core/packages/runtime-core/src/componentOptions.ts

import {
  ComponentInternalInstance,
  Data,
  SetupContext,
  ComponentInternalOptions,
  Component,
  ConcreteComponent,
  InternalRenderFunction,
  LifecycleHooks
} from './component'
import {
  isFunction,
  extend,
  isString,
  isObject,
  isArray,
  EMPTY_OBJ,
  NOOP,
  hasOwn,
  isPromise
} from '@vue/shared'
import { computed } from './apiComputed'
import {
  watch,
  WatchOptions,
  WatchCallback,
  createPathGetter
} from './apiWatch'
import { provide, inject } from './apiInject'
import {
  onBeforeMount,
  onMounted,
  onBeforeUpdate,
  onUpdated,
  onErrorCaptured,
  onRenderTracked,
  onBeforeUnmount,
  onUnmounted,
  onActivated,
  onDeactivated,
  onRenderTriggered,
  DebuggerHook,
  ErrorCapturedHook
} from './apiLifecycle'
import {
  reactive,
  ComputedGetter,
  WritableComputedOptions,
  toRaw,
  proxyRefs,
  toRef
} from '@vue/reactivity'
import {
  ComponentObjectPropsOptions,
  ExtractPropTypes,
  ExtractDefaultPropTypes
} from './componentProps'
import { EmitsOptions } from './componentEmits'
import { Directive } from './directives'
import {
  CreateComponentPublicInstance,
  ComponentPublicInstance
} from './componentPublicInstance'
import { warn } from './warning'
import { VNodeChild } from './vnode'
import { callWithAsyncErrorHandling } from './errorHandling'
import { UnionToIntersection } from './helpers/typeUtils'
import { deepMergeData } from './compat/data'
import { DeprecationTypes } from './compat/compatConfig'
import {
  CompatConfig,
  isCompatEnabled,
  softAssertCompatEnabled
} from './compat/compatConfig'
import {
  AssetTypes,
  COMPONENTS,
  DIRECTIVES,
  FILTERS
} from './helpers/resolveAssets'

/**
 * Interface for declaring custom options.
 *
 * @example
 * ```ts
 * declare module '@vue/runtime-core' {
 *   interface ComponentCustomOptions {
 *     beforeRouteUpdate?(
 *       to: Route,
 *       from: Route,
 *       next: () => void
 *     ): void
 *   }
 * }
 * ```
 */
export interface ComponentCustomOptions {}

export type RenderFunction = () => VNodeChild

type ExtractOptionProp<T> = T extends ComponentOptionsBase<
  infer P,
  any,
  any,
  any,
  any,
  any,
  any,
  any
>
  ? unknown extends P ? {} : P
  : {}

export interface ComponentOptionsBase<
  Props,
  RawBindings,
  D,
  C extends ComputedOptions,
  M extends MethodOptions,
  Mixin extends ComponentOptionsMixin,
  Extends extends ComponentOptionsMixin,
  E extends EmitsOptions,
  EE extends string = string,
  Defaults = {}
>
  extends LegacyOptions<Props, D, C, M, Mixin, Extends>,
    ComponentInternalOptions,
    ComponentCustomOptions {
  setup?: (
    this: void,
    props: Props &
      UnionToIntersection<ExtractOptionProp<Mixin>> &
      UnionToIntersection<ExtractOptionProp<Extends>>,
    ctx: SetupContext<E>
  ) => Promise<RawBindings> | RawBindings | RenderFunction | void
  name?: string
  template?: string | object // can be a direct DOM node
  // Note: we are intentionally using the signature-less `Function` type here
  // since any type with signature will cause the whole inference to fail when
  // the return expression contains reference to `this`.
  // Luckily `render()` doesn't need any arguments nor does it care about return
  // type.
  render?: Function
  components?: Record<string, Component>
  directives?: Record<string, Directive>
  inheritAttrs?: boolean
  emits?: (E | EE[]) & ThisType<void>
  // TODO infer public instance type based on exposed keys
  expose?: string[]
  serverPrefetch?(): Promise<any>

  // Internal ------------------------------------------------------------------

  /**
   * SSR only. This is produced by compiler-ssr and attached in compiler-sfc
   * not user facing, so the typing is lax and for test only.
   * @internal
   */
  ssrRender?: (
    ctx: any,
    push: (item: any) => void,
    parentInstance: ComponentInternalInstance,
    attrs: Data | undefined,
    // for compiler-optimized bindings
    $props: ComponentInternalInstance['props'],
    $setup: ComponentInternalInstance['setupState'],
    $data: ComponentInternalInstance['data'],
    $options: ComponentInternalInstance['ctx']
  ) => void

  /**
   * Only generated by compiler-sfc to mark a ssr render function inlined and
   * returned from setup()
   * @internal
   */
  __ssrInlineRender?: boolean

  /**
   * marker for AsyncComponentWrapper
   * @internal
   */
  __asyncLoader?: () => Promise<ConcreteComponent>
  /**
   * cache for merged $options
   * @internal
   */
  __merged?: ComponentOptions

  // Type differentiators ------------------------------------------------------

  // Note these are internal but need to be exposed in d.ts for type inference
  // to work!

  // type-only differentiator to separate OptionWithoutProps from a constructor
  // type returned by defineComponent() or FunctionalComponent
  call?: (this: unknown, ...args: unknown[]) => never
  // type-only differentiators for built-in Vnode types
  __isFragment?: never
  __isTeleport?: never
  __isSuspense?: never

  __defaults?: Defaults
}

export type ComponentOptionsWithoutProps<
  Props = {},
  RawBindings = {},
  D = {},
  C extends ComputedOptions = {},
  M extends MethodOptions = {},
  Mixin extends ComponentOptionsMixin = ComponentOptionsMixin,
  Extends extends ComponentOptionsMixin = ComponentOptionsMixin,
  E extends EmitsOptions = EmitsOptions,
  EE extends string = string
> = ComponentOptionsBase<
  Props,
  RawBindings,
  D,
  C,
  M,
  Mixin,
  Extends,
  E,
  EE,
  {}
> & {
  props?: undefined
} & ThisType<
    CreateComponentPublicInstance<{}, RawBindings, D, C, M, Mixin, Extends, E>
  >

export type ComponentOptionsWithArrayProps<
  PropNames extends string = string,
  RawBindings = {},
  D = {},
  C extends ComputedOptions = {},
  M extends MethodOptions = {},
  Mixin extends ComponentOptionsMixin = ComponentOptionsMixin,
  Extends extends ComponentOptionsMixin = ComponentOptionsMixin,
  E extends EmitsOptions = EmitsOptions,
  EE extends string = string,
  Props = Readonly<{ [key in PropNames]?: any }>
> = ComponentOptionsBase<
  Props,
  RawBindings,
  D,
  C,
  M,
  Mixin,
  Extends,
  E,
  EE,
  {}
> & {
  props: PropNames[]
} & ThisType<
    CreateComponentPublicInstance<
      Props,
      RawBindings,
      D,
      C,
      M,
      Mixin,
      Extends,
      E
    >
  >

export type ComponentOptionsWithObjectProps<
  PropsOptions = ComponentObjectPropsOptions,
  RawBindings = {},
  D = {},
  C extends ComputedOptions = {},
  M extends MethodOptions = {},
  Mixin extends ComponentOptionsMixin = ComponentOptionsMixin,
  Extends extends ComponentOptionsMixin = ComponentOptionsMixin,
  E extends EmitsOptions = EmitsOptions,
  EE extends string = string,
  Props = Readonly<ExtractPropTypes<PropsOptions>>,
  Defaults = ExtractDefaultPropTypes<PropsOptions>
> = ComponentOptionsBase<
  Props,
  RawBindings,
  D,
  C,
  M,
  Mixin,
  Extends,
  E,
  EE,
  Defaults
> & {
  props: PropsOptions & ThisType<void>
} & ThisType<
    CreateComponentPublicInstance<
      Props,
      RawBindings,
      D,
      C,
      M,
      Mixin,
      Extends,
      E,
      Props,
      Defaults,
      false
    >
  >

export type ComponentOptions<
  Props = {},
  RawBindings = any,
  D = any,
  C extends ComputedOptions = any,
  M extends MethodOptions = any,
  Mixin extends ComponentOptionsMixin = any,
  Extends extends ComponentOptionsMixin = any,
  E extends EmitsOptions = any
> = ComponentOptionsBase<Props, RawBindings, D, C, M, Mixin, Extends, E> &
  ThisType<
    CreateComponentPublicInstance<
      {},
      RawBindings,
      D,
      C,
      M,
      Mixin,
      Extends,
      E,
      Readonly<Props>
    >
  >

export type ComponentOptionsMixin = ComponentOptionsBase<
  any,
  any,
  any,
  any,
  any,
  any,
  any,
  any,
  any,
  any
>

export type ComputedOptions = Record<
  string,
  ComputedGetter<any> | WritableComputedOptions<any>
>

export interface MethodOptions {
  [key: string]: Function
}

export type ExtractComputedReturns<T extends any> = {
  [key in keyof T]: T[key] extends { get: (...args: any[]) => infer TReturn }
    ? TReturn
    : T[key] extends (...args: any[]) => infer TReturn ? TReturn : never
}

export type ObjectWatchOptionItem = {
  handler: WatchCallback | string
} & WatchOptions

type WatchOptionItem = string | WatchCallback | ObjectWatchOptionItem

type ComponentWatchOptionItem = WatchOptionItem | WatchOptionItem[]

type ComponentWatchOptions = Record<string, ComponentWatchOptionItem>

type ComponentInjectOptions =
  | string[]
  | Record<
      string | symbol,
      string | symbol | { from?: string | symbol; default?: unknown }
    >

interface LegacyOptions<
  Props,
  D,
  C extends ComputedOptions,
  M extends MethodOptions,
  Mixin extends ComponentOptionsMixin,
  Extends extends ComponentOptionsMixin
> {
  compatConfig?: CompatConfig

  // allow any custom options
  [key: string]: any

  // state
  // Limitation: we cannot expose RawBindings on the `this` context for data
  // since that leads to some sort of circular inference and breaks ThisType
  // for the entire component.
  data?: (
    this: CreateComponentPublicInstance<
      Props,
      {},
      {},
      {},
      MethodOptions,
      Mixin,
      Extends
    >,
    vm: CreateComponentPublicInstance<
      Props,
      {},
      {},
      {},
      MethodOptions,
      Mixin,
      Extends
    >
  ) => D
  computed?: C
  methods?: M
  watch?: ComponentWatchOptions
  provide?: Data | Function
  inject?: ComponentInjectOptions

  // assets
  filters?: Record<string, Function>

  // composition
  mixins?: Mixin[]
  extends?: Extends

  // lifecycle
  beforeCreate?(): void
  created?(): void
  beforeMount?(): void
  mounted?(): void
  beforeUpdate?(): void
  updated?(): void
  activated?(): void
  deactivated?(): void
  /** @deprecated use `beforeUnmount` instead */
  beforeDestroy?(): void
  beforeUnmount?(): void
  /** @deprecated use `unmounted` instead */
  destroyed?(): void
  unmounted?(): void
  renderTracked?: DebuggerHook
  renderTriggered?: DebuggerHook
  errorCaptured?: ErrorCapturedHook

  // runtime compile only
  delimiters?: [string, string]

  /**
   * #3468
   *
   * type-only, used to assist Mixin's type inference,
   * typescript will try to simplify the inferred `Mixin` type,
   * with the `__differenciator`, typescript won't be able to combine different mixins,
   * because the `__differenciator` will be different
   */
  __differentiator?: keyof D | keyof C | keyof M
}

export type OptionTypesKeys = 'P' | 'B' | 'D' | 'C' | 'M' | 'Defaults'

export type OptionTypesType<
  P = {},
  B = {},
  D = {},
  C extends ComputedOptions = {},
  M extends MethodOptions = {},
  Defaults = {}
> = {
  P: P
  B: B
  D: D
  C: C
  M: M
  Defaults: Defaults
}

const enum OptionTypes {
  PROPS = 'Props',
  DATA = 'Data',
  COMPUTED = 'Computed',
  METHODS = 'Methods',
  INJECT = 'Inject'
}

function createDuplicateChecker() {
  const cache = Object.create(null)
  return (type: OptionTypes, key: string) => {
    if (cache[key]) {
      warn(`${type} property "${key}" is already defined in ${cache[key]}.`)
    } else {
      cache[key] = type
    }
  }
}

type DataFn = (vm: ComponentPublicInstance) => any

export let shouldCacheAccess = true

export function applyOptions(
  instance: ComponentInternalInstance,
  options: ComponentOptions,
  deferredData: DataFn[] = [],
  deferredWatch: ComponentWatchOptions[] = [],
  deferredProvide: (Data | Function)[] = [],
  asMixin: boolean = false
) {
  if (__COMPAT__ && isFunction(options)) {
    options = options.options
  }

  const {
    // composition
    mixins,
    extends: extendsOptions,
    // state
    data: dataOptions,
    computed: computedOptions,
    methods,
    watch: watchOptions,
    provide: provideOptions,
    inject: injectOptions,
    // lifecycle
    beforeMount,
    mounted,
    beforeUpdate,
    updated,
    activated,
    deactivated,
    beforeDestroy,
    beforeUnmount,
    destroyed,
    unmounted,
    render,
    renderTracked,
    renderTriggered,
    errorCaptured,
    // public API
    expose
  } = options

  const publicThis = instance.proxy!
  const ctx = instance.ctx
  const globalMixins = instance.appContext.mixins

  if (asMixin && render && instance.render === NOOP) {
    instance.render = render as InternalRenderFunction
  }

  // applyOptions is called non-as-mixin once per instance
  if (!asMixin) {
    shouldCacheAccess = false
    callSyncHook(
      'beforeCreate',
      LifecycleHooks.BEFORE_CREATE,
      options,
      instance,
      globalMixins
    )
    shouldCacheAccess = true
    // global mixins are applied first
    applyMixins(
      instance,
      globalMixins,
      deferredData,
      deferredWatch,
      deferredProvide
    )
  }

  // extending a base component...
  if (extendsOptions) {
    applyOptions(
      instance,
      extendsOptions,
      deferredData,
      deferredWatch,
      deferredProvide,
      true
    )
  }
  // local mixins
  if (mixins) {
    applyMixins(instance, mixins, deferredData, deferredWatch, deferredProvide)
  }

  const checkDuplicateProperties = __DEV__ ? createDuplicateChecker() : null

  if (__DEV__) {
    const [propsOptions] = instance.propsOptions
    if (propsOptions) {
      for (const key in propsOptions) {
        checkDuplicateProperties!(OptionTypes.PROPS, key)
      }
    }
  }

  // options initialization order (to be consistent with Vue 2):
  // - props (already done outside of this function)
  // - inject
  // - methods
  // - data (deferred since it relies on `this` access)
  // - computed
  // - watch (deferred since it relies on `this` access)

  if (injectOptions) {
    resolveInjections(injectOptions, ctx, checkDuplicateProperties)
  }

  if (methods) {
    for (const key in methods) {
      const methodHandler = (methods as MethodOptions)[key]
      if (isFunction(methodHandler)) {
        // In dev mode, we use the `createRenderContext` function to define methods to the proxy target,
        // and those are read-only but reconfigurable, so it needs to be redefined here
        if (__DEV__) {
          Object.defineProperty(ctx, key, {
            value: methodHandler.bind(publicThis),
            configurable: true,
            enumerable: true,
            writable: true
          })
        } else {
          ctx[key] = methodHandler.bind(publicThis)
        }
        if (__DEV__) {
          checkDuplicateProperties!(OptionTypes.METHODS, key)
        }
      } else if (__DEV__) {
        warn(
          `Method "${key}" has type "${typeof methodHandler}" in the component definition. ` +
            `Did you reference the function correctly?`
        )
      }
    }
  }

  if (!asMixin) {
    if (deferredData.length) {
      deferredData.forEach(dataFn => resolveData(instance, dataFn, publicThis))
    }
    if (dataOptions) {
      // @ts-ignore dataOptions is not fully type safe
      resolveData(instance, dataOptions, publicThis)
    }
    if (__DEV__) {
      const rawData = toRaw(instance.data)
      for (const key in rawData) {
        checkDuplicateProperties!(OptionTypes.DATA, key)
        // expose data on ctx during dev
        if (key[0] !== '$' && key[0] !== '_') {
          Object.defineProperty(ctx, key, {
            configurable: true,
            enumerable: true,
            get: () => rawData[key],
            set: NOOP
          })
        }
      }
    }
  } else if (dataOptions) {
    deferredData.push(dataOptions as DataFn)
  }

  if (computedOptions) {
    for (const key in computedOptions) {
      const opt = (computedOptions as ComputedOptions)[key]
      const get = isFunction(opt)
        ? opt.bind(publicThis, publicThis)
        : isFunction(opt.get)
          ? opt.get.bind(publicThis, publicThis)
          : NOOP
      if (__DEV__ && get === NOOP) {
        warn(`Computed property "${key}" has no getter.`)
      }
      const set =
        !isFunction(opt) && isFunction(opt.set)
          ? opt.set.bind(publicThis)
          : __DEV__
            ? () => {
                warn(
                  `Write operation failed: computed property "${key}" is readonly.`
                )
              }
            : NOOP
      const c = computed({
        get,
        set
      })
      Object.defineProperty(ctx, key, {
        enumerable: true,
        configurable: true,
        get: () => c.value,
        set: v => (c.value = v)
      })
      if (__DEV__) {
        checkDuplicateProperties!(OptionTypes.COMPUTED, key)
      }
    }
  }

  if (watchOptions) {
    deferredWatch.push(watchOptions)
  }
  if (!asMixin && deferredWatch.length) {
    deferredWatch.forEach(watchOptions => {
      for (const key in watchOptions) {
        createWatcher(watchOptions[key], ctx, publicThis, key)
      }
    })
  }

  if (provideOptions) {
    deferredProvide.push(provideOptions)
  }
  if (!asMixin && deferredProvide.length) {
    deferredProvide.forEach(provideOptions => {
      const provides = isFunction(provideOptions)
        ? provideOptions.call(publicThis)
        : provideOptions
      Reflect.ownKeys(provides).forEach(key => {
        provide(key, provides[key])
      })
    })
  }

  // asset options.
  // To reduce memory usage, only components with mixins or extends will have
  // resolved asset registry attached to instance.
  if (asMixin) {
    resolveInstanceAssets(instance, options, COMPONENTS)
    resolveInstanceAssets(instance, options, DIRECTIVES)
    if (__COMPAT__ && isCompatEnabled(DeprecationTypes.FILTERS, instance)) {
      resolveInstanceAssets(instance, options, FILTERS)
    }
  }

  // lifecycle options
  if (!asMixin) {
    callSyncHook(
      'created',
      LifecycleHooks.CREATED,
      options,
      instance,
      globalMixins
    )
  }
  if (beforeMount) {
    onBeforeMount(beforeMount.bind(publicThis))
  }
  if (mounted) {
    onMounted(mounted.bind(publicThis))
  }
  if (beforeUpdate) {
    onBeforeUpdate(beforeUpdate.bind(publicThis))
  }
  if (updated) {
    onUpdated(updated.bind(publicThis))
  }
  if (activated) {
    onActivated(activated.bind(publicThis))
  }
  if (deactivated) {
    onDeactivated(deactivated.bind(publicThis))
  }
  if (errorCaptured) {
    onErrorCaptured(errorCaptured.bind(publicThis))
  }
  if (renderTracked) {
    onRenderTracked(renderTracked.bind(publicThis))
  }
  if (renderTriggered) {
    onRenderTriggered(renderTriggered.bind(publicThis))
  }
  if (beforeUnmount) {
    onBeforeUnmount(beforeUnmount.bind(publicThis))
  }
  if (unmounted) {
    onUnmounted(unmounted.bind(publicThis))
  }

  if (__COMPAT__) {
    if (
      beforeDestroy &&
      softAssertCompatEnabled(DeprecationTypes.OPTIONS_BEFORE_DESTROY, instance)
    ) {
      onBeforeUnmount(beforeDestroy.bind(publicThis))
    }
    if (
      destroyed &&
      softAssertCompatEnabled(DeprecationTypes.OPTIONS_DESTROYED, instance)
    ) {
      onUnmounted(destroyed.bind(publicThis))
    }
  }

  if (isArray(expose)) {
    if (!asMixin) {
      if (expose.length) {
        const exposed = instance.exposed || (instance.exposed = proxyRefs({}))
        expose.forEach(key => {
          exposed[key] = toRef(publicThis, key as any)
        })
      } else if (!instance.exposed) {
        instance.exposed = EMPTY_OBJ
      }
    } else if (__DEV__) {
      warn(`The \`expose\` option is ignored when used in mixins.`)
    }
  }
}

function resolveInstanceAssets(
  instance: ComponentInternalInstance,
  mixin: ComponentOptions,
  type: AssetTypes
) {
  if (mixin[type]) {
    extend(
      instance[type] ||
        (instance[type] = extend(
          {},
          (instance.type as ComponentOptions)[type]
        ) as any),
      mixin[type]
    )
  }
}

export function resolveInjections(
  injectOptions: ComponentInjectOptions,
  ctx: any,
  checkDuplicateProperties = NOOP as any
) {
  if (isArray(injectOptions)) {
    for (let i = 0; i < injectOptions.length; i++) {
      const key = injectOptions[i]
      ctx[key] = inject(key)
      if (__DEV__) {
        checkDuplicateProperties!(OptionTypes.INJECT, key)
      }
    }
  } else {
    for (const key in injectOptions) {
      const opt = injectOptions[key]
      if (isObject(opt)) {
        ctx[key] = inject(
          opt.from || key,
          opt.default,
          true /* treat default function as factory */
        )
      } else {
        ctx[key] = inject(opt)
      }
      if (__DEV__) {
        checkDuplicateProperties!(OptionTypes.INJECT, key)
      }
    }
  }
}

function callSyncHook(
  name: 'beforeCreate' | 'created',
  type: LifecycleHooks,
  options: ComponentOptions,
  instance: ComponentInternalInstance,
  globalMixins: ComponentOptions[]
) {
  for (let i = 0; i < globalMixins.length; i++) {
    callHookWithMixinAndExtends(name, type, globalMixins[i], instance)
  }
  callHookWithMixinAndExtends(name, type, options, instance)
}

function callHookWithMixinAndExtends(
  name: 'beforeCreate' | 'created',
  type: LifecycleHooks,
  options: ComponentOptions,
  instance: ComponentInternalInstance
) {
  const { extends: base, mixins } = options
  const selfHook = options[name]
  if (base) {
    callHookWithMixinAndExtends(name, type, base, instance)
  }
  if (mixins) {
    for (let i = 0; i < mixins.length; i++) {
      callHookWithMixinAndExtends(name, type, mixins[i], instance)
    }
  }
  if (selfHook) {
    callWithAsyncErrorHandling(
      __COMPAT__ && isArray(selfHook)
        ? selfHook.map(h => h.bind(instance.proxy!))
        : selfHook.bind(instance.proxy!),
      instance,
      type
    )
  }
}

function applyMixins(
  instance: ComponentInternalInstance,
  mixins: ComponentOptions[],
  deferredData: DataFn[],
  deferredWatch: ComponentWatchOptions[],
  deferredProvide: (Data | Function)[]
) {
  for (let i = 0; i < mixins.length; i++) {
    applyOptions(
      instance,
      mixins[i],
      deferredData,
      deferredWatch,
      deferredProvide,
      true
    )
  }
}

function resolveData(
  instance: ComponentInternalInstance,
  dataFn: DataFn,
  publicThis: ComponentPublicInstance
) {
  if (__DEV__ && !isFunction(dataFn)) {
    warn(
      `The data option must be a function. ` +
        `Plain object usage is no longer supported.`
    )
  }
  shouldCacheAccess = false
  const data = dataFn.call(publicThis, publicThis)
  shouldCacheAccess = true
  if (__DEV__ && isPromise(data)) {
    warn(
      `data() returned a Promise - note data() cannot be async; If you ` +
        `intend to perform data fetching before component renders, use ` +
        `async setup() + <Suspense>.`
    )
  }
  if (!isObject(data)) {
    __DEV__ && warn(`data() should return an object.`)
  } else if (instance.data === EMPTY_OBJ) {
    instance.data = reactive(data)
  } else {
    // existing data: this is a mixin or extends.
    if (
      __COMPAT__ &&
      isCompatEnabled(DeprecationTypes.OPTIONS_DATA_MERGE, instance)
    ) {
      deepMergeData(instance.data, data, instance)
    } else {
      extend(instance.data, data)
    }
  }
}

export function createWatcher(
  raw: ComponentWatchOptionItem,
  ctx: Data,
  publicThis: ComponentPublicInstance,
  key: string
) {
  const getter = key.includes('.')
    ? createPathGetter(publicThis, key)
    : () => (publicThis as any)[key]
  if (isString(raw)) {
    const handler = ctx[raw]
    if (isFunction(handler)) {
      watch(getter, handler as WatchCallback)
    } else if (__DEV__) {
      warn(`Invalid watch handler specified by key "${raw}"`, handler)
    }
  } else if (isFunction(raw)) {
    watch(getter, raw.bind(publicThis))
  } else if (isObject(raw)) {
    if (isArray(raw)) {
      raw.forEach(r => createWatcher(r, ctx, publicThis, key))
    } else {
      const handler = isFunction(raw.handler)
        ? raw.handler.bind(publicThis)
        : (ctx[raw.handler] as WatchCallback)
      if (isFunction(handler)) {
        watch(getter, handler, raw)
      } else if (__DEV__) {
        warn(`Invalid watch handler specified by key "${raw.handler}"`, handler)
      }
    }
  } else if (__DEV__) {
    warn(`Invalid watch option: "${key}"`, raw)
  }
}

export function resolveMergedOptions(
  instance: ComponentInternalInstance
): ComponentOptions {
  const raw = instance.type as ComponentOptions
  const { __merged, mixins, extends: extendsOptions } = raw
  if (__merged) return __merged
  const globalMixins = instance.appContext.mixins
  if (!globalMixins.length && !mixins && !extendsOptions) return raw
  const options = {}
  globalMixins.forEach(m => mergeOptions(options, m, instance))
  mergeOptions(options, raw, instance)
  return (raw.__merged = options)
}

export function mergeOptions(
  to: any,
  from: any,
  instance?: ComponentInternalInstance | null,
  strats = instance && instance.appContext.config.optionMergeStrategies
) {
  if (__COMPAT__ && isFunction(from)) {
    from = from.options
  }

  const { mixins, extends: extendsOptions } = from

  extendsOptions && mergeOptions(to, extendsOptions, instance, strats)
  mixins &&
    mixins.forEach((m: ComponentOptionsMixin) =>
      mergeOptions(to, m, instance, strats)
    )

  for (const key in from) {
    if (strats && hasOwn(strats, key)) {
      to[key] = strats[key](to[key], from[key], instance && instance.proxy, key)
    } else {
      to[key] = from[key]
    }
  }
  return to
}