Crank: Catching errors in a simple function component

[waynebaylor]

If you take the example from the docs about catching errors:

function Thrower() { 
  throw new Error("Hmmm");
}

function *Catcher() {
  try {
    yield <Thrower />;
  } catch (err) {
    return <div>Error: {err.message}</div>;
  }
}

and modify Catcher so it's a simple function instead of a generator:

function Thrower() { 
  throw new Error("Hmmm");
}

function Catcher() {
  try {
    return <Thrower />;
  } catch (err) {
    return <div>Error: {err.message}</div>;
  }
}

then the catch block doesn't get executed.

Not sure if it's a bug or if my expectations are off 😄
Example: https://codesandbox.io/s/catch-error-simple-function-chfpx

[brainkim]

Sweats bullets

Not a bug! The way error handling works is that, when an error is thrown, we walk up the component tree and pass the error into any generator components via the throw() method. The best way to conceptualize the throw() method is to imagine that it resumes the generator but throws an error from the position suspended yield operator. There is no corresponding way to throw errors with return statements, so this feature is exclusive to generator components.

Let me know your thoughts on this!

[waynebaylor]

Yeah that makes sense, I hadn't thought about the throws() part.

[waynebaylor]

I think I was forgetting that in general executing <SomeComponent/> isn't the same as rendering. If there are errors during the rendering then Crank needs some way to get that info back into the components, like using throws().