feat: initial code of baseWatch

Author: LittleSound

packages/reactivity/src/baseWatch.ts

@@ -0,0 +1,397 @@
+import {
+  EMPTY_OBJ,
+  isObject,
+  isArray,
+  isFunction,
+  hasChanged,
+  NOOP,
+  isMap,
+  isSet,
+  isPlainObject,
+  isPromise
+} from '@vue/shared'
+import { warn } from './warning'
+import { ComputedRef } from './computed'
+import { ReactiveFlags } from './constants'
+import { DebuggerOptions, ReactiveEffect, EffectScheduler } from './effect'
+import { isShallow, isReactive } from './reactive'
+import { Ref, isRef } from './ref'
+
+// contexts where user provided function may be executed, in addition to
+// lifecycle hooks.
+export enum BaseWatchErrorCodes {
+  WATCH_GETTER = 'BaseWatchErrorCodes_WATCH_GETTER',
+  WATCH_CALLBACK = 'BaseWatchErrorCodes_WATCH_CALLBACK',
+  WATCH_CLEANUP = 'BaseWatchErrorCodes_WATCH_CLEANUP'
+}
+
+export interface SchedulerJob extends Function {
+  id?: number
+  pre?: boolean
+  active?: boolean
+  computed?: boolean
+  /**
+   * Indicates whether the effect is allowed to recursively trigger itself
+   * when managed by the scheduler.
+   *
+   * By default, a job cannot trigger itself because some built-in method calls,
+   * e.g. Array.prototype.push actually performs reads as well (#1740) which
+   * can lead to confusing infinite loops.
+   * The allowed cases are component update functions and watch callbacks.
+   * Component update functions may update child component props, which in turn
+   * trigger flush: "pre" watch callbacks that mutates state that the parent
+   * relies on (#1801). Watch callbacks doesn't track its dependencies so if it
+   * triggers itself again, it's likely intentional and it is the user's
+   * responsibility to perform recursive state mutation that eventually
+   * stabilizes (#1727).
+   */
+  allowRecurse?: boolean
+}
+
+export type WatchEffect = (onCleanup: OnCleanup) => void
+
+export type WatchSource<T = any> = Ref<T> | ComputedRef<T> | (() => T)
+
+export type WatchCallback<V = any, OV = any> = (
+  value: V,
+  oldValue: OV,
+  onCleanup: OnCleanup
+) => any
+
+type OnCleanup = (cleanupFn: () => void) => void
+
+export interface BaseWatchOptions<Immediate = boolean> extends DebuggerOptions {
+  immediate?: Immediate
+  deep?: boolean
+  once?: boolean
+  scheduler?: Scheduler
+  handlerError?: HandleError
+  handlerWarn?: HandleWarn
+}
+
+export type WatchStopHandle = () => void
+
+// initial value for watchers to trigger on undefined initial values
+const INITIAL_WATCHER_VALUE = {}
+
+export type Scheduler = (context: {
+  effect: ReactiveEffect
+  job: SchedulerJob
+  isInit: boolean
+}) => void
+
+const DEFAULT_SCHEDULER: Scheduler = ({ job }) => job()
+
+export type HandleError = (err: unknown, type: BaseWatchErrorCodes) => void
+
+const DEFAULT_HANDLE_ERROR: HandleError = (err: unknown) => {
+  throw err
+}
+
+export type HandleWarn = (msg: string, ...args: any[]) => void
+
+const cleanupMap: WeakMap<ReactiveEffect, (() => void)[]> = new WeakMap()
+let activeEffect: ReactiveEffect | undefined = undefined
+
+export function onEffectCleanup(cleanupFn: () => void) {
+  if (activeEffect) {
+    const cleanups =
+      cleanupMap.get(activeEffect) ||
+      cleanupMap.set(activeEffect, []).get(activeEffect)!
+    cleanups.push(cleanupFn)
+  }
+}
+
+export function baseWatch(
+  source: WatchSource | WatchSource[] | WatchEffect | object,
+  cb: WatchCallback | null,
+  {
+    immediate,
+    deep,
+    once,
+    onTrack,
+    onTrigger,
+    scheduler = DEFAULT_SCHEDULER,
+    handlerError = DEFAULT_HANDLE_ERROR,
+    handlerWarn = warn
+  }: BaseWatchOptions = EMPTY_OBJ
+): WatchStopHandle {
+  if (cb && once) {
+    const _cb = cb
+    cb = (...args) => {
+      _cb(...args)
+      unwatch()
+    }
+  }
+
+  const warnInvalidSource = (s: unknown) => {
+    handlerWarn(
+      `Invalid watch source: `,
+      s,
+      `A watch source can only be a getter/effect function, a ref, ` +
+        `a reactive object, or an array of these types.`
+    )
+  }
+
+  let getter: () => any
+  let forceTrigger = false
+  let isMultiSource = false
+
+  if (isRef(source)) {
+    getter = () => source.value
+    forceTrigger = isShallow(source)
+  } else if (isReactive(source)) {
+    getter = () => source
+    deep = true
+  } else if (isArray(source)) {
+    isMultiSource = true
+    forceTrigger = source.some(s => isReactive(s) || isShallow(s))
+    getter = () =>
+      source.map(s => {
+        if (isRef(s)) {
+          return s.value
+        } else if (isReactive(s)) {
+          return traverse(s)
+        } else if (isFunction(s)) {
+          return callWithErrorHandling(
+            s,
+            handlerError,
+            BaseWatchErrorCodes.WATCH_GETTER
+          )
+        } else {
+          __DEV__ && warnInvalidSource(s)
+        }
+      })
+  } else if (isFunction(source)) {
+    if (cb) {
+      // getter with cb
+      getter = () =>
+        callWithErrorHandling(
+          source,
+          handlerError,
+          BaseWatchErrorCodes.WATCH_GETTER
+        )
+    } else {
+      // no cb -> simple effect
+      getter = () => {
+        // TODO: move to scheduler
+        // if (instance && instance.isUnmounted) {
+        //   return
+        // }
+        if (cleanup) {
+          cleanup()
+        }
+        const currentEffect = activeEffect
+        activeEffect = effect
+        try {
+          return callWithAsyncErrorHandling(
+            source,
+            handlerError,
+            BaseWatchErrorCodes.WATCH_CALLBACK,
+            [onEffectCleanup]
+          )
+        } finally {
+          activeEffect = currentEffect
+        }
+      }
+    }
+  } else {
+    getter = NOOP
+    __DEV__ && warnInvalidSource(source)
+  }
+
+  if (cb && deep) {
+    const baseGetter = getter
+    getter = () => traverse(baseGetter())
+  }
+
+  // TODO: support SSR
+  // in SSR there is no need to setup an actual effect, and it should be noop
+  // unless it's eager or sync flush
+  // let ssrCleanup: (() => void)[] | undefined
+  // if (__SSR__ && isInSSRComponentSetup) {
+  //   // we will also not call the invalidate callback (+ runner is not set up)
+  //   onCleanup = NOOP
+  //   if (!cb) {
+  //     getter()
+  //   } else if (immediate) {
+  //     callWithAsyncErrorHandling(cb, handlerError, BaseWatchErrorCodes.WATCH_CALLBACK, [
+  //       getter(),
+  //       isMultiSource ? [] : undefined,
+  //       onCleanup
+  //     ])
+  //   }
+  //   if (flush === 'sync') {
+  //     const ctx = useSSRContext()!
+  //     ssrCleanup = ctx.__watcherHandles || (ctx.__watcherHandles = [])
+  //   } else {
+  //     return NOOP
+  //   }
+  // }
+
+  let oldValue: any = isMultiSource
+    ? new Array((source as []).length).fill(INITIAL_WATCHER_VALUE)
+    : INITIAL_WATCHER_VALUE
+  const job: SchedulerJob = () => {
+    if (!effect.active || !effect.dirty) {
+      return
+    }
+    if (cb) {
+      // watch(source, cb)
+      const newValue = effect.run()
+      if (
+        deep ||
+        forceTrigger ||
+        (isMultiSource
+          ? (newValue as any[]).some((v, i) => hasChanged(v, oldValue[i]))
+          : hasChanged(newValue, oldValue))
+      ) {
+        // cleanup before running cb again
+        if (cleanup) {
+          cleanup()
+        }
+        const currentEffect = activeEffect
+        activeEffect = effect
+        try {
+          callWithAsyncErrorHandling(
+            cb,
+            handlerError,
+            BaseWatchErrorCodes.WATCH_CALLBACK,
+            [
+              newValue,
+              // pass undefined as the old value when it's changed for the first time
+              oldValue === INITIAL_WATCHER_VALUE
+                ? undefined
+                : isMultiSource && oldValue[0] === INITIAL_WATCHER_VALUE
+                  ? []
+                  : oldValue,
+              onEffectCleanup
+            ]
+          )
+          oldValue = newValue
+        } finally {
+          activeEffect = currentEffect
+        }
+      }
+    } else {
+      // watchEffect
+      effect.run()
+    }
+  }
+
+  // important: mark the job as a watcher callback so that scheduler knows
+  // it is allowed to self-trigger (#1727)
+  job.allowRecurse = !!cb
+
+  let effectScheduler: EffectScheduler = () =>
+    scheduler({
+      effect,
+      job,
+      isInit: false
+    })
+
+  const effect = new ReactiveEffect(getter, NOOP, effectScheduler)
+
+  const cleanup = (effect.onStop = () => {
+    const cleanups = cleanupMap.get(effect)
+    if (cleanups) {
+      cleanups.forEach(cleanup => cleanup())
+      cleanupMap.delete(effect)
+    }
+  })
+
+  const unwatch = () => {
+    effect.stop()
+    // TODO: move to doWatch
+    // if (instance && instance.scope) {
+    //   remove(instance.scope.effects!, effect)
+    // }
+  }
+
+  if (__DEV__) {
+    effect.onTrack = onTrack
+    effect.onTrigger = onTrigger
+  }
+
+  // initial run
+  if (cb) {
+    if (immediate) {
+      job()
+    } else {
+      oldValue = effect.run()
+    }
+  } else {
+    scheduler({
+      effect,
+      job,
+      isInit: true
+    })
+  }
+
+  return unwatch
+}
+
+export function traverse(value: unknown, seen?: Set<unknown>) {
+  if (!isObject(value) || (value as any)[ReactiveFlags.SKIP]) {
+    return value
+  }
+  seen = seen || new Set()
+  if (seen.has(value)) {
+    return value
+  }
+  seen.add(value)
+  if (isRef(value)) {
+    traverse(value.value, seen)
+  } else if (isArray(value)) {
+    for (let i = 0; i < value.length; i++) {
+      traverse(value[i], seen)
+    }
+  } else if (isSet(value) || isMap(value)) {
+    value.forEach((v: any) => {
+      traverse(v, seen)
+    })
+  } else if (isPlainObject(value)) {
+    for (const key in value) {
+      traverse(value[key], seen)
+    }
+  }
+  return value
+}
+
+export function callWithErrorHandling(
+  fn: Function,
+  handleError: HandleError,
+  type: BaseWatchErrorCodes,
+  args?: unknown[]
+) {
+  let res
+  try {
+    res = args ? fn(...args) : fn()
+  } catch (err) {
+    handleError(err, type)
+  }
+  return res
+}
+
+export function callWithAsyncErrorHandling(
+  fn: Function | Function[],
+  handleError: HandleError,
+  type: BaseWatchErrorCodes,
+  args?: unknown[]
+): any[] {
+  if (isFunction(fn)) {
+    const res = callWithErrorHandling(fn, handleError, type, args)
+    if (res && isPromise(res)) {
+      res.catch(err => {
+        handleError(err, type)
+      })
+    }
+    return res
+  }
+
+  const values = []
+  for (let i = 0; i < fn.length; i++) {
+    values.push(callWithAsyncErrorHandling(fn[i], handleError, type, args))
+  }
+  return values
+}