useEffect be called on re-render in HMR will cause problems

[brickspert]

import React, { useEffect, useState } from 'react';

export default () => {
  const [count, setState] = useState(0);

  useEffect(() => {
    setState(s => s + 1);
  }, []);

  return (
    <div>
      {count}
    </div>
  )
}

Without HRM, the count Maximum will be 1.

But with HRM, the count increases with updates.

Is this the expected behavior?

Another bad example, react-use's useUpdateEffect will be called at the same time of useEffect when HRM.

import React, { useState } from 'react';
import  { useUpdateEffect } from 'react-use';

export default () => {

  useEffect(() => {
     console.log('mount')
  }, []);

 useUpdateEffect(()=>{
     console.log('updateEffect')
 }, []);

  return (
    <div>
       hello world
    </div>
  )
}

[brickspert]

related facebook/react#21019

[pmmmwh]

This is expected behaviour, you can see Dan's explanation in the linked issue on why this is the case.