fix(resource-proxy): support API group discovery requests

Signed-off-by: immanuwell <pchpr.00@list.ru>

Author: immanuwell

agent/resource.go

@@ -434,20 +434,35 @@ func (a *Agent) getAvailableResources(ctx context.Context, gvr schema.GroupVersi
 	return res, err
 }
 
-// getAvailableAPIs retrieves a list of available APIs for a given group and version.
+// getAvailableAPIs retrieves discovery data for a given group and version.
 // If group and version are empty, all available APIs are returned.
 // If group is empty and version is not, all APIs for the given version are returned.
-// If group and version are not empty, all APIs for the given group and version are returned.
+// If group is not empty and version is empty, metadata for the given API group is returned.
+// If group and version are both set, all APIs for the given group and version are returned.
 //
 // It does not yet support the new aggregated API.
 func (a *Agent) getAvailableAPIs(ctx context.Context, group, version string) (*unstructured.Unstructured, error) {
 	groupVersion := fmt.Sprintf("%s/%s", group, version)
 	var groupList *v1.APIGroupList
+	var groupInfo *v1.APIGroup
 	var resourceList *v1.APIResourceList
 	var err error
 
 	if group == "" && version == "" {
 		groupList, err = a.kubeClient.Clientset.Discovery().ServerGroups()
+	} else if group != "" && version == "" {
+		groupList, err = a.kubeClient.Clientset.Discovery().ServerGroups()
+		if err == nil {
+			for i := range groupList.Groups {
+				if groupList.Groups[i].Name == group {
+					groupInfo = &groupList.Groups[i]
+					break
+				}
+			}
+			if groupInfo == nil {
+				err = fmt.Errorf("api group %s not found", group)
+			}
+		}
 	} else if group == "" && version != "" {
 		resourceList, err = a.kubeClient.Clientset.Discovery().ServerResourcesForGroupVersion(version)
 	} else {
@@ -458,7 +473,9 @@ func (a *Agent) getAvailableAPIs(ctx context.Context, group, version string) (*u
 	}
 
 	var obj map[string]any
-	if groupList != nil {
+	if groupInfo != nil {
+		obj, err = runtime.DefaultUnstructuredConverter.ToUnstructured(groupInfo)
+	} else if groupList != nil {
 		obj, err = runtime.DefaultUnstructuredConverter.ToUnstructured(groupList)
 	} else if resourceList != nil {
 		obj, err = runtime.DefaultUnstructuredConverter.ToUnstructured(resourceList)

agent/resource_test.go

@@ -1289,6 +1289,20 @@ func Test_getAvailableAPIs(t *testing.T) {
 		assert.Contains(t, firstVersion, "version")
 	})
 
+	t.Run("Successfully get API group metadata when only group is specified", func(t *testing.T) {
+		agent := &Agent{
+			context:    context.Background(),
+			kubeClient: kube.NewDynamicFakeClient(),
+		}
+
+		result, err := agent.getAvailableAPIs(context.Background(), "apps", "")
+		assert.NoError(t, err)
+		assert.NotNil(t, result)
+		assert.Equal(t, "apps", result.Object["name"])
+		assert.Contains(t, result.Object, "versions")
+		assert.Contains(t, result.Object, "preferredVersion")
+	})
+
 	t.Run("Returns error for non-existent API group", func(t *testing.T) {
 		agent := &Agent{
 			context:    context.Background(),
@@ -1299,6 +1313,17 @@ func Test_getAvailableAPIs(t *testing.T) {
 		assert.Error(t, err)
 		assert.Nil(t, result)
 	})
+
+	t.Run("Returns error for non-existent API group without version", func(t *testing.T) {
+		agent := &Agent{
+			context:    context.Background(),
+			kubeClient: kube.NewDynamicFakeClient(),
+		}
+
+		result, err := agent.getAvailableAPIs(context.Background(), "nonexistent", "")
+		assert.Error(t, err)
+		assert.Nil(t, result)
+	})
 }
 
 func Test_processIncomingDeleteResourceRequest(t *testing.T) {

principal/resource.go

@@ -35,6 +35,10 @@ import (
 // capture groups. It also supports Kubernetes subresources.
 const resourceRequestRegexp = `^/(?:api|apis|(?:api|apis/(?P<group>[^\/]+))/(?P<version>v[^\/]+)(?:/(?:namespaces/(?P<namespace>[^\/]+)/)?)?(?:(?P<resource>[^\/]+)(?:/(?P<name>[^\/]+)(?:/(?P<subresource>[^\/]+))?)?)?)$`
 
+// resourceGroupRequestRegexp matches API group discovery requests such as
+// /apis/apps, which do not include an explicit version.
+const resourceGroupRequestRegexp = `^/apis/(?P<group>[^\/]+)$`
+
 // requestTimeout is the timeout that's being applied to requests for any live
 // resource.
 //

principal/resource_regex_test.go

@@ -198,3 +198,37 @@ func TestResourceRequestRegexp(t *testing.T) {
 		})
 	}
 }
+
+func TestResourceGroupRequestRegexp(t *testing.T) {
+	re, err := regexp.Compile(resourceGroupRequestRegexp)
+	require.NoError(t, err)
+
+	tests := []struct {
+		path      string
+		group     string
+		shouldHit bool
+	}{
+		{path: "/apis/apps", group: "apps", shouldHit: true},
+		{path: "/apis/networking.k8s.io", group: "networking.k8s.io", shouldHit: true},
+		{path: "/apis", shouldHit: false},
+		{path: "/apis/apps/v1", shouldHit: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.path, func(t *testing.T) {
+			matches := re.FindStringSubmatch(tt.path)
+			if !tt.shouldHit {
+				assert.Nil(t, matches)
+				return
+			}
+
+			require.NotNil(t, matches)
+			names := re.SubexpNames()
+			for i, name := range names {
+				if name == "group" {
+					assert.Equal(t, tt.group, matches[i])
+				}
+			}
+		})
+	}
+}

principal/server.go

@@ -541,6 +541,12 @@ func NewServer(ctx context.Context, kubeClient *kube.KubernetesClient, namespace
 	if s.resourceProxyEnabled {
 		// TODO(jannfis): Enable fetching APIs and resource counts
 		s.resourceProxy, err = resourceproxy.New(s.resourceProxyListenAddr,
+			// Kubernetes API group discovery, for example /apis/apps
+			resourceproxy.WithRequestMatcher(
+				resourceGroupRequestRegexp,
+				[]string{"get"},
+				s.processResourceRequest,
+			),
 			// For matching resource requests from the Argo CD API
 			resourceproxy.WithRequestMatcher(
 				resourceRequestRegexp,