Error Link
Handle and inspect errors in your GraphQL network stack.
Use the onError link to perform custom logic when a GraphQL or network error occurs. You pass this link a function that's executed if an operation returns one or more errors:
import { onError } from "@apollo/client/link/error";// Log any GraphQL errors or network error that occurredconst errorLink = onError(({ graphQLErrors, networkError }) => {if (graphQLErrors)graphQLErrors.forEach(({ message, locations, path }) =>console.log(`[GraphQL error]: Message: ${message}, Location: ${locations}, Path: ${path}`));if (networkError) console.log(`[Network error]: ${networkError}`);});
This function is called after the GraphQL operation completes and execution is moving back up your link chain. The function should not return a value unless you want to retry the operation.
Options
The function you provide the onError link is passed an object with the following fields:
| Name / Type | Description |
|---|---|
| The details of the GraphQL operation that produced an error. |
| The (possibly modified) GraphQL result from the server, passed by the next link down the chain (i.e., the link closer to the terminating link). |
| An array of GraphQL errors that occurred while executing the operation, if any. |
| A network error that occurred while attempting to execute the operation, if any. |
| A function that calls the next link down the chain. Calling |
Error categorization
An error is passed as a networkError if a link further down the chain called the error callback on the observable. In most cases, graphQLErrors is the errors field of the result from the last next call.
A networkError can contain additional fields, such as a GraphQL object in the case of a failing HTTP status code. In this situation, graphQLErrors is an alias for networkError.result.errors if the property exists.