fix referrers api response issue (#18430)

1, add fitler artifactType to header when the api is called with filter
2, give an empty json body on non aritfact scenario
3, give an empty array on non accessory scenario
4, fix the artifact type filter issue

Signed-off-by: Wang Yan <wangyan@vmware.com>

src/server/registry/referrers.go

@@ -38,6 +38,10 @@ func (r *referrersHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	repository := router.Param(ctx, ":splat")
 	reference := router.Param(ctx, ":reference")
 	at := req.URL.Query().Get("artifactType")
+	var filter string
+	if at != "" {
+		filter = "artifactType"
+	}
 
 	// Check if the reference is a valid digest
 	if _, err := digest.Parse(reference); err != nil {
@@ -45,25 +49,20 @@ func (r *referrersHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	result := &ocispec.Index{}
-
 	// Get the artifact by reference
 	art, err := r.artifactManager.GetByDigest(ctx, repository, reference)
 	if err != nil {
 		if errors.IsNotFoundErr(err) {
-			// If artifact not found, return empty index
-			newListReferrersOK().WithPayload(result).WriteResponse(w)
+			// If artifact not found, return empty json
+			newListReferrersOK().WithPayload(nil).WriteResponse(w)
 			return
 		}
 		lib_http.SendError(w, err)
 		return
 	}
 
-	// Query accessories with matching subject artifact digest and artifactType
+	// Query accessories with matching subject artifact digest
 	query := q.New(q.KeyWords{"SubjectArtifactDigest": art.Digest, "SubjectArtifactRepo": art.RepositoryName})
-	if at != "" {
-		query = q.New(q.KeyWords{"SubjectArtifactDigest": art.Digest, "SubjectArtifactRepo": art.RepositoryName, "Type": at})
-	}
 	total, err := r.accessoryManager.Count(ctx, query)
 	if err != nil {
 		lib_http.SendError(w, err)
@@ -76,7 +75,7 @@ func (r *referrersHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	}
 
 	// Build index manifest from accessories
-	var mfs []ocispec.Descriptor
+	mfs := make([]ocispec.Descriptor, 0)
 	for _, acc := range accs {
 		accArt, err := r.artifactManager.GetByDigest(ctx, repository, acc.GetData().Digest)
 		if err != nil {
@@ -90,10 +89,18 @@ func (r *referrersHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 			Annotations:  accArt.Annotations,
 			ArtifactType: accArt.MediaType,
 		}
-		mfs = append(mfs, mf)
+		// filter by the artifactType since the artifactType is actually the config media type of the artifact.
+		if at != "" {
+			if accArt.MediaType == at {
+				mfs = append(mfs, mf)
+			}
+		} else {
+			mfs = append(mfs, mf)
+		}
 	}
 
 	// Populate index manifest
+	result := &ocispec.Index{}
 	result.SchemaVersion = ReferrersSchemaVersion
 	result.MediaType = ReferrersMediaType
 	result.Manifests = mfs
@@ -102,6 +109,7 @@ func (r *referrersHandler) ServeHTTP(w http.ResponseWriter, req *http.Request) {
 	baseAPI := &handler.BaseAPI{}
 	newListReferrersOK().
 		WithXTotalCount(total).
+		WithFilter(filter).
 		WithLink(baseAPI.Links(ctx, req.URL, total, query.PageNumber, query.PageSize).String()).
 		WithPayload(result).WriteResponse(w)
 }
@@ -111,6 +119,10 @@ type listReferrersOK struct {
 
 	 */
 	Link string `json:"Link"`
+	/*Filter refers to the filter used to fetch the referrers
+
+	 */
+	Filter string `json:"Filter"`
 	/*The total count of accessories
 
 	 */
@@ -119,7 +131,7 @@ type listReferrersOK struct {
 	/*
 	  In: Body
 	*/
-	Payload *ocispec.Index `json:"body,omitempty"`
+	Payload interface{} `json:"body,omitempty"`
 }
 
 // newListReferrersOK creates newlistReferrersOK with default headers values
@@ -133,6 +145,12 @@ func (o *listReferrersOK) WithLink(link string) *listReferrersOK {
 	return o
 }
 
+// WithFilter adds the filter to the get referrers
+func (o *listReferrersOK) WithFilter(filter string) *listReferrersOK {
+	o.Filter = filter
+	return o
+}
+
 // WithXTotalCount adds the xTotalCount to the list accessories o k response
 func (o *listReferrersOK) WithXTotalCount(xTotalCount int64) *listReferrersOK {
 	o.XTotalCount = xTotalCount
@@ -140,7 +158,7 @@ func (o *listReferrersOK) WithXTotalCount(xTotalCount int64) *listReferrersOK {
 }
 
 // WithPayload adds the payload to the list accessories o k response
-func (o *listReferrersOK) WithPayload(payload *ocispec.Index) *listReferrersOK {
+func (o *listReferrersOK) WithPayload(payload interface{}) *listReferrersOK {
 	o.Payload = payload
 	return o
 }
@@ -153,6 +171,10 @@ func (o *listReferrersOK) WriteResponse(rw http.ResponseWriter) {
 	if link != "" {
 		rw.Header().Set("Link", link)
 	}
+	filter := o.Filter
+	if filter != "" {
+		rw.Header().Set("OCI-Filters-Applied", filter)
+	}
 	xTotalCount := swag.FormatInt64(o.XTotalCount)
 	if xTotalCount != "" {
 		rw.Header().Set("X-Total-Count", xTotalCount)
@@ -162,7 +184,7 @@ func (o *listReferrersOK) WriteResponse(rw http.ResponseWriter) {
 	payload := o.Payload
 	if payload == nil {
 		// return empty index
-		payload = &ocispec.Index{}
+		payload = struct{}{}
 	}
 
 	enc := json.NewEncoder(rw)

src/server/registry/referrers_test.go

@@ -3,7 +3,15 @@ package registry
 import (
 	"context"
 	"encoding/json"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
 	beegocontext "github.com/beego/beego/v2/server/web/context"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+
+	"github.com/goharbor/harbor/src/lib/errors"
 	accessorymodel "github.com/goharbor/harbor/src/pkg/accessory/model"
 	basemodel "github.com/goharbor/harbor/src/pkg/accessory/model/base"
 	"github.com/goharbor/harbor/src/pkg/artifact"
@@ -11,10 +19,6 @@ import (
 	"github.com/goharbor/harbor/src/testing/mock"
 	accessorytesting "github.com/goharbor/harbor/src/testing/pkg/accessory"
 	arttesting "github.com/goharbor/harbor/src/testing/pkg/artifact"
-	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
-	"net/http"
-	"net/http/httptest"
-	"testing"
 )
 
 func TestReferrersHandlerOK(t *testing.T) {
@@ -75,6 +79,42 @@ func TestReferrersHandlerOK(t *testing.T) {
 	}
 }
 
+func TestReferrersHandlerEmpty(t *testing.T) {
+	rec := httptest.NewRecorder()
+	digestVal := "sha256:6c3c624b58dbbcd3c0dd82b4c53f04194d1247c6eebdaab7c610cf7d66709b3b"
+	req, err := http.NewRequest("GET", "/v2/test/repository/referrers/sha256:6c3c624b58dbbcd3c0dd82b4c53f04194d1247c6eebdaab7c610cf7d66709b3b", nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	input := &beegocontext.BeegoInput{}
+	input.SetParam(":reference", digestVal)
+	*req = *(req.WithContext(context.WithValue(req.Context(), router.ContextKeyInput{}, input)))
+
+	artifactMock := &arttesting.Manager{}
+	accessoryMock := &accessorytesting.Manager{}
+
+	artifactMock.On("GetByDigest", mock.Anything, mock.Anything, mock.Anything).
+		Return(nil, errors.NotFoundError(nil))
+
+	handler := &referrersHandler{
+		artifactManager:  artifactMock,
+		accessoryManager: accessoryMock,
+	}
+
+	handler.ServeHTTP(rec, req)
+
+	// check that the response has the expected status code (200 OK)
+	if rec.Code != http.StatusOK {
+		t.Errorf("Expected status code %d, but got %d", http.StatusOK, rec.Code)
+	}
+	index := &ocispec.Index{}
+	json.Unmarshal([]byte(rec.Body.String()), index)
+	fmt.Println(index)
+	if index.SchemaVersion != 0 && len(index.Manifests) != -0 {
+		t.Errorf("Expected empty response body, but got %s", rec.Body.String())
+	}
+}
+
 func TestReferrersHandler400(t *testing.T) {
 	rec := httptest.NewRecorder()
 	digestVal := "invalid"