NestedFolderPicker: Migrate to app platform API (#106926)

* Add /children endpoint

* Update folder client

* Add comment

* Add feature toggle

* Add new version of useFoldersQuery

* Error handling

* Format

* Rename feature toggle

* Remove options and move root folder constant

* Fix feature toggle merge

* Add feature toggle again

* Rename useFoldersQuery files

* Update API spec

* Fix test

* Add test

* Better typings

---------

Co-authored-by: Clarity-89 <homes89@ukr.net>

pkg/registry/apis/folders/register.go

@@ -192,6 +192,11 @@ func (b *FolderAPIBuilder) UpdateAPIGroupInfo(apiGroupInfo *genericapiserver.API
 	storage[resourceInfo.StoragePath("counts")] = &subCountREST{searcher: b.searcher}
 	storage[resourceInfo.StoragePath("access")] = &subAccessREST{b.folderSvc, b.ac}
 
+	// Adds a path to return children of a given folder
+	storage[resourceInfo.StoragePath("children")] = &subChildrenREST{
+		lister: storage[resourceInfo.StoragePath()].(rest.Lister),
+	}
+
 	apiGroupInfo.VersionedResourcesStorageMap[folders.VERSION] = storage
 	b.storage = storage[resourceInfo.StoragePath()].(grafanarest.Storage)
 	return nil

pkg/registry/apis/folders/sub_children.go

@@ -0,0 +1,73 @@
+package folders
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	"k8s.io/apimachinery/pkg/apis/meta/internalversion"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apiserver/pkg/registry/rest"
+
+	folders "github.com/grafana/grafana/apps/folder/pkg/apis/folder/v1beta1"
+)
+
+type subChildrenREST struct {
+	lister rest.Lister
+}
+
+var _ = rest.Connecter(&subChildrenREST{})
+var _ = rest.StorageMetadata(&subChildrenREST{})
+
+// RootFolderName Hardcoded magic const to get root folders without parent.
+var RootFolderName = "general"
+
+func (r *subChildrenREST) New() runtime.Object {
+	return &folders.FolderList{}
+}
+
+func (r *subChildrenREST) Destroy() {
+}
+
+func (r *subChildrenREST) ProducesMIMETypes(verb string) []string {
+	return nil
+}
+
+func (r *subChildrenREST) ProducesObject(verb string) interface{} {
+	return &folders.FolderList{}
+}
+
+func (r *subChildrenREST) ConnectMethods() []string {
+	return []string{"GET"}
+}
+
+func (r *subChildrenREST) NewConnectOptions() (runtime.Object, bool, string) {
+	return nil, false, "" // true means you can use the trailing path as a variable
+}
+
+func (r *subChildrenREST) Connect(ctx context.Context, name string, opts runtime.Object, responder rest.Responder) (http.Handler, error) {
+	obj, err := r.lister.List(ctx, &internalversion.ListOptions{})
+	if err != nil {
+		return nil, err
+	}
+	allFolders, ok := obj.(*folders.FolderList)
+	if !ok {
+		return nil, fmt.Errorf("could not list folders")
+	}
+
+	return http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
+		children := &folders.FolderList{}
+		parentName := ""
+
+		if name != RootFolderName {
+			parentName = name
+		}
+		for _, folder := range allFolders.Items {
+			if parentName == getParent(&folder) {
+				children.Items = append(children.Items, folder)
+			}
+		}
+
+		responder.Object(http.StatusOK, children)
+	}), nil
+}

pkg/services/featuremgmt/registry.go

@@ -1734,6 +1734,16 @@ var (
 			FrontendOnly:      true,
 			Expression:        "false", // extensions will be disabled by default
 		},
+		{
+			Name:              "foldersAppPlatformAPI",
+			Description:       "Enables use of app platform API for folders",
+			Stage:             FeatureStageExperimental,
+			Owner:             grafanaFrontendSearchNavOrganise,
+			HideFromAdminPage: true,
+			HideFromDocs:      true,
+			FrontendOnly:      true,
+			Expression:        "false",
+		},
 	}
 )
 

pkg/services/featuremgmt/toggles_gen.csv

@@ -226,3 +226,4 @@ preferLibraryPanelTitle,privatePreview,@grafana/dashboards-squad,false,false,fal
 tabularNumbers,GA,@grafana/grafana-frontend-platform,false,false,false
 newInfluxDSConfigPageDesign,privatePreview,@grafana/partner-datasources,false,false,false
 enableAppChromeExtensions,experimental,@grafana/plugins-platform-backend,false,false,true
+foldersAppPlatformAPI,experimental,@grafana/grafana-search-navigate-organise,false,false,true

pkg/services/featuremgmt/toggles_gen.go

@@ -914,4 +914,8 @@ const (
 	// FlagEnableAppChromeExtensions
 	// Set this to true to enable all app chrome extensions registered by plugins.
 	FlagEnableAppChromeExtensions = "enableAppChromeExtensions"
+
+	// FlagFoldersAppPlatformAPI
+	// Enables use of app platform API for folders
+	FlagFoldersAppPlatformAPI = "foldersAppPlatformAPI"
 )

pkg/services/featuremgmt/toggles_gen.json

@@ -1257,6 +1257,22 @@
         "hideFromDocs": true
       }
     },
+    {
+      "metadata": {
+        "name": "foldersAppPlatformAPI",
+        "resourceVersion": "1751377081192",
+        "creationTimestamp": "2025-07-01T13:38:01Z"
+      },
+      "spec": {
+        "description": "Enables use of app platform API for folders",
+        "stage": "experimental",
+        "codeowner": "@grafana/grafana-search-navigate-organise",
+        "frontend": true,
+        "hideFromAdminPage": true,
+        "hideFromDocs": true,
+        "expression": "false"
+      }
+    },
     {
       "metadata": {
         "name": "formatString",

pkg/tests/apis/folder/folders_test.go

@@ -88,6 +88,15 @@ func TestIntegrationFoldersApp(t *testing.T) {
 						"get"
 					]
 				},
+				{
+					"name": "folders/children",
+					"singularName": "",
+					"namespaced": true,
+					"kind": "FolderList",
+					"verbs": [
+						"get"
+					]
+				},
 				{
 					"name": "folders/counts",
 					"singularName": "",

pkg/tests/apis/openapi_snapshots/folder.grafana.app-v1beta1.json

@@ -915,6 +915,55 @@
         }
       ]
     },
+    "/apis/folder.grafana.app/v1beta1/namespaces/{namespace}/folders/{name}/children": {
+      "get": {
+        "tags": [
+          "Folder"
+        ],
+        "description": "connect GET requests to children of Folder",
+        "operationId": "getFolderChildren",
+        "responses": {
+          "200": {
+            "description": "OK",
+            "content": {
+              "*/*": {
+                "schema": {
+                  "$ref": "#/components/schemas/com.github.grafana.grafana.apps.folder.pkg.apis.folder.v1beta1.FolderList"
+                }
+              }
+            }
+          }
+        },
+        "x-kubernetes-action": "connect",
+        "x-kubernetes-group-version-kind": {
+          "group": "folder.grafana.app",
+          "version": "v1beta1",
+          "kind": "FolderList"
+        }
+      },
+      "parameters": [
+        {
+          "name": "name",
+          "in": "path",
+          "description": "name of the FolderList",
+          "required": true,
+          "schema": {
+            "type": "string",
+            "uniqueItems": true
+          }
+        },
+        {
+          "name": "namespace",
+          "in": "path",
+          "description": "object name and auth scope, such as for teams and projects",
+          "required": true,
+          "schema": {
+            "type": "string",
+            "uniqueItems": true
+          }
+        }
+      ]
+    },
     "/apis/folder.grafana.app/v1beta1/namespaces/{namespace}/folders/{name}/counts": {
       "get": {
         "tags": [