#no-will-update-set-state

#Configuration

import { defineConfig, reactPlugin } from '@rslint/core';

export default defineConfig([
  reactPlugin.configs.recommended,
  {
    rules: {
      'react/no-will-update-set-state': 'error',
    },
  },
]);

Disallow this.setState inside componentWillUpdate.

Updating the state during a component update (before render) is a no-op — the update is already in flight, so calling setState here either triggers an infinite loop or is silently dropped.

#Rule Details

This rule flags any this.setState call whose enclosing class method, class field initializer, or object-literal property is keyed componentWillUpdate. When settings.react.version is >= 16.3.0 (or unset — treated as latest), the rule additionally flags the same pattern keyed UNSAFE_componentWillUpdate, matching the renamed alias shipped in React 16.3.

By default, calls inside a nested function (regular or arrow) are allowed — enable disallow-in-func to forbid them too.

Examples of incorrect code for this rule:

var Hello = createReactClass({
  componentWillUpdate: function () {
    this.setState({
      name: this.props.name.toUpperCase(),
    });
  },
});

class Hello extends React.Component {
  componentWillUpdate() {
    this.setState({
      name: this.props.name.toUpperCase(),
    });
  }
}

Examples of correct code for this rule:

var Hello = createReactClass({
  componentWillUpdate: function () {
    someNonMemberFunction(arg);
    this.someHandler = this.setState;
  },
});

var Hello = createReactClass({
  componentWillUpdate: function () {
    someClass.onSomeEvent(function (data) {
      this.setState({
        data: data,
      });
    });
  },
});

#Rule Options

{ "react/no-will-update-set-state": ["error", "disallow-in-func"] }

With disallow-in-func set, the rule also flags this.setState calls inside nested functions:

var Hello = createReactClass({
  componentWillUpdate: function () {
    someClass.onSomeEvent(function (data) {
      this.setState({
        data: data,
      });
    });
  },
});

#React Version

Unlike no-did-update-set-state / no-did-mount-set-state, this rule is not a no-op at any React version — componentWillUpdate is unsafe on every release. The React version only controls whether UNSAFE_componentWillUpdate (the 16.3+ renamed alias) is also flagged, matching eslint-plugin-react's shouldCheckUnsafeCb.

#Original Documentation

• eslint-plugin-react / no-will-update-set-state