270,6 +286,104 @@ func TestReferrers(t *testing.T) {
 	}
 }
 
+func TestReferrers_BadFetch(t *testing.T) {
+	s := testStorage{
+		store:     memory.New(),
+		badValues: set.New[digest.Digest](),
+	}
+	ctx := context.Background()
+
+	// generate test content
+	var blobs [][]byte
+	var descs []ocispec.Descriptor
+	appendBlob := func(mediaType string, artifactType string, blob []byte) {
+		blobs = append(blobs, blob)
+		descs = append(descs, ocispec.Descriptor{
+			MediaType:    mediaType,
+			ArtifactType: artifactType,
+			Annotations:  map[string]string{"test": "content"},
+			Digest:       digest.FromBytes(blob),
+			Size:         int64(len(blob)),
+		})
+	}
+	generateImageManifest := func(config ocispec.Descriptor, subject *ocispec.Descriptor, layers ...ocispec.Descriptor) {
+		manifest := ocispec.Manifest{
+			MediaType:   ocispec.MediaTypeImageManifest,
+			Config:      config,
+			Subject:     subject,
+			Layers:      layers,
+			Annotations: map[string]string{"test": "content"},
+		}
+		manifestJSON, err := json.Marshal(manifest)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(ocispec.MediaTypeImageManifest, manifest.Config.MediaType, manifestJSON)
+	}
+	generateArtifactManifest := func(subject *ocispec.Descriptor, blobs ...ocispec.Descriptor) {
+		artifact := spec.Artifact{
+			MediaType:    spec.MediaTypeArtifactManifest,
+			ArtifactType: "artifact",
+			Subject:      subject,
+			Blobs:        blobs,
+			Annotations:  map[string]string{"test": "content"},
+		}
+		manifestJSON, err := json.Marshal(artifact)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(spec.MediaTypeArtifactManifest, artifact.ArtifactType, manifestJSON)
+	}
+	generateIndex := func(subject *ocispec.Descriptor, manifests ...ocispec.Descriptor) {
+		index := ocispec.Index{
+			MediaType:    ocispec.MediaTypeImageIndex,
+			ArtifactType: "index",
+			Subject:      subject,
+			Manifests:    manifests,
+			Annotations:  map[string]string{"test": "content"},
+		}
+		indexJSON, err := json.Marshal(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(ocispec.MediaTypeImageIndex, index.ArtifactType, indexJSON)
+	}
+	appendBlob("image manifest", "image config", []byte("config"))    // Blob 0
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("foo"))   // Blob 1
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("bar"))   // Blob 2
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("hello")) // Blob 3
+	generateImageManifest(descs[0], nil, descs[1])                    // Blob 4
+	generateImageManifest(descs[0], &descs[4], descs[2])              // Blob 5
+	generateArtifactManifest(&descs[5], descs[3])                     // Blob 6
+	generateIndex(&descs[6], descs[5:8]...)                           // Blob 7
+	s.badValues.Add(descs[5].Digest)
+	s.badValues.Add(descs[6].Digest)
+	s.badValues.Add(descs[7].Digest)
+
+	eg, egCtx := errgroup.WithContext(ctx)
+	for i := range blobs {
+		eg.Go(func(i int) func() error {
+			return func() error {
+				err := s.Push(egCtx, descs[i], bytes.NewReader(blobs[i]))
+				if err != nil {
+					return fmt.Errorf("failed to push test content to src: %d: %v", i, err)
+				}
+				return nil
+			}
+		}(i))
+	}
+	if err := eg.Wait(); err != nil {
+		t.Fatal(err)
+	}
+
+	for i := 4; i < 7; i++ {
+		_, err := Referrers(ctx, &s, descs[i], "")
+		if !errors.Is(err, ErrBadFetch) {
+			t.Errorf("Store.Referrers(%d) error = %v, want %v", i, err, ErrBadFetch)
+		}
+	}
+}
+
 func equalDescriptorSet(actual []ocispec.Descriptor, expected []ocispec.Descriptor) bool {
 	if len(actual) != len(expected) {
 		return false

From d29c51ac56386d8db25e205f5679ff731060176a Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Tue, 26 Dec 2023 17:16:28 +0800
Subject: [PATCH 11/13] increase coverage

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 registry/repository_test.go | 125 +++++++++++++++++++++++++++++++++---
 1 file changed, 115 insertions(+), 10 deletions(-)

diff --git a/registry/repository_test.go b/registry/repository_test.go
index 8d025101..efeb6d4e 100644
--- a/registry/repository_test.go
+++ b/registry/repository_test.go
@@ -39,8 +39,9 @@ var ErrBadFetch = errors.New("bad fetch error")
 
 // testStorage implements content.ReadOnlyGraphStorage
 type testStorage struct {
-	store     *memory.Store
-	badValues set.Set[digest.Digest]
+	store    *memory.Store
+	badFetch set.Set[digest.Digest]
+	badJson  set.Set[digest.Digest]
 }
 
 func (s *testStorage) Push(ctx context.Context, expected ocispec.Descriptor, reader io.Reader) error {
@@ -48,9 +49,12 @@ func (s *testStorage) Push(ctx context.Context, expected ocispec.Descriptor, rea
 }
 
 func (s *testStorage) Fetch(ctx context.Context, target ocispec.Descriptor) (io.ReadCloser, error) {
-	if s.badValues.Contains(target.Digest) {
+	if s.badFetch.Contains(target.Digest) {
 		return nil, ErrBadFetch
 	}
+	if s.badJson.Contains(target.Digest) {
+		return io.NopCloser(bytes.NewReader([]byte("bad json"))), nil
+	}
 	return s.store.Fetch(ctx, target)
 }
 
@@ -74,8 +78,9 @@ func (rl *TestReferrerLister) Referrers(ctx context.Context, desc ocispec.Descri
 
 func TestReferrers(t *testing.T) {
 	s := testStorage{
-		store:     memory.New(),
-		badValues: set.New[digest.Digest](),
+		store:    memory.New(),
+		badFetch: set.New[digest.Digest](),
+		badJson:  set.New[digest.Digest](),
 	}
 	ctx := context.Background()
 
@@ -288,8 +293,9 @@ func TestReferrers(t *testing.T) {
 
 func TestReferrers_BadFetch(t *testing.T) {
 	s := testStorage{
-		store:     memory.New(),
-		badValues: set.New[digest.Digest](),
+		store:    memory.New(),
+		badFetch: set.New[digest.Digest](),
+		badJson:  set.New[digest.Digest](),
 	}
 	ctx := context.Background()
 
@@ -356,9 +362,9 @@ func TestReferrers_BadFetch(t *testing.T) {
 	generateImageManifest(descs[0], &descs[4], descs[2])              // Blob 5
 	generateArtifactManifest(&descs[5], descs[3])                     // Blob 6
 	generateIndex(&descs[6], descs[5:8]...)                           // Blob 7
-	s.badValues.Add(descs[5].Digest)
-	s.badValues.Add(descs[6].Digest)
-	s.badValues.Add(descs[7].Digest)
+	s.badFetch.Add(descs[5].Digest)
+	s.badFetch.Add(descs[6].Digest)
+	s.badFetch.Add(descs[7].Digest)
 
 	eg, egCtx := errgroup.WithContext(ctx)
 	for i := range blobs {
@@ -384,6 +390,105 @@ func TestReferrers_BadFetch(t *testing.T) {
 	}
 }
 
+func TestReferrers_BadJson(t *testing.T) {
+	s := testStorage{
+		store:    memory.New(),
+		badFetch: set.New[digest.Digest](),
+		badJson:  set.New[digest.Digest](),
+	}
+	ctx := context.Background()
+
+	// generate test content
+	var blobs [][]byte
+	var descs []ocispec.Descriptor
+	appendBlob := func(mediaType string, artifactType string, blob []byte) {
+		blobs = append(blobs, blob)
+		descs = append(descs, ocispec.Descriptor{
+			MediaType:    mediaType,
+			ArtifactType: artifactType,
+			Annotations:  map[string]string{"test": "content"},
+			Digest:       digest.FromBytes(blob),
+			Size:         int64(len(blob)),
+		})
+	}
+	generateImageManifest := func(config ocispec.Descriptor, subject *ocispec.Descriptor, layers ...ocispec.Descriptor) {
+		manifest := ocispec.Manifest{
+			MediaType:   ocispec.MediaTypeImageManifest,
+			Config:      config,
+			Subject:     subject,
+			Layers:      layers,
+			Annotations: map[string]string{"test": "content"},
+		}
+		manifestJSON, err := json.Marshal(manifest)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(ocispec.MediaTypeImageManifest, manifest.Config.MediaType, manifestJSON)
+	}
+	generateArtifactManifest := func(subject *ocispec.Descriptor, blobs ...ocispec.Descriptor) {
+		artifact := spec.Artifact{
+			MediaType:    spec.MediaTypeArtifactManifest,
+			ArtifactType: "artifact",
+			Subject:      subject,
+			Blobs:        blobs,
+			Annotations:  map[string]string{"test": "content"},
+		}
+		manifestJSON, err := json.Marshal(artifact)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(spec.MediaTypeArtifactManifest, artifact.ArtifactType, manifestJSON)
+	}
+	generateIndex := func(subject *ocispec.Descriptor, manifests ...ocispec.Descriptor) {
+		index := ocispec.Index{
+			MediaType:    ocispec.MediaTypeImageIndex,
+			ArtifactType: "index",
+			Subject:      subject,
+			Manifests:    manifests,
+			Annotations:  map[string]string{"test": "content"},
+		}
+		indexJSON, err := json.Marshal(index)
+		if err != nil {
+			t.Fatal(err)
+		}
+		appendBlob(ocispec.MediaTypeImageIndex, index.ArtifactType, indexJSON)
+	}
+	appendBlob("image manifest", "image config", []byte("config"))    // Blob 0
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("foo"))   // Blob 1
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("bar"))   // Blob 2
+	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("hello")) // Blob 3
+	generateImageManifest(descs[0], nil, descs[1])                    // Blob 4
+	generateImageManifest(descs[0], &descs[4], descs[2])              // Blob 5
+	generateArtifactManifest(&descs[5], descs[3])                     // Blob 6
+	generateIndex(&descs[6], descs[5:8]...)                           // Blob 7
+	s.badJson.Add(descs[5].Digest)
+	s.badJson.Add(descs[6].Digest)
+	s.badJson.Add(descs[7].Digest)
+
+	eg, egCtx := errgroup.WithContext(ctx)
+	for i := range blobs {
+		eg.Go(func(i int) func() error {
+			return func() error {
+				err := s.Push(egCtx, descs[i], bytes.NewReader(blobs[i]))
+				if err != nil {
+					return fmt.Errorf("failed to push test content to src: %d: %v", i, err)
+				}
+				return nil
+			}
+		}(i))
+	}
+	if err := eg.Wait(); err != nil {
+		t.Fatal(err)
+	}
+
+	for i := 4; i < 7; i++ {
+		_, err := Referrers(ctx, &s, descs[i], "")
+		if err == nil {
+			t.Errorf("Store.Referrers(%d) error = %v, want Json Unmarshall error", i, err)
+		}
+	}
+}
+
 func equalDescriptorSet(actual []ocispec.Descriptor, expected []ocispec.Descriptor) bool {
 	if len(actual) != len(expected) {
 		return false

From 8b7299c4d1aed21825463fb5fd8c1498c7a3d5fd Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Tue, 26 Dec 2023 17:40:33 +0800
Subject: [PATCH 12/13] increase coverage

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 registry/repository_test.go | 192 ++++++++++++++++++------------------
 1 file changed, 96 insertions(+), 96 deletions(-)

diff --git a/registry/repository_test.go b/registry/repository_test.go
index efeb6d4e..4a7626d3 100644
--- a/registry/repository_test.go
+++ b/registry/repository_test.go
@@ -361,7 +361,7 @@ func TestReferrers_BadFetch(t *testing.T) {
 	generateImageManifest(descs[0], nil, descs[1])                    // Blob 4
 	generateImageManifest(descs[0], &descs[4], descs[2])              // Blob 5
 	generateArtifactManifest(&descs[5], descs[3])                     // Blob 6
-	generateIndex(&descs[6], descs[5:8]...)                           // Blob 7
+	generateIndex(&descs[6])                                          // Blob 7
 	s.badFetch.Add(descs[5].Digest)
 	s.badFetch.Add(descs[6].Digest)
 	s.badFetch.Add(descs[7].Digest)
@@ -390,104 +390,104 @@ func TestReferrers_BadFetch(t *testing.T) {
 	}
 }
 
-func TestReferrers_BadJson(t *testing.T) {
-	s := testStorage{
-		store:    memory.New(),
-		badFetch: set.New[digest.Digest](),
-		badJson:  set.New[digest.Digest](),
-	}
-	ctx := context.Background()
+// func TestReferrers_BadJson(t *testing.T) {
+// 	s := testStorage{
+// 		store:    memory.New(),
+// 		badFetch: set.New[digest.Digest](),
+// 		badJson:  set.New[digest.Digest](),
+// 	}
+// 	ctx := context.Background()
 
-	// generate test content
-	var blobs [][]byte
-	var descs []ocispec.Descriptor
-	appendBlob := func(mediaType string, artifactType string, blob []byte) {
-		blobs = append(blobs, blob)
-		descs = append(descs, ocispec.Descriptor{
-			MediaType:    mediaType,
-			ArtifactType: artifactType,
-			Annotations:  map[string]string{"test": "content"},
-			Digest:       digest.FromBytes(blob),
-			Size:         int64(len(blob)),
-		})
-	}
-	generateImageManifest := func(config ocispec.Descriptor, subject *ocispec.Descriptor, layers ...ocispec.Descriptor) {
-		manifest := ocispec.Manifest{
-			MediaType:   ocispec.MediaTypeImageManifest,
-			Config:      config,
-			Subject:     subject,
-			Layers:      layers,
-			Annotations: map[string]string{"test": "content"},
-		}
-		manifestJSON, err := json.Marshal(manifest)
-		if err != nil {
-			t.Fatal(err)
-		}
-		appendBlob(ocispec.MediaTypeImageManifest, manifest.Config.MediaType, manifestJSON)
-	}
-	generateArtifactManifest := func(subject *ocispec.Descriptor, blobs ...ocispec.Descriptor) {
-		artifact := spec.Artifact{
-			MediaType:    spec.MediaTypeArtifactManifest,
-			ArtifactType: "artifact",
-			Subject:      subject,
-			Blobs:        blobs,
-			Annotations:  map[string]string{"test": "content"},
-		}
-		manifestJSON, err := json.Marshal(artifact)
-		if err != nil {
-			t.Fatal(err)
-		}
-		appendBlob(spec.MediaTypeArtifactManifest, artifact.ArtifactType, manifestJSON)
-	}
-	generateIndex := func(subject *ocispec.Descriptor, manifests ...ocispec.Descriptor) {
-		index := ocispec.Index{
-			MediaType:    ocispec.MediaTypeImageIndex,
-			ArtifactType: "index",
-			Subject:      subject,
-			Manifests:    manifests,
-			Annotations:  map[string]string{"test": "content"},
-		}
-		indexJSON, err := json.Marshal(index)
-		if err != nil {
-			t.Fatal(err)
-		}
-		appendBlob(ocispec.MediaTypeImageIndex, index.ArtifactType, indexJSON)
-	}
-	appendBlob("image manifest", "image config", []byte("config"))    // Blob 0
-	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("foo"))   // Blob 1
-	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("bar"))   // Blob 2
-	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("hello")) // Blob 3
-	generateImageManifest(descs[0], nil, descs[1])                    // Blob 4
-	generateImageManifest(descs[0], &descs[4], descs[2])              // Blob 5
-	generateArtifactManifest(&descs[5], descs[3])                     // Blob 6
-	generateIndex(&descs[6], descs[5:8]...)                           // Blob 7
-	s.badJson.Add(descs[5].Digest)
-	s.badJson.Add(descs[6].Digest)
-	s.badJson.Add(descs[7].Digest)
+// 	// generate test content
+// 	var blobs [][]byte
+// 	var descs []ocispec.Descriptor
+// 	appendBlob := func(mediaType string, artifactType string, blob []byte) {
+// 		blobs = append(blobs, blob)
+// 		descs = append(descs, ocispec.Descriptor{
+// 			MediaType:    mediaType,
+// 			ArtifactType: artifactType,
+// 			Annotations:  map[string]string{"test": "content"},
+// 			Digest:       digest.FromBytes(blob),
+// 			Size:         int64(len(blob)),
+// 		})
+// 	}
+// 	generateImageManifest := func(config ocispec.Descriptor, subject *ocispec.Descriptor, layers ...ocispec.Descriptor) {
+// 		manifest := ocispec.Manifest{
+// 			MediaType:   ocispec.MediaTypeImageManifest,
+// 			Config:      config,
+// 			Subject:     subject,
+// 			Layers:      layers,
+// 			Annotations: map[string]string{"test": "content"},
+// 		}
+// 		manifestJSON, err := json.Marshal(manifest)
+// 		if err != nil {
+// 			t.Fatal(err)
+// 		}
+// 		appendBlob(ocispec.MediaTypeImageManifest, manifest.Config.MediaType, manifestJSON)
+// 	}
+// 	generateArtifactManifest := func(subject *ocispec.Descriptor, blobs ...ocispec.Descriptor) {
+// 		artifact := spec.Artifact{
+// 			MediaType:    spec.MediaTypeArtifactManifest,
+// 			ArtifactType: "artifact",
+// 			Subject:      subject,
+// 			Blobs:        blobs,
+// 			Annotations:  map[string]string{"test": "content"},
+// 		}
+// 		manifestJSON, err := json.Marshal(artifact)
+// 		if err != nil {
+// 			t.Fatal(err)
+// 		}
+// 		appendBlob(spec.MediaTypeArtifactManifest, artifact.ArtifactType, manifestJSON)
+// 	}
+// 	generateIndex := func(subject *ocispec.Descriptor, manifests ...ocispec.Descriptor) {
+// 		index := ocispec.Index{
+// 			MediaType:    ocispec.MediaTypeImageIndex,
+// 			ArtifactType: "index",
+// 			Subject:      subject,
+// 			Manifests:    manifests,
+// 			Annotations:  map[string]string{"test": "content"},
+// 		}
+// 		indexJSON, err := json.Marshal(index)
+// 		if err != nil {
+// 			t.Fatal(err)
+// 		}
+// 		appendBlob(ocispec.MediaTypeImageIndex, index.ArtifactType, indexJSON)
+// 	}
+// 	appendBlob("image manifest", "image config", []byte("config"))    // Blob 0
+// 	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("foo"))   // Blob 1
+// 	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("bar"))   // Blob 2
+// 	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("hello")) // Blob 3
+// 	generateImageManifest(descs[0], nil, descs[1])                    // Blob 4
+// 	generateImageManifest(descs[0], &descs[4], descs[2])              // Blob 5
+// 	generateArtifactManifest(&descs[5], descs[3])                     // Blob 6
+// 	generateIndex(&descs[6], descs[5:8]...)                           // Blob 7
+// 	s.badJson.Add(descs[5].Digest)
+// 	s.badJson.Add(descs[6].Digest)
+// 	s.badJson.Add(descs[7].Digest)
 
-	eg, egCtx := errgroup.WithContext(ctx)
-	for i := range blobs {
-		eg.Go(func(i int) func() error {
-			return func() error {
-				err := s.Push(egCtx, descs[i], bytes.NewReader(blobs[i]))
-				if err != nil {
-					return fmt.Errorf("failed to push test content to src: %d: %v", i, err)
-				}
-				return nil
-			}
-		}(i))
-	}
-	if err := eg.Wait(); err != nil {
-		t.Fatal(err)
-	}
+// 	eg, egCtx := errgroup.WithContext(ctx)
+// 	for i := range blobs {
+// 		eg.Go(func(i int) func() error {
+// 			return func() error {
+// 				err := s.Push(egCtx, descs[i], bytes.NewReader(blobs[i]))
+// 				if err != nil {
+// 					return fmt.Errorf("failed to push test content to src: %d: %v", i, err)
+// 				}
+// 				return nil
+// 			}
+// 		}(i))
+// 	}
+// 	if err := eg.Wait(); err != nil {
+// 		t.Fatal(err)
+// 	}
 
-	for i := 4; i < 7; i++ {
-		_, err := Referrers(ctx, &s, descs[i], "")
-		if err == nil {
-			t.Errorf("Store.Referrers(%d) error = %v, want Json Unmarshall error", i, err)
-		}
-	}
-}
+// 	for i := 4; i < 7; i++ {
+// 		_, err := Referrers(ctx, &s, descs[i], "")
+// 		if err != nil {
+// 			t.Errorf("Store.Referrers(%d) error = %v, want Json Unmarshall error", i, err)
+// 		}
+// 	}
+// }
 
 func equalDescriptorSet(actual []ocispec.Descriptor, expected []ocispec.Descriptor) bool {
 	if len(actual) != len(expected) {

From 404b39d175f5345dc811d48edda675b5e6d3341c Mon Sep 17 00:00:00 2001
From: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
Date: Tue, 26 Dec 2023 17:45:35 +0800
Subject: [PATCH 13/13] increase coverage

Signed-off-by: Xiaoxuan Wang <wangxiaoxuan119@gmail.com>
---
 registry/repository_test.go | 105 ------------------------------------
 1 file changed, 105 deletions(-)

diff --git a/registry/repository_test.go b/registry/repository_test.go
index 4a7626d3..b41340ef 100644
--- a/registry/repository_test.go
+++ b/registry/repository_test.go
@@ -41,7 +41,6 @@ var ErrBadFetch = errors.New("bad fetch error")
 type testStorage struct {
 	store    *memory.Store
 	badFetch set.Set[digest.Digest]
-	badJson  set.Set[digest.Digest]
 }
 
 func (s *testStorage) Push(ctx context.Context, expected ocispec.Descriptor, reader io.Reader) error {
@@ -52,9 +51,6 @@ func (s *testStorage) Fetch(ctx context.Context, target ocispec.Descriptor) (io.
 	if s.badFetch.Contains(target.Digest) {
 		return nil, ErrBadFetch
 	}
-	if s.badJson.Contains(target.Digest) {
-		return io.NopCloser(bytes.NewReader([]byte("bad json"))), nil
-	}
 	return s.store.Fetch(ctx, target)
 }
 
@@ -80,7 +76,6 @@ func TestReferrers(t *testing.T) {
 	s := testStorage{
 		store:    memory.New(),
 		badFetch: set.New[digest.Digest](),
-		badJson:  set.New[digest.Digest](),
 	}
 	ctx := context.Background()
 
@@ -295,7 +290,6 @@ func TestReferrers_BadFetch(t *testing.T) {
 	s := testStorage{
 		store:    memory.New(),
 		badFetch: set.New[digest.Digest](),
-		badJson:  set.New[digest.Digest](),
 	}
 	ctx := context.Background()
 
@@ -390,105 +384,6 @@ func TestReferrers_BadFetch(t *testing.T) {
 	}
 }
 
-// func TestReferrers_BadJson(t *testing.T) {
-// 	s := testStorage{
-// 		store:    memory.New(),
-// 		badFetch: set.New[digest.Digest](),
-// 		badJson:  set.New[digest.Digest](),
-// 	}
-// 	ctx := context.Background()
-
-// 	// generate test content
-// 	var blobs [][]byte
-// 	var descs []ocispec.Descriptor
-// 	appendBlob := func(mediaType string, artifactType string, blob []byte) {
-// 		blobs = append(blobs, blob)
-// 		descs = append(descs, ocispec.Descriptor{
-// 			MediaType:    mediaType,
-// 			ArtifactType: artifactType,
-// 			Annotations:  map[string]string{"test": "content"},
-// 			Digest:       digest.FromBytes(blob),
-// 			Size:         int64(len(blob)),
-// 		})
-// 	}
-// 	generateImageManifest := func(config ocispec.Descriptor, subject *ocispec.Descriptor, layers ...ocispec.Descriptor) {
-// 		manifest := ocispec.Manifest{
-// 			MediaType:   ocispec.MediaTypeImageManifest,
-// 			Config:      config,
-// 			Subject:     subject,
-// 			Layers:      layers,
-// 			Annotations: map[string]string{"test": "content"},
-// 		}
-// 		manifestJSON, err := json.Marshal(manifest)
-// 		if err != nil {
-// 			t.Fatal(err)
-// 		}
-// 		appendBlob(ocispec.MediaTypeImageManifest, manifest.Config.MediaType, manifestJSON)
-// 	}
-// 	generateArtifactManifest := func(subject *ocispec.Descriptor, blobs ...ocispec.Descriptor) {
-// 		artifact := spec.Artifact{
-// 			MediaType:    spec.MediaTypeArtifactManifest,
-// 			ArtifactType: "artifact",
-// 			Subject:      subject,
-// 			Blobs:        blobs,
-// 			Annotations:  map[string]string{"test": "content"},
-// 		}
-// 		manifestJSON, err := json.Marshal(artifact)
-// 		if err != nil {
-// 			t.Fatal(err)
-// 		}
-// 		appendBlob(spec.MediaTypeArtifactManifest, artifact.ArtifactType, manifestJSON)
-// 	}
-// 	generateIndex := func(subject *ocispec.Descriptor, manifests ...ocispec.Descriptor) {
-// 		index := ocispec.Index{
-// 			MediaType:    ocispec.MediaTypeImageIndex,
-// 			ArtifactType: "index",
-// 			Subject:      subject,
-// 			Manifests:    manifests,
-// 			Annotations:  map[string]string{"test": "content"},
-// 		}
-// 		indexJSON, err := json.Marshal(index)
-// 		if err != nil {
-// 			t.Fatal(err)
-// 		}
-// 		appendBlob(ocispec.MediaTypeImageIndex, index.ArtifactType, indexJSON)
-// 	}
-// 	appendBlob("image manifest", "image config", []byte("config"))    // Blob 0
-// 	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("foo"))   // Blob 1
-// 	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("bar"))   // Blob 2
-// 	appendBlob(ocispec.MediaTypeImageLayer, "layer", []byte("hello")) // Blob 3
-// 	generateImageManifest(descs[0], nil, descs[1])                    // Blob 4
-// 	generateImageManifest(descs[0], &descs[4], descs[2])              // Blob 5
-// 	generateArtifactManifest(&descs[5], descs[3])                     // Blob 6
-// 	generateIndex(&descs[6], descs[5:8]...)                           // Blob 7
-// 	s.badJson.Add(descs[5].Digest)
-// 	s.badJson.Add(descs[6].Digest)
-// 	s.badJson.Add(descs[7].Digest)
-
-// 	eg, egCtx := errgroup.WithContext(ctx)
-// 	for i := range blobs {
-// 		eg.Go(func(i int) func() error {
-// 			return func() error {
-// 				err := s.Push(egCtx, descs[i], bytes.NewReader(blobs[i]))
-// 				if err != nil {
-// 					return fmt.Errorf("failed to push test content to src: %d: %v", i, err)
-// 				}
-// 				return nil
-// 			}
-// 		}(i))
-// 	}
-// 	if err := eg.Wait(); err != nil {
-// 		t.Fatal(err)
-// 	}
-
-// 	for i := 4; i < 7; i++ {
-// 		_, err := Referrers(ctx, &s, descs[i], "")
-// 		if err != nil {
-// 			t.Errorf("Store.Referrers(%d) error = %v, want Json Unmarshall error", i, err)
-// 		}
-// 	}
-// }
-
 func equalDescriptorSet(actual []ocispec.Descriptor, expected []ocispec.Descriptor) bool {
 	if len(actual) != len(expected) {
 		return false