Mutate seems to swallow errors, contrary to some documentation.

[zjr]

Hello,

If I try something like the following:

import { mutate } from 'swr';
…
try {
  const foo = await mutate('bar', async () => {
    throw new Error('an error occurred');
  });
  
  console.log({ foo }); // { foo: undefined }
} catch (e) {
  // this is never executed
  console.error(e);
}

Mutate swallows the error and it's never heard from. However, the docs seem to state that I should be able to catch this. Here's what the docs say:

try {
  const user = await mutate('/api/user', updateUser(newUser))
} catch (error) {
  // Handle an error while updating the user here
}

That is here: https://github.com/vercel/swr#returned-data-from-mutate.

What's going on?

[zjr]

Is it supposed to be that I would do:

try {
  await mutate('bar', await (async () => {
    throw new Error('an error occurred');
  })());
} catch (e) {
  console.error(e);
}

so that the function is run and evaluated and it's results are passed to mutate?

[huozhi]

@zjr I've tried to run your code snippet in codesandbox, and I did recieved the error in the console. see the trace below

did you try the latest version of swr (0.2.3 by the date I reply this thread)?

[huozhi]

@zjr thanks for the stable repro example. I think it's related to 477 .
after looking into the like it because it enters the revalidate stage first then return before error thrown.

[zjr]

Thanks @huozhi, should I open a new issue for this? I ask because the one you've mentioned is closed.

[huozhi]

@zjr yeah I think we should have another issue to track this, I was wrong before so I added a delete line for that comment. sorry for the confusion here.

the issue will be titled like "mutate swallow errors when using along with useSWR hook".

[zjr]

Alright, I've created that here: #556

[zjr]

For posterity, this is fixed by: #557.