Using `react-reconciler` to reimplement `findDOMNode`

findDOMNode.ts

import { Component } from 'react'
//@ts-ignore
import { findCurrentHostFiber } from 'react-reconciler/reflection'

// https://github.com/facebook/react/blob/main/packages/shared/ReactInstanceMap.js#L18
export function getInstance(key: any) {
  return key._reactInternals
}

// https://github.com/facebook/react/blob/main/packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js#L167
type PublicInstance = Element | Text

// https://github.com/facebook/react/blob/main/packages/react-dom-bindings/src/client/ReactFiberConfigDOM.js#L322
function getPublicInstance(instance: PublicInstance): PublicInstance {
  return instance
}

// https://github.com/facebook/react/blob/main/packages/react-reconciler/src/ReactFiberReconciler.js#L153
function findHostInstance(component: Component): PublicInstance | null {
  const fiber = getInstance(component)
  if (fiber === undefined) {
    if (typeof component.render === 'function') {
      throw new Error('Unable to find node on an unmounted component.')
    } else {
      const keys = Object.keys(component).join(',')
      throw new Error(`Argument appears to not be a ReactComponent. Keys: ${keys}`)
    }
  }
  const hostFiber = findCurrentHostFiber(fiber)
  if (hostFiber === null) {
    return null
  }
  return getPublicInstance(hostFiber.stateNode)
}

// https://github.com/facebook/react/blob/main/packages/react-dom/src/client/ReactDOMClient.js#L43
export function findDOMNode(componentOrElement: Component<any, any>): null | Element | Text {
  return findHostInstance(componentOrElement)
}