Suspense: add messaging when suspense promise neither resolves nor rejects

Do you want to request a feature or report a bug? Request a feature

What is the current behavior? If you throw a promise that neither resolves nor rejects, you hit the suspense fallback UI indefinitely and receive no console messaging that helps you debug this.

Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React? All versions that allow for suspense

Proposed feature Log a warning to the console if a suspense promise takes longer than a certain amount of time to settle. Here is some code demonstrating what that could look like inside of the react codebase:

try {
  renderComponent(...);
} catch (err) {
  if (err && err.then) {
    const timeoutId = setTimeout(() => {
      console.warn(`A suspense promise triggered in component <Foo /> did not resolve nor reject after 3 seconds. If the promise never settles, the suspense fallback UI will be shown forever.`)
    }, 3000)

    err.finally(() => {
      clearTimeout(timeoutId);
    })

    // Now actually do all the suspense magicks...
  }
}

[sebmarkbage]

I agree that it was a mistake to expose it in the first place (even if it’s undocumented) but I think the solution would that will rather be to completely deprecate the confusing API and replace it with the higher level one.

I do think that relying on undocumented behavior is a bad pattern that we as an industry need to start moving away from. It puts unreasonable expectations on library authors.

The reason it is strongly worded is because there are a number of issues all related to misusing this undocumented API. I understand that it’s ultimately our problem but it’s a bit annoying. That’s not your fault tho.

[joeldenning]

I think the solution would that will rather be to completely deprecate the confusing API and replace it with the higher level one.

👍 for me the important thing is that Suspense can be used directly. Making a higher level API for it could help with that.

I do think that relying on undocumented behavior is a bad pattern that we as an industry need to start moving away from. It puts unreasonable expectations on library authors.

The reason it is strongly worded is because there are a number of issues all related to misusing this undocumented API. I understand that it’s ultimately our problem but it’s a bit annoying. That’s not your fault tho.

Fair enough. Myself and 2-3 developers I’ve been working with on this project have definitely entered the waters of experimental and undocumented APIs. We have enjoyed learning (reverse engineering?) the behavior of the Suspense API as we’ve gone, even though it’s taken us a while and we’ve had some surprises along the way. We have known we’re in uncharted territory a bit and understand the costs and pains of that. I do not think it is your fault that we’ve spent a few days figuring it out. We’re the kind of developers who enjoying getting into the nitty gritty 😄