refactor!: drop custom directives (#274)

benchmark/tsconfig.json

@@ -19,6 +19,7 @@
     "paths": {
       "vue": ["../packages/vue/src"],
       "@vue/vapor": ["../packages/vue-vapor/src"],
+      "vue/vapor": ["../packages/vue-vapor/src"],
       "@vue/*": ["../packages/*/src"]
     }
   },

packages/runtime-vapor/__tests__/apiCreateVaporApp.spec.ts

@@ -153,7 +153,7 @@ describe('api: createVaporApp', () => {
     expect(host.innerHTML).toBe(`foobar!barbaz!`)
   })
 
-  test('directive', () => {
+  test.todo('directive', () => {
     const spy1 = vi.fn()
     const spy2 = vi.fn()
 

packages/runtime-vapor/__tests__/directives.spec.ts

@@ -19,7 +19,7 @@ import { makeRender } from './_utils'
 
 const define = makeRender()
 
-describe('directives', () => {
+describe.todo('directives', () => {
   it('should work', async () => {
     const count = ref(0)
 

packages/runtime-vapor/__tests__/directives/directives.spec.ts

@@ -15,7 +15,7 @@ import { makeRender } from '../_utils'
 
 const define = makeRender()
 
-describe('directives', () => {
+describe.todo('directives', () => {
   it('should work', async () => {
     const count = ref(0)
 

packages/runtime-vapor/__tests__/directives/vModel.spec.ts

@@ -27,7 +27,7 @@ const setDOMProps = (el: any, props: Array<[key: string, value: any]>) => {
   })
 }
 
-describe('directive: v-model', () => {
+describe.todo('directive: v-model', () => {
   test('should work with text input', async () => {
     const spy = vi.fn()
 

packages/runtime-vapor/__tests__/directives/vShow.spec.ts

@@ -28,7 +28,7 @@ const createDemo = (defaultValue: boolean) =>
     on(n1 as HTMLElement, 'click', () => handleClick)
     return n0
   })
-describe('directive: v-show', () => {
+describe.todo('directive: v-show', () => {
   test('basic', async () => {
     const { host } = createDemo(true).render()
     const btn = host.querySelector('button')

packages/runtime-vapor/__tests__/for.spec.ts

@@ -194,7 +194,7 @@ describe('createFor', () => {
     expect(host.innerHTML).toBe('<!--for-->')
   })
 
-  test('should work with directive hooks', async () => {
+  test.fails('should work with directive hooks', async () => {
     const calls: string[] = []
     const list = ref([0])
     const update = ref(0)

packages/runtime-vapor/__tests__/if.spec.ts

@@ -134,7 +134,7 @@ describe('createIf', () => {
     expect(host.innerHTML).toBe('<!--if-->')
   })
 
-  test('should work with directive hooks', async () => {
+  test.todo('should work with directive hooks', async () => {
     const calls: string[] = []
     const show1 = ref(true)
     const show2 = ref(true)

packages/runtime-vapor/src/apiCreateFor.ts

@@ -1,10 +1,10 @@
 import {
+  type EffectScope,
   type ShallowRef,
-  getCurrentScope,
+  effectScope,
   isReactive,
   proxyRefs,
   shallowRef,
-  traverse,
   triggerRef,
 } from '@vue/reactivity'
 import { isArray, isObject, isString } from '@vue/shared'
@@ -18,17 +18,11 @@ import { type Block, type Fragment, fragmentKey } from './apiRender'
 import { warn } from './warning'
 import { currentInstance } from './component'
 import { componentKey } from './component'
-import { BlockEffectScope, isRenderEffectScope } from './blockEffectScope'
-import {
-  createChildFragmentDirectives,
-  invokeWithMount,
-  invokeWithUnmount,
-  invokeWithUpdate,
-} from './directivesChildFragment'
 import type { DynamicSlot } from './componentSlots'
+import { renderEffect } from './renderEffect'
 
 interface ForBlock extends Fragment {
-  scope: BlockEffectScope
+  scope: EffectScope
   state: [
     item: ShallowRef<any>,
     key: ShallowRef<any>,
@@ -53,8 +47,6 @@ export const createFor = (
   let oldBlocks: ForBlock[] = []
   let newBlocks: ForBlock[]
   let parent: ParentNode | undefined | null
-  const update = getMemo ? updateWithMemo : updateWithoutMemo
-  const parentScope = getCurrentScope()!
   const parentAnchor = __DEV__ ? createComment('for') : createTextNode()
   const ref: Fragment = {
     nodes: oldBlocks,
@@ -62,25 +54,17 @@ export const createFor = (
   }
 
   const instance = currentInstance!
-  if (__DEV__ && (!instance || !isRenderEffectScope(parentScope))) {
+  if (__DEV__ && !instance) {
     warn('createFor() can only be used inside setup()')
   }
 
-  createChildFragmentDirectives(
-    parentAnchor,
-    () => oldBlocks.map(b => b.scope),
-    // source getter
-    () => traverse(src(), 1),
-    // init cb
-    getValue => doFor(getValue()),
-    // effect cb
-    getValue => doFor(getValue()),
-    once,
-  )
+  const update = getMemo ? updateWithMemo : updateWithoutMemo
+  once ? renderList() : renderEffect(renderList)
 
   return ref
 
-  function doFor(source: any) {
+  function renderList() {
+    const source = src()
     const newLength = getLength(source)
     const oldLength = oldBlocks.length
     newBlocks = new Array(newLength)
@@ -265,7 +249,7 @@ export const createFor = (
     idx: number,
     anchor: Node = parentAnchor,
   ): ForBlock {
-    const scope = new BlockEffectScope(instance, parentScope)
+    const scope = effectScope()
 
     const [item, key, index] = getItem(source, idx)
     const state = [
@@ -283,11 +267,9 @@ export const createFor = (
     })
     block.nodes = scope.run(() => renderItem(proxyRefs(state)))!
 
-    invokeWithMount(scope, () => {
-      // TODO v-memo
-      // if (getMemo) block.update()
-      if (parent) insert(block.nodes, parent, anchor)
-    })
+    // TODO v-memo
+    // if (getMemo) block.update()
+    if (parent) insert(block.nodes, parent, anchor)
 
     return block
   }
@@ -326,7 +308,6 @@ export const createFor = (
     }
 
     if (needsUpdate) setState(block, newItem, newKey, newIndex)
-    invokeWithUpdate(block.scope)
   }
 
   function updateWithoutMemo(
@@ -344,13 +325,11 @@ export const createFor = (
       (!isReactive(newItem) && isObject(newItem))
 
     if (needsUpdate) setState(block, newItem, newKey, newIndex)
-    invokeWithUpdate(block.scope)
   }
 
   function unmount({ nodes, scope }: ForBlock) {
-    invokeWithUnmount(scope, () => {
-      removeBlock(nodes, parent!)
-    })
+    removeBlock(nodes, parent!)
+    scope.stop()
   }
 }
 

packages/runtime-vapor/src/apiCreateIf.ts

@@ -1,15 +1,7 @@
+import { renderEffect } from './renderEffect'
 import { type Block, type Fragment, fragmentKey } from './apiRender'
-import { getCurrentScope } from '@vue/reactivity'
+import { type EffectScope, effectScope } from '@vue/reactivity'
 import { createComment, createTextNode, insert, remove } from './dom/element'
-import { currentInstance } from './component'
-import { warn } from './warning'
-import { BlockEffectScope, isRenderEffectScope } from './blockEffectScope'
-import {
-  createChildFragmentDirectives,
-  invokeWithMount,
-  invokeWithUnmount,
-  invokeWithUpdate,
-} from './directivesChildFragment'
 
 type BlockFn = () => Block
 
@@ -26,8 +18,7 @@ export const createIf = (
   let branch: BlockFn | undefined
   let parent: ParentNode | undefined | null
   let block: Block | undefined
-  let scope: BlockEffectScope | undefined
-  const parentScope = getCurrentScope()!
+  let scope: EffectScope | undefined
   const anchor = __DEV__ ? createComment('if') : createTextNode()
   const fragment: Fragment = {
     nodes: [],
@@ -35,37 +26,17 @@ export const createIf = (
     [fragmentKey]: true,
   }
 
-  const instance = currentInstance!
-  if (__DEV__ && (!instance || !isRenderEffectScope(parentScope))) {
-    warn('createIf() can only be used inside setup()')
-  }
-
   // TODO: SSR
   // if (isHydrating) {
   //   parent = hydrationNode!.parentNode
   //   setCurrentHydrationNode(hydrationNode!)
   // }
 
-  createChildFragmentDirectives(
-    anchor,
-    () => (scope ? [scope] : []),
-    // source getter
-    condition,
-    // init cb
-    getValue => {
-      newValue = !!getValue()
-      doIf()
-    },
-    // effect cb
-    getValue => {
-      if ((newValue = !!getValue()) !== oldValue) {
-        doIf()
-      } else if (scope) {
-        invokeWithUpdate(scope)
-      }
-    },
-    once,
-  )
+  if (once) {
+    doIf()
+  } else {
+    renderEffect(() => doIf())
+  }
 
   // TODO: SSR
   // if (isHydrating) {
@@ -75,17 +46,20 @@ export const createIf = (
   return fragment
 
   function doIf() {
-    parent ||= anchor.parentNode
-    if (block) {
-      invokeWithUnmount(scope!, () => remove(block!, parent!))
-    }
-    if ((branch = (oldValue = newValue) ? b1 : b2)) {
-      scope = new BlockEffectScope(instance, parentScope)
-      fragment.nodes = block = scope.run(branch)!
-      invokeWithMount(scope, () => parent && insert(block!, parent, anchor))
-    } else {
-      scope = block = undefined
-      fragment.nodes = []
+    if ((newValue = !!condition()) !== oldValue) {
+      parent ||= anchor.parentNode
+      if (block) {
+        scope!.stop()
+        remove(block, parent!)
+      }
+      if ((branch = (oldValue = newValue) ? b1 : b2)) {
+        scope = effectScope()
+        fragment.nodes = block = scope.run(branch)!
+        parent && insert(block, parent, anchor)
+      } else {
+        scope = block = undefined
+        fragment.nodes = []
+      }
     }
   }
 }

packages/runtime-vapor/src/blockEffectScope.ts

@@ -1,36 +0,0 @@
-import { EffectScope } from '@vue/reactivity'
-import type { ComponentInternalInstance } from './component'
-import type { DirectiveBindingsMap } from './directives'
-
-export class BlockEffectScope extends EffectScope {
-  /**
-   * instance
-   * @internal
-   */
-  it: ComponentInternalInstance
-  /**
-   * isMounted
-   * @internal
-   */
-  im: boolean
-  /**
-   * directives
-   * @internal
-   */
-  dirs?: DirectiveBindingsMap
-
-  constructor(
-    instance: ComponentInternalInstance,
-    parentScope: EffectScope | null,
-  ) {
-    super(false, parentScope || undefined)
-    this.im = false
-    this.it = instance
-  }
-}
-
-export function isRenderEffectScope(
-  scope: EffectScope | undefined,
-): scope is BlockEffectScope {
-  return scope instanceof BlockEffectScope
-}

packages/runtime-vapor/src/component.ts

@@ -1,4 +1,4 @@
-import { isRef } from '@vue/reactivity'
+import { EffectScope, isRef } from '@vue/reactivity'
 import {
   EMPTY_OBJ,
   hasOwn,
@@ -31,7 +31,6 @@ import {
   createAppContext,
 } from './apiCreateVaporApp'
 import type { Data } from '@vue/runtime-shared'
-import { BlockEffectScope } from './blockEffectScope'
 
 export type Component = FunctionalComponent | ObjectComponent
 
@@ -161,7 +160,7 @@ export interface ComponentInternalInstance {
   root: ComponentInternalInstance
 
   provides: Data
-  scope: BlockEffectScope
+  scope: EffectScope
   comps: Set<ComponentInternalInstance>
 
   rawProps: NormalizedRawProps
@@ -283,7 +282,7 @@ export function createComponentInstance(
     parent,
     root: null!, // set later
 
-    scope: null!,
+    scope: new EffectScope(true /* detached */)!,
     provides: parent ? parent.provides : Object.create(_appContext.provides),
     type: component,
     comps: new Set(),
@@ -358,7 +357,6 @@ export function createComponentInstance(
     // [VaporLifecycleHooks.SERVER_PREFETCH]: null,
   }
   instance.root = parent ? parent.root : instance
-  instance.scope = new BlockEffectScope(instance, parent && parent.scope)
   initProps(instance, rawProps, !isFunction(component), once)
   initSlots(instance, slots)
   instance.emit = emit.bind(null, instance)

packages/runtime-vapor/src/componentLifecycle.ts

@@ -2,7 +2,7 @@ import { invokeArrayFns } from '@vue/shared'
 import type { VaporLifecycleHooks } from './enums'
 import { type ComponentInternalInstance, setCurrentInstance } from './component'
 import { queuePostFlushCb } from './scheduler'
-import { type DirectiveHookName, invokeDirectiveHook } from './directives'
+import type { DirectiveHookName } from './directives'
 
 export function invokeLifecycle(
   instance: ComponentInternalInstance,
@@ -24,8 +24,6 @@ export function invokeLifecycle(
       }
       post ? queuePostFlushCb(fn) : fn()
     }
-
-    invokeDirectiveHook(instance, directive, instance.scope)
   }
 
   function invokeSub() {

packages/runtime-vapor/src/directives.ts

@@ -1,27 +1,6 @@
-import { invokeArrayFns, isBuiltInDirective, isFunction } from '@vue/shared'
-import {
-  type ComponentInternalInstance,
-  currentInstance,
-  isVaporComponent,
-  setCurrentInstance,
-} from './component'
-import {
-  EffectFlags,
-  ReactiveEffect,
-  getCurrentScope,
-  pauseTracking,
-  resetTracking,
-  traverse,
-} from '@vue/reactivity'
-import {
-  VaporErrorCodes,
-  callWithAsyncErrorHandling,
-  callWithErrorHandling,
-} from './errorHandling'
-import { type SchedulerJob, queueJob, queuePostFlushCb } from './scheduler'
+import { isBuiltInDirective } from '@vue/shared'
+import { type ComponentInternalInstance, currentInstance } from './component'
 import { warn } from './warning'
-import { type BlockEffectScope, isRenderEffectScope } from './blockEffectScope'
-import { normalizeBlock } from './dom/element'
 
 export type DirectiveModifiers<M extends string = string> = Record<M, boolean>
 
@@ -98,168 +77,7 @@ export function withDirectives<T extends ComponentInternalInstance | Node>(
     return nodeOrComponent
   }
 
-  let node: Node
-  if (isVaporComponent(nodeOrComponent)) {
-    const root = getComponentNode(nodeOrComponent)
-    if (!root) return nodeOrComponent
-    node = root
-  } else {
-    node = nodeOrComponent
-  }
-
-  let bindings: DirectiveBinding[]
-  const instance = currentInstance!
-  const parentScope = getCurrentScope() as BlockEffectScope
-
-  if (__DEV__ && !isRenderEffectScope(parentScope)) {
-    warn(`Directives should be used inside of RenderEffectScope.`)
-  }
-
-  const directivesMap = (parentScope.dirs ||= new Map())
-  if (!(bindings = directivesMap.get(node))) {
-    directivesMap.set(node, (bindings = []))
-  }
-
-  for (const directive of directives) {
-    let [dir, source, arg, modifiers] = directive
-    if (!dir) continue
-    if (isFunction(dir)) {
-      dir = {
-        mounted: dir,
-        updated: dir,
-      } satisfies ObjectDirective
-    }
-
-    const binding: DirectiveBinding = {
-      dir,
-      instance,
-      value: null, // set later
-      oldValue: undefined,
-      arg,
-      modifiers,
-    }
-
-    if (source) {
-      if (dir.deep) {
-        const deep = dir.deep === true ? undefined : dir.deep
-        const baseSource = source
-        source = () => traverse(baseSource(), deep)
-      }
-
-      const effect = new ReactiveEffect(() =>
-        callWithErrorHandling(
-          source!,
-          instance,
-          VaporErrorCodes.RENDER_FUNCTION,
-        ),
-      )
-      const triggerRenderingUpdate = createRenderingUpdateTrigger(
-        instance,
-        effect,
-      )
-      effect.scheduler = () => queueJob(triggerRenderingUpdate)
-
-      binding.source = effect.run.bind(effect)
-    }
-
-    bindings.push(binding)
-
-    callDirectiveHook(node, binding, instance, 'created')
-  }
+  // NOOP
 
   return nodeOrComponent
 }
-
-function getComponentNode(component: ComponentInternalInstance) {
-  if (!component.block) return
-
-  const nodes = normalizeBlock(component.block)
-  if (nodes.length !== 1) {
-    warn(
-      `Runtime directive used on component with non-element root node. ` +
-        `The directives will not function as intended.`,
-    )
-    return
-  }
-
-  return nodes[0]
-}
-
-export function invokeDirectiveHook(
-  instance: ComponentInternalInstance | null,
-  name: DirectiveHookName,
-  scope: BlockEffectScope,
-): void {
-  const { dirs } = scope
-  if (name === 'mounted') scope.im = true
-  if (!dirs) return
-  const iterator = dirs.entries()
-  for (const [node, bindings] of iterator) {
-    for (const binding of bindings) {
-      callDirectiveHook(node, binding, instance, name)
-    }
-  }
-}
-
-function callDirectiveHook(
-  node: Node,
-  binding: DirectiveBinding,
-  instance: ComponentInternalInstance | null,
-  name: DirectiveHookName,
-) {
-  if (name === 'beforeUpdate') binding.oldValue = binding.value
-  const { dir } = binding
-  const hook = dir[name]
-  if (!hook) return
-
-  const newValue = binding.source ? binding.source() : undefined
-  binding.value = newValue
-  // disable tracking inside all lifecycle hooks
-  // since they can potentially be called inside effects.
-  pauseTracking()
-  callWithAsyncErrorHandling(hook, instance, VaporErrorCodes.DIRECTIVE_HOOK, [
-    node,
-    binding,
-  ])
-  resetTracking()
-}
-
-export function createRenderingUpdateTrigger(
-  instance: ComponentInternalInstance,
-  effect: ReactiveEffect,
-): SchedulerJob {
-  job.id = instance.uid
-  return job
-  function job() {
-    if (!(effect.flags & EffectFlags.ACTIVE) || !effect.dirty) {
-      return
-    }
-
-    if (instance.isMounted && !instance.isUpdating) {
-      instance.isUpdating = true
-      const reset = setCurrentInstance(instance)
-
-      const { bu, u, scope } = instance
-      const { dirs } = scope
-      // beforeUpdate hook
-      if (bu) {
-        invokeArrayFns(bu)
-      }
-      invokeDirectiveHook(instance, 'beforeUpdate', scope)
-
-      queuePostFlushCb(() => {
-        instance.isUpdating = false
-        const reset = setCurrentInstance(instance)
-        if (dirs) {
-          invokeDirectiveHook(instance, 'updated', scope)
-        }
-        // updated hook
-        if (u) {
-          queuePostFlushCb(u)
-        }
-        reset()
-      })
-      reset()
-    }
-  }
-}

packages/runtime-vapor/src/directivesChildFragment.ts

@@ -1,155 +0,0 @@
-import { ReactiveEffect, getCurrentScope } from '@vue/reactivity'
-import {
-  type Directive,
-  type DirectiveHookName,
-  createRenderingUpdateTrigger,
-  invokeDirectiveHook,
-} from './directives'
-import { warn } from './warning'
-import { type BlockEffectScope, isRenderEffectScope } from './blockEffectScope'
-import { currentInstance } from './component'
-import { VaporErrorCodes, callWithErrorHandling } from './errorHandling'
-import { queueJob, queuePostFlushCb } from './scheduler'
-
-/**
- * used in createIf and createFor
- * manage directives of child fragments in components.
- */
-export function createChildFragmentDirectives(
-  anchor: Node,
-  getScopes: () => BlockEffectScope[],
-  source: () => any,
-  initCallback: (getValue: () => any) => void,
-  effectCallback: (getValue: () => any) => void,
-  once?: boolean,
-): void {
-  let isTriggered = false
-  const instance = currentInstance!
-  const parentScope = getCurrentScope() as BlockEffectScope
-  if (__DEV__) {
-    if (!isRenderEffectScope(parentScope)) {
-      warn('child directives can only be added to a render effect scope')
-    }
-    if (!instance) {
-      warn('child directives can only be added in a component')
-    }
-  }
-
-  const callSourceWithErrorHandling = () =>
-    callWithErrorHandling(source, instance, VaporErrorCodes.RENDER_FUNCTION)
-
-  if (once) {
-    initCallback(callSourceWithErrorHandling)
-    return
-  }
-
-  const directiveBindingsMap = (parentScope.dirs ||= new Map())
-  const dir: Directive = {
-    beforeUpdate: onDirectiveBeforeUpdate,
-    beforeMount: () => invokeChildrenDirectives('beforeMount'),
-    mounted: () => invokeChildrenDirectives('mounted'),
-    beforeUnmount: () => invokeChildrenDirectives('beforeUnmount'),
-    unmounted: () => invokeChildrenDirectives('unmounted'),
-  }
-  directiveBindingsMap.set(anchor, [
-    {
-      dir,
-      instance,
-      value: null,
-      oldValue: undefined,
-    },
-  ])
-
-  const effect = new ReactiveEffect(callSourceWithErrorHandling)
-  const triggerRenderingUpdate = createRenderingUpdateTrigger(instance, effect)
-  effect.scheduler = () => {
-    isTriggered = true
-    queueJob(triggerRenderingUpdate)
-  }
-
-  const getValue = () => effect.run()
-
-  initCallback(getValue)
-
-  function onDirectiveBeforeUpdate() {
-    if (isTriggered) {
-      isTriggered = false
-      effectCallback(getValue)
-    } else {
-      const scopes = getScopes()
-      for (const scope of scopes) {
-        invokeWithUpdate(scope)
-      }
-      return
-    }
-  }
-
-  function invokeChildrenDirectives(name: DirectiveHookName) {
-    const scopes = getScopes()
-    for (const scope of scopes) {
-      invokeDirectiveHook(instance, name, scope)
-    }
-  }
-}
-
-export function invokeWithMount(
-  scope: BlockEffectScope,
-  handler?: () => any,
-): any {
-  if (isRenderEffectScope(scope.parent) && !scope.parent.im) {
-    return handler && handler()
-  }
-  return invokeWithDirsHooks(scope, 'mount', handler)
-}
-
-export function invokeWithUnmount(
-  scope: BlockEffectScope,
-  handler?: () => void,
-): any {
-  try {
-    return invokeWithDirsHooks(scope, 'unmount', handler)
-  } finally {
-    scope.stop()
-  }
-}
-
-export function invokeWithUpdate(
-  scope: BlockEffectScope,
-  handler?: () => void,
-): any {
-  return invokeWithDirsHooks(scope, 'update', handler)
-}
-
-const lifecycleMap = {
-  mount: ['beforeMount', 'mounted'],
-  update: ['beforeUpdate', 'updated'],
-  unmount: ['beforeUnmount', 'unmounted'],
-} as const
-
-function invokeWithDirsHooks(
-  scope: BlockEffectScope,
-  name: keyof typeof lifecycleMap,
-  handler?: () => any,
-) {
-  const { dirs, it: instance } = scope
-  const [before, after] = lifecycleMap[name]
-
-  if (!dirs) {
-    const res = handler && handler()
-    if (name === 'mount') {
-      queuePostFlushCb(() => (scope.im = true))
-    }
-    return res
-  }
-
-  invokeDirectiveHook(instance, before, scope)
-  try {
-    if (handler) {
-      return handler()
-    }
-  } finally {
-    queuePostFlushCb(() => {
-      invokeDirectiveHook(instance, after, scope)
-    })
-  }
-}

packages/runtime-vapor/src/renderEffect.ts

@@ -12,7 +12,6 @@ import {
   queuePostFlushCb,
 } from './scheduler'
 import { VaporErrorCodes, callWithAsyncErrorHandling } from './errorHandling'
-import { invokeDirectiveHook } from './directives'
 
 export function renderEffect(cb: () => void): void {
   const instance = getCurrentInstance()
@@ -58,24 +57,17 @@ export function renderEffect(cb: () => void): void {
     if (instance && instance.isMounted && !instance.isUpdating) {
       instance.isUpdating = true
 
-      const { bu, u, scope } = instance
-      const { dirs } = scope
+      const { bu, u } = instance
       // beforeUpdate hook
       if (bu) {
         invokeArrayFns(bu)
       }
-      if (dirs) {
-        invokeDirectiveHook(instance, 'beforeUpdate', scope)
-      }
 
       effect.run()
 
       queuePostFlushCb(() => {
         instance.isUpdating = false
         const reset = setCurrentInstance(instance)
-        if (dirs) {
-          invokeDirectiveHook(instance, 'updated', scope)
-        }
         // updated hook
         if (u) {
           queuePostFlushCb(u)