input DX improvement opportunity

[oliviertassinari]

Do you want to request a feature or report a bug?

A feature

What is the current behavior?

No warning is raised in the following snipped:

import React from "react";

export default class TextFields extends React.Component {
  state = {
    name: "Before timeout"
  };

  componentDidMount() {
    // emulate loading some data with AJAX
    setTimeout(() => {
      console.log("Updating name after timeout");
      this.setState({
        name: "After timeout"
      });
    }, 100);
  }

  render() {
    return <input id="name" label="Name" defaultValue={this.state.name} />;
  }
}

https://codesandbox.io/s/k248z9ro15

What is the expected behavior?

I believe we have the opportunity to raise a warning in development. It would inform users they can't update the defaultValue property. This problem was raised to my attention in mui/material-ui#11150.

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?

React 16.3.2

[jquense]

I see how this is generally a bug in this case however defaultValue can be updated to some effect, since it's the value used as the fallback in some situations, like a form reset

[oliviertassinari]

@jquense Alright, does it mean there is no DX improvement opportunity? Should we close this issue?

[gaearon]

Yeah I think we can’t warn without legit false positives.