Dealing with network errors

When you use the useResource() hook, React will suspend rendering while the network request takes place. But what happens if there is a network failure? It will throw the network error. When this happens you'll want to have an error boundary set up to handle it. Most likely you'll want to place one specifically for network errors at the same place you put your <Suspense>. What you do with the error once you catch it, is of course up to you.

Error Boundary

This library provides NetworkErrorBoundary component that only catches network errors and sends them to a fallback component you provide. Other errors will rethrow.

import { Suspense } from 'react';
import { NetworkErrorBoundary } from 'rest-hooks';
import { RouteChildrenProps } from 'react-router';

const App = ({ location }: RouteChildrenProps) => (
  <Suspense fallback={<Spinner />}>
    <NetworkErrorBoundary>
      <Routes />
    </NetworkErrorBoundary>
  </Suspense>
)

Alternatively you could create your own error boundary where you might try dispatching the errors to another provider to use in a transient popup.

Additionally you could also use one error boundary for any error type and handle network errors there.

Without Error Boundary

Error boundaries provide elegant ways to reduce complexity by handling many errors in the react tree in one location. However, if you find yourself wanting to handle error state manually you can adapt the useStatefulResource() hook.

Errors from Mutates (imperative)

Since mutations are called imperatively, their function will throw an error if there is a network error like 400 because the form values were invalid.

Let's look at the update form example from the introduction.

import { useFetcher } from 'rest-hooks';
import ArticleResource from 'resources/article';

export default function UpdateArticleForm({ id }: { id: number }) {
  const article = useResource(ArticleResource.detail(), { id });
  const update = useFetcher(ArticleResource.update());
  // update as (body: Readonly<Partial<ArticleResource>>, params?: Readonly<object>) => Promise<any>
  return (
    <Form
      onSubmit={e => update({ id }, new FormData(e.target))}
      initialValues={article}
    >
      <FormField name="title" />
      <FormField name="content" type="textarea" />
      <FormField name="tags" type="tag" />
    </Form>
  );
}

The function we pass to <Form /> calls the update fetch. This means that it will pass through any errors that occur with that fetch.

To handle this the Form component should control form error state.

function Form({ onSubmit, initialValues, children }: FormState) {
  const [errors, setErrors] = useState<null | Error>(null);
  const formData = useFormData(); // this is an example interface

  const handleSubmit = useCallback(() => {
    try {
      return onSubmit(formData);
    } catch(e) {
      // We set the form error state when we catch an error from our network call
      setErrors(e);
    }
  }, [setErrors, onSubmit]);

  return (
    <form onSubmit={handleSubmit}>
      {/* Show the form errors at the top */}
      <FormError error={error} />
      {children}
    </form>
  )
}