fix(proxy): fix tag list endpoint in proxy mode (#4846)

internal/client/repository.go

@@ -345,7 +345,66 @@ func (t *tags) Lookup(ctx context.Context, digest v1.Descriptor) ([]string, erro
 }
 
 func (t *tags) List(ctx context.Context, limit int, last string) ([]string, error) {
-	panic("not implemented")
+	if limit < 0 {
+		tags, err := t.All(ctx)
+		if err != nil {
+			return tags, err
+		}
+		// return io.EOF, indicating that there are no more tags to list
+		return tags, io.EOF
+	}
+	v := url.Values{}
+	v.Add("n", strconv.Itoa(limit))
+	if last != "" {
+		v.Add("last", last)
+	}
+	listURLStr, err := t.ub.BuildTagsURL(t.name, v)
+	if err != nil {
+		return nil, err
+	}
+
+	listURL, err := url.Parse(listURLStr)
+	if err != nil {
+		return nil, err
+	}
+
+	preAlloc := 1000
+	if limit < preAlloc {
+		preAlloc = limit
+	}
+	tags := make([]string, 0, preAlloc)
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, listURL.String(), nil)
+	if err != nil {
+		return nil, err
+	}
+	resp, err := t.client.Do(req)
+	if err != nil {
+		return tags, err
+	}
+	defer resp.Body.Close()
+
+	if err := HandleHTTPResponseError(resp); err != nil {
+		return tags, err
+	}
+
+	b, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return tags, err
+	}
+
+	tagsResponse := struct {
+		Tags []string `json:"tags"`
+	}{}
+	if err := json.Unmarshal(b, &tagsResponse); err != nil {
+		return tags, err
+	}
+	tags = append(tags, tagsResponse.Tags...)
+	// if there is a Link header, return nil to indicate that there are more tags to list
+	// otherwise return io.EOF to indicate that there are no more tags to list
+	if link := resp.Header.Get("Link"); link != "" {
+		return tags, nil
+	}
+	return tags, io.EOF
 }
 
 func (t *tags) Tag(ctx context.Context, tag string, desc distribution.Descriptor) error {

internal/client/repository_test.go

@@ -1660,6 +1660,88 @@ func TestManifestTagsPaginated(t *testing.T) {
 	}
 }
 
+func TestManifestTagsListPaginated(t *testing.T) {
+	s := httptest.NewServer(http.NotFoundHandler())
+	defer s.Close()
+
+	repo, _ := reference.WithName("test.example.com/repo/tags/list")
+	tagsList := []string{"tag1", "tag2", "funtag"}
+	var m testutil.RequestResponseMap
+	for i := range 3 {
+		body, err := json.Marshal(map[string]any{
+			"name": "test.example.com/repo/tags/list",
+			"tags": []string{tagsList[i]},
+		})
+		if err != nil {
+			t.Fatal(err)
+		}
+		queryParams := make(map[string][]string)
+		if i > 0 {
+			queryParams["n"] = []string{"1"}
+			queryParams["last"] = []string{tagsList[i-1]}
+		} else {
+			queryParams["n"] = []string{"1"}
+		}
+
+		// Test both relative and absolute links.
+		relativeLink := "/v2/" + repo.Name() + "/tags/list?n=1&last=" + tagsList[i]
+		var link string
+		switch i {
+		case 0:
+			link = relativeLink
+		case len(tagsList) - 1:
+			link = ""
+		default:
+			link = s.URL + relativeLink
+		}
+
+		headers := http.Header(map[string][]string{
+			"Content-Length": {fmt.Sprint(len(body))},
+			"Last-Modified":  {time.Now().Add(-1 * time.Second).Format(time.ANSIC)},
+		})
+		if link != "" {
+			headers.Set("Link", fmt.Sprintf(`<%s>; rel="next"`, link))
+		}
+
+		m = append(m, testutil.RequestResponseMapping{
+			Request: testutil.Request{
+				Method:      http.MethodGet,
+				Route:       "/v2/" + repo.Name() + "/tags/list",
+				QueryParams: queryParams,
+			},
+			Response: testutil.Response{
+				StatusCode: http.StatusOK,
+				Body:       body,
+				Headers:    headers,
+			},
+		})
+	}
+	s.Config.Handler = testutil.NewHandler(m)
+
+	r, err := NewRepository(repo, s.URL, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	ctx := dcontext.Background()
+	tagService := r.Tags(ctx)
+
+	last := ""
+	for i := range 3 {
+		tags, err := tagService.List(ctx, 1, last)
+		if err != nil && err != io.EOF {
+			t.Fatal(err)
+		}
+		if len(tags) != 1 {
+			t.Fatalf("Wrong number of tags returned: %d, expected 1", len(tags))
+		}
+		if tags[0] != tagsList[i] {
+			t.Fatalf("Wrong tag returned: %s, expected %s", tags[0], tagsList[i])
+		}
+		last = tags[0]
+	}
+}
+
 func TestManifestUnauthorized(t *testing.T) {
 	repo, _ := reference.WithName("test.example.com/repo")
 	_, dgst, _ := newRandomOCIManifest(t, 6)