They're referring to https://react.dev/learn/you-might-not-need-an-effect#adjusting-some-state-when-a-prop-changes https://react.dev/learn/you-might-not-need-an

They're referring to https://react.dev/learn/you-might-not-need-an-effect#adjusting-some-state-when-a-prop-changes https://react.dev/learn/you-might-not-need-an-effect#adjusti..., where they literally call setFoor in the render method. I guess this makes sense, but it's weird after all the "never do anything stateful in render"