Controlled inputs with the potential for `undefined` value

Upgraded to React 15rc1 today, and a new warning appears to have cropped up:

Warning: SearchBox is changing a uncontrolled input of type text to be controlled. Input elements should not switch from uncontrolled to controlled (or viceversa). Decide between using a controlled or uncontrolled input element for the lifetime of the component. More info: https://fb.me/react-controlled-components

The component it’s referring to is indeed a controlled component for the duration of its lifetime:

<input
  type="text"
  className="typeahead"
  onKeyUp={::this.controlsHandler}
  onChange={::this.changeHandler}
  value={this.props.search.get('term')}
  ref={(i) => this._input = i}
/>

The problem, I’ve realized, is that on first render, this.props.search.get('term') returns undefined, because its value is only populated with text put into the input.

I expect this is a pretty common pattern for controlled components?

Otherwise loving the release - having all SVG attributes at my disposal is very exciting 😃

[deser]

How about removing this warning? It really annoying and makes me write unnecessary checks. To my mind it is normal when in flux Store you have some data which is undefined

[cdxOo]

React has no way of knowing if you intended to render a component with an empty value or if you intended for the component to be uncontrolled. It is a source of bugs.

While i can see the point, that this might be a source of bugs. I kind of disagree on the first part. The value property is part of the props object. Therefor you can use Object.keys() to figure out if that key has been intentionally added to the props object or if it hasn’t been. The key will exist if you explicitely set the property even if its value is undefined. When going with this approach <MyInput value={ undefined } /> would be a controlled component and <MyInput /> would be uncontrolled.