Bug: react-devtools profiler doesn't show props

According to docs, it’s possible to see props and state of a component at each commit. https://reactjs.org/blog/2018/09/10/introducing-the-react-profiler.html#browsing-commits

Yet, in every project I’ve tried all I see is the names of changed props, but not their values, like the gif from docs claims.

React version: 16.12.0 extension: 4.4.0 (1/3/2020) … Created from revision f749045a5 on 1/3/2020

Steps To Reproduce

1. create counter app with CRA or another method
2. open profiler and change state
3. observe how only the name of the prop is visible, but not its value

function App() {
  let [a, setA] = useState(0);

  return (
    <div className="App">
      <button onClick={() => setA(v => v + 1)}>inc</button>
      <Kid a={a} />
    </div>
  );
}

function Kid() {
  return null;
}

The current behavior

current behavior

The expected behavior

expected behavior

Am I doing something wrong or has this feature been removed? I know you can see props in the inspector, but there it’s only the most recent ones.

[bvaughn]

The blog post you linked to was for a previous version of DevTools. That version created immutable copies of all props and state values (using immutable) which allowed the Profiler UI to show past values. However this came with the cost of introducing a lot of overhead for large apps.

Last year, I rewrote DevTools primarily to make it a lot faster (and also to add some new features that would have been difficult to build on the old one). You can read more about that rewrite here if you’re interested: https://reactjs.org/blog/2019/08/15/new-react-devtools.html

The relevant change here is that we no longer do the immutable clone, so the Profiler UI cannot show previous values. It can still tell you which props or state changed though- but it will only show their names. This is by design, as a performance trade off.

Sorry for the confusion.

[AlexOxorn]

Couldn’t this be a toggle-able option? I get that changing the default behavior, but what if someone needed the old behavior. Sometimes knowing which prop changed is of little help if I can’t figure out how it changed.