9.19 throws setState(...): You passed an undefined or null state object; instead, use forceUpdate()

[hyperknot]

Upgrading to 9.19 started throwing a React warning with React 15.6:

Warning: setState(...): You passed an undefined or null state object; instead, use forceUpdate()

I'm using it like this:

import AutoSizer from 'react-virtualized/dist/commonjs/AutoSizer'
import List from 'react-virtualized/dist/commonjs/List'

@observer
export class FeatureList extends React.Component {
  rowRenderer({ key, index, style }) {
    return <FeatureListItem key={key} style={style} feature={featureStore.featureArray[index]} />
  }

  render() {
    if (!mapUIStore.ready) return null

    return (
      <ul id="panel-items-list">
        <AutoSizer>
          {({ height, width }) => (
            <Observer>
              {() => (
                <List
                  width={width}
                  height={height}
                  rowCount={featureStore.count}
                  rowHeight={31}
                  rowRenderer={this.rowRenderer}
                  scrollToIndex={mapUIStore.scrollToIndex}
                />
              )}
            </Observer>
          )}
        </AutoSizer>
      </ul>
    )
  }
}

The warning happens when scrollToIndex is updated.

[wuweiweiwu]

Can you provide a codesandbox with a repro?

And perhaps a more detailed error message?

[hyperknot]

OK, I'll have a look at making one.

[wuweiweiwu]

react 16 allows return null from setState to avoid a re-render.

https://teamtreehouse.com/library/returning-null-from-setstate.

I would suggest upgrading react. but it's also just a warning in dev.

I'll look into refactoring some setState calls to avoid setting null

Hope that helps!

[hyperknot]

I've especially downgraded to React 15.6 until the Chrome translate bug is fixed in React 16.

But I don't understand this already seems to be a breaking change, then why is it just a minor release?

[wuweiweiwu]

Its because there was no changes that weren't backwards compatible following semvar and the rewrite to 16.x lifecycle functions had no api changes.

[wuweiweiwu]

@TrySound Should this be a breaking changes?

[TrySound]

Yep this is a breaking change. Try to fix it. We will return null in v10.

[wuweiweiwu]

Gotcha